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help with exhaust manifold to downpipe gasket leak

Joined
Jun 8, 2016
Location
Santa Barbara, CA
Hello, I had to drop my exhaust to get at my transmission cooler lines and now I am having trouble sealing the flange between the downpipe and the exhaust manifold. I did some searching, and found this thread, which had some good information, but left me with questions

I purchased a new gasket, made by victor reinz dana. I simply wiped off the mating surfaces and threw the gasket in. When I was pushing the downpipe back up onto the three studs I noticed that the two didn't want to mate perfectly flat, and I was getting a gap at the stud that is in the bottom right of the photo. (Before you say this is a sign of a bad engine mount, I replaced the right side mount with a HD mount last year, along with the trans mount. So I don't think the engine is sagging.) I used the bolt to close the gap on that side, and it didn't give me too much resistance. I then added anti-seize to the bolts and tightened to 28 ft-pd. I noticed I had a leak and upped the torque to 35 and then 40, both times I didn't notice any change in the leak.

The bolts I'm using are probably the stock bolts from 1983, they are not flanged and are 15mm (gasket looks original, has Volvo stamped on it). With the anti-seize they spin on, so I'm sure I am applying a good clamping force to the flange.

I have a couple thoughts. Maybe the downpipe is getting held up by either the weight of the exhaust or the bracket that holds it to the trans. When I have the downpipe in place, I cannot move either 'fork' of the bracket without a pry bar because they are wedged up so tight against the plate attached to the trans (which they get clamped to). Do I need to separate the exhaust to take the weight hanging off the back off of it off, or move the bracket on the downpipe (which is bolted to the downpipe with some extremely rusty bolts). Second question is, are flanged nuts going to help at all in this situation? Third idea is to inspect the header and downpipe some more. I noticed that the downpipe had some jagged edges around where the through-hole for exhaust gas is. The part that has me confused, is that I can see a clear indentation in the gasket where I drew the red line. So the gasket was getting smushed, but not along the edge of the through-hole where it is supposed to form a seal. This makes me think I did have enough force to overcome any torque from the exhaust hanging off. (I had the downpipe supported with a jack about where it goes from 2-to-1, on the double pipe part.) Lastly, would anyone recommend trying two gaskets, just to have more material to squish?

Thanks for any and all help
photo https://imgur.com/a/o6KZzOg
o6KZzOg
 
Loosening the bracket to bellhousing should help it seat better, then tighten the bracket after the bolts to the manifold. Not really getting what your saying about an indentation on the gasket unless it was seated wrong once and crushed before installing correctly.

Doubling up for protection is always a good idea.
 
Here is a photo of the actual gasket, that should help clarify what I mean. In the photo, I can see in the center of the photo, the gasket is indented (from being crushed) towards the edge of the gasket. On the left side of the photo much closer to the through-hole for exhaust, where (correct me if I'm wrong) it is supposed to crush the gasket and form a seal
 
Did you wire brush or scrape the mating surfaces clean?
I like to use a thin smear of copper RTV on those gaskets if the flanges are beat up.
 
No, I didn't. I just wiped it with a clean rag and brake cleaner. Do you wire brush the surfaces? I can try that, I thought that might scratch the mating surface, and scratches cause leaks. But I didn't consider that rush powder also causes leaks. I could try to polish the surfaces with a dremel if you think thats the best option. There was some jagged bits on the downpipe along where the pipe comes through the metal plate (that the nuts push on). should I file those down. I was afraid to do anything to the surfaces in fear that I would damage them.

Thank you for the help and tips, I appreciate it.
 
Usually there’s a bunch of gasket material left if someone used a graphite composite gasket. And rust. Lots of rust.

Those steel gaskets need 2 nice flat surfaces to seal. So you’re probably going to want to loosen up the center section of the exhaust so it can wiggle freely.

When all that fail, Ultra Copper RTV.
 
Is it good enough to break the exhaust at the resonator, or are you saying to break it at the cat? And there was no gasket material left that I could see, it was a volvo steel gasket (original I think).
 
Is it good enough to break the exhaust at the resonator, or are you saying to break it at the cat? And there was no gasket material left that I could see, it was a volvo steel gasket (original I think).

Either one should be fine, what ever is easiest. And make sure the DP is loose at the bellhousing bracket as well.
 
alright hate to drop in as a n00b, but this car is an '83; is a 94 turbo going to have a gasket between the downpipe and exhaust also?? I picked up a 940 I'm fixing up and don't remember there being a gasket between them....
 
alright hate to drop in as a n00b, but this car is an '83; is a 94 turbo going to have a gasket between the downpipe and exhaust also?? I picked up a 940 I'm fixing up and don't remember there being a gasket between them....

No, a turbo car does not have the gasket discussed above.

The downpipe seals to the turbine housing with a conical seal.
 
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