Manifold Exhaust Leak - How Difficult

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Billy1972
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Mon Mar 18, 2019 1:08 pm

Hi,

Saturday my exhaust started blowing after a long drive and I'm 99% sure its coming from the manifold gasket?

How big a job is it to replace the manifold gasket/s on a 1987 (31.12.87) 325i convertible?

Is it the 2 x heat protector gaskets I need?

Thanks
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aimlessrock
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Mon Mar 18, 2019 1:31 pm

assuming the studs don't shear its straight forward.- take your time
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Brianmoooore
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Mon Mar 18, 2019 1:59 pm

aimlessrock wrote:
Mon Mar 18, 2019 1:31 pm
assuming the studs don't shear its straight forward.- take your time
The reason its's blowing is probably because a stud has already sheared. The cast iron manifolds on RHD M20s are prone to warping, putting extra strain on the end studs, and breaking them. Even if you find no studs are broken (and manage to keep it that way), use a straight edge to check that the manifold face is still flat, and if it isn't, take it to an engine rebuilder to get it ground flat.
Take the greatest care not to shear studs - cut the nut off if necessary with a nut splitter. As a minimum soak them for a couple of days with rust releasing fluid.i
There is a tool available that is ideal for this job, but they're not cheap. It's a RF induction heater, where you place a small coil of about three turns of wire around the nut, which heats the nut to red hot when the power is turned on, which should release the most stubborn nuts. If you have a friendly garage, it may be worth finding out if they have one, taking the car there and loosen all the nuts up for you.
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Billy1972
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Mon Mar 18, 2019 4:49 pm

Hi, many thanks for the updates. It's going on the ramps on Saturday so i'll have a good look and check the studs. If it just needs gaskets which do I require because I've done a quick eBay look and there seems to be a couple of variations? Also should the iron manifold be broken is there anywhere you would recommend for a replacement? Thanks
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aimlessrock
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Tue Mar 19, 2019 8:54 am

if you manifold turns out to be cracked and beyond repair then put up a post in the wanted section.
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BenHar
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Tue Mar 19, 2019 2:18 pm

I think the OP is talking about the joint between the manifold and the downpipe.

The broken stud references are to the manifold to head joint.

Ben
Billy1972
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Wed Mar 27, 2019 10:46 am

After being on ramp and from looking underneath I'm missing a stud which means it could be missing or more than likely broken off into the head.

So guessing this is a big job now and if it's a broken stud am I looking at an engine out to remove it?
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BenHar
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Wed Mar 27, 2019 1:04 pm

Just need to remove the manifold.

With any luck there will still be some of the stud to get hold of.

Ben
Billy1972
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Wed Mar 27, 2019 1:06 pm

If not then is it an engine out job?
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Brianmoooore
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Wed Mar 27, 2019 1:31 pm

It would be a lot easier with the engine out (or cylinder head off), but is possible with everything except the manifold still in situ.
The most important thing is not to make the problem worse by drilling a pilot hole in the stud off centre or not straight, or, most importantly, by breaking a stud extractor off in the hole
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