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.

31 thoughts on “Mercedes Sprinter – Engine Oil in Coolant Water – Oil Cooler Leak – Fix

  1. Just a perfect description is there any chance that it could be caused by loose fitting heat exchanger to the filter housing. I could also see a track where oil passed in to the water compartment.
    The reason is that we still are getting traces of oil in the water after only replacing the gasket at this stage not sure weather or not we should replace the heat exchanger.
    Brian

    1. Hi Brian,
      When this happens and water gets into the oil it can take a long time to really clear, many weeks and in some case a couple of thousand miles! I would not be to hasty to think you still had a problem. However while possible it is very unlikely that the oil could leak into the water via the gasket, even I think if the cooler was loose. I suspect the oil would just prefer to leak easily away out from the seam between the two parts as it would to penetrate a further seal against water pressure. I have pictured the rear of the oil cooler with a gasket overlay showing the ‘gaps’ between ports and seal positions. Only the larger thicker portions of the gasket form part of the seal, the other parts are just there to hold things in position for manufacture and assembly and do not seal against anything. See what you think – maybe the cooler body is still faulty.
      Sprinter oil cooler and gasket
      All the best
      Steve

    1. Hi Simon,
      If its a 4 cylinder Sprinter up to 2006 then if you identify the oil filter it lies directly behind it. See third photograph down on the post.
      All the best
      Steve

  2. My Sprinter 2002 got diagnost gasket fail. But After reading your comment, I don’t know.
    Sprinter 2002 issues:
    1-Oil light flashing
    2- losing coolant thru pipe under the cap
    3- pressure on radiator even if the truck is parked for few days
    4- bubbling on radiator, and smell fuel
    5- oil very clean no water
    6-Temperature on dashboard don’t go over 80
    What do you think
    Engine noise is perfect

    1. Hi Cristiano,
      If you have no signs of thick tar type emulsified oil in the water header tank I doubt on this occasion it is the oil cooler that has failed. It is likely there is a slight head gasket failure or even a light crack in the head. It would be worth engaging a trusted independent repair shop to do some checks for you on the system to be sure.
      Hope that helps.
      Best regards
      Steve

  3. Replaced oil cooler went fine for about 2000 miles then started getting excessive oil in water tank again could it be the cooler again or something else

    1. Hi Graham,
      For large amounts of oil in the water with no water in the oil at all is generally the oil cooler breached. Did you fit a new one? If not then there is a chance the used one has developed the same fault. Before you start to think its anything else its worth closer inspection. I found that by adding Jizer to the coolant and running the engine it helped emulsify the oil and enable it to be flushed out with a hose pipe – My goodness that is a messy job as you well know!
      All the best
      Steve

  4. 2002 sprinter 311 CDI
    Hi just changed my head gasket and head after a failed injector bolt caused the head to crack/leak, The van is now running ok, but it as milky oil on the filler cap. no oil in the water head tank! Is this just the water that as got into the oil when the the head was removed??

    1. Hi Russ,
      Chances are if you didn’t change the oil after the head gasket replacement you are correct in that some coolant would have leaked into the oil during head removal. It should start to reduce the more the vehicle is used however an oil change would be the recommended course of action.
      Hope this helps,
      All the best
      Steve

  5. I own a C200 CDI year 2002 with oil cooler just replaced for a new one due to a tar type emulsified oil in the wáter header tank. However, after draining wáter from the radiator , changing new oil to the engine, and mounting a new oil cooler, I found the header tank is again with tar type oil mixed with wáter. I wonder if this is normal after the aforementioned procedure or there is any other course of action to be taken to enable the oil cooler to work properly. I appreciate your comments in advance. Best regards, Beridiano

    1. Hi Beridiano,
      The tar stays for months! You can speed things along by removing the radiator and inverting it, back-flushing with water to remove what has settled in the base of the radiator. Oil cooler failure makes a real mess and to be honest it will take six months or more for it to start to clear. Keep an eye on the rubber seal on the coolant reserve as this is affected by the oil and will grow/soften to the point of it not sealing correctly. Once the vast majority of the oil has gone fit a new radiator cap.
      Hope that helps
      Steve

  6. Hi. I have a 05 vito. Header tank is full of oil. But starts and runs spot on. But there is a bit of back pressure. Do you think it could be the oil cooler ?. Or head gasket cheer

    1. Hi Matthew,
      More likely oil cooler than head gasket, often head gasket failures push water into oil (seen on dipstick) and not the other way around. My advice would be to replace the oil cooler and gasket first – five bolts and a fiddle to refit is better than a head gasket job! Do be advised its a messy job to clear the oil sludge from the system and to do do this properly the rad will have to be removed and backlashed with a solvent (Jizer) as the oil emulsion sinks to the lowest part and lurks in there blocking the side tanks and passage of water across the radiator matrix. Be prepared- its a mess!

      All the best
      Steve

  7. Hi Steve,

    I have a 2003 Sprinter and the fellow I bought it from stripped the #1 glow plug threads and just used a bolt to plug the hole and left the glow plug connected to the harness via a zip-tie. I was not smart enough to unplug it until I made time to re-tap/insert to fix threads and forgot about the exposed glow plug. About 5 months later, I believe the glow plug relay failed in the ON position (glow plug light stayed on during entire trips) and the glow plug got hot and fell on the harness catching it and the fuel line between filter and pump on fire. Van shut down and I put it out using a bottle of water.

    I replaced the harness, plugs, fuel lines, relay and oil cooler hose with new.

    I then proceeded to add back the coolant I drained and 3 extra gallons went in. Apparently it ended up in the oil pan. Some experts are telling me it might be the head gasket, cracked head or block, but after reading your article I am leaning on a burnt up oil cooler seal or a warped oil cooler or possibly unsolder-ed internal oil cooler plates.

    What are your thoughts? I really appreciate your help.

    Thanks much
    Dan

    1. Hi Dan,
      I would have expected if the oil cooler were at fault there be oil in the water and not the other way round. Unless of course you didn’t run the engine at all , then we are looking for something more significant. Take of the oil cooler and have it pressure tested this will at least prove this component. It could be that the bolt in the glow plug hole has crashed the aluminium casting and somehow violated the water jacket to oil ways. Weird how this happened after the rebuild and not before but worth a look.

      Let me know what you find, its a puzzler!

      All the best
      Steve

      1. Hi Steve, and thanks for your reply.

        The engine was not started, since the small fire and parts replacement. So that is a good thing because water in oil can quickly kill the main bearings and seize the engine.

        No, the bolt covering the glow plug hole did not cause any damage, it was there for tens of thousands of miles. I reamed the hole and put an insert following strict procedures using a special kit. Everything was a breeze.

        The damage is strictly from the harness and fuel line fire. Everything worked flawlessly up to that point.

        I did talk to a diesel expert today and he said that almost always, when you have coolant going into the oil, it is a failed oil cooler.

        I am suspecting since the fire was next to the cooler, it overheated it and failed the rubber gasket or cooler plates. No head gasket or hairline crack would dump such large quantities of fluid so fast especially with a cold engine.

        I will have the Van towed back home from dealer because they suggested a warped head, failed head gasket, or head/block crack. But I would rather take my changes with the cooler first.

        What are your thoughts? Why do you suggest that coolers don’t fail with coolant in oil but the other way around? Due to pressure differential? My problem is on a cold engine. I wish I had X-ray eyes!

        Thanks for your time.
        Dan

      2. Hi Dan
        The normal passage of ‘oil – into – water’ would be in the case of an oil cooler failure where the engine was run up. The higher pressure oil would migrate into the water system because it would simply overpower the coolant pressure by the order of several times if the engine was run. You now confirm the engine as not run, so a major breach of the coolant system into the oil is certain – just from where!

        The oil cooler is made from stamped aluminium sections pressed into a finned pancake. It is possible that it is damaged and the coolant as it is filled passes directly through the filter housing back to the sump. It may even flow back down the return into the sump. Four screws will take off the oil cooler and once off you will be able to test it. For a quick test, take off the screw on oil-filter cap, remove the oil filter element and look if there is water in the filter bowl. Top up the radiator bottle with water and wait to see if any water is running from the cooler into the filter bowl. Obviously water could be moving through the lower oil way to the sump but its worth at least a look to make you feel better!

        The orange gasket is not expensive for the oil cooler, its easier if you stick it to the cleaned cast surface behind the filter housing and position it in the locating tracks with some Victor Reinz gasket sealer (v sticky) Then offer up the cooler as flat as possible and once in contact with the gasket apply pressure to keep the gasket in position as you slide the cooler to align the screw holes. Once in position and two opposed screws have it held check with a torch and inspection mirror that the gasket is still perfectly in place before adding the other fixings and tightening them evenly. I wondered if this why the gasket was orange to facilitate checking as you will find its very dark down there!

        Hope that helps,
        All the best
        Steve

  8. I have a 2004 sprinter (ex ambo) fitted out as a RV. had a milky type leak. Took to RACV service centre. Told me it was oil cooler leak. No blk tar type leaking. The temp gauge didn’t go up. I had to drive the van about 40 mins. To RACV. After the leak at my house.the oil lamp did come during the trip. But i carry oil. I topped it up and the light went off. Didn’t come on again. Thanks. Sue

    1. Hi Sue,
      If the oil level is falling dramatically and not leaking out anywhere – then it must be going somewhere, and quickly! I would drain down the coolant and have a look for the lost oil, making sure its not solidifying and collecting as a grey heavy gooey emulsion in the bottom of the radiator.
      All the best
      Steve

  9. en how did it breach the turbo seal from the hot/cold side? Did it enter through the turbo oil discharge port? Still it has to breach the seal! What a mess, I now have to clean the after-cooler and turbo!

    Well back to the oil-cooler (coolant motor oil mix) issue. I took off the filter/cap and radiator cap and blew air and immediately the oil started rising and bubbling. I was ecstatic thinking it was just a failed oil-cooler. But after I removed the oil-cooler and blew through the radiator cap, same thing, which tells me there is a breach elsewhere other than the oil cooler. Nevertheless I bought a new cooler and gasket.

    So tomorrow I will remove the injectors and perform a leak-down test on each cylinder and listen to see where the breach is. This should give me some insight if the gasket is breached, cracked piston, or fissure in the head. It seems to be something big as I blew very softly and it immediately transferred to the oil.

    A few questions:

    1. How did oil/diesel mixture flood the turbo and after/cooler?

    2. Could the glow plugs being on during the two trips of 1 hour total driving time, cause such a catastrophic breach, or do you suspect the dealer did something fuzzy such as hydraulocking or possibly cracking my engine? It ran perfectly before I decided to change the wiring harness and do the intake manifold recall at dealer.

    3. How do I make sure the valves are closed on each cylinder before I insert air?

    4. After siting in coolant for so long, do you recommend me rotating the engine to find TDC on each cylinder?

    5. What kind of damage do you think occurred to the engine with so much antifreeze in there?

    6. Should I pull this engine out? Or is there something I can hang my hat on that I might have missed?

    Thanks for all your help.
    Dan

  10. Hi Steve,

    I received my Sprinter from the dealer yesterday and promised to give you an update.

    To my surprise, although they told me they did an oil flush, water and oil were all over the tow-truck which gushed out through the dip-stick, and I pulled out over 5 gallons of coolant from the oil pan. Coolant sat in the engine for over 2 weeks – imagine that, all main and rod bearings were immersed in corrosive coolant! Although they claimed the engine was not cranked, I saw portions of fuel in the brand new transparent fuel lines indicating the engine was indeed cranked. I don’t have the electric pump in the tank. I immediately sent the manager and email evidencing the details – very irresponsible for a certified dealership.

    After draining the coolant, I filled up the engine to the brim with diesel to help flush and absorb all the moisture and left it overnight. This morning I noticed that the turbo was full of oil and diesel which filled the after-cooler half-way and spilled into the air box. Any explanation how this happened? Did the fluid enter the piston chambers and out the exhaust port? Then how did it breach the turbo seal from the hot/cold side? Did it enter through the turbo oil discharge port? Still it has to breach the seal! What a mess, I now have to clean the after-cooler and turbo!

    Well back to the oil-cooler (coolant motor oil mix) issue. I took off the filter/cap and radiator cap and blew air and immediately the oil started rising and bubbling. I was ecstatic thinking it was just a failed oil-cooler. But after I removed the oil-cooler and blew through the radiator cap, same thing, which tells me there is a breach elsewhere other than the oil cooler. Nevertheless I bought a new cooler and gasket.

    So tomorrow I will remove the injectors and perform a leak-down test on each cylinder and listen to see where the breach is. This should give me some insight if the gasket is breached, cracked piston, or fissure in the head. It seems to be something big as I blew very softly and it immediately transferred to the oil.

    A few questions:

    1. How did oil/diesel mixture flood the turbo and after/cooler?

    2. Could the glow plugs being on during the two trips of 1 hour total driving time, cause such a catastrophic breach, or do you suspect the dealer did something fuzzy such as hydraulocking or possibly cracking my engine? It ran perfectly before I decided to change the wiring harness and do intake manifold recall at dealer.

    3. How do I make sure the valves are closed on each cylinder before I insert air?

    4. After siting in coolant for so long, do you recommend me rotating the engine to find TDC on each cylinder?

    5. What kind of damage do you think occurred to the engine with so much antifreeze in there?

    6. Should I pull this engine out? Or is there something I can hang my hat on that I might have missed?

    Thanks for all your help.
    Dan

    1. Steve,

      It ended up being a colapsed cylinder wall on #3. Probably due to thermal stress. Almost an entire 2″ section came out from top to bottom of the cylinder wall.

      Dan

  11. Hi Steve,

    My daughter has a 2006 E350 Mercedes Benz that never showed signs of overheating but one day on her way back to LSU she heard a loud pop and the car started steaming. She pulled right over and there was a creamy yellowish fluid dripping from the coolant reservoir. Upon exploration we noticed that the big radiator hose had completed disconnected from the radiator and the coolant reservoir was full of this loose creamy yellowish fluid. There is no water in the oil, just oil in the coolant. The auto mechanic changed the radiator and the oil cooler gasket and flushed the coolant system but says there is still a lot of oil entering the coolant reservoir. Should the oil cooler itself be changed or could it be a blown head gasket?

    1. Hi Pamela
      I would change the oil cooler to be sure, some places do pressure testing, maybe a place that re-cores radiators could help with this pressure testing.
      All the best
      Steve

  12. Hello Steve,
    I have a 2006 Sprinter 2500 and recently replaced my radiator, hoses, etc… due to a slow leak. I must note that this small leak went on for months while I just topped the radiator off when needed. The engine ran fine with no issues. Since I use the van for work daily I had to wait for my slow season. When I removed the radiator I noticed the substance described in these posts so I’m afraid that its the oil cooler. My question is: other research showed that it is a massive job where the turbo and other parts have to be removed to get to the oil cooler. Is this true for the 2006? Thank you

    Javier

  13. Worth mentioning that when tightening back the new oil cooler, the bolts don’t need to be super tight because your screwing into aluminum. I recently did this and easily stripped 2 bolt holes like an idiot. I wish I had known I was screwing into aluminum

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