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fasteddie313 fasteddie313 is offline
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Join Date: Mar 2014
Posts: 37
The wastegate is a part that is very important to have working correctly because if it fails you will overboost and possibly blow your engine in a split second if other protective measures are not in place or fail also. I recommend rebuilding it for peace of mind in any case..

It is quite a simple device for the most part but new diaphragms are a bit expensive and you should replace the studs with new because they are prone to breakage upon disassembly due to the heat they must withstand in normal usage.

I have been through a 930 WG a time or 2 and have set up a system and a jig for removing broken studs and have been 100% successful at saving the original threaded holes as well. I already have the correct tools for the job and a successful setup.

To do a proper rebuild includes replacing the diaphragm and studs, the main parts should be reusable, just under $200 in parts. The valve guide may also be in need of replacement but it is less likely and easily doable but would add to the expense and you don't really know until you are in there.

I will offer to rebuild your wastegate for $250 including a new diaphragm with proper studs, nuts, and gaskets (quality parts from TiAL). Add $10 each for extracting any broken studs saving the original threaded holes. Plus return shipping.

Replacing the valve guide could also add to the expense if it is needed but I am not in a position to quote exact cost on that. I would guess around $100 for a new valve guide + or -.. As far as I know it would have to be made by a machine shop but it is very likely your guide is fine.

Of course it is possible that main components such as the valve, seat, and housings could need to be replaced but I feel that is highly unlikely and if so I am confident I could source good replacement parts at quite reasonable costs.

These pics are early in my first attempt (eventually successful) but now I know what works and what doesn't and have a proven setup.. The valve seat plate did NOT want to come off this WG until I really put a hurtin on the remainder of the studs..

In my experience broken studs are very common. I attempt to easy out first but have had no success with that but it's worth a shot. What I end up doing is drilling out the original stud as much as possible before getting into the threads and then tapping the remains of the stud out of the original threads.

I like to locate my setup off of an existing good hole so I know my direction is true but that is not possible with all of the studs broken, but once I get one hole fixed I can then locate from it to be very precise.

After drilling out the studs as far as possible I can use a pick/punch to clear the first few threads so the tap will start in the threads and tap out the rest of the stud's threads from the housings threads.
I tap in the drill press with the same setup (not under power) in order to keep my tap and work perfectly straight (already located) to give the best chance of perfectly saving the original housings threads.

This 930 WG had 6 of its 8 studs broke off and I was able to clear every one of the holes saving the original threads without issue with this method..

Also, I do have another 930 WG on hand with new studs installed to replace yours should I happen to make a mistake I would eat it and give you mine..

If you don't want to trust your WG to me that is fine and perfectly understandable, at least from this post you will have a good idea of what a WG rebuild entails and what you are up against..
80 931S LSD-G31 Big Breaks FMIC
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Last edited by fasteddie313; 08-20-2015 at 09:19 AM..
Old 08-20-2015, 09:01 AM
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