mx5cartalk.com

Half way up the mountain to Cabramurra yesterday I heard something go tink tink tink under my car then every time I applied load to the engine it made a whole heap of noise like a leaky exhaust gasket.

When I got home I found that 2 of the bolts holding the exhaust side of the turbo housing to the the bearing assemply had fallen out and all the others were loose. I would have lost a 3rd bolt but the oil drain fitting stopped it from falling out, it was finger tight and 1/3 of the way to falling out. The bolt holes go all the way through the housing so the exhaust was escaping through the bolt holes.

I replaced the 2 missing bolts and tightened all the others and it's all all quiet again. It's taken 2 years and 50k km for the bolts to work their way loose but I would have thought they would be a set and forget thing for the life of the turbo.

Does anyone know if there should be some kind of locktight stuff used to hold the bolts in or did the guys that reassembled the turbo after applying the heat coating just not torque the bolts up tight enough? Anyone else ever had these bolts fall out or come loose on a GT2560r turbo?

Did they put them on with washers? (BTW - not heard of this one before)

There weren't any washers on the turbo in the car or on my old turbo

FM has a fix for this, it's discussed elsewhere on the forum I think

Spring washers wont help this, and I cant think of any Loctite's products that might ...

The Turbine housing gets 'a little hot' and has massive heat stress.... in that it goes through a number of heat / cool cycles every time you drive it ...
This will soften the heat-treating of any spring or locking washers you put in there ...

you could try a mechanical locking type washer (like the one below, but slightly better quality )


other than that, torque to manufacturers specs and ALWAYS USE NEW BOLTS .... the same heat stress issues change the plasticity of the bolts and makes them next to useless to reuse ....

Good luck
J

get the Nissan RB20 housing studs.
not cheap though at $8 each, get their retaining clips as well ($6 each you need 2)
The nuts for those studs are also $8

I've just replaced the manifold to head nuts and stud, checked them today and all were nice and still torqued as per friday before the run. Not bad considering i hit the hot end of the temp guage when i got stuck behind the commodore running up the mountain.

I had this same problem just last week, driving along the expressway into uni and the exhaust got really loud, found out later on what the problem was. It is amazing how much noise can come out of an 8mm hole!

I don't know of any solution other than to replace them and periodically tighten/check them. I have even tried those nordlock washers on my manifold studs and they are pretty useless also.

Ampz, I am pretty sure he actually means the bolts which hold the turbine housing to the CHRA.

Cheers, Tim

Yeah, not the nuts/studs holding the turbo to the manifold, the bolts holding the turbo together. There's about 8 on the compressor side and 8 on the turbo side.

Garry, It might be worth talking to Bryan Miller from Eastern Race Parts in Sydney (02 9526 6666). He supplies (among other things) nuts and bolts to most of the professional race teams in the country and is extremely knowlegable on fasteners. I was discussing my manifold problem with him and he can supply special nuts that will allow me to get a spanner to them in place. You will need to know the dimensions of the bolts in question and ask him what he would recommend. Won't be cheap, but I'm guessing you don't want to do them again.

50,000 is a pretty good innings. Whether any "Loctite" was used will I am guessing be impossible to tell. As far as I am aware it is normal to use a washer under a bolt which I think is beneficial for applying an even load. The Loctite approach is also quite a normal and useful process. The Nissan fasteners may be good but who knows unless there is some data to support. If one is aware of loosening of fasteners on our around the turbo then a routine maintenance of re torquing or replacement of fasteners might be wise. On aircraft it was common to actually wire fasteners in place though I am not sure if that is still practised. Talking to a a fastener expert as suggested would be worthwhile.

Thanks for the advice guys. Surprisingly for an SP they are easy to get to so a regular tightness check is no big deal. I'll wait for a while and see if they stay done up before I worry to much.

BD,

I'm not sure why your manifold nuts are coming loose. When the Mazda dealer replaced the head on my car they would have refitted the manifold. They appear to have just used the regular MX5 studs and nuts and after 100k km everything is still done up nice and tight. I checked them on Sunday night when I was looking for the exhaust leak.

oh crap, you mean the chra bolts came loose?
I've never had that happen to me in 15 years of turbo ownership and modifying!
Loctite will be useless in that application anyways as the heat will just burn it off.
Are the bolts interlocked by the chra plate?
If so check that the plate is not warped (had this happen on a T3 once).

You're lucky the impeller didn't contact the housing.

ampz may be right about the temperature. However their are a lot of Loctite products and something may be suitable. I am sure you could get technical advice if one of the products is going to be effective- eg product 268?? Try this link //www.type2.com/library/chemicals/loctite.htm

Drop in to autobarn of bursons and tell them what the problem is. There are nuts available (copper I think) that will lock on better, or there are clips availalble to stop the bolts un-doing. It's a pretty common with imports once the turbo has been swapped or removed a couple of times. Dump pipe bolts also like to loosen themselves in a similar way once they have been disturbed so check them also.