[Closed] VW Golf Mk5 (2008) turbo overboost problem - advice please

Have you checked the hoses associated with the turbo for any leaks, you should here a rushing/hissing under load that would be the first place I’d look.

Wolly - unfortunately my car knowledge is non existent. But I don't fancy paying many hundreds of pounds for a new turbo plus fitting if chances are the problem won't get worse. If the likelihood is that it'll start happening more often then I would be inclined to get another car.

I had a very similar issue on an Astra tdi. Tried all the usual suggestions but never solved it

keep using the car to pootle back and forward to work

This was exactly what I was doing, ie not driving it hard enough. I changed my job, the driving got harder and faster and the problem went away in a couple of very black clouds out the back

Diesels eh?

i'm far from an expert but

that a new turbo is probably the way to go

Get it into a VAG specialist. can recomend one near southampton...

I won't try and sell it on here

If it's one of the intercooler hoses the whoosh noise should be noticeable (certainly was on my Mondeo) and it will belch a load of soot at the same time.

When you say it has an overboost issue is that something is that coming from fault codes or the garage?

Does it do it in other gears?

Turning off and on again resolving it sounds more electrical than mechanical to me.

VW specialist or different independent for a second opinion I'd say.

I took it to my local non-dealership garage yesterday, hoping it was a sensor/simple(ish) fix but the mechanic has said that a new turbo is probably the way to go.

That sounds like bollocks.

If the turbo works, then the turbo works. If it suddenly cuts out when there's a fault under certain conditions, then the ECU is detecting something possibly risky and going into limp mode to protect itself.

Given that it happens when you are accelerating hard, this is almost certainly overboost, meaning that it has detected too much boost pressure into the engine. Normally, there are these vanes in the exhaust that capture more or less exhaust gas to make the turbo spin. The engine opens them up wide when you floor it but as the revs climb and more exhaust comes out, it has to close them up a bit to avoid making too much boost pressure.

The vanes can get oil and grimy and get gummed up, so that they don't open and close properly and get sticky. So if the engine cannot shut them up quickly when it's sticky, it'll detect overboost and you'll be in limp mode.

Given that the car works ok the rest of the time it's probably jsut sticky and needs cleaning. You can use a variety of spray-in cleaners to clean it up; you can get under there and wiggle it free, or you can take it off and clean it with a toothbrush.

If you are near Cardiff I can take a look.

Fairly common issue with VAG turbo diesels. Could be a split hose but more likely the turbo is cloggged up inside, the vanes get coated in carbon. The standard advice is new turbo as they're made difficult to service, ie riveted casing, but the best advice is to find a turbo specialist who'll be happy to take the turbo apart and service as required. Definitely cheaper than a refirb or new unit. Find a VAG turbo servicing specialist, Google is your friend. There's one in Stevenage if you're in the south east.

Thanks for the offers to take a look and where specialists are - unfortunately I'm up North and all the people in the know seem to be dahn sauf.

Does it do it in other gears?

As others have said its gummed up games on the turbo.
Most garages will recommend replacement of turbo.
Had the same issue in a VW Touran.
The wife just kept running it as she was more gentle on the throttle.
Eventually traded it in after a couple of years of it first happening.

Random Question, where do you buy your fuel? Supermarket or branded?

Have search on "n75 sensor faults". It may help.

Splash-man, that is along the line with what I'm thinking. I know it could go catastrophically wrong, but it's not so long ago that I had the timing belt changed and feel that the car owes me at least a few more months.

where do you buy your fuel?

Sticky vanes in the turbo sounds likely. A mate of mine has a 2.0 tdi and that would go into limp mode every so often because of that issue.

Google “mr muscle turbo”. As above, probably turbo vanes sticking.

Fixed two VAG tdis of mine and done as a preventative measure on my current.

Alternatively new turbo or get it cleaned by someone who knows what their doing.

Edit: maybe try Forte Turbo cleaner, this gave one of my Tdis another 6months, although I think I messed up the gearbox by ragging it a bit too much (280k on the clock)

unfortunately I'm up North and all the people in the know seem to be dahn sauf.

Where in the North are you?

I know a few people I’d recommend in North or West Yorkshire.

I can't comment on your specific issue but my B.I.L had turbo issues on his 330d which he kind of ignored until it completely failed and resulted in catastrophic damage to the engine. Many thousands to repair.

Anyway, as abovem check the plumbing for a boost leak, check the maf and if needs be get the turbo rebuilt.

My motor home has a blow off valve that bleeds off excess turbo pressure and occasionally jams shut leading to the exact symptoms you're seeing.

Where in the North are you?

Recently had the same problem here on a T-reg Audi A4. Read around a few websites and a few suggested the problem being that the engine wasn't being revved enough. I was tending to change gear before 3000rpm trying not to be hard on the engine but it seems this was making it worse. The website I found (can't remember what it was) suggested putting car into 3rd and then flooring the accelerator at 1200rpm. If it loses power, switch off and restart and then repeat the exercise. If it is still consistently losing power after the 3rd attempt then it may be the turbo is stuffed (according to what I read - I know squat about car mechanics).

In my case second time round it was fine. Tried it a few times going up and down the A3 and discovered acceleration I had no idea existed (well for a 19 year old diesel anyway). Next thing I did was fill the tank with premium diesel. Now I regularly run the engine to 4000rpm and it is running perfectly - not had the issue in the last few hundred miles and just passed MOT without advisories. Probably blow up tomorrow..

Sticky vanes as others mention.

Exact same symptoms on my 04 VW T5. Tried various turbo cleaners but nothing was effective. Ended up getting the turbo internal replaced by “the turbo guy” (google them) on south side of Glasgow. £200ish plus the removal/refitting from memory.

You could try doing 80mph in 4th for an extended period of time. That might help burn it all off. Or it's definitely worth a can of Forte turbo cleaner. Forte is supposed only to be sold to the trade but they are always selling it on on eBay.

Following. My 16 year old Mk4 Golf has developed same issue

You could try doing 80mph in 4th for an extended period of time.

You mean 70mph yeah? 😉

70 in 3rd.

As I had something similar happen with a B5 Passat which turned out to be the boost sensor. I would pull the connecter off the boost sensor, give it a spin and see if it drives any different. sensor on my car was on the hose between the intercooler and the inlet manifold.

I had a Honda which shut itself down under high boost periods. Turned out it was under fueling due to a blocked fuel filter.