W124 E36 AMG oil related problem

Palfrem

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Here's an interesting one.

For the last couple of weeks the yellow oil light has been coming on / going off intermittently.
There's plenty of oil and the oil pressure gauge shows a solid 3 bar

Talked to my indy and it was agreed that the sensor is probably u/s

They've now fitted the correct new sensor but the oil light is still coming on and off.

On investigation, the water expansion tank has about a litre of dark brown / black engine oil in it!
This is completely mystifying, as the golden yellow oil on the dipstick is at the correct level and has not gone down at all.

There is no mayonnaise on the oil filler cap and it runs really well. No blue smoke.

It's almost like someone has deliberately put used oil in the expansion tank!
The garage are also at a loss as to the cause.

They'll remove the expansion tank, clean it and flush the cooling system and I will drive it about for while and see how it goes.

Anyone have any ideas please?
 

Will

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Sounds like the head gasket is on the way out?

Oil and water mixing - oil floats and rises up into the header tank (highest point in the cooling system)

Cooling system runs around say 1bar when up to pressure, oil pressure is higher when engine is revved. The oil gets pushed through the leaking gasket into the coolant passages.

I think it’s not unusual for M104s to have head gasket issues?
 
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Palfrem

Palfrem

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Thanks Will,

I thought head gasket, but the oil is so black and discoloured in relation to the lovely golden oil on the dipstick.
 

Will

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I think the light brown oil mixes with the blueish coolant plus any corrosion etc if turns a dark muddy brown chocolate sort of colour usually.
 
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Palfrem

Palfrem

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I'll be booking it in to MB next week as my indy don't seem to be too interested.
Thanks for your help though.
 

grober

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Think the E36 was bored[ slightly] but mainly stroked [ used the longer throw diesel crankshaft] to get the extra cc's so the CHG will be oversize. Think iirc they tend to leak oil at the front of the head [ drivers side] where I assume the main oil feed gallery to the valve gear is so I would suspect that's where the CHG is gone. Are the garage going to do a compression test?
 

Bellow

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I think the light brown oil mixes with the blueish coolant plus any corrosion etc if turns a dark muddy brown chocolate sort of colour usually.

I'd be tempted to test that theory by putting small amounts of each in a jar and watch what happens overnight. If as suggested it goes dark - virtually a diagnosis that fits Grober's suspicions.
 

d w124

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As ^ might be gearbox cooler,remember that they have it built into the rad
 
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Palfrem

Palfrem

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My indy has now removed tank / cleaned it / flushed system. Yellow light still on.
I'm not keen on driving it at the moment in case I do more damage.
I have suggested my indy take a look at the oil cooler and replace rad if required.
Thanks for all your suggestions
 

SG1

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This is interesting to me as I have exactly the same car with the exact same problem!!

My car is a 1994 C124 E36 AMG. On doing some basic general checks under the bonnet as I always do I found lots of black coloured oil in my coolant tank. The car runs perfectly fine and drives fine without any problems other than an electrical issue which is another story!

More interesting is the fact the head gasket has already been done by a Mercedes main dealer five thousand miles ago and I have the relevant invoice. My MB specialist checked over the car whilst I was there and we carried out a compression test which was all normal.

So..it seems a bit of a mystery where the oil has appeared from. Yes it could be the gearbox oil cooler but the oil looks like engine oil which my specialist has confirmed. I haven't had any further checks carried out as I have an intermittent electrical issue which I need to resolve first but it is definitely odd that the head gasket has already been done and the car runs fine!?
 

Will

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SG1,

The compression test won’t tell you if the head gasket has failed between a coolant passage and an oil way. In the same way as you can have an oil leak externally from the head to the outside of the block you can have oil leaking under pressure into the cooling system.

Having had one head gasket replacement also doesn’t mean it can’t go again especially if there’s an underlying issue with the head or block for example.

I would perhaps skim off some of the oil and have it analysed to be certain it’s engine oil, but if you’re already pretty sure I think you can skip that.

The other consideration is that if it has previously had oil contamination in the cooling system (from before the previous HG was done) it may prove very difficult to remove all traces of oil from the system - it would be everywhere. I would probably skim off as much oil as possible, flush the system and refill with fresh coolant and monitor it as a starting point.
 
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Palfrem

Palfrem

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I'm still waiting on my indy to come back to me.

Frustrating!
 
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Palfrem

Palfrem

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Looks like my indy have effectively thrown in the towel and have suggested I take it to MB
I've asked them to confirm ATF level is OK first.
 

SG1

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Looks like my indy have effectively thrown in the towel and have suggested I take it to MB
I've asked them to confirm ATF level is OK first.

Oh dear. To be honest I'm not sure what Mercedes themselves would actually know about a W124 or M104 engine so not sure if it would be beneficial taking it there.

I'm not sure where you are located but there will be good specialists out there who know W124's well and would take it on willingly - I'm based in Kent/London.
 
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Palfrem

Palfrem

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I'm in Shirley, just south of Brum, near J4 of the M42.

This episode has made me begin to wonder about the long term viability of maintaining old cars without a reliable spannerist on hand.

Seriously considering getting this car fixed and having a parting of the ways.
 

Tonygw

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This does sound very much like an internally cracked oil cooler. This would allow oil into the cooling system. I doubt its the head gasket as that would show on the oil filler cap.
 

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