1996 C280 W202 I6 Auto - Oil Leak at the Rear of the Engine

N15DWE

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Hello again,

Apologies to those who read my previous post (I tried to delete it)...

Bought myself a very tidy C280 with the I6 engine and failed to recognise the leak coming from the very back of the engine.

I've attached a picture to show where it's coming from. The substance is oil (not ATF) so I'm beginning to think it might be the RMS? Milege is 71,500 miles with only 2000 miles or so covered per year since 2012.

This is my first time owning a Merc of any sort, especially with an I6 engine, so any advice of what it might be would be really appreciated.

Thank you in advance and I apologise if there are already posts about the same issue on the forum.
 

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GP801

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Does it still have the under tray fitted under the engine? Common to get leaks from the upper seal or the crankshaft seal on the front of the engine and the oil then blows back along the under tray and appear at the rear. It then gets everywhere. If it really is coming from the rear then the gasket for the oil filter/cooler housing may have failed. Quite a big job to fix as lots of bits need to be removed to get access. Its the same engine as in our 124 and we have had all these jobs done over the years.
 
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N15DWE

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Thanks for replying. This picture was taken directly below the transmission stick, so at the back of the engine.

It seems to be coming from somewhere above this cross member material - maybe getting it up on a reamp will reveal the problem.

There is one piece of plastic tray at the front of the engine and this is clean. In fact the rest of the underside is clean, excpet this part of the car in the picture. Already I'm starting to feel sick at the notion of taking a car to bits to fix leaks.
 

GP801

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If the tray is clean that pretty much rules out the front seals. I think you are right in that it needs to go on a ramp and be properly cleaned off before running it to find the source of the leak. Generally these are very robust engines. Ours is on 190,000 miles with very few issues other than the oil leaks and new tappets. Good luck.
 
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N15DWE

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If the tray is clean that pretty much rules out the front seals. I think you are right in that it needs to go on a ramp and be properly cleaned off before running it to find the source of the leak. Generally these are very robust engines. Ours is on 190,000 miles with very few issues other than the oil leaks and new tappets. Good luck.
I need to get the brake-fluid changed anyway, as there is no history of this being done in the last few years. What leaks have you dealt with over the years that I might need to be mindful of?
 

Smiley

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It is most likely the head gasket that is leaking right at the back. Common problem on that engine.
 

Martyn_n

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Oh that doesn't sound good. Is it an expensive fix?
If you cannot do it yourself then it would be expensive. I am not too sure but your engine may also suffer from the degrading wiring loom which would need replacing / repairing before attempting the head gasket which will further increase the cost if it hasn't already been sorted.
I did my own head gasket and it was a very satisfying job but if I had to pay someone else I would consider parking over a drip tray!
 
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N15DWE

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If you cannot do it yourself then it would be expensive. I am not too sure but your engine may also suffer from the degrading wiring loom which would need replacing / repairing before attempting the head gasket which will further increase the cost if it hasn't already been sorted.
I did my own head gasket and it was a very satisfying job but if I had to pay someone else I would consider parking over a drip tray!
I would be happy to attempt any car repair work, so long as I wouldn't need more than basic tools and patience... For a head gasket, like other things I've done in the past on cars, I would just need a 'how to guide' and the list of parts.

Regards the wiring looms it does look in very good shape, considering it's 25 years old (or had already been replaced). Perhaps the wiring loom issue was more prevalent on earlier cars!

I only bought this a couple of weeks back and the previous owner kept it so clean I neglected to look that far back underneath for a leak (not realising an I6 engine is quite that long).
 

Martyn_n

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I wasn't sure whether your car would be affected by the loom issues, it looks like you are ok as if it was bad it's pretty obvious. The only special tools I recall having to buy was the splined socket for the head bolts. You also need to buy / fashion a puller for the pin that supports the cam chain guide.
 
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N15DWE

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I wasn't sure whether your car would be affected by the loom issues, it looks like you are ok as if it was bad it's pretty obvious. The only special tools I recall having to buy was the splined socket for the head bolts. You also need to buy / fashion a puller for the pin that supports the cam chain guide.
Thanks. Hopefully pretty straightforward then, if the head gasket the cause.

I think I'll get it on a ramp and have a specialist confirm what the leak is and take it from there.

I tried to looking online for a manual for a W202 but the only one I could find easily was a Haynes for C180 up to C250 engines. Do you know where I might be able to source a manual for a C280 inline 6 variant please?
 

Martyn_n

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I don't know of any manual, some people have bought DVDs off ebay that might help. I have attached a few pdf that should help.
 

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Dickster

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You might want to monitor the extent of the leak before a possible expensive fix. My rockers were leaking quite badly for the first two years ownership - now fixed - but only used a litre of oil every 3k plus miles. My leak was more annoying because oil dropped onto the headers and made a strong smell.
 

Martyn_n

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You might want to monitor the extent of the leak before a possible expensive fix. My rockers were leaking quite badly for the first two years ownership - now fixed - but only used a litre of oil every 3k plus miles. My leak was more annoying because oil dropped onto the headers and made a strong smell.
That was my approach too, though with hindsight I think the oil that was leaking onto the exhaust manifold was actually from the rocker cover gasket rather than the head gasket which is below the headers.

EDIT: Just noticed that you were actually talking about the rocker gasket rather than the head gasket, apologies!
 
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N15DWE

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I don't know of any manual, some people have bought DVDs off ebay that might help. I have attached a few pdf that should help.
Thanks Martyn, I'll print these out at work tomorrow.

So I've been out there to jack it up and wipe excess oil from the area in the picture, smells more like ATF than oil (couldnt tell by the colour of it on blue roll. There is a minor seepage of engine oil coming from the head gasket at the front corner (offside) of the engine. The smell of the oil is clearly stronger compared to the leak I'm worried about.

The last recorded service in 2018 (3000 mile ago) states gearbox service, I wonder if that disturbed anything?
 

Martyn_n

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Thanks Martyn, I'll print these out at work tomorrow.

So I've been out there to jack it up and wipe excess oil from the area in the picture, smells more like ATF than oil (couldnt tell by the colour of it on blue roll. There is a minor seepage of engine oil coming from the head gasket at the front corner (offside) of the engine. The smell of the oil is clearly stronger compared to the leak I'm worried about.

The last recorded service in 2018 (3000 mile ago) states gearbox service, I wonder if that disturbed anything?
An over or under torqued gearbox sump can leak after a service. The head gasket usually leaks at the offside rear, if it is at the front it may be where the u shaped gasket (item 24 on the second pdf) between the upper and lower chain covers meets the head / block (I hope that make sense)
 
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N15DWE

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An over or under torqued gearbox sump can leak after a service. The head gasket usually leaks at the offside rear, if it is at the front it may be where the u shaped gasket (item 24 on the second pdf) between the upper and lower chain covers meets the head / block (I hope that make sense)
Hi Martyn,

I think I understand so I've attached some pictures of what I could find. No visable oil leaking at the back of the engine, so I was wondering if you might have instructions for the gearbox along with these PDFs you've already sent. I suspect a service error may have caused an ATF leak.

Thank you again.
 

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Martyn_n

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Hi Martyn,

I think I understand so I've attached some pictures of what I could find. No visable oil leaking at the back of the engine, so I was wondering if you might have instructions for the gearbox along with these PDFs you've already sent. I suspect a service error may have caused an ATF leak.

Thank you again.
Sorry, I only downloaded the ones I needed and I can't for the life of me remember where they came from. Personally I would not be too fussed by that amount of oil around the front of the engine though I would suggest that the gasket I mentioned is the culprit (or rather the sealant where the gasket meets the head).
 

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