Loose Turbo Bolts - growing problem

[Eddy]

You buy a new car...that's what's next! If it ain't the turbo bolts, it's blowing intercooler hoses

Hoyhoy.

Tim, me is without an income & me is stubborn.

[Timbo]

Hoyhoy.

Tim, me is without an income & me is stubborn.

Eddy, I'd prefer to think of you as "patient"

[abreut]

Well I can join the list of people afflicted with this problem as well now. I actually have a mk1 golf with a 16vt so my scenario is a little different, but essentially its the same thing happening and it has happened at the last 2 trackdays now. I have been searching for a reason and I stumbled on this thread with great interest.

Last time I made sure everything was 100% tight before the trackday but by run 14 I blew the turbo to manifold gasket and it sounded like a tractor. The turbo was loose, I could actually rock it slightly.

I actually have m8 x 1.25 studs and nuts holding my turbo on but I don't think it is the nuts or studs coming loose so much as the studs stretching. My theory is that they lose their tensile strength through heat and then the yanking of the substantial exhaust is stretching them. I am going to check the length of the studs compared to an original set to test this theory, but I find it hard to believe that not 1 but 4 proper exhaust-grade lock nuts could come loose in 14 timed runs of Oran park just through vibration. The last 2 times I have bought crappy single layer gaskets and I think that this may have exacerbated the problem too, maybe a multilayer gasket would take up some of the load instead of the studs.

From reading this thread I have gathered that this problem mostly happens to polos but not to the same engine in the mkIV golf, and that they may have different exhaust setups. I think someone suggested it could be a difference in the exhaust setups which was interesting to hear. I have also noticed that its not just us but heaps of turbo-ed miatas, nissans, lotuses, xr6 turbos report issues with turbos coming loose especially when used at trackdays. People wonder why some people never have a problem and others are plagued by it.

I have only one brace going from the downpipe to the block which only really braces in one plane. I am going to strengthen it so that it provides support in all three planes. I have a flex joint but it is just under the car not near the turbo, maybe it would be a good idea to fit one closer as well. I am looking forward to hearing more developments in this thread, I really want to sort this issue out before the next track day!

[mikepologti]

were all hoping jimmy releases his invention in the near future no doubt if you wanted somthing similar , maybe jimmy could help you out.

[Jmac]

Ive now seen a couple of AGU golf with loose bolts too, un modified too so there really isnt a trend. The K04 i wirelocked recently doesnt get tracked now and it still came loose. I seen it recently and the bolts are still good and wire locking intact. The invention i have has come to a bit of a halt as it needs some fine tuning, in practice the last part didnt come into place the way i wanted it too. If it works it will stop the heads turning but wont stop stretch as such and i tend to agree that they must be stretching. Be nice if you could put a dab of weld on the bolt to manifold, and if the bolt ever need to be removed the dab of weld would snap off no probs. Hmm the problme is universal really , affects buses, trucks and all sorts of cars, back when i was doing my apprenticeship the Audi 80 TDI were bad for it and i also looked at a Sierra Cosworth that came loose. The Cossie had a poor result mind u
Still thinking
Cheers
Jmac

[abreut]

Would be good if there was a type of gasket that was able to take up the expansion and contraction instead of the bolts having to stretch.

I think removing any exhaust weight load will help too.

Maybe we need water-cooled bolts so they don't get too hot

[Skywalker]

I recently stated hearing a rough idling sound at times from my exhaust..When theres even a slight press of the accelerator the sound cant be heard..but at idle i have noticed it. It started after i took car to a highish speed on one occasion i think. Is this loose turbo bolts? Or in the loose turbo bolts case is that sound one would hear from the engine bay?

Thanks!

[Jmac]

loose bolts would cause a dip in power and the noise would be more apparent when you accel, as the turbo is pressurising trying to create boost, which gets blown out of the gasket where the loose bolts are. This is why they sound like a tractor when it happens.
Jmac

[Skywalker]

loose bolts would cause a dip in power and the noise would be more apparent when you accel, as the turbo is pressurising trying to create boost, which gets blown out of the gasket where the loose bolts are. This is why they sound like a tractor when it happens.
Jmac

Thanks guess thats not whats happnin with me (yet). Good to know

[woosh73]

loose turbo bolts / fix

Quote:
Originally Posted by woosh73
having a full time business on the side ( www.captain thread.com) problem : turbo bolts are loose. i caught up with h100vw ( top bloke ) . who showed me the problem

1. redo the thread with a helicoil to make the thread tighter
2. ( i would recommend this one ) - convert the bolt to a stud and use spring washers and nuts.

By the way if anyone wants anything fixed ( see my website ) mention that your a member and we'll look after you.


This is my business , my staff are experts in threads / bolts. This is the cheapest and the best way of alleviating the problem.
( Option 2 )
If you live in Adelaide and you have the problem give us a call. Then post up the result and the thread will stop.

Sorry about the forcefullness but we've done this before and it's 100% successfull.

[Jmac]

I thought about doing the stud and nut thing a way back but couldnt get 50mm studs for the job, also had one needing 70mm bolts as it is getting an ATP larger manifold coupled to it, even took it along to a couple of turbo places, also one bolt mob but they just had a blank expression and zero interest so gave it a miss, Ive done this repair to an XR6 turbo and worked well but havent heard of it being done to a Polo, be good to hear some feedback from someone who has as my lock device is a bit away. PLENTY of interested parties await the feedback
Cheers
Jmac

[woosh73]

loose bolts

You can get longer studs , and thicker diameter , we just cut the thread to suit.

[gldgti]

are all the VAG setups mentioned using M8 bolts? and they have a triangular flange right, with only 3 bolts or studs?

even my old T2 setup on my diesel had impressive DP bracketry, since the VW T2 flange was 3x M8 bolts (well 2 bolts and 1 stud). This isnt a lot considering the whole lot can glow well past cherry red if your really up it.

I'm surprised no-one has been gathering EGT data - i would bet money that this happens when cars spend certain lenths of time above a certain EGT threshhold. Why everyone that does a trackday in a turbo car doesnt have an EGT guage is beyond me.

anyway, from an engineering perspective all the evidence does indeed suggest that the setup is getting too hot and the bolts cant cope. you only need to go above 650*C before lots of things start to happen, creep sets in in the bolt material and even without an exhaust hanging off them, eventually they will stretch to a point at which theres no tention in them (while hot). depending on thermal expansion coefficients of the bolt steel and the manifold material, they may or may not still be tight once cooled down. evidence seems to suggest not.

forget the grade of the bolt, if they arent up to withstanding the temperature it doesnt matter how strong they are at 25*C.

the only way fo fix the problem at the source would be to change to larger diameter bolts as the thread man has suggested, or run a tune that results in lower EGT's.

[woosh73]

bolts

We have had huge success with the TD landrovers which had the same issues with the turbos and encreased the bolts on the exhaust manifold bolts with success.

[Eddy]

Hoyhoy.

This looks interesting.
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