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[paulr]

When doing the exhaust manifold how important is it to use the correct torque value of 20 Nm and not to tighten them tighter? The reason I am asking is I have done the gasket once before but didnt torque it just tightened it good and tight and it seemed fine ie no blowing, but over time (about 6 months) its started blowing again. Now if it was a warped manifold wouldnt it have started leaking straight away

[Marks DTM Calib]

What type of gasket did you use....a pattern composte type or the considerably better multilayer metal type?

20Nm should be more than enough if the manifold is flat....check it with a staright edge before fitting.

[paulr]

it was a multilayer metal type

[JasonH]

Bad luck. I wasn't able to get a torque wrench on all the studs so I had to guess the torque on a couple and it's been fine.

I'd try nipping up the studs - not too much - and see if any have worked loose.

[paulr]

will check studs when I do the gasket. Am I correct in thinking exhaust assembly paste like Holts firegum is no good at the manifold? How much is a manifold if worst comes to the worst (hope not)

[JasonH]

Don't use paste you'll never get a good even spread. I think it will make things worse.

The metal laminiated gaskets are the best and should be fine (perhaps even to reuse?).

I think a stud or two may have come loose.

The manfolds can warp a little - normally at the back near the down pipe and the rear stud shears itself off (usually with the help of some corrosion).

Most people say you can just flat them off with some emery paper.

A new manifold is £162 + VAT but there are lots about at breakers. Bound to be a few spare on this forum. It's not like they wear out.

But before you do all this check the manifold to downpipe joint. You can feel around it (cold engine for a few seconds) and should be able to detect a leak.

[paulr]

well done it now. it was the manifold to downpipe joint. Sorted out my coolant leak as well (touch wood) the metal coolant pipe thats bolted to the back of the engine

[JasonH]

Good news indeed  

[The Cambelt Kid]

well done it now. it was the manifold to downpipe joint. Sorted out my coolant leak as well (touch wood) the metal coolant pipe thats bolted to the back of the engine

Is the manifold/downpipe joint a big job at all?  as i think mine may be blowing??  I remember driving my car off the end of my drive when i first bought her and as i did i think i caught the lower part of the cats on the concrete, just as the front wheels dropped off the drive.  It's wasn't a heavy blow to the car, more of a slight knock, although i fear i may have caused some damage!

I hope that if there is damage that it's not the manifold gasket/studs...  

[JasonH]

If the car is something like post 98 it has fancy helicoil insert nuts on the exhaust manifold to downpipe studs.

With a bit of penetrating oil these should come undone. I think I had to show one my blow torch as well.

When undone you can just slip off the horrible fragile gasket and slip another one on. The gaskets cost about £5 each.

You can undo the nuts from underneath relatively easily you just need to add a couple of socket extensions together to reach the nut.