Hi All-

I recently installed a Radix that I purchased used and have been having some issues with it. Namely, a lack of smooth power when in boost, and recently a whistling sound under heavy vaccum. See 40PSI fuel pressure at idle, and around 62-63 @6psi boost. Boost gauge reads 18-20" vaccum at idle, and 6psi full boost.

I've eliminated all but one source as the vaccum leak, and that is the brake booster fitting. The unit I purchased came from an H2, apparently an 04, because it had a plug where the Vaccum brake booster fitting should have been. Having an 03 SS, I need that fitting, and used what I thought was the correct size from Advance Auto.

This past weekend I pulled the whole assembly off to inspect everything to make sure that the intake manifold gaskets weren't torn and there wasn't signs of leaking around the ports. All was well. I adjusted the booster hose a bit and re-tightened the clamp and now the truck seems to run a bit better, but still slightly "un-smooth" in 3rd gear kick-down, and the whistle appeared under heavy vaccum.

So my question(s) are. Does this sound like just this minor vaccum issue? And does anybody have an idea what the correct fitting I need is? I've gone through the radix parts list and cannot find it, but assume it is something like a 3/8" NPT to 1/2" barb?

Thanks!

 

Fuel pressure not right at idle should be some where around 58-60.wot pressure is fine.Do you have a manual for your application.You can download from magnasons site.three fittings on rear blower j tube small line is for boost bypass second middle line is drivers side pcv and third is a threaded pipe barb that go's to the brake booster.IF YOU WANT TO PM ME WITH YOUR NUMBER I CAN TALK YOU THROUGH WHAT YOU MIGHT BE WRONG AND MISSING.

 

Oops, meant 50psi at idle, not 40. Smooth transition from 50 to 62-63 for WOT.
boost bypass and PCV intact, no problems, it is that threaded pipe barb that I need the sizing to to ensure I have the right one.

I'll shoot you a PM in the morning, I'm headin off now. Thanks!

 

sounds like your internal by-pass valve is sticking. check for carbon, nicks in
the bore or bending in the plate. it is real easy to damage this.

hope this helps

 

Thanks for the advice. Am I able to check this stuff with the blower in the truck still? And wouldn't my boost gauge show the boost bleeding off if that is the case? Can definitely hear the whistle as I cross into boost from vaccum...

 

you have to pull the blower off to check the bypass valve.

if you dont get any more ideas call magnacharger before you pull it off again.

 

Okay, thanks. So I would just pull it off and then pull the plenum off the rear?
Replaced my brake booster fitting with the correct one last night, seems to have made a difference, although I'm starting to think you could be right about the bypass thing. 3/4 throttle today I could actually hear the "whine" of the compressor change slightly coinciding with the power surges... Perhaps the "stop" on the bypass actuator is not set correctly. I had to replace that last month, but it was acting up before it was replaced, so Dunno.
Thanks for your ideas though, it's all I really have to go on.