Intercooler question C5 2003 2.2hdi

[waynedance]

My intercooler has a little oil at its base, been like this for over 12 months, do clean if off now and again with brake cleaner.

The car runs fine and turbo kicks in as it should, is it normal to have a little oil?

[waynedance]

Are the intercoolers the same on the 2.0 and 2.2?

[cachaciero]

Pretty sure the 2.0 ltr and 2.2 Inter-coolers are identical. The fact that there is oil at the base is a sure sign that the inter-cooler is leaking. Question is how serious is this?, mine also has a leak but if I try and blank the output pipe with my hand at medium revs I can't hold the pressure and there is no audible indication of a big leak from the cooler so I live with it, but there is still the nagging question "is this one of the reasons for poor fuel consumption?"

cachaciero

[waynedance]

By the output pipe do you mean the one at the top?
Forgive me but how does the intercooler work, where is the oil from?

I guess the only way to cure the build up of oil is to renew the intercooler ??? or can you remove and clean out or something
I am something of a perfectionist and do not like the fact that oil gathers there.

[cachaciero]

The output pipe is the large one that runs from the top of the inter-cooler to the inlet manifold.
What does the intercooler do?

The turbo sucks in air and compresses it, as the air is compressed it increases in temperature quite considerably, hot air going into an engine is generally not good because hot air at a given flow has less mass and hence less oxygen than cold air at the same flow, the amount of oxygen going in is not so critical as there is generally more than enough oxygen for complete combustion even with hot air but we do need as big a mass as possible going into the cylinder. So to achieve this the hot air of the turbo is passed through the inter-cooler, technically an air to air heat exchanger, this cools the charge air and so increases it's mass, higher air mass into the cylinder equates to more power.

Where does the oil come from?

Two sources, the engine breather goes into the low pressure inlet side of the turbo, and the turbo itself is lubricated with engine oil and some of this will likely get past the seals into the outlet side of the turbo particularly at low turbo revs. The oil will tend to collect at low points in the system when the engine is shut off one of which is the bottom of the intercooler, thus with even a very small leak at the base of the intercooler when the engine is next run oil will be forced out through the leak until it gets hot and thin enough to be carried away by the air flow into the engine.

cachaciero

[waynedance]

Superb, thanks for explaining that.
So a little oil getting past the seals in the turbo is normal and makes it way back in to the engine via the intercooler. Is that right?
Do I need to worry about the intercooler or just leave it?

Thanks in advance, guess I just look for faults when there not there.

[cachaciero]

Well oil from the turbo doesn't exactly get back to the engine sump, it gets sucked in to the combustion chamber and burnt the residue going down the exhaust pipe, it is for this reason that a lot of newer engines with FAPS are supposed to use "low ash" oil,i.e oil which has low residual ash when burnt.

Back to your problem my advice would be to disconnect the rubber pipe to the inlet manifold and with the engine running try to blank the hose with the palm of your hand at say 2K revs if you can't do that easily and you can't hear any whistling or other sounds of air leakage from the inter-cooler I wouldn't (~don't in my case) worry about it to much, however worth cleaning the oil and crud of the intercooler on a regular basis as a build up will reduce the ability of the inter-cooler to cool and that may be more important than a small amount of leakage as I believe that the inter-cooler is less than ideal size for the 2.2 even when all is working correctly.

The Turbo pressure sensor which is used by the ECU is on the top of the inter-cooler, if the pressure was to get too low due to the leakage you would get the dreaded pollution warning coupled with a marked loss of performance, actually you might notice the performance loss before it got bad enough to trigger the warning.

cachaciero

[waynedance]

I will take the pipe off and do the check. Imap take the intercooler of and give it a clean or can you do while fitted?

[cachaciero]

Would suggest doing it in situ, spray the intercooler with carb cleaner or similar oil emusifier and then blast with a hose or jetwash to wash the oil away.

One other thing you could do if you have the bumper off to do the cleaning is to spray the intercooler with soapy water and then run the engine at idle with the pipe blanked off with luck you will see bubbles forming in the area of the leak. If it's a small leak degreasing and applying a small amount of a metal filled epoxy should be an effective repair. (wait for the epoxy to cure 24 hrs for a good epoxy).

cachaciero