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240 Leaking Exhaust | Manifold-Header Junction

Rusty_ratchet

Rusty_ratchet

Member
Joined
Apr 14, 2015
Location
Southwest
My mom's '91 240 has an exhaust leak at the junction between the exhaust manifold and header pipe. I replaced the gasket (OEM Volvo) and studs and it still leaks. I do not believe there are any cracks in the manifold or header pipe. I also made sure that the bolts are tight. Any ideas for things I should look into?
 
Last edited:
hiperfauto said:
Most likely one of the pipes is broken at the weld to the flange.
Click to expand...

Thanks I can check that. I am pretty sure the gasket is leaking though. I checked it by connecting an shop vac to the tail pipe and sprayed soapy water on the area. There were a lot of bubbles coming out of the junction where the gasket is located.
 
How well did you clean and inspect the gasket surface on the manifold? If the surface is rough or rusty, it may require re-surfacing.
 
I don't have an opinion on exhaust sealing compounds because I don't use them. I have a machine shop close by, so I'll have the manifold re-surfaced if necessary. Leaks at the slip joints are usually caused by improperly installed or inferior clamps.
 
OP, did your mom have a new downpipe installed? Those you get these days, regardless of whether from the Volvo dealer or elsewhere are not as carefully made as they were back in the day. Poor welds at the flange and warped flanges are what I'm thinking of.

Take it apart and get a straightedge on it if you don't immediately see the soot trail from a cracked pipe. I've used the shop vac to locate the problem area, but the problem itself needs a good pair of eyes to find.

exh483.jpg
 
hiperfauto said:
How well did you clean and inspect the gasket surface on the manifold? If the surface is rough or rusty, it may require re-surfacing.
Click to expand...

I just gave it a quick clean. The surface didn't look too bad to me, but I don't have much experience with this. By re-surfacing you mean take the header pipe and manifold to a machine shop?
 
cleanflametrap said:
OP, did your mom have a new downpipe installed? Those you get these days, regardless of whether from the Volvo dealer or elsewhere are not as carefully made as they were back in the day. Poor welds at the flange and warped flanges are what I'm thinking of.

Take it apart and get a straightedge on it if you don't immediately see the soot trail from a cracked pipe. I've used the shop vac to locate the problem area, but the problem itself needs a good pair of eyes to find.

exh483.jpg
Click to expand...

No, I am pretty sure it is the original down pipe. I'll check for warped flanges when I get home from work today. Thanks!
 
Rusty_ratchet said:
No, I am pretty sure it is the original down pipe. I'll check for warped flanges when I get home from work today. Thanks!
Click to expand...

OK, if original, I doubt it is warped. I'd suspect that cracked pipe hiperfauto warned about. Close inspection will eventually reveal the leak. Sometimes I wonder if our lives are all about the challenge of keeping gases and liquids where they belong.
 
Is the support bracket still in place on the bottom of the down pipe?

This bracket helps support the pipe and takes most of the overhung load off of the gasket joint.

I've fixed a few leaking exhaust leaks at this flange by simply installing and tightening the flange bolts before installing the bracket....clean and lube the bolts (small amount of Copper anti-seize is what I use) on the manifold, make sure the flange is pulled up square and tight....then torque the bolts to spec.
At that point, attach the bracket to the pipe and tighten all the bracket bolts.

On some cars, people in the past have removed this bracket and failed to re-install it.
Same effect.
 
coalminer said:
Is the support bracket still in place on the bottom of the down pipe?

This bracket helps support the pipe and takes most of the overhung load off of the gasket joint.

I've fixed a few leaking exhaust leaks at this flange by simply installing and tightening the flange bolts before installing the bracket....clean and lube the bolts (small amount of Copper anti-seize is what I use) on the manifold, make sure the flange is pulled up square and tight....then torque the bolts to spec.
At that point, attach the bracket to the pipe and tighten all the bracket bolts.

On some cars, people in the past have removed this bracket and failed to re-install it.
Same effect.
Click to expand...

Yes, it has the bracket.
 
This is the surface that I believe is causing the issues. All I have done do it is try to clean off the anti-seize. I believe there is a very slight ridge around where the old gasket was. Should I lightly clean the surface with a wire brush?
34420789642_add0edc84b_k.jpg


It's probably nearly impossible to inspect a weld in a photo, particularly when there is anti-seize. This is an attempt.
33739605364_2b0d0c462b_k.jpg


34420784032_ca17819c6d_k.jpg
 
Go ahead and clean it with a wire wheel first, then use a flat file.

The pipes and flange look good. I don't see any cracks.

What does the manifold look like?
 
I cleaned up the top flange of the header pipe with a wire wheel as shown below.
34585961415_e33419f252_k.jpg


I started cleaning up the flange on the exhaust manifold, but it looks good and feels smooth (no bumps, ridges, etc). This is a photo before I started cleaning it. The photo after cleaning was out of focus.

34585961795_70c098b14d_k.jpg



The exhaust still leaks. I can feel puffs of air coming out of the flange and the car sounds like a tractor, so I will repeat the shop vac / soapy water treatment tomorrow just to double check that it is the flange and not a weld.
 
Starting from clean, like that, you should be able to see the tracks from the leak when you disassemble it next, if not with an inspection mirror. Sure looks in good shape over the internet. :)
 
cleanflametrap said:
Starting from clean, like that, you should be able to see the tracks from the leak when you disassemble it next, if not with an inspection mirror. Sure looks in good shape over the internet. :)
Click to expand...

Thanks, that's good to know.

Not to get sidetracked, but last night I noticed that the header pipe flexes and can be lengthened /shortened. This occurs at the point shown in this photo, but is under the heat shield of my header pipe. Is it supposed to be like this? I am wondering if it is not, and a weld under the heat shield is broken.
 
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