Nick Read

Just got a set of silicone intercooler hoses for my 98 WRX, so first job was to get the IC off. But when I got it off, it was filmed with oil all over the inside. Most was black and caked on - old in other words - but there were a couple of spots of fresher oil in there as well. Worst area I could see was in the old Y-pipe underneath, which is basically the lowest point in the intercooler system and it looked like it had just pooled there and crudded up. Dump valve pipe was pretty clean, throttle body was oily, compressor outlet was coated in old oil sludge in a swirled pattern that looked like oil or oil vapour had come in from the induction pipe been blown through.

Anyway, I got pretty liberal with the degreaser and hot water through the innards of the oily IC, blew it out dry with a hairdryer, straightened all the fins, and then reassembled everything. The new hoses went on perfectly, no probs at all.

I'm not sure whether this is an existing problem or something that I already fixed. When I bought it the previous owner had accidentally filled it up a little too much with oil and I had untold overboost problems until I cleaned out all the boost control /turbo piping and solenoid, which sorted it right out. But I suppose some of the excess oil must have come through into the induction piping from the air filter to the turbo? I'll check it again in a month's time to see if the IC is still clean inside or whether there's evidence of an ongoing oil control problem.

Took the Scoob out for a burn after putting everything back and it definitely feels slightly livelier with a nice clean IC and the new hoses. Maybe it's my imagination though LOL

So the question is:

1. Is there any other reason I've not thought of why there would be oil in the IC? e.g. oil leaking through from the turbo itself, rather than being blown through from the induction tract? How would I tell the difference?

2. Is there any performance disadvantage to simply disconnecting the oil breather hose from the induction tract and sticking a breather filter on it - I'd rather it was vented rather than burnt! If it starts blowing oil again, I'd rather it dumped it on the my driveway than back into the inlet.

All opinions welcome!

Merv

iTrader: (12)

Fitting a catch can should cure it.

Aztec Performance Ltd

iTrader: (234)

Overfilling typically causes oil in the i/c from the breathers. I routed my to the ground and havent had a problem since.

Bob

Nick Read

So the answer is to simply reroute the breather pipe to a breather filter or catch can. Are there ANY disadvantages to this at all - e.g. on my old Clio, scavenging of oil vapours from the crankcase properly relied on the induction tract vacuum pulling the vapours through. With the breather pipe free, there was no longer a vacuum drawing the vapours out. I would imagine this would be the same with the Subaru engine - without the vacuum there, the vapours will sit there with no reason to vent? Crankcase vapours aren't something I've looked into a great deal, so is there anyone who can give me the lowdown on this subject?

RON

There is a difference between a subaru and a clio, the subaru has a turbo, and therefore works under increased pressure, therefore there will be an element of blow-by past the rings, and therefore into the crankcase, this will push the fumes if any from the area, into your catch can.....

Nick Read

Well I turbocharged my Clio 16v, an engine notorious for running through a litre of oil every 1000 miles in NA form, but once it was turbocharged this stopped the oil consumption dead in its tracked - we suspected that the boost pressure in the cylinders actually sealed the rings better...

But anyway, what you're saying is that Subarus are SUPPOSED to have a small amount of blow-by and therefore positive pressure in the crankcase? So by taking the induction tract vacuum out of the equation, crankcase oil vapours will still be pushed out of the breather pipe?