T3 Wastegate issue

[veeman]

I've got a 1.6TD with the T3 turbo (rebuilt 30k ago) on it in my caddy.  I have a Giles pump, intercooler and 2.5 inch exhaust / downpipe. Safety blow off valve is blocked.

Previously I was running a "grainger" pressure valve on the wastegate line of the turbo and could reach 15-16 psi no problem (stock pump with tweaks).  Now, I had Giles turn up the pump to run around 18 psi (stock head gasket), but never got to turn the boost up that high.

After I got the pump back on the boost would go up to 16 psi in third, fourth gear, but then would back off back to 11-12 if I kept in it.  Keeping it at moderate throttle and feathering the throttle would allow me to keep higher levels of boost, but it wasn't consistent.

Recently, boost has been even lower.  I can romp on it in all gears and get to 11-12 psi but nothing more.  I unscrewed the grainger valve all the way - no change.

I thought it was the grainger valve and so I switched it out for another more "commercial" type of pneumatic controller. No change.

Finally, I blocked the wastegate signal line completely.  No real change (slightly higher boost maybe 12-13 psi). I would have expected 20+ psi on that test.

So...I'm thinking the wastegate is having an issue.  Those of you with experience with this turbo, does it sound like it's stuck partially open or that maybe part of the valve or seat is burnt?   Don't think the turbo is shot due to the recent rebuild.

Is it just a coincidence that it'll reach stock levels of boost even though the wastegate is blocked (shouldn't open at all)?

Any advice?

[veeman]

Pics of the turbo when I put the engine together:

[zukgod1]

Well it sounds like your wastegate is stuck slightly open.

I cant remember right now how that come off the housing to clean either.
Hopefully someone will chime in.

[andy2]

I'd doubt there is an issue with the wastegate.

Do you have an intercooler?
Possible leaking connections/intercooler?
Possible leaking LDA hose?
Remove the inlet hose on the turbo to check the shaft for excessive play
Do you have an EGT gage?Are EGT's lower or higher than normal with the lower boost?
Any Black smoke?Air filter restricted?
The pump could be starving for fuel if the filter is restricted.

[golfmk1tdr]

I also believe my vastegate is faulty and I can't find any info on how wastegate valve works here or how to dissasemble it, really annoying all wastegate info is on lever type wastegate not this valve type or how do you call it.

I think I will try to acces wastegate with engine on car but I would really like to know what I am doing, does turning the wastegate valve do anyting? You can turn it with hex but I don't know what it does and I don't want it to come apart completely (in case I unbolt it):

I am saving for holset turbo but since that will take a while I want to make this turbo work like it should so please report if you know how to deal with this wastegate or how you solved (if you did) your problem.

Sorry for ancient thread bump but I don't feel like starting new thread for this...