Does anyone know what this sludge is all about?

[babyblueCE]

Hello. I was generally topping up fluids in the car and came across this sludge build up in my coolant expansion tank. Does anyone know why this sludge is in the tank?

 

[rorf]

Either the wrong coolants have been used or your cylinder head gasket is leaking oil into the coolant which is very common with these engines at about 100 000 miles.

 

[renault12ts]

Or, a simpler, cheaper, more common cause is a build up during cold weather due to the car being used for short journeys rather than long ones.

 

[redbaron]

looks like condensation to me..

 

[Auto-mobile]

You need to get it checked, that's going to be head gasket.

 

[rorf]

Or, a simpler, cheaper, more common cause is a build up during cold weather due to the car being used for short journeys rather than long ones.

This only happens under the oil cap - definitely not the radiator cap

 

[Beno]

I'd go with he condensation/winter as well but if your worried take it to a garage for a coolant sniff test (They check the coolant for HC in the coolant)

 

[rorf]

Looking closer at your pics that coolant looks brown and dirty - the killer of Mercs.

Amazes me how many owners do not change the rad fluid every 3 years using ONLY Mercedes coolant.

I have a 30 year old Mini that has only used the best of coolants and the radiator and cooling passages are spotless - coolant changed every 3 years.

 

[WG M-B]

It's going to be hg or oil cooler

 

[Will]

You head gasket has gone.

Will

 

[grober]

Head gasket. Check for water in the engine oil also --- oil will be very black with thin wisps of white [ bit like a tracer colour on wiring insulation]if the water has got into the oil. The other possibility as has been mentioned is the cooling coil inside the radiator which acts as a heat exchanger for the automatic transmission has corroded thro allowing coolant to mix with the auto transmission fluid- are you experiencing weird autobox behavior?

 

[horatio]

Definitely HG- the gasket corrodes and leaks oil into the coolant rather than go pop. I wouldn't panic because its not a huge job tbh.

 

[tonyc280]

That looks like emulsified engine oil on your filler cap. Almost certainly your Head Gasket gone ! Tony.

 

[tonyc280]

Head gasket. Check for water in the engine oil also --- oil will be very black with thin wisps of white [ bit like a tracer colour on wiring insulation]if the water has got into the oil. The other possibility as has been mentioned is the cooling coil inside the radiator which acts as a heat exchanger for the automatic transmission has corroded thro allowing coolant to mix with the auto transmission fluid- are you experiencing weird autobox behavior?

Learning something about Merc's every day from your posts mate. Never too old to learn !

 

[babyblueCE]

Thanks guys for the info. Ive checked the engine oil and theres no traces of water in there. Dont seem to be getting weird gearbox problems. Car seems to be driving fine having changed the coolant and spark plugs. Topped the car up with oil also dont seem to be having issues regarding anything else at the moment. Would it be wise to get the car checked to see if the head gasket has gone or would changing my radiator suffice?

 

[Will]

Thanks guys for the info. Ive checked the engine oil and theres no traces of water in there. Dont seem to be getting weird gearbox problems. Car seems to be driving fine having changed the coolant and spark plugs. Topped the car up with oil also dont seem to be having issues regarding anything else at the moment. Would it be wise to get the car checked to see if the head gasket has gone or would changing my radiator suffice?

Your head gasket has almost certainly gone. This is a common issue on 8-valve M102 engines.

I suspect you have a breach of the gasket seal between an oil way and a coolant passage. Usually this seems to happen towards to rear of the engine

The reason you have oil showing in the coolant and not coolant in the oil is that the coolant only runs up to around 1 bar in closed operation when up to temperature (pressurised). The oil is under higher pressure so tends to leak from the oil into the coolant rather than the other way round.

Oil is also lighter than coolant so finds it's way up to the highest point - top of your header tank.

It's best to get this diagnosed and fixed as soon as possible. As it currently stands you probably will only need a new gasket set plus fluids, but if the leak worsens and the gasket lets go from between the coolant passages and the cylinder bore you can suffer from corrosion on the alloy head which can be much more expensive to repair.

For reference, and original MB OE 'Elring' gasket set is around £30 from GSF car parts. I would not recommend using an alternative brand at this price point.

You can measure and probably use the head bolts again if within spec. Other than this you'll need to flush the cooling system, and obviously require new oil, oil filter, coolant and a cam cover gasket. Possibly a few small items - downpipe bolts if in poor condition and possibly a couple of other parts if perished (breather hoses etc). Might as well replace spark plugs if required.

The head is unlikely to be warped and can be meticulously cleaned and refitted - should not require skimming.

As I say, best to get this checked out and repaired as soon as you can not is not a difficult job but can be a little time consuming. Make sure whoever does the work is familiar with MB engines - there is a specific way of resetting and replacing the timing chain tensioner.

 

[rascalmaster]

has your coolant level dropped drastically?

is there presence of water in your oil?

if no to both; don't panic just yet as certain amount of condensation is normal on older mb engines ;-)

 

[babyblueCE]

This is the thing ive got no coolant or water in the oil. Have checked the oil and dont see sign of this. Will, i will definitely get this checked out by a mechanic, before i come to any conclusions with what i want to do with the engine. The car is almost hitting 195000 so need to balance cost with necessity of getting it done. Was going though a thread on how the head gasket can changed, it is time consuming so labour could probably set me back minimum £500. I did have this in my expansion tank around 12 months ago and i changed the coolant. Had to change my rad about 9 months ago but tried a cheap fix by putting rad leak stop fluid in the tank but this didn't work. I have seen signs of oil in the expansion tank so as Will said my head has probably gone.

 

[Will]

has your coolant level dropped drastically?

is there presence of water in your oil?

if no to both; don't panic just yet as certain amount of condensation is normal on older mb engines ;-)

He has oil in the coolant expansion tank, not condensation on the oil filler cap!

 

[Will]

This is the thing ive got no coolant or water in the oil. Have checked the oil and dont see sign of this. Will, i will definitely get this checked out by a mechanic, before i come to any conclusions with what i want to do with the engine. The car is almost hitting 195000 so need to balance cost with necessity of getting it done. Was going though a thread on how the head gasket can changed, it is time consuming so labour could probably set me back minimum £500. I did have this in my expansion tank around 12 months ago and i changed the coolant. Had to change my rad about 9 months ago but tried a cheap fix by putting rad leak stop fluid in the tank but this didn't work. I have seen signs of oil in the expansion tank so as Will said my head has probably gone.

I have seen this on several 8-valve M102 engines. Like I say, you don't always get water in the oil - that's normally when the coolant is leaking into the bores and runs past the rings etc - or when the gasket has failed catastrophically. A minor trace of coolant/water in the oil may boil off in normal use and go undetected anyway.

The parts/consumables are cheap as I've mentioned - probably around £100 + labour. It's possible to DIY this repair if you're confident with tools/engines - otherwise you probably want to find a competent independant to keep costs to a minimum. As I say, it's not a particularly complicated job just time consuming. You need to be meticulous with some aspects of this job to ensure a quality repair that will last