New manifold gasket...

[Arthurdaily]

Dear all, I need to replace the manifol gaskt on a minor, and was wondring if it seems as easy as it sounds, ie undue the nuts, e sure old gaskt scraped off and all carbon removed, thn put new gasket on..... rough bits away from block, manifold back on and tighten up !

Is that it?? Do you ned any gasket salant or anything? Thanks!

[IslipMinor]

Yes, basically as you have described. Would be worth soaking the manifold nuts in WD40 or thin oil for an hour or two before you try to undo them. If they haven't been undone for a while, you could also warm the engine up and apply the WDS40/oil to the manifold studs while hot and while it is cooling down - the oil will be drawn into the threads by capillary action, and can help. The nuts are brass, or should be, and to undo them, be very careful and turn them gently backwards and forwards, applying more thin oil/WD40 as you go. If you have any steel nuts already fitted, be extra careful as they could be very rusty and seized - more oil and heat cycles can help!

Once the nuts are undone, with care you should be able to ease the whole manifold away from the head without need to undo the down pipe, which is normally much more bother than the head joint.

Clean both head and manifold faces completely, put the gasket over the studs with no sealant at all, grease the studs liberally, but not the gasket, and then replace the manifold. A little more grease on the studs and unless the brass nuts are in very good condition, 6 new brass nuts (they are 5/16" UNF).

Hope you don't have a broken stud - good luck!

[Arthurdaily]

Hi8, thanks for a really clear answer!!

[bmcecosse]

Why do you need to renew the gasket ? Most unusual......

[Arthurdaily]

It appears to be blowing - though I'll be checking it again completely when I get a new battery and bits and bobs to get it started again... it was actually the previous owner who said it needed a new manifold gasket actually... I suppose to test it you just look for leaks when the engine is running?

[chrisryder]

a good way to check for an exhaust leak is to get a friend/enemy to put their hand over the tail pipe while you look for hisses and leaks.

it's a very good idea to do this when the engine is cold. otherwise hot tailpipe and hands don't mix.

prolonged blocking of the tail pipe will make the engine stall. if it doesn't, you've probably got a leak!

of course, this only applies to the exhaust bit of the gasket. it could be the inlets that leak...

[MarkyB]

Very unusual for the gasket to leak, my money would be on the manifold to downpipe joint, that's the common fault.

[Arthurdaily]

Ih, the manifold to exhaust is definately leaking!

[JOWETTJAVELIN]

These gaskets do go... I had one blow a piece off and there was a knocking from the engine when the gas escaped. I was amazed at the amount of power regained when I had a new one put on.