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mark houghton mark houghton is offline
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Join Date: Jul 2008
Location: Central Washington State
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Quote:
Originally Posted by 9dreizig View Post
That's a pretty big leak, I can see light around the whole valve! I would think that there would at least be some resistance when I back blew some air in there..
T
OK Todd, I'm with you on that. Light showing through is not a good thing. I presume at some point you have completely disassembled the WG, valve and all? My guess would be either a bent valve stem, seriously corroded/carboned-up guide, or warped valve seat. Take it appart if you haven't already, clean out the guide and stem, get some valve grinding compound and hand-lap the valve seat. If none of that helps, then it's shot. Something is sticking somewhere, even with all that spring pressure it still won't fully seat. There was a post awhile back on Rennlist that dealt with having a machinist make a new guide. That's an option for you.

Finally, here's one more thing to think about...the recirculation valve assembly may be defective. If the piston is stuck in the up position, you won't build any or very little boost at all. Here's a cut-and-paste from a description I gave awhile back:
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"The recirculation valve basically takes the place of a blow off valve in later model turbo engines. Essentially what it does is to redirect the pressurized air from the intercooler/engine intake manifold, back to the front intake end of the turbo. This takes place under sudden change in engine vacuum (as in when you lift your foot off the throttle to shift). The sudden increase in vaccum is transmitted via a small hose to the piston assembly, causing the piston to rise and uncover a port to redirect the pressurized air. This balances the pressure between the intake and outflow ends of the turbin, allowing it to freewheel. This, as opposed to the high pressures residing post-turbo with no place to go when you lift your foot off the pedal. The air pressure would otherwise have to travel backwards through the turbo - causing it to slow down dramatically, put undue wear-and-tear on the turbo, and create a huge turbo lag when you put your foot back on the go pedal."
Old 08-13-2008, 12:50 PM
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