Wastegate Valve Seat Removal

[twoqu]

Has anyone ever removed the wastegate valve seat? If so how?
I have previously removed one by using the valve as a drift and beating on it. This time I want to dismantle it a little more carefully so as to assess typical wear of the valve and seat.

[twoqu]

Slide hammer experiment tomorrow!

[martinws]

I took mine apart last weekend to get a look at the valve stem and possibly getting it remade. The seat came out with a little gentle prying with a screw driver.
Possibly heat up the main body whilst dripping water on the seat to keep it cool.

[Error404]

Mine came out with a gentle tap when I stripped mine for inspection & a tidy up
Seat looked perfect, there was some very slight scoring on the stem. I took a thou off it in the lathe and polished it.

EDIT: Guide looked good, I'm not sure what kind of clearance there should be but it didn't feel too loose. I think the guide would need to be pressed out

[martinws]

I got the guide out with a small imperial socket(can't remember the size) as a drift and had to give it a good whack to get the first bit of movement.

This was actually a spare gate. I have a lot of leakage down the guide on my car and keep getting max boost exceeded faults.

[twoqu]

Thanks for the replies!
I managed to extract the seat by tapping it out using the valve by hand. A few in and outs and it was dislodged.
As expected the bottom 1/3 is quite heavily galled on one side with some damage near the top of the stem as well.
The valve itself has a surprising small contact margin. The valve has a stem of 9.90mm with a @37mm diameter head whilst the seat ID is @34mm and the OD is @38mm which leaves a 1.5mm margin.
Assuming the valve is not coated it should be possible to clean and have the stem honed. That would leave the valve guide to either be relined in situ or depending on the potential for damage, removed and replaced. Not sure on the material used for the guide as it looks grey (cast iron) rather than bronze as per a usual valve guide.
I know some companies such as EFI Express offer recon assemblies with guide replaced but I have not seen a replacement guide available. Unless anyone know where to obtain one from.
That would just leave gauging a guide clearance. For example would it need to be in the exhaust valve/guide region or is it dependent on the materials of the components as well as the environment.
So a bit more research is necessary.
MartinWS, as you have the guide removed can you post any useful dimensions!

[twoqu]

The valve has T-T33204 stamped on it at the top. Unable to find any information.
Of course even if an OE replacement guide were available it would not necessarily be helpful as the only way to clean the valve stem up would reduce its OD, thereby increasing whatever clearance there was.
Talking of clearance, its difficult to get an accurate measurement. Possibily in the 9.96mm ID range for the guide?
After market wastegate guide material seems to be stainless alloy such as Nitronic 60 which has anti galling properties.. Naturally if a batch of guides were machined we could reset a clearance assuming it was acceptable to clean the valve up in the first place. The EFI Express recon includes a new valve.
The valve stem clearance issue comes up a lot on Porsche sites but without an answer other than they throw the towel in and buy an aftermarket one. The OE wastegate is sort of iconic and durable apart from the diaphram and inevitable wear and tear, so if it can be put back to as good as new then I see no reason to discard it.
There also appears to be a company in Germany offering a 46MM Audi wastegate which presumably uses Porsche components!

[twoqu]

It does seem that cast iron guides and chrome plated valve stems are good practice in high temp/low(no) lubrication applications. Ironically its supposed to prevent galling which does appear to be the cause of a sticky wastegate. I have managed to slide something measured at 9.95mm down the guide so can only assuming the ID is going to be nearer a round 10mm.
Whilst the manufacture of the guides is probably doable once the dimensions are known, it would leave the issue of the valve itself. Cleaning one up would in theory deplete the plating (if it is plated). One possibility would be to investigate grinding/replating used valves which is probably cost prohibitive. The other is to replace both with matching materials which is what presumably EFI Express have done.

[newsh]

People who recondition motorcycle fork tubes use a process of heavy duty chrome plating and then grinding to size. If this is cost effective on a 2 ft long 50mm diameter tube then it should be reasonable for a valve stem. I just wonder if it would actually stay on there with the amount of heat it has to put up with.

[twoqu]

Its used quite extensively in the Marine industry as well. To be clear the process is hard chrome plating.
Of course if it could be applied a bit thicker than original that would allow the existing guide to be reamed out. I have seen one valve company quote a thickness of 0.3 -0.4mm which sounds like a lot. But even the extra 0.1mm might be enough.
If it stayed put for another 10 years thats reasonable considering the age of our wastegates.

[newsh]

Yes, that's it, hard chrome. I've got a couple of wastegates here, one of them is the original from my car which did 200,000 miles, it's a bit loose but probably still works ok.

[twoqu]

Done some more measuring of the valve. It is still 9.90mm for 2/3rds of length from top to bottom until it hits a noticable wear patch on one side where it gets as low as 9.83mm. Essentially that represents the movement within the guide of the valve stem from open to closed that is in the exhaust gas. Below it is a @10mm region that is slightly larger than the 9.90mm but I have not cleaned off carbon or indeed other material.
VAG seems to like round figures for the ID of its valve guides, 7mm for 20V and 8mm for the 10V. So I am wondering if indeed the ID of the guide should be 10mm which would leave a guide clearance of almost double of the 10/20V exhaust valves. Of course we are dealing with different environments and materials and no lubrication whatsoever.
I poked a 10mm drill shank (which didn't measure 10mm!) up and down the guide which cleaned some crap out of it and for the first time the valve slid down the guide under its own weight.

[twoqu]

I dug the old 10V wastegate out that I damaged previously trying to extract the guide. Interestingly (or not if no one is interested!) I noticed that the guide is a bright shiney colour rather than the dull grey of the 20V. So it would appear that Audi changed the guide material between the 10V and 20V for some reason. The 10V is non magnetic whilst the 20V is magnetic, supporting that it is cast iron of some sort.
The 10V Valve is in much better condition apart from a bit of discolouration and is still 9.90mm all the way down. The guide also appears to be smooth and undamaged internally. Attempts to measure the ID come out at 10.0mm.
I tried to press the guide from the 10V but the force only suceeded in distorting the mounting flange which is why I would prefer to not touch the guide. Seems to me a better way would be to either increase the OD of the valve stem by rechroming it or indeed have an over size stem new valve made and ream the existing guide out slightly. Of course without knowing for certain what an acceptable valve stem clearance is for a wastegate it would be trial and error!
I have asked EFI Express if they sell the valve/guide seperately as freight/duty/taxes makes the recon service prohibitively expensive.

[diesel des]

I'm interested! I think these audi wastgate are very durable compared to some aftermarket ones. Keep us updated as to how you get on.

[EspenW]

Interesting thread

Do some of you who have reconditioned/renewed the wastegate any logs, etc that show difference before after?
I can hear some leakage through the WG valve guide when doing a boost leak test, but never looked more into it as it is common.
However, reading more, I realized that a bad/sticking valve can cause boost taper at high rpm.
My T04E50 with KKK #8 tapers to 1.6ish at redline (from 2.2peak) in 3rd gear and up (tapers to 1.5 in 2nd gear). Not sure if this is due to the compressor simply not being able to deliver more at high rpm or if exhaust gas leaks past a bad WG valve.