Vacuum to wastegate

MGPA1935

Member
Evening All
i have my 90hp engine now running however the wastegate vacuum seems to be constant, when detached the engine runs and revs sweetly however return the vacuum pipe and starting and running not good. I suspect the vacuum control box is at fault. Any advise welcome also where can I obtain a control box?
 
Check all the pipe work is correctly fitted to the correct ports. Check the thoroughly the pipes individually for blockages, splits, porous and loose fittings. Only once all that is correct think about the control box. Have seen pipes nearly completely blocked before now. Also seen porous and loose pipes.
 
Thanks, will do again however the engine has only been run for a short time and it was noticed the control box was warm, could a solenoid be stuck?
 
More likely a turbo pressure air has been fitted to the wrong port instead of a vent or vacuum. Got to check each pipe individually end to end and then correctly fitted onto the correct component. Or someone has connected the internal vales incorrectly.
 
If you end up buying a vacuum control box make sure you get EXACTLY the right model, the letter on the end of the part code is important, whether it be a C (from memory) or whatever - I have two "spares" that are the wrong letter and don't work.
 
What part number is already fitted? AndyP could be on to something if it already has the wrong part number fitted.

For an ATL engine the part number is 6Q0906625G

Perhaps @AndyP may be able to check the 2 with the wrong part number letter to see if they are "G". The "F" model is for the BHC engine.
 
What part number is already fitted? AndyP could be on to something if it already has the wrong part number fitted.

For an ATL engine the part number is 6Q0906625G

Perhaps @AndyP may be able to check the 2 with the wrong part number letter to see if they are "G". The "F" model is for the BHC engine.

Yes, so after a quick check in my junk box, the one labelled 6Q0906625B has 2003/Polo written on the back (by a breaker I assume), the other is identical, but with no letter suffix (6Q0906625) definitely didn't work either. I think I recollect that the car would start but not run, until I got a 6Q0906625G and it was 100% first time.

The "G" models appear to be much rarer, more expensive and while some eBay seller claim compatibility with others versions etc., my experience with the TDi90 suggests otherwise.
 
For example, this seller claims it's a C or G, when it looks like it's actually neither when you compare their image with mine:
s-l16002.jpg


These are my spares:
PXL_20220421_111622096.MP.jpg
 
Morning

Thank you for your input.

My engine is ATL and the control box is marked with 600906625C interestingly has a blue/green cross and barcode label on the back, possibly the cross is a breakers mark?

Andy (sorry Andy should have said Audifan 08.08hrs) is saying it should be a G model, do I need to check with Audi?

I am starting to feel my car has had quite a chequered history.

I purchased the car privately, on test seemed to drive nicely, on drive home she dropped into limp, I was a bit cross. Starting was a problem and limp mode a regular nuisance but I persevered. I then felt a front wheel bearing was going and purchased the necessary but found in fact it was a universal drive shaft failure.

So after speaking with a couple of people it was considered the turbo needed attention, I decided to take the engine out and rebuild the front suspension, brakes, drive shafts. While engine out the turbo was rebuilt and did clutch and timing belt, turned out dual mass was shot and replaced with single mass.

All in all not the best car purchase. I have over the years rebuilt many pre and post war cars, anything with a black box is a bit more of a challenge, an A2 I was hoping should perhaps be considered a classic!!

706FD5D3-BDA5-47E4-AD57-B76F90B6F5A4.jpeg


97F27E97-3AAA-4467-A125-9BB298FF3334.jpeg


D2B1F582-31E7-4AE2-BC7A-91E07CB14D12.jpeg
 
Last edited:
Evening All
i have my 90hp engine now running however the wastegate vacuum seems to be constant, when detached the engine runs and revs sweetly however return the vacuum pipe and starting and running not good. I suspect the vacuum control box is at fault. Any advise welcome also where can I obtain a control box?
Hi MGPA1935,
I may be wrong but the 90 bop is fitted with a Variable vane turbo which doesn’t have a wastegate!
The air/vacuum line operates the vane actuator, this must be free to move with only finger tip pressure with the actuator disconnected or it will lead to limp mode from over or under boost (has a VCDS scan been carried out?)
If a waste gate turbo has been fitted it will be the wrong turbo.
Hope that helps
Keith.
 
Morning Keith

Shows my ignorance, you are right it is a vane actuator, the turbo being rebuilt is as you say free to rotate by finger tip. I was impressed by the difference, the vanes were virtually solid, hence the advice I got to get the turbo out.

Thanks for your input.
 
Good morning

I have checked with Audi, the correct part No is 6Q0 960 625 C which has been superseded by G. Not available in UK and would be on back order from Germany possible delivery in a few weeks £350-£400.

I have ordered the one on eBay and fingers crossed will do the job.

Thanks again for help.

Best
Richard
 
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