Oil Cooler!

**Ralph1Malph** · 28th June 2021, 03:26 PM

Hello All,
Well, a trip to the Indy has seen my leaks diagnosed.
Leaky engine coolant connector assy (replaced only 4yrs ago, but leaking from the rear connection); and leaking oil cooler assy.
I did prioritise the coolant connector assy, but now notice oily residue in the coolant overflow bottle.

I've searched and read, and read and searched the interwebs, but can't get a definitive explanation regards how the oil gets into the coolant.
I understand the external leaks through the mating surface gasket, thus filling the valley, but can only assume the coolant galleries inside the assy corrode or fail and allow oil into the coolant?

I'm keen to understand this as it means the difference between changing the gasket ($50) or the whole assy ($500)!

I'm compiling a parts list and am going to buy from England coz I'm able to let her sit, unused in the meantime.

List so far:
Gasket,
Coolant connector assy,
Overflow bottle,
Bottle cap.

I'm going to do all this myself, with time I don't have, but I have more time than money!

Whilst I've got it all apart, is there anything else I should do?

Cheers
Ralph

**loanrangie** · 28th June 2021, 04:45 PM

Touch wood no leaks thus far but have you had the belts done ?, cheap from the UK if you need the kit or any suspension bushes, compressor service kit etc.

**Ralph1Malph** · 28th June 2021, 06:28 PM

Originally Posted by loanrangie

Touch wood no leaks thus far but have you had the belts done ?, cheap from the UK if you need the kit or any suspension bushes, compressor service kit etc.

Belts ok due to HPFP replacement 4 yrs ago. I will order a bunch of sway bar and track rod bushes tho!

**PerthDisco** · 28th June 2021, 08:35 PM

There’s an o-ring for the oil cooler to coolant assembly connection you need to order separately and replace at same time. This becomes very hard after time. Worth doing the o-rings on the intake manifold also.

**shanegtr** · 29th June 2021, 03:52 PM

Originally Posted by Ralph1Malph

I've searched and read, and read and searched the interwebs, but can't get a definitive explanation regards how the oil gets into the coolant.
I understand the external leaks through the mating surface gasket, thus filling the valley, but can only assume the coolant galleries inside the assy corrode or fail and allow oil into the coolant?

It would be an internal leak between the oil and coolant galleries. Since the oil is generally under higher pressure than coolant the oil will generally leak in that way. Ive had a successful detection of coolant into the oil from the oil cooler through oil analysis earlier this year

**Ralph1Malph** · 29th June 2021, 07:05 PM

Originally Posted by shanegtr

It would be an internal leak between the oil and coolant galleries. Since the oil is generally under higher pressure than coolant the oil will generally leak in that way. Ive had a successful detection of coolant into the oil from the oil cooler through oil analysis earlier this year

Yes, I suspected that! A new oil cooler is the order of the day then!

**DiscoJeffster** · 29th June 2021, 07:54 PM

Originally Posted by Ralph1Malph

Yes, I suspected that! A new oil cooler is the order of the day then!

I stripped mine down after removal. Yes they break down internally as the seals give way.

**Eric SDV6SE** · 1st July 2021, 10:09 PM

Originally Posted by shanegtr

It would be an internal leak between the oil and coolant galleries. Since the oil is generally under higher pressure than coolant the oil will generally leak in that way. Ive had a successful detection of coolant into the oil from the oil cooler through oil analysis earlier this year

Makes sense to me, as if it was the other way around, coolant in oil would be a far worse problem.

Nearly 12years on and no issues, but don't want to temp lady fate too much. Keeping an eagle out on the oil cooler and coolant system for any signs.

**shanegtr** · 4th July 2021, 08:12 PM

Originally Posted by Eric SDV6SE

Makes sense to me, as if it was the other way around, coolant in oil would be a far worse problem.

Nearly 12years on and no issues, but don't want to temp lady fate too much. Keeping an eagle out on the oil cooler and coolant system for any signs.

Still have the potential for it to go the other way around - when you shut off the engine you'll now have zero oil pressure but still pressure in the coolant system

**LukeD4** · 3rd April 2022, 11:35 PM

Hi team, new here.

I have just purchased a 300,000 km D4 TDV6 MY10 i only paid 13g for it and its in pretty good nic with a long service history $9500 receipt at 256,000 ks etc.

Any way i took it to my Indi close by and the only thing he could pick up was the fact the coolant bottle had a dark tinge and that there was water in there not coolant, he done all the usual checks for head gasket etc and all seems well so he thought maybe an egr cooler had been leaking exhaust into the cooling system as there was slight contamination.

Ive drained the cooling system and what came out was clear clean water but with some what on an oil slick and oil residue in it. as the water poured out it was clear but only in the bucket you could see the oil.

Now im thinking its more oil cooler than egr coolers, there are no other signs or symptoms of anything and it seems this is the same as whats going on here.

No water in my oil or anything like that either.

Thoughts?

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