W124 E320 1994 oil in coolant

[Happybunny]

Guys, any help appreciated. Coffee coloured stuff in coolant. Garage flushed it out and refilled coolant and new oil as aprt of service. Cappucino reappeared. garage thought may be an oil intercooler problem as mechanic had previously tried to fix what he thought was a blown head gasket on another similar model and this hadn't done the trick. Bought manual from MB club- no details. Russian site has good drawings though, and intercooler is integral to oil filter. Can see rigid pipe carrying coolant going there from top of thermostat housing.

OIl temp OK, presuure OK. Power OK. Some coolant evaporated as oil floats in coolant and oil level goes down a bit. No oil leaks. No smoke/steam in exhaust. No bubbles from coolant when thermostat opens and does not pressurise (apart from 20 psi or whatever the releif valve is set at). No water/bubbles/emilsion in oil. Auto box OK.

What are the chances of oil intercooler having sprung a leak- might be worth it before taking the head off? Apart from changing the intercooler, is there any diagnostic confirmation? Don't suppose it would hurt if there was a way of sealing the intercooler so oil does not leak out and bypass the coolant?

Best car I have ever owned. Pillarless coupe, Auto. Just superb power!. 180K+

Happybunny (... well temporarily not!)

 

[Bolide]

You have four possibilities:

1 - condensation in oil due to short journeys
2 - blown cylinder head gasket
3 - corroded radiator allowing automatic gearbox oil to mix with coolant
4 - corroded heat exchanger allowing engine oil to mix with coolant

The normal final result of a blown cylinder head gasket is exhaust gas pressurising the coolant circuit. If this is not happening now I suggest driving the car and keeping an eye on coolant & oil levels & quality plus engine temperature. I'm sure the situation will change and the cause will become apparent

280 and 320 engines are famous for CHG failure but, in my experience, they very rarely actually fail but are replaced to solve oil leaks

Nick Froome
www.w124.co.uk

 

[Happybunny]

Thank you Nick.

Can rule out short journeys. Oil is renewed usually every 6000 miles/6 months and there is no "mayonaise" in oil or oil filler cap.

Can rule out corroded radiator. Was replaced 18 months ago and the stuff in the coolant is engine oil not transmission fluid. (smell and colour).

That leaves cylinder head gasket or heat exchanger (oil intercooler). CHG is £mega, heat exchanger hopefully not so. Any way of determining which?


Also, is there a good engine flush? American MB sites suggest use a wrong type which emulsyfies oil into solids and that will clog up the water pump.

Happybunny

 

[Happybunny]

Solution oil in coolant

Partial results so far: beware of those who immediately go for head gasket failure diagnosis!
Cut the rigid pipe from top of thermostat housing to water cooled oil cooler (sits near oil filter housing near top rear of engine- need to remove inlet manifold to get access). Bypassed oil cooler hoses and connected hose from rigid pipe to the flexible pipe out of oil cooler to maintain cooler circuit. Copious quantiy of engine flush. Presto! no more gunk in coolant. Now clear for few weeks.
Oil cooler now leaks oil all over the engine and driveway- proves oil coming out of water inlet pipes to the oil cooler, so that's where the two were mixing.
Now to see if I can fit new oil cooler and restore plumbing. Part is £200 and something plus VAT- still cheaper than a head gasket!

 

[television]

Pleased that you have found it, is there a cheaper alternative out there by using an after market cooler

 

[kth286]

bunny

You have to ask yourself why it has gone bad in the first place.

It is likely because of cheap anti-freeze being used (or very diluted)

Ensure you only use Mercedes brand and that it is 50% mix.

Mercedes is ph neutral to ensure that the mix of materials in the coolant circuit is fully protected.

Mix of materials are numerous and include: alloys (head) cast iron (block) rubber (pipes)

plastics, and copper to mention a few.

You may have heard of peope having to back flush their radiators to unclog them in an attempt to solve a cooling problem.

The question is where does all this sediment come from ?

Well, it is all of the coolant circuit internals gradually being eaten away by acidic coolant and the bits are now floating around in the coolling system.

For longevity only use the Mercedes brand ant-freeze product. A bit more expensive perhaps, but cheap in the long run, and designed to do the job properly.

 

[television]

bunny

You have to ask yourself why it has gone bad in the first place.

It is likely because of cheap anti-freeze being used (or very diluted)

Ensure you only use Mercedes brand and that it is 50% mix.

Mercedes is ph neutral to ensure that the mix of materials in the coolant circuit is fully protected.

Mix of materials are numerous and include: alloys (head) cast iron (block) rubber (pipes)

plastics, and copper to mention a few.

You may have heard of peope having to back flush their radiators to unclog them in an attempt to solve a cooling problem.

The question is where does all this sediment come from ?

Well, it is all of the coolant circuit internals gradually being eaten away by acidic coolant and the bits are now floating around in the coolling system.

For longevity only use the Mercedes brand ant-freeze product. A bit more expensive perhaps, but cheap in the long run, and designed to do the job properly.

You cant argue with the above, you know it makes sense