New bolts for exhaust elbow.

[Thresher]

Having managed with great difficulty to remove the stubs of the sheared bolts from the cooling pipe that attaches to the exhaust on my volvo md5b I now have to fit replacements.
They have lasted 35 years so I'm sure it won't happen again before the engine is replaced but what can be done to prolong the life of the replacement bolts. Should I use stainless steel bolts? add grease? some other compound to keep the two surfaces apart? I have some chromium oxide paste, could I use that?

 

[Poignard]

I'd use Coppaslip. There may be better things but I happen to have a tin of it.

 

[cryan]

Copaslip, copaslip, copaslip. Not only will it stop galli g and seizing it slows corrosion too. When I was an apprentice one of the old boys told me to never put a thread or gasket together dry unless the manual specifically states it. A very wise man!

 

[Thresher]

Coppaslip it is then. What is galli g?

 

[Poignard]

Coppaslip it is then. What is galli g?

Galling is something that happens with stainless steel nuts and bolts, for example. Sometimes, when they are tightened together the mating surfaces bind, making it very difficult, or even impossible to get them apart.

One way round it is to use an anti-galling compound on the threads, eg AG90 ( http://www.actioncan.co.uk/portfolio/ag-90-anti-gallinganti-seizing-lubricant-h1-food-grade/ ). Coppaslip or ordinary grease can also be used but I'm not sure if they are as effective.

Last time I had this happen was with a bolt and nut holding down a mast step. I was doing a trial assembly and didn't bother to treat the threads because I didn't intend to tighten down hard. Even so, it was imposible to unscrew it and there was no access to allow of sawing through it. It was Sunday morning and I was in a hurry so I had to buy a nut-splitter from Halfords (rubbish quality, btw!) to break the nut free.

Now I carry a tin of AG90 on board and use it on any s/s threads before assembly.

 

[cryan]

Coppaslip it is then. What is galli g?

Its galling written on a dodgy keyboard. Galling is as above

Also when I say copaslip I mean it in the generic (all ball point pens are Biros) sense. Other brands are available and just as good.