Exhaust Manifold Nut Tightness?

[jjbunn]

I had a leak from one of the studs on my exhaust manifold, so bought a set of new studs, lock nuts and gaskets, and fitted them (with red Loctite on the studs).

At first I didn't tighten the locknuts too much, but there seemed to be exhaust gas leaking from all four ports. I tightened them down pretty well, but no real change. The manifold appears to fit very snugly, so I'm baffled.

Now I'm wondering about the gaskets: should I have used some sort of sealant on the gaskets?

The other possibility is that in the meantime my head gasket has sprung a leak, but I prefer not to contemplate that :-)

I'd welcome any advice, thanks!

[TobyB]

The nuts typically need to be as tight as you can get them with a combination wrench,

and they also want a re- tightening a couple of times after you do the job.

If it leaked for a while, it may have eaten the gasket, after which no amount

of tight will help- sorry.

No, no sealant, but anti- seize on the studs does make things easier next time.

If you got them pretty tight at first, you might have a warped exhaust manifold-

unusual, but not hard to fix-

just get it cut flat by a machinist.

Might also be a crack- they do crack sometimes, especially with lean mixtures.

Probably not the head.

Don't let it leak any longer than it has to- it can damage both the head

and the manifold.

hth

t

[Napes]

Correct torque on these nuts is 22-24 lb-ft.

http://www.bmw2002faq.com/content/view/48/32/

Bob Napier

[c.d.iesel]

the face of the exhaust manifold will over decades

and 1,000's of miles of leaking, heat cycles become

very rough and uneven so sealing is not happening.

Remove the manifold and resurface it on a glass

surface with course Emory cloth taped down.

After your first pass you'll see how warped and

nasty that sealing surface is. Keep sanding untill

the sealing surface it true and clean - THEN

reassemble with NEW heat-shield-one-piece

320i gasket.

[BillWilliams]

If you will replace that exhaust gasket, there is one from a later car that incorporates a heat shield to protect the plug wires. It works pretty good.

Copper nuts help too when the removal day comes around.

[BillWilliams]

Looks like Bob, Uncle CD and I woke up at the same time.

[Hans]

If you want to use a torque wrench, you will need thin wall socket - or better still 1/4" drive with wobble extension to set in there, PLUS crow's foot adapter for some of bottom ones as I recall. Easier to install off the car.

[jjbunn]

Thanks for all the advice. I'll try loosening the nuts are re-torquing to 22ftlbs.

[jjbunn]

This turned out to be something different: it was the valve cover that wasn't tightened down enough, so oil was seeping through it and burning off on the exhaust headers.

I'd replaced the valve cover gasket, and been overly cautious about tightening the acorn nuts.

[BillWilliams]

In your initial post you said "exhaust gases were leaking". How are exhaust gases leaking from your valve cover?

[c.d.iesel]

jj - you should have wavy (not split) washers under those

acorn nutts , please.

[jjbunn]

In your initial post you said "exhaust gases were leaking". How are exhaust gases leaking from your valve cover?

I put 2 and 2 together and made 5 - I assumed the smoke I was seeing was from the exhaust manifold I'd just refitted, whereas it was in fact from oil burning. The smoke looked like it was appearing from the manifold.

[jjbunn]

jj - you should have wavy (not split) washers under those

acorn nutts , please.

OK! Right now I have regular washers under them, so will get some wavy ones.

[lilmo]

Last set of valve cover acorn nutz I ordered from BMW had built-in flat washers. They were taller, too. What's up with that?