Silicone Intercooler Pipes for the Forester

In trying to track down a minor fuel leak under my hood, I noticed what appeared to be a very timeworn hose--and though large parts of said hose were hidden away from sight, its purpose was clear: the hose led from turbocharger to intercooler, and I can't imagine having that hose fail while driving would lead to good times.  So after a bit of research, I ordered not the cheaply-built OEM plastic pipe but a snazzy silicone set which would stand up to the temperatures of a turbocharged engine better and look good at the same time.  Replacing the turbo hoses would involve my first real bit of mechanical disassembly under the hood and give me some good practice for future maintenance.

The intercooler with its fancy new silicone Y-pipe installed

Between the appropriate Haynes repair manual and Peaty's excellent instructions over at the SubaruForester.org forums, the process wasn't too difficult and something any amateur mechanic could tackle--the hardest part was working the old hoses loose and getting the intercooler out without bending any of the delicate metal radiator vanes (you can see some bent vanes in the photo above--not due to my handiwork, I can assure you).

The original intercooler pipes--cheap plastic covered with foam wrapping

I made sure to clean the fittings well--they had a little bit of cooked blow-by oil on them from the turbocharger, but not as much as I'd feared.  Still, there was enough oil that it makes me wonder if I might need to replace the turbocharger itself in the next couple of years; I'll definitely give it a good once-over when I have the intake manifold apart when the weather gets a bit nicer.  I did after all have the engine throw an AVCS-related code a couple of years ago, most likely due to an oil filter screen dropping down into the AVCS body--and in the process, the turbo could have starved for oil a bit and taken on a bit of excess wear.

While I had the intercooler off, I also gave the engine a treatment of Sea Foam straight in through the throttle body, given it hadn't had an upper cleaning for at least 20,000 miles (if ever--I asked for one at my 60k service, but am not sure the mechanic actually performed it or not).  On the 2004 Forester XT, there just isn't a vacuum line which feeds all four cylinders equally, so applying the cleaner straight into the throttle body is a necessity and cleans the throttle butterfly, too.  Surprisingly, the Sea Foam didn't yield quite as much smoke as I'd expected--some folks describe the effect as a spy-gadget smokescreen as atomized carbon deposits make their way out the exhaust--maybe the mechanic had actually done an engine upper cleaning after all.

I went with the Samco intercooler hose set for the 2006-and-newer Subaru Impreza WRX (part TCS332).  Samco doesn't make a Forester XT-specific hose set, but two of the three pipes in the WRX one are directly compatible with the 2004 FXT: the Y-pipe (the replacement of which had started this whole exercise) and the short coupler between the intercooler outlet and the throttle body.  The third hose, the blowoff valve recirculator hose, won't work in the 2004 Forester XT due to being the completely wrong shape, but my original BOV recirc hose looks fine.

Putting the intercooler back on wasn't too hard--the hoses were significantly easier to reattach than they had been to remove.  After a bit of idling in the driveway to make sure nothing was leaking, I took the car out for a spin.

The completed installation

I do need to work on the vanes on the intercooler a bit; bugs and even some small pebbles (!) sucked in through the hood air scoop have left their marks on the delicate metal. It's a painstaking task with a safety pin, though, and something I don't want to do when it's near-freezing outside.

Next up: maintenance on some of the oil supply lines to inspect (and in two cases completely remove) poorly-designed filter screens from inside the banjo bolt union screws.  One of these already caused a "check engine" code on my car a couple of years ago--thankfully without doing apparent damage to the oil control valves--while another can critically starve the turbo of the oil it needs to spin at 100,000+ RPM.  I've still got plans to take apart the intake manifold and fix the cold-weather leaky fuel line problem affecting so many Subarus, but that's a task for warmer weather and a long weekend.  After that, I may install the OEM turbo boost gauge to see just what sort of output I'm getting from my stock turbocharger.