Oil cooler - How to test?

[DelphiDude]

Hi,

I have a Mercedes S-class S320 and recently I have come across a problem which I have not dealt with before. I'm not a mechanic but like to do almost all jobs on the car myself.

What I'm requesting help for is that few days ago I saw oil in the water coolant tank. The car had a puddle of oil under the engine and the oil was coming out from the overflow pipe on the coolant reservoir. I knew this was serious because normally this means head gasket problem or a cracked head cylinder and I knew this was a job that I couldn't do myself.

I started calling around for quotes on the head gasket replacement and almost all garages are asking for more than £1000. While speaking to these garages I was recommended by one that it might be the Oil cooler next to the oil filter housing.

This has given me some hope as I think this might be the case because I have not seen coolant in the engine but oil in the coolant reservoir and radiator.

I would like to ask you, what is the likely hood that it is the Oil cooler and not head gasket and how to test if oil cooler is really faulty.

Your help is much appreciated and I would like to thank you in advance.

Regards
Waqas

 

[peterwhayward]

Hello and welcome Waqas.

 

[kth286]

which S class do you have ? as we then know which engine you have.

 

[grahamcol]

To the op. If you need professional help, I know a Merc specialist who is very good and who may be cheaper than those you've tried so far. Post back if you need to.

 

[grober]

this of any help http://www.neoriginal.ru/cat/mb/part__1_1_19Y_112_944_/18_060_220_065_944

 

[DelphiDude]

To Peter: Thank you for your welcome note. I appreciate the warm welcome I have received.

To David: Thank you David for your comment, the car is S-class W220

To Grahamcol: Thank you for your comment, would your contact be able give quote in Shirley Solihull as I've declared SORN for a short time.

To Grober: Thank you for the diagram it will be very useful. I have replaced the oil filter housing seals previously and I know If I had this diagram, I would not have missed the smaller seal, for which I remember I had to re-open the housing and fit the seal. Also I have bookmarked this website as the content is excellent. A little difficult to navigate but for a free service it is a great website. Thank you.

 

[kth286]

so it's a V6 engine ? at least access is good, compared to my straight 6 (104 320) engine.

Normally the oil cooler would only leak if the coolant change regime were ignored and corrosion started within the structure.

Why have you been into the seal replacement previously ?

May this be the cause of the problem - as you have admitted you are not a technician?

What miles on engine ?

Sure it is not auto gearbox fluid in the coolant ?

 

[DelphiDude]

Hi David,

Thank you very much for your help.

Normally the oil cooler would only leak if the coolant change regime were ignored and corrosion started within the structure.

I’m very careful with keeping all of the required fluids at the right level in the car and can confirm that coolant has never been low on the car. Also during the current problem I never let the engine overheat and stopped the car as soon as I knew something was wrong.

Why have you been into the seal replacement previously ?
Many months ago I had a strange oil leak in the car, which was always ruining the serpentine belt. It took me a while to find out where the leak was. It was directly below the oil filter housing and upon research I found out that it is usually the oil filter housing seal. I got the relevant seals from Mercedes and the problem was solved. I never saw a single drop on the belt again. I also changed the belt as well as the tension wheel for the belt on the car.

May this be the cause of the problem - as you have admitted you are not a technician?
I have given it a serious thought that maybe I did something wrong, but I can’t see how I could have. This is why I registered on the forum because I thought maybe I might have made a mistake on the oil cooler housing. The cooler has two holes, which I believe are for the input and output of oil, and I don’t think I could have done anything to damage them, especially when there was no oil leak after I had finished. I’m not a mechanic but I have strong engineering background in electronics, software programming and some mechanical disciplines. I do most of the brakes, discs and servicing on my car myself.

What miles on engine ?
I’ve done over 270,000 miles. I use my car a lot on the motor way, usually around 4k+ a month. I believe I’m having this problem because I’ve used the car so much. The engine runs very smooth and I have kept the car in good shape, which is why I have the intention to update the car and keep it for some more time.


Sure it is not auto gearbox fluid in the coolant ?
I have never worked on the gearbox fluid so I’m not sure, but can say that the engine did not have much oil left after the current issue and that most the oil is in the radiator and water cooling system. Also the cars computer tells me to top up engine oil. Not sure if this also relates to gearbox fluid.
The oil in the coolant looks very much like engine oil mixed with water.
Also I contacted Mercedes yesterday for prices and they told me that oil cooling system + seals are around £140 inc. VAT, which is much cheaper than a head gasket replacement.

What I really want to know is how can I test the oil cooler, is it just a case of a pressure test and also how often do they actually go. Considering my car has done 270k, is it not likely that it is the cooler, or would it be something else?

Once again thanks for your help, look forward to further comments.

Regards

Waqas

 

[grober]

You might find this an interesting article http://www.alueurope.eu/wp-content/...pplications-Power-train-7-Heat-exchangers.pdf
Since the cooler is probably aluminium alloy with braised steel connections corrosion is a distinct possibility or vibration induced stress cracks.

 

[grahamcol]

Waqas, I don't think my chap would do that side. He's based in Walsall. Good luck with it all though.

 

[DelphiDude]

Thank you Grahamcol.

Thank you Graeme for the diagram you have shared.
The article is certainly interesting. I guess it is often over looked how complex car parts are these days and what goes into the engineering of them.

Here is my progress so far;

Yesterday I started work on the car and have removed the following

Coolant housing (it's full of oil)
Serpentine belt (safe so far, no oil on it)
cooling fan (also clean and undamaged)
and all of the radiator pipes. (all pipes look good but full of oil)

I can see now there is a lot of oil in almost every coolant pipe including in the thermostatic valve. (as shown in the picture)

I plan to remove the radiator and oil cooler today. Could I please get some advise on the following today.

1. The oil you see in the attachment, does it look like engine oil mixed with water and not transmission oil as suggested by member kth286 and does it look likely to be faulty oil cooler?

2. The radiator is now loose and I have removed all of the pipes but the bottom part is catching on something. I have removed the bolts, which holds the air conditioning cooling radiator pipes and the top two bolts which connect the air conditioning radiator to the coolant radiator and top two bolts on the support arch. Do I have to do something from underneath the car or is it just matter of applying force and extracting it.

3. Do I understand this correctly that the radiator is going to come out from the top and not the bottom.

Thank you for all your help so far, I hope to share more progress with you and hopefully this would save someone time and money in the future.

Regards
Waqas

 

[grober]

That's a lot of oil! Normally CHG's start with just a traces of oil in the coolant. Likewise transmission fluid mixing with coolant is barely noticeable at first and if often only spotted when the autobox starts giving problems. The fact that you are loosing large quantities of engine oil point to it being engine oil rather than transmission oil. Whats your gearbox fluid level like? But this is armchair or computer desk remote diagnosis- difficult to tell when the problem is not in front of you.

 

[DelphiDude]

Thank you Graeme,

I too believe that it is engine oil because of the consistency and the amount. I have a large tray under the car and that too is full. The quantity looks correct for engine oil and water in the radiator combined.

I am going to open the oil cooler soon and I'm hoping as many have suggested on the internet that the oil cooler is faulty and that it might be interchanging oil with water.

You asked about the transmission oil level. Unfortunately I don't know how to check that. What I can say though is that before the warning light came up for low oil level in the engine there was no smoke and there was no performance issue on the car. When I opened the hood all I saw was the oil filled in the coolant reservoir.

If it was the head gasket, could it output so much oil in the cooling system so quickly?

I'm hoping it is the oil cooler as it is not expensive to replace.

Thanks again for your help, look forward to further comments.

 

[DelphiDude]

Hi Graeme,

Forgot to ask, what is CHG's?

Thanks.

 

[grober]

CHG= Cylinder head gasket. Seems to be too much oil so suddenly for a CHG Amount of oil would indicate large scale transfer of oil.

THE TRANSMISSION FLUID can be checked via a dipstick tube at the rear of the engine. In the old days you got a dipstick with the car now the tube is capped off. You can buy aftermarket transmission dipsticks for Mercedes online if you wish to check but I don't think that's where your problem lies

 

[star]

I hope that I'm not the bearer of bad news, we had an ML 320 in a couple of years ago that had the same problem but worse, tested both oil coolers (eventually by passed both), still the same symtoms. Removed heads and had them crack tested etc, no visable gasket faults. Refited, still the same problem.
So after some more head scratching, we came to the diagnoses that either a seal had failed on the front cover or an internal crack not found in head or block. It must be a high pressure oil feed to push oil into the water jacket otherwise water would be in the oil.

I hope you find an easier solution.

 

[kth286]

for my previous generation 320 engine, the oil cooler test in the Merc manual is:-

* block off one of the holes so it is airtight.

* pump air into other port/hole to approx pressure of 1.3 bar

* whilst holding cooler under warm water.

* if you see bubles appearing, then you have a leak and unit should be replaced.

 

[star]

for my previous generation 320 engine, the oil cooler test in the Merc manual is:-

* block off one of the holes so it is airtight.

* pump air into other port/hole to approx pressure of 1.3 bar

* whilst holding cooler under warm water.

* if you see bubles appearing, then you have a leak and unit should be replaced.

Yes that's the way we did it but also ran with them by passed.

 

[DelphiDude]

Hi,

Thank you very much for all the help you have given so far. I really appreciate the number of people who have come forward to offer advice. I won't name everyone but just want everyone to know that your help is very valuable and I appreciate it.

I have now taken the oil cooler out and I hope it is not as bad as in the case of what member "Star" has pointed out regarding Mercedes ML.

I am going to follow the advice from kth286 and going to find the relevant parts for pressure testing. I believe I have understood the instructions correctly.

kth286; do you know if there is a kit or connectors available for this task as the input and output for oil is simply a flat service with two holes, or do you think this test would also be sufficient if it was applied from the water pipes. I am referring to the flat service, which joins to the oil filter housing.

Regards
Waqas

 

[star]

It might be easier to take it to an old fashion rad repairer to test as they should have adapters etc.