308 hdi - oil in coolant

[ewald]

Hi all - brand new member here, with a puzzling problem.

I recently found that engine oil was getting into the coolant reservoir - no temperature problems, just oil level dropped and a layer of oil in the reservoir.
My local garage changed the oil cooler and flushed the system - all ok for a 20 mile round trip. The following day after the usual 25 mile commute (each way) there was 1/2 litre of oil in the reservoir again.
They then removed the head - no sign of gasket problems, leaks or cracks.

They are suggesting an internal crack in the head or block - they feel that the easiest option is a secondhand engine.

Before doing this, has anyone any experience/ useful suggestions?

The car is a 2011 Peugeot 308 with the 1.6 hdi engine

Many thanks

[GiveMeABreak]

So a couple of possibilities...

Does it look anything like this?

This is what will happen if a lot of oil starts to get into the expansion tank - it looks like mayonnaise.

Now unless I'm mistaken the 308 106 HDi has an air cooled oil cooler. The engine coolant variant uses the engine coolant system to cool the oil - and this is where a failure can result in oil getting back into the coolant system. Post your VIN up so we know what variant you have.

So if you have an air cooled oil cooler, that rules that possibility out.

That leaves a crack in the cylinder block or a misaligned head gasket as there aren't really any other places for oil to get into the coolant system.

Until you find out for sure, be VERY mindful of the engine temperature - but not recommended to drive it if possible as the more you do, the more damage will be done. Obviously when you find the problem, you'll need to fully drain and flush the radiator and the cooling system thoroughly.

[ewald]

The oil still looks like oil if that makes sense - not mayonnaise.
We have changed the oil cooler, problem still remains.
How likely is a cracked block? This is a 2011 car with about 50,000 miles.
Not being driven at the moment, as the head is off

Thanks

[white exec]

Do post your VIN, so we can exactly identify the engine components.

[Stickyfinger]

To me that looks like the water system did not get cleaned very well.

What method/products did you use to flush the cooling system with ?

Caveat: Yes, it could still be leaking, until then run it with the cap off to reduce the pressure on the water side to prevent water>>>into>>>>oil

[ewald]

VIN VF3**************[VIN obfuscated, can be read by forum staff]
Engine no JBCM0037864

The engine was flushed twice (with an engine flushing liquid), for the first 40 miles the coolant was fairly clean, Subsequently the oil leaked again. Could this be temperature related? (ie a crack opening up at a certain temp?)

There is no water in the engine oil

[Stickyfinger]

I would think a leaking head gasket rather than a cracked block....but without more investigation (pressure tested head/inspected)

Define "flushed twice"...what "product"

Mayo can be a bastard to remove and look terrible for ages. Try whipping the rad out, use VERY HOT water and detergent, see what comes out. (do not flow detergent around the engine). I would whip off the oil cooler again as well and test that as well, new can also be faulty

[ewald]

I don't know what flushing product was used - done by a garage.
There is no mayo in the header tank - just fairly clean oil.
The head gasket, head and block appear good - no evidence of leakage/cracks, gasket degradation.

[white exec]

Oil is usually injected into water (rather than the other way round), because the oil is under greater pressure.

Most usual cause is the oil-water heat exchanger (engine oil cooler) perforating/corroding internally.
It sits close to the oil filter.

This can be diagnosed/checked/isolated fairly easily if there are two coolant (water) pipes connected to it:
- disconnect these water hoses, and join them together (a short length of 15mm copper pipe can sometimes be used)
- this will prevent any further oil getting into the cooling system from the oil cooler
- clean out the cooling system thoroughly, hooking out floating black oil from the header tank with pieces of rolled up kitchen roll; oil will cling, leaving coolant behind
(Recommended system cleaner is LiquiMoly Radiator Cleaner #2506 300ml; buy 2 and keep the second one as standby.)
- see whether any oil leaks from the exposed pipe snouts on the oil cooler; if it does continue to leak oil, it is perforated
- see whether any more oil appears in quantity in the header tank; if it does, then the leak is elsewhere, eg head gasket of an engine block problem

Once black oil has got into the cooling system, it can be a very lengthy job to get rid of it all. Even after the leak is stopped, unless a really good system cleaner is used (after fishing out the worst with tissue - it usually collects, mercifully, at the highest point: the header tank), it can continue to emerge there. You have to use your judgement here . . . if the quantity is decreasing, you are winning. If it doesn't get any better, the leak is still there.

Don't drive meaningful distances with oil in coolant, and expect you might get a "low coolant level" warning, as the liquid-sensing probes get coated with insulating oil.

Do use the recommended cleaner. Detergents etc will not shift it.

In order of likelihood:
- perforated/leaky oil cooler (or oil still in the system even though cooler was replaced)
- head gasket
- cracked block

[RichardW]

On a 1.6 HDi the oil cooler is a complex affair under the oil filter. Oil water mixing is prevented only by 4 'O' rings between the filter housing and cooler, but also a secondary multi seal behind the filter housing. Did they replace all the O-rings? A crack in the head or block seems unlikely, unless it has been overheated.

[rebuilder86]

Quote
Oil is usually injected into water (rather than the other way round), because the oil is under greater pressure.

I dont want to alienate myself in these forums, but i must state what ive learned.
At hot idle, oil pressure can be incredibly low, like 4 psi. But always, at idle, when hot, oil pressure is lower than cooling system pressure. ONLY AT IDLE.
During these times the flow is the other way, water/coolant into oil, and your oil dipstick shows the classic milkshake. I am not talkign abotu a head gasket failure, where oil is under NO PRESSURE and all coolant enters the oil sump.

[white exec]

You're right, under hot idle conditions, this is quite likely.

If the car has been driven, oil pressure will have been up to a normal figure (typically 3∼5bar, ∼60psi) and dirty engine oil will have been injected into the cooling system (running at something less than pressure cap lift-off pressure of ∼1.4 bar). This oil will remain there, and will easily be spotted (usually floating on top of the water in the header tank).

My guess is that at hot idle, as you suggest, some relatively clean coolant (the ingested oil being "up at the top") would get pushed back into the engine oil, via the 'holed' oil cooler lower down the system. Ignored, the header tank would get progressively more full of oil, and the sump receive more and more coolant.

[rebuilder86]

The solution is, we should just have one fluid, oilant.

[white exec]

[WhitwellMike]

Hi, I know it's an old post but did you solve this?

Mike