How do you check for a bad oil cooler?

**A1EK** · 07-01-2017,06:19 PM

I flushed my coolant as it was full of sludge, two weeks later it's getting oily again but not quite as bad so I've flushed out for one more time today just to see if that helps.

As the oil in the engine looks OK and not sludgy and there is not any white exhaust smoke , I am suspecting a bad oil cooler could be the root cause. Can anyone tell me how to best check the oil cooler is okay and not leaking oil into the coolant water? Is there a rubber seal that should be replaced etc?

Thanks

**zollaf** · 07-01-2017,06:21 PM

remove the oil cooler and take it to somewhere that can pressure test it, but make sure they do it with the oil side pressurised. its easy to pressurise the coolant side as its just 2 hoses, but the oil side needs a bit more setting up. any engine builders should be able to do this for you.

**A1EK** · 07-01-2017,06:37 PM

Thanks for the info. I've got a pressure pump in my garage so may try it out. Is there any obvious signs to eye when I remove the cooler that will suggest it's leaking oil?

**nevo** · 07-01-2017,10:09 PM

Your coolant header tank and coolant will be a horrible grey colour,if you do want to test it pressurise the coolant side and stick it in a bucket of water.

**zollaf** · 07-01-2017,11:44 PM

i have had them before where you can pressure test the coolant side and not have a a leak, even at 70 odd psi. pressurise the oil side and it leaks at 10 psi, figure that one out. since its leaking oil into the coolant and not the other way round, its imperative to do it this way or you may not be able to positively rule it out. obviously it may leak from the coolant side being pressurised in which case yes, its duff, but if it doesnt then its not ruled it out.

**Crasher** · 08-01-2017,02:10 AM

Oil in water, new oil cooler, water in oil, scrap car-unless it is the R5 TDI in which case, fit a new water pump....

**nevo** · 08-01-2017,01:09 PM

Leaking one way and not the other,very strange indeed,don't doubt you zollaf but it does seem to be defying the laws of physics,as you say,work that one out.

**A1EK** · 08-01-2017,02:32 PM

I've only just bought the car, to me the oil cooler looks quite new and so does the filter. I guess there's a chance that it's been replaced but the system was not properly flushed out?

**Crasher** · 08-01-2017,04:15 PM

That one way leak pressure test effect Zolly mentions is due to the solder cracks internally acting as a one way valve when pressures is applied, it happens all the time on the old VAG style cooler. The Golf 2 was notorious for it.

I use commercial grade non foaming detergent to wash the system out and Citric acid works well.

Even the later designs still suffer

**A1EK** · 08-01-2017,06:25 PM

Mi

Originally Posted by Crasher

That one way leak pressure test effect Zolly mentions is due to the solder cracks internally acting as a one way valve when presume is applied, it happens all the time on the old VAG style cooler. The Golf 2 was notorious for it.

I use commercial grade non foaming detergent to wash the system out and Citric acid works well.

Even the later designs still suffer

I've uploaded two photos, I flushed the coolant yesterday and today there is clearly fresh oil in the water. The do stick oil however looks okay, so I'm going to buy a new cooler or used one online.
PS my oil cooler looks a different type to the one you posted.