Technical Sprinter

Technical Sprinter

Mercedes Sprinter – Scraping noise from front brakes – Brake pad replacement


A customers Sprinter MWB van pulled onto the yard and as it slowed to halt it made a loud metal-on-metal scraping sound.  The driver leapt out and explained the noise, which really did not need any explaining!  He had just ‘popped in’ to get it fixed before he continued on his 150 mile round trip delivery run before the closedown for Christmas.

Mercedes Sprinter Front Brake Pad Replacement 1

Looking at the rust coloured dust deposited on the front wheel rim it was obvious it was the front pads that were ‘non-existent’, closer inspection revealed that the near side pad set was so worn the steel backing had begun to score the outer face of the brake disc.  With little to no time to do a complete repair, the object was to get him safely on his way and revisit the repair with ordered and supplied replacement brake discs in the New Year. So a quick pad change was needed… Hopefully this will explain how to do this.

Mercedes Sprinter Front Brake Pad Replacement 2

While the vehicle is still on the ground, use your ‘weapon of choice’ on the wheel studs. In our case this is a 1 inch drive socket bar with 19mm socket and long ‘slipper’ tube for extra leverage . It was used on both front wheel bolt sets before lifting the vehicle with the trolley jack. If you get a stubborn wheel bolt, take the largest hammer in the tool box and hit the head of the wheel bolt ‘square on’ as hard as you can at least a couple of times, try again with the bar and often this is all that is needed to free off the bolt.

Mercedes Sprinter Front Brake Pad Replacement 3

Once in the air, (A good safe place to locate the trolley jack cup on either side, is under the triangular steel spring clamp plates bolted to the front subframe) take off the wheel and turn the steering to orientate the brake caliper as far out from under the wheel arch as possible.  Pull out both upper and lower bungs from the ends of the slide pin rubber weather shields at the rear and using a 7mm hexagon wrench undo both slide pins and remove them.

Mercedes Sprinter Front Brake Pad Replacement 4

Using two stout screwdrivers release the rattle spring from the face of the caliper by prying it away from the disc while releasing the hooked ears from their locating holes in the sliding portion of the brake (two photos down).  Once removed place to one side.  Again use a stout screwdriver or lever to push back the hydraulic piston into the caliper. Once this is almost flush with the casting, you are assured that the new pads will slot straight in without problem.

Mercedes Sprinter Front Brake Pad Replacement 5

Remove the sliding part of the caliper and place it on the top of the steering knuckle so that the flexible hose is not stressed in any way. The inboard brake pad will still be attached to the caliper piston with a three pronged spring affair.  Simply pull out the pad from this locator and discard it, do the same with the outboard pad that is probably still sitting in its slots on the hanger casting.  It is worth cleaning the rust from the brake disc at this point as the new pads will bed in quicker.  You can do this by striking gently the outside edge of the disc working your way around its circumference to break away the accumulated scale and rust, finishing off with a file to remove any lips formed on the braking surface.  Finally clean off with a scraper or wire brush the sliding surfaces where the pads touch/rest on the casting of the caliper and then apply a thin smear of brake grease to these points.  In this case, as I was to be revisiting the repair in just a few days, I did not use any grease and just slotted in the new pad set.

Mercedes Sprinter Front Brake Pad Replacement 6

Offer up the caliper sliding section and when it is fitted snugly, replace the two slide pins using the 7mm hex wrench.  If the slide pins are dirty clean them up with a wire brush and also apply a light coating of brake grease before assembly. Tighten both slide pins and replace the plastic bungs.  Now replace the rattle spring, locating it into its two holes and making sure the two long sprung arms of the leaf spring are located behind the fixed part of the carrier (the hanger) to apply the necessary pressure.

Mercedes Sprinter Front Brake Pad Replacement 7

Mercedes Sprinter Front Brake Pad Replacement 8

Hop into the cab and ‘pad’ the brake pedal in short pumps to seat the pads against the disc, and then check your work. Once satisfied replace the road wheel and lower the jack.  Continue to change the pads in the other side to complete the job.

In this case the brake disc is badly scored and really should not have had just pads fitted without replacing the brake disc itself.  Bedding in time, pad wear and brake efficiency will ultimately be effected.  Just replacing the pads in a situation like this should only be done in a ‘get-you-by’ situation and driven onward with care until the earliest time you can replace the discs/pads as a set. (You will also need yet another new set of brake pads to compliment the fresh brake discs you will be fitting)

Mercedes Sprinter Front Brake Pad Replacement 9

There is fitted to this model and all Mercedes vehicles, a pad wear sensor, this had a broken wire at the caliper and because it is of the earlier single wire type, no dash indication of ‘pad-low’ was shown (the indicator relies soley on the single sensor wire contacting ground to illuminate the dash lamp, this would happen as the pad wears down below the pocket in the pad material where the sensor tip is located, eventually touching and grounding it to the brake disc surface).  The later ‘two wire’ sensor versions, as fitted to 2006 on vehicles NCV3 Sprinter and W639 Vito etc, display a lamp if the sensor circuit is broken or grounded, which in turn reduces the chances of the above occurring without warning.  See this posting on wear sensor replacement.

Mercedes Sprinter Cabin Heater Not Getting Warm – Heater Matrix Replacement


This article is specific to the Right hand drive (Left hand drive should be similar) Mercedes Sprinter pre 2006, T1N, without air conditioning or Automatic temperature control (ATC)

Well, winter is here again and one of the long wheel base 2005 Mercedes Sprinters had been running cool in the cabin heater department for some weeks, it had now got to the point the driver was complaining about the cold so we were compelled to take a look.

Sprinter Dash panel removal

The first port of call was to change the engine coolant thermostat, as it was running cool on the gauge, so needed that job doing anyway.  Needless to say in doing so, there was no improvement to the cabin temperature and further investigation was needed.

Both the supply and return pipes to the heater matrix under the bulkhead, engine side, were very warm – so hot water was obviously making it to the cabin heater.  This particular van had the diesel-fired coolant ‘pre-heater’ removed (ESPAR) from the front left inner wing and all the steel pipe bypassed, as it had started to rot and leak in several places.  This is quite common on older Sprinters and this steel rigid pipework runs mostly out of sight behind the bodywork, up above the heater blower housing.  This makes it near impossible to detect any leaks, let alone repair it, so it had been bypassed some time back as a repair measure.

Removing the front dash panel inside the cab and dropping forward the heater controls to check the flap and valve controls, proved that all was well here and the supply valve in particular (green actuator cable jacket) was working correctly, opening and closing the supply water valve to the matrix.  Often the rotary heater control that varies the temperature is broken, not allowing the cable to push back inside the outer to actuate the valve fully open.  There is a steel clip and plastic retaining moulding that breaks away from the control panel, rendering the rotary control unless often resulting in a complete replacement control panel being required. (£££)

The next stage is to remove the top dash section that houses the radio binnacle, this is held with fixings behind the speaker grilles left and right, along with various other fixing screws following the front edge of the dash lip.  You will need to remove the speedo front trim and the back cover – the instruments need not be removed.  Once this is removed you can now see the top of the heater box and in a small open void to the right, the aluminium supply and return pipes routed to the heater matrix.  Extending a finger to touch the supply and return proved that both were scorching hot, indicating the heater valve was open and water was at least circulating this far.  Extending a finger inside the square fresh air ducts and hooking it back to the cabin, you will find a small section of plastic housing missing. This enables you to actually touch the heater matrix element – on the left and right sides these were cold! – even though the flow and return pipes were boiling hot.  This indicated that coolant flow through the heater matrix was restricted and in effect the water was just flowing in and straight out without causing any part of the radiator section to warm, thus no cabin heat.  Its worth noting that if you have the fan off, the matrix will eventually warm through but with the fan running, as soon as air begins to flow across the matrix it rapidly chills it to an almost non-existent heat. No warn water conduction.

So we need to change the heater matrix.  What a huge job. The complete dashboard has to be removed, including steering column to gain access to the heater box.  The heater box itself then has to be split into two halves to replace the heater matrix inside.  That can take anywhere between 8 to 10 hours to complete, we did not have the time available and the van was due out in a short number of hours.

The tools you will require are a battery drill, 1/8 inch drill bit, sturdy flat blade screwdriver, hacksaw blade, 6mm 1/4 drive socket and ratchet, aluminium strip, pop rivets (or self tapping screws) and silicone sealant.

Sprinter Heater Matrix removal 1

Drill a small row of holes in the top of the plastic heater box to enable you to insert a hacksaw blade and cut along where the yellow lines are indicated on the image below.  Take care when drilling and sawing to only cut the plastic box and nothing beneath. You will be fairly safe if you cut only where the yellow lines indicate.  Once you have cut along the top of the box, use a broad screwdriver to remove the cut section, you may have to lever and snap away a small section of plastic that remains from either side of the top section so that it can be lifted away.  It should now look like this.

Sprinter Heater Matrix removal 2

Now you will need to cut a small section from the right of the grey dash under-layer to gain full access to the three 6mm pins that hold the compression plate connecting  the heater matrix pipe spigots to the valve body, this is clamped against captive nuts in the plastic water valve flange assembly.   The extra access section on the right you will need to cut away can be seen by comparing the two photographs above.  Once the three 6mm pins and plate are removed drain down some coolant from the system, the easiest way to achieve this is to simply remove the thermostat bypass hose.  This joins the thermostat housing to the coolant expansion bottle, once this has drained down carefully pull the matrix pipes out from the valve block (there is just enough clearance).  There is a swaged end and rubber O ring on each pipe, make sure you do not damage them. While holding the pipes pulled free from the valve block, pull the heater matrix up and out of the heater box.  Either replace the heater matrix with a new/replacement unit or back flush the original unit upside down, tapping it to loosen the collected scale and rust that finds its way into the matrix tubes.  Most of the rust and debris I am sure, came from the decomposition of the steel circulation pipes mentioned earlier.  It is worth mentioning that to simply flush the matrix from under the bonnet/hood in situ would achieve very little, as the unit has to be inverted to dislodge any accumulated debris or silt. There is no true ‘inlet’ and ‘outlet’ with a totally chambered enclosed flow between the two, heating water simply enters the header at the top and exits further along its length.  A great deal of the heating of the matrix is mainly by conduction in the heated water down through the matrix tubes beneath the header.

Sprinter Heater Matrix

Install the newly flushed heater matrix, refill the coolant system and test your repair, the matrix should now be evenly very hot all over its surfaces and not just the top header section.  If this was a success with no leaks, rebuild the heater box using small cut aluminium plates and pop rivets, making sure to close up the saw cuts as well as possible and restore as close as possible the original shape of the heater box.  Apply a smear of silicone sealant to the saw cuts making good any air gaps that remain.  Once the sealer has dried, rebuild the dashboard top section and replace the heater panel and front trim.

Job done – all your handy-work is completely hidden under the top dash cover – nothing is visible to the naked eye, revealing anything other that you did not take out the complete dashboard to replace the matrix!

Sprinter Heater Matrix removal 3

Time taken 3 hours vs 8-10 hours labour – make your own mind up!

Mercedes Sprinter Clutch Replacement (T1N, NCV3, VW Crafter and other MB)


Clutch replacement on any vehicle can be an expensive job, especially if you are entrusting the job to a main dealer.  Although large scale and a little mauling, clutch replacement on Mercedes models can be well within the capability of a competent DIY’er with only a limited number of tools.  In this post we shall look at the replacement of the clutch mechanism (including Dual Mass Flywheel DMF) on the Mercedes Sprinter – both older and newer models.

Mercedes Sprinter / Crafter Clutch replacement

There are several important details often overlooked about the Self Adjusting Clutch mechanism or SAC, that the installer has to be aware of so that things go smoothly.  You will no doubt have read many horror stories on the web of people installing SAC clutch units only to find that on re-assembly they have no functioning clutch, then having to take it all apart again to do it properly!  The first thing to understand is how the clutch actually self-adjusts over its life and in this understanding it will allow you to assemble things in the correct manner, so when you put that last bolt in place you are certain things will work as they were designed.  If you are fitting used components, such as a second hand DMF (flywheel) or even a complete used clutch, this knowledge is ever more important.  You would also additionally need to know how check this if you were stripping and replacing the original clutch and flywheel from an engine only to replace it later, say if you were replacing a leaking rear crank shaft seal for instance.

You will remember from days of old that clutches on older vehicles used to have a different bite point as they aged, either right at the bottom or top of stroke depending on design.  This is not the case today with advancements in clutch technology.  Mercedes clutches and other vehicles too, now have circular adjusting mechanisms built into the cover plate and spring that move to compensate as the clutch wears, maintaining the release spring pressure and finger position.  This means that as a SAC clutch ages, it maintains the same spring operating position and ensures a constant actuating force to engage/disengage the clutch over its life.  Indeed it is almost impossible to tell if a modern clutch is ‘new’ or only ‘weeks from failing’ by the pedal position and feel alone – all thanks to the SAC.

When you purchase a new clutch kit you will almost always find that the clutch has been ‘set’, and is ready for installation. However it is always best to check that things are correct before fitting as I have known due to rough handling even new cover plates ‘spring’ into a full adjustment position – clearly fitting this as-is would result most probably in a non functioning clutch.

Mercedes SAC Clutch

From the illustration above you will see the cover plate/spring assembly has an adjustment ring. (2)  Simply put, this circular ring is allowed to rotate if required a few degrees when the diaphragm spring is fully compressed (when the clutch is operated) Its rotational resting position is controlled by the combined action of a sensor diaphragm spring (5) and the main diaphragm spring (4), allowing the plate to slide round slightly, facilitating changing the pivot point of the main clutch springs as the driven plate wears. There are three small springs that pre-load the adjusting ring so that as the clutch wears the adjustment ring is forced to rotate slightly to drive what is in effect a ‘wedge’ into the forming clearances of the cover plate diaphragm spring at its pivot point, thus allowing clearances to be ‘auto adjusted’ within the installed cover plate.  More information about the SAC from LUK if you wish to view here.

The adjustment ring’s spring position can be seen to be fully extended on this worn clutch cover plate below, the photograph below that shows the adjustment ring in ‘set’ position, this is how the clutch needs to look before fitment. Always check this before installing the cover plate, even if just out of the box!  There are many expensive tools used for correctly setting the adjustment of the pressure plate once installed on the vehicle, whilst these are great to own, unless you fit clutches every day it is hard to justify their purchase, this post outlines how it is possible to carry out this work without the special setting tools.

SAC cover plate showing adjustment ring spring positions for a worn clutch

Mercedes clutch SAC adjustment ring spring set position

If you are using a used clutch, or simply refitting your original plate, it is important to check or reset the adjustment ring to the ‘set’ position shown in the photograph directly above. This can be achieved in a press used between the stamped steel cover plate edges and the diaphragm springs.  If you do not have access to a means of compressing the diaphragm springs so that the adjustment ring can be counter rotated and reset, you may wish to read on, but use great care – as there is a fantastic amount of pressure behind those diaphragm spring fingers and a truly huge amount of force is needed to compress them!  The following is an emergency measure, only to be used to get you out of trouble and is definitely not by any means a recommendation.

On a solid driveway, place a hydraulic trolley jack under the rear axle of the vehicle and raise it enough to fit the cover plate, supported on three stout short wooden blocks of the same size, resting on the flange/outer lips of the stamped steel plate only, NOT the pressure plate (form the wooden blocks into a triangular formation).  Using a very large socket that will generously cover the hole in the centre of the diaphragm springs, align this with the axle beam or lower shock absorber mount – use solid wood packing as needed.  When in position bring down the jack ‘very slowly’ to allow the axle weight of the vehicle in controlled contact with the socket via the wooden packing, depressing fully the diaphragm spring, almost to the cover limit stop. (shown in cut away diagram above)  Now carefully rotate the adjustment ring anticlockwise with a stout screwdriver until it rests fully against its stop and the three small springs are fully compressed.  Once achieved, jack the vehicle once more and remove the cover plate that is now set for installation.  Throughout this procedure please consider your own safety at each step of the way!

2005 Sprinter T1N Gearbox Removal

Now you can begin to remove the gearbox and fit your clutch.

Working from ramps with additional additional 4-6 inch raising blocks if you have them, is the best way to achieve enough space to work comfortably around the gearbox, leaving yourself enough room to manoeuvre freely and eventually remove the gearbox from beneath the vehicle.  I always jack the vehicle onto ramps, this allows you to place one ramp forward and the other facing rearward, thus locking the vehicle from rolling either way to supplement the handbrake and rear wheel chocks.

Disconnect the battery before starting any work, as you will no doubt disturb the starter motor during the job. Also on later Sprinters,  W639 Vito and VW Crafter models remove the complete air box from under the bonnet, this prevents any strain on the plastic components, as the engine naturally tilts backwards when the gearbox support is removed.

Sprinter hoses and gear cables held out of the way

Use a trolley jack to support the plate that supports the back of the gearbox near the output flange.  Undo all the bolts that hold the support plate to the chassis rails on either side, allow the jack to be lowered and removed. This will drop  the rear edge of the gearbox down a little so that the rear gearbox mounting pin can be removed and the support plate taken out from beneath the vehicle.

Using a 16mm socket remove the four propshaft flange bolts from the gearbox output shaft.  You will now have to remove the drop protection ‘horse-shoe’ brackets and the two centre bearing bolts to allow you to drop the prop sufficiently to allow you enough flex for it to be moved out of the working area to one side of the vehicle.

Sprinter with DMF removed

Now remove the gear selector cables, make sure you mark the shaft positions in the plastic ball-ends (amount of insertion) before you release them and tie them to one side. Put a latex glove under the cap of the brake/clutch shared master cylinder, before clamping off the flexible clutch hose from the chassis to gearbox. With a small screwdriver or pick, detach the hydraulic connection retainer clip from the gearbox hose coupling, keeping this in a safe place.  Pull out the hose and again tie it out of the way of the working area.  Remove any electrical connector or plug and tuck them out of harms way.

Now using at least a 24 inch extension bar and reverse torx socket remove all the ring bolts from the bell housing. There is no need to fully remove the starter motor, just let it rest in position.  It will be held in place by its thick cable. On T1N models up to 06, you will have to remove the exhaust support (2 x 12mm nuts) as this sits sandwiched directly behind the gearbox and will prevent removal unless fully removed.

Sprinter DMF Flywheel removed

When you get to the last bell housing bolt, support the gearbox centre on the hydraulic jack, remove the final bolt. From the back of the gearbox pull, the casting should now separate from the engine block.  Manoeuvre the gearbox back and lower the jack. Take the gearbox from under the vehicle.  This is a great time to check for leaks or damage/wear to the selector mechanism. Checking the gearbox oil level is easier at this point too!

From inside the bell housing you can check the rotary smoothness of the thrust bearing, this is part of the release slave cylinder mechanism and cannot be replaced on its own. If you can afford it, always replace the slave cylinder when replacing the clutch, often if you purchase a complete kit it comes as a component part.

DMF Mercedes Sprinter Centre Bearing

Always inspect the centre bearing in the DMF, if this is damaged it is not available as separate part from Mercedes only as part of the complete DMF flywheel! The bearing itself is a special construction of a blind roller bearing made by INA that acts directly on the input shaft end of the gearbox, this is concentrically inserted into yet another single row ball bearing race pressed into the DMF.

Remove the clutch cover/pressure plate from the DMF, locking the flywheel with a small crow bar or broad screwdriver on the ring gear. You may have to pry the cover off its locating dowels, be aware it is heavy and it could catch you by surprise and fall on you!  Once this is out, you can inspect the flywheel face for damage. The outer DMF section of the flywheel should only rotate independently about 10-15mm in each direction at its circumference in relation to the other fixed half, any more than this indicates the likelihood of a worn DMF.  If you decide to replace this, you will need a long, large torx bit to undo the eight flywheel mounting bolts from the crankshaft. Once removed pry the flywheel from the crankshaft, it sits on a single dowel peg and can take some working to and fro to remove it.   Always inspect the centre bearing in the DMF, if this is damaged it is sadly not available as separate part from Mercedes, only as part of the complete DMF flywheel!  The bearing itself is a special construction of a blind roller bearing made by INA, that acts directly on the input shaft end of the gearbox, this is concentrically inserted into yet another single row ball bearing race which is directly pressed into the DMF.

Replacement of all the parts is exactly as the removal, although be sure to reference the ‘set’ position of the clutch before refitting.

Sprinter gearbox inspection hole and bleed nipple >2006

Bleeding the clutch system can only be achieved with a Gunsons EzBleed or other pressure bleeding equipment, no amount of pedal pressing, as you would assume similar to brake systems will not work – trust me, you will be very lucky to achieve success otherwise.  Once you have a good pedal feel and the slave cylinder can be seen to be pressing the diaphragm springs back and forth fully through the inspection hole, start the engine. Now press the clutch pedal several times, you should often hear a light clunk, this is the clutch adjustment ring finding its own position.  Select a gear and test the clutch, all should be well.  If for some reason it appears as if the clutch is not fully disengaging and baulking you from selecting a gear, check your work regarding air in the hydraulic system, if re-bleeding it proves to be good, then try starting the engine in gear, handbrake on, with the clutch down, this will often by inertia, force the adjustment ring from its set position to its new working position, a second pedal press should now settle it into its new operating position and you should have a good responsive light clutch.

VW Crafter Gearbox showing concentric slave cylinder and thrust bearing

I hope you have found this information useful.

Mercedes Sprinter – Engine Oil in Coolant Water – Oil Cooler Leak – Fix


As many of you probably know oil seen in the header tank is often the sign of imminent head gasket failure. But before condemning any Mercedes CDI diesel engine to head gasket failure, especially if the vehicle is otherwise running well and not throwing out white smoke from the exhaust or maybe you would have expected to find some water in the oil, there is one place to check first.  The engine oil cooler.

Mercedes Sprinter Oil Cooler Leak Problem 1

The engine oil cooler on Sprinter and other Mercedes CDI engines through the range of commercials and passenger cars is a pancake aluminium pressed fin block, that sits directly behind the oil filter housing on the right side of the engine looking in.  This heat exchanger has two sets of internal galleries, one for engine coolant and the other for engine oil.  This provides conductive cooling of the engine oil shifting its heat to the circulating cooling water system.  What happens is that the internal galleries corrode, usually due to lack of inhibitants in the antifreeze or the mix ratio simply being ‘to weak’ to prevent corrosion. Over time the internal galleries can perforate from one to the other and the resulting high pressure oil in the primary high pressure circuit moving through the oil filter, is forced into the water system and onward to the header tank if it finds an easier path through a pin hole or crack.

Mercedes Sprinter Oil Cooler Leak Problem 2

Depending on the severity of the leak, this can be anything from small trace amounts of oil appearing in the water or as in our case, huge oil migration.  So bad in fact that the driver first discovered that his oil light came on, later when he topped up the oil with over 4 litres it lasted for only 40 minutes of normal driving before the oil light illuminated once more!  When the vehicle came back to the yard we checked the water reserve and it was full to the brim with black ‘tar like’ oil emulsion, so bad that it was clogging the cooling system.

Mercedes Sprinter Oil Cooler Leak Problem 3

On removing the bottom hose from the radiator we drained the system of about 2 litres of oil, we removed about another 3 litres of tar from the expansion tank.  The van ran perfectly in every way except for the massive oil loss into the water system.  Rightly we suspected the culprit to be the oil cooler, as in our opinion, no head gasket failure would act in dumping these quantities of oil in this uncontrolled way.

To remove and replace the oil cooler first drain the coolant system (if you hadn’t already!) Then remove the top induction hose from the intercooler to the inlet manifold for access.  Undo the hose clip and remove the flexible water hose from the oil cooler and tuck it out of the way.  There are five reverse torx oil cooler bolts that are slightly awkward to access that hold the thicker pancake cooler’s back plate to the alloy oil filter casting. Once removed, the cooler can be pulled free, up and out of the engine bay.

Mercedes Sprinter Oil Cooler Leak Problem 4

Often even if you block off and blow air into the water gallery (the cleanest port for your mouth!) of the suspect oil cooler, it is impossible to detect a leak of even the size we had, between oil and water ways. So if you suspect it – change it.  You will always need a new orange sealing gasket to face between the replacement oil cooler and oil filer housing.  It costs around £4.00 and an old gasket should never be fitted, as it rarely seals due to its complexity.  You will most probably need the use of a ‘shaving mirror’ to clean the recess and place the new gasket in its correct positional groove on the rear of the oil filter housing – even a spot of gasket sealer here and there, just to hold it vertically in place while you rebuild, may be required.

Mercedes Sprinter Oil Cooler Leak Problem 5

Lower the new plate cooler into position and carefully push it flat against the gasket on the filter housing, keeping pressure, ‘slide’ the plate to align the fixing holes and refit all the reverse torx holding pins.  Check with a torch that the gasket has not moved during the procedure by looking into the small air gap between the two mating parts, when you are sure all is well, tighten up the bolts.

Mercedes CDI Oil Cooler Gasket

Mercedes Part Number – A6111840280

Refit the flexible coolant hose, put back the induction hose and refill the system with coolant.  Depending on how well you managed to flush the system of old oil, it will find its way into the coolant reserve for a number of weeks.  With a warm engine, squeeze the top hose rhythmically while scraping emerging oil residue from the top of the filler cap.  Keep topping up with water as you go, when you have removed as much of this black sludge as possible, refit the radiator cap and monitor the oil level over the next few days, de-oiling it again when you can.  Eventually it will clear, but it takes time and is dirty work.

Monitor the engine oil level over the next few days to make sure all is well.

Sprinter Fuel Rail Pressure Regulator Problems – Poor Starting


The Mercedes CDI series of diesel engines have an electronically controlled fuel pressure regulator mounted on the end of the fuel distribution rail. This controls, as the name suggests, the fuel rail pressure. It relies on the seal made between a single small O-ring which is backed by a split fibre backing ring.  What happens over time is that the O-ring wears and often fails allowing pressurised fuel to bypass the valve and ebb away the required running pressure that the injectors need.  Often the problem becomes more noticeable once the engine is warm and poor starting results.

Usual symptoms for this can be laboured starting when warm and occasional non starting, if the fuel rail cannot maintain the required minimum of approximately 300 bar at crank to allow the injectors to fire.  If it is possible to monitor rail pressure using Live-Data, you may see the rail pressure dancing between 266 and 550 bar. Instability of pressure when holding a steady throttle will be the clue as to a problem with the fuel pressure control.  If you do not have access to a compatible code reader thankfully the repair is simple and not costly so easy and cheap to eliminate as a cause of poor warm/hot starting. (Under £10)

Sprinter fuel pressure regulator fault 1

Remove the upper section of the inlet manifold to allow access to the rear of the fuel rail, just under and against the bulkhead/firewall.  Identify the electrical connector and remove it, select a 1/4 drive socket wrench and appropriate small reverse torx socket and short extension.  Remove the two opposing pins on the regulator flange (left and right as fitted).  Pull out the fuel pressure regulator from the end of the fuel rail.

Sprinter fuel pressure regulator fault 2

Keeping the device clean, remove both the green O-ring and fibre backing ring from the tip of the regulator and replace with new components.  Refit the regulator assembly to the rail.  It makes it easier if you have the left hand threaded pin in place in the regulator flange mounting hole, before offering it into place. (left hand in fitting position, if standing at front of engine)  Once the two pins are re-fitted the electrical connector can be attached and the intake manifold upper half rebuilt.

Sprinter fuel pressure regulator fault 3

Back of the fuel rail where the regulator mounts (normally hidden from view)

It is important to note that a failing fuel injector can also deprive the fuel rail of its operating pressure. If you suspect that this is the case, perhaps after changing the regulator O-ring to find there is no difference to the fault then you must carry out or entrust a garage to do a diagnostic ‘leak-off test’ to prove the injector system is sound.  WARNING a failing fuel injector that is passing unmetered  amounts of fuel can soon damage the engine catastrophically, either through piston overheat or engine seizure and any suspected problems must be investigated promptly!  See this interesting and descriptive forum post regarding leak-off testing.

Sprinter fuel pressure regulator fault 4

Fuel rail pressure regulator seal kit part number