OM651 Oil Cooler Leaks

[Nedski]

Hi all, I'm new to this forum so just a quick hello before getting on with my first post

Was searching for info on leaks from the oil cooler housing as got a very small leak developing in what look likes the location directly behind the plastic oil filter housing where two transfer oil guides locate with the engine casing, so was initially thinking of ordering a couple of packings (A0199970445 & A0199970545) to replace the ones on this plastic housing, but then came across this video on youtube which details an oil leak from the oil cooler housing check valve seal, which sits directly above the transfer oil guides, so my leak could be coming from there not the transfer oil guides.....

Mercedes OM651: Engine oil cooler check valve gasket replacement

Further reading lead me to this post from last year, which also details an oil leak from the oil cooler check valve (thermostat housing?).........

OM651 oil leaks - oil cooler | Engine

After a quick search of MB parts lists, it does not look like the check valve seal is a procurable item on its own as it is not shown as a broken out part. Before I start pulling bits off the engine, I'd like to get all the parts in hand, so my question is, does anyone know if this seal can be procured separately and if so, what the part number is? Or alternatively the dimensions (ID, OD & Cross Section) of the seal so one can bought?

 

[Nedski]

The seal in the check valve is confirmed as a none procurable item by MB, so need to find out seal ID, OD and CS dims, then find a viton seal that'll fit otherwise it's a complete new oil cooler, which is bonkers!

If anyone has an old oil cooler assembly sitting in their workshop, would be grateful if you could measure the check valve seal dims.........

 

[gurpz]

It is very annoying that this particular O ring is not available seperatly but all the other ones are. Buy yourself a quality oil filter for a M112/M113 engined car. I found that one of the O rings included is a perfect exact snug fit for this and cured this exact oil leak.

 

[Nedski]

Many thanks, will try that......

 

[Nedski]

Just to close this out. The oil leak was from the oil cooler check valve. The seal was a flat as a pancake!

To get access to the check valve wasn't that bad.

Remove air intake duct to air filter housing and then remove serpentine belt.

Simply loosen coolant thermostat housing mounting bolts and then remove hose from thermostat housing to radiator. Put rubber glove over end of hose and use elastic band to hold in place. Tuck hose out the way.

Then remove short right hand side L shaped coolant hose from pump outlet to underside thermostat housing.

Once the hose is removed, you have good access to two torx flange screws. Loosen them and check valve pops out (along with lots of oil, so be prepared for that).

Problem is the check valve then contacts the water pump outlet pipe, so you'll need to remove water pump housing. I did this without needing to completely dismantle water pump. Just had to manipulate it enough so that check valve could be slid out. You'll need knew water pump to head seal.

I didn't need to fully remove thermostat housing.

Viton O ring size I used to replace existing was 21mm ID with 3mm C/S and 70 shore hardness. 3.5mm C/S was too big for sure as check valve wouldn't reseat with that size without risk of pinching.

I torqued the x2 torx screws up to ~10Nm and also used some high temp loctite for added security as couldn't find MB published torque anywhere.

Three weeks in and lots of miles driven and no leaks.

 

[indigoskywalker]

ELRING 867.720​

 

[Nedski]

^unfortunately that Elring Kit does not include the O ring seal for the oil cooler check valve. You will have to source your own O ring, hence why I spelt out the O ring dimensions in an earlier post.

Just to update that 10k miles on and the check valve is not leaking at all, so the size I posted above does the job.

 

[BlackC55]

We replace the whole cooler as we have had the coolers leaking internally between the coolant and the engine oil. The cooler is an inexpensive part.

 

[Nedski]

^agreed they're not an expensive part, but if there is no evidence of water/oil contamination in system, then seems a bit OTT to simply replace the whole oil cooler assembly for a leak from either the check valve or oil filter housing transfer tube O rings!

Also, getting access to replace that oil cooler is a mare as it requires lots of labour time to remove the EGR cooler, intake etc, so costs soon rack up. Changing that check valve packing was only a mornings work even though I'd never done it before.

 

[OneForTheRoad]

^agreed they're not an expensive part, but if there is no evidence of water/oil contamination in system, then seems a bit OTT to simply replace the whole oil cooler assembly for a leak from either the check valve or oil filter housing transfer tube O rings!

Also, getting access to replace that oil cooler is a mare as it requires lots of labour time to remove the EGR cooler, intake etc, so costs soon rack up. Changing that check valve packing was only a mornings work even though I'd never done it before.

That's an option available to a diyer , a reputable garage or main dealer , won't fix things , they replace complete units ,because they don't want to do it twice .

 

[BlackC55]

That's an option available to a diyer , a reputable garage or main dealer , won't fix things , they replace complete units ,because they don't want to do it twice .

And if we know there is a potential issue with the part long term.