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Audi A3 Turbocharger Overboost

A turbocharger replacement is needed

The dreaded P0234 Turbocharger Overboost code appeared on my car a few months ago,  (January 2022) to be exact.

The code was 000564 – Boost Pressure Regulation, P0234 – 000 – Limit Exceeded (Overboost Condition) – Intermittent.

I’ve been driving my car for another few months, however the performance of the car has been getting slowly worse overtime. I’m at the stage now where if I boot it in lower gears when the revs get to around 3000 the car will start to smoke pretty heavily, and if I go up a hill I used to be able to climb up easily in around 4th gear, the car almost feels flat. The Audi now drives as if it has no Turbo or Torque. I’m summising this is because the VNT vanes are jammed up, rather than Turbocharger damage, because it’s a common fault with the BKD engine.

ADMIN NOTE : The flat car and poor performance was caused by the same hose popping due to failing turbo. Look for oil stains as a sign

Browse eBay to buy rebuild kits, new CHRA cores, new Turbos, or Turbo parts [ AFFILIATE LINK – OPENS IN NEW WINDOW ]


I had already decided I was going to be buying a genuine Garrett GT1749V Turbocharger from Darkside Developments, alongside a new Oil Line for the car. Instead of purchasing the factory line from the dealer I’ll be buying this too.

If you’re a reader of my blog, you may recall a few months ago I popped a boost hose when coming home, and had an intermittent performance issue that I wasn’t able to identify. I now suspect all of these items were related to the Turbocharger. After all, when the boost hose pops on the car, a lot of the time it’s a red herring on the VAG platform and potential signs of another failure, or fault that has been unidentified. Sometimes you’re lucky and it’s simply a boost hose with poor ears due to bad design from VAG, but sometimes you’re not.

My problems seemed to occur after I overfilled the engine oil, rather than drain it off, I tried burning it off by idling the Engine more. That didn’t work, but I think I made the problems worse, as the overboost condition seemed to occur around the same time as I overfilled the engine oil. Now, the Turbocharger won’t be happening immediately, although it will probably be done in the next month or so, I’m busy collecting everything to do it right first time.

I jacked up the car on the weekend, and hooked up my Mityvac to the factory Turbocharger, and the VNT vanes on this appear to be VERY seized. To the point where the rod barely moves. I’m assuming that it’s not the actuator, because my car still pulls well in the lower gears, and upper gears until it hits overboost. So obvious the vaccum is still being applied, it’s just not there fully.

I could use the old Mr Muscle to clear up the VNT vanes (which I might do until the Turbo is replaced), although the preferred method is to strip down the Turbocharger and clean it completely. In order to strip down the Turbocharger however, you have to remove it anyway. It’s going to take just as long to remove / reinstall / clean it as putting on a new Turbocharger so I thought what’s the point.

Given that I don’t know the condition of my factory Turbocharger I’d rather opt to replace it entirely. The replacement will cost me in the region of £800-900 because I’m installing myself, and opting to use a Genuine Garrett unit rather than the aftermarket Mellett ones.

I could remove my factory Turbo and clean it, and it could fail shortly after. The factory Turbocharger on my car has lasted a total of 135,000 miles already (and could probably do more if cleaned). However, I’m about the 3rd or 4th owner of my vehicle, so have no idea how it was driven before me. I feel more comfortable when I fit the parts myself, because I know the work that’s gone into the vehicle to maintain it.

Replacing the turbo I’ve budgeted around £900 (I’m buying Oil, New Feed / Drain Pipes, etc). Even if the replacement Garrett lasts 50,000 miles, that’s still around 5 years of driving for me. £900/60 = £15 per month for a new Turbocharger and reliability with peace of mind. Realistically I expect the Turbo will last me around 100k + but who knows. Either way, it makes my car far more reliable, and is one of the bigger items that tends to go on cars. So it’s easier doing it now, rather than it taking out someting in the long run.

The benefit of replacing the Turbocharger, is that I’ll have my old unit to keep as a spare. I’ll be inspecting and cleaning it. Then rebuilding it with a 360′ Thrust bearing and some upgraded bearings. I don’t care about a performance increase with the Turbocharger, or faster spool times. I simply want a stronger unit than factory made with the same spool up. Then I can just sit this on a shelf keeping it pretty until I ever need it, or use it for a future project (I’m debating about making a self contained Turbo with built in Oil System)

I’ll be posting pictures of my old Turbocharger / New Turbocharger when they’re received, as a comparison. So I can strip down and inspect the old one to see how badly damaged it was at a later date

UPDATE – The turbocharger has now been replaced, performance is back

UPDATE 2 – Turbo Charger teardown photos


Browse eBay to buy rebuild kits, new CHRA cores, new Turbos, or Turbo parts [ AFFILIATE LINK – OPENS IN NEW WINDOW ]
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