1972 350 exhaust leaks at the middle joint (transmission hanger)

[Patrick H.]

Hi all,

The orange 72 is about to leave for the summer. Before it leaves I need to repair an exhaust leak. Currently it is leaking from both the left and right side joints where the front pipe meets the rear pipe at the transmission hanger (see photo). I tried tightening the clamps, adjusted them a bit front and back, and it still leaks. They are leaking at the slip joint, not at the slits cut into the pipes to allow one to ride over the other. The slits are fully covered/blocked by the joint. The system was installed recently and there is no corrosion - you can see that in the photo.

I thought about using a band-style clamp, but a wide clamp such as the one below has a large piece sticking up that won't allow me to then use a conventional u-clamp to secure the exhaust to the hanger without modification of one of the parts.
I also thought about taking apart the joint, applying exhaust sealant and then putting it back together. However, I'm afraid of the sealant becoming like cement and making future repairs or leaks that much harder.

Any suggestions from others as to how best to stop the leak?

Patrick

[Joe L.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

Hi all,

The orange 72 is about to leave for the summer. Before it leaves I need to repair an exhaust leak. Currently it is leaking from both the left and right side joints where the front pipe meets the rear pipe at the transmission hanger (see photo). I tried tightening the clamps, adjusted them a bit front and back, and it still leaks. They are leaking at the slip joint, not at the slits cut into the pipes to allow one to ride over the other. The slits are fully covered/blocked by the joint. The system was installed recently and there is no corrosion - you can see that in the photo.

I thought about using a band-style clamp, but a wide clamp such as the one below has a large piece sticking up that won't allow me to then use a conventional u-clamp to secure the exhaust to the hanger without modification of one of the parts.
I also thought about taking apart the joint, applying exhaust sealant and then putting it back together. However, I'm afraid of the sealant becoming like cement and making future repairs or leaks that much harder.

Any suggestions from others as to how best to stop the leak?

Patrick

Patrick------

The leak condition you describe is usually caused by the pipes not being perfectly aligned at the joint. In other words, if the front pipe is, essentially, "immoveable" and the rear pipe is "adjusted" to correct some alignment issue, the problem can be created. Usually, it can be seen by just a very slight gap on some portion of the circumference of the joint. Correcting it can be a PIA. I think I'd try using an enclosed type ("guillotine") clamp instead of the open style clamps.

You can't use the type of clamp you picture at the crossmember joint (but you can use it at the muffler extension-to-pipe joint).

[Russ S.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

Take it apart and coat with high temp(red) silicone sealant and reassemble. It won't make it hard to take apart later.

[Dick W.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

Hi all,

The orange 72 is about to leave for the summer. Before it leaves I need to repair an exhaust leak. Currently it is leaking from both the left and right side joints where the front pipe meets the rear pipe at the transmission hanger (see photo). I tried tightening the clamps, adjusted them a bit front and back, and it still leaks. They are leaking at the slip joint, not at the slits cut into the pipes to allow one to ride over the other. The slits are fully covered/blocked by the joint. The system was installed recently and there is no corrosion - you can see that in the photo.

I thought about using a band-style clamp, but a wide clamp such as the one below has a large piece sticking up that won't allow me to then use a conventional u-clamp to secure the exhaust to the hanger without modification of one of the parts.
I also thought about taking apart the joint, applying exhaust sealant and then putting it back together. However, I'm afraid of the sealant becoming like cement and making future repairs or leaks that much harder.

Any suggestions from others as to how best to stop the leak?

Patrick

Permatex/Loctite have a very good sealer that you can carefully work around the leak. Not hard to take apart in the future

[Terry M.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

Chevrolet used a sealant at that joint for a reason. You can see the symbol in the AIM. I use a exhaust sealant from WURTH, but I no longer can remember where I got the tube.

[Randall K.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

I had a similar problem with my '72 454. I loosened the hangers at the back end, propped up the tail pipe with wood for a tight fit, and then shoved the whole assembly forward to get more pipe engaged between the front and back end. Tighten the clamps at the pipe junction, tighten the hangers, and then remove the wood props. Worked for me...

Randy

[Patrick H.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

I had a similar problem with my '72 454. I loosened the hangers at the back end, propped up the tail pipe with wood for a tight fit, and then shoved the whole assembly forward to get more pipe engaged between the front and back end. Tighten the clamps at the pipe junction, tighten the hangers, and then remove the wood props. Worked for me...

Randy

We did something similar last year when it started to leak. It's baaaaack.

[Randall K.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

I've repeated this as well. As long as it doesn't leak at the relicensing safety inspection...

[Patrick H.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

I've repeated this as well. As long as it doesn't leak at the relicensing safety inspection...

No such thing here in Michigan - though the car is licensed in Illinois.
I don't mind avoiding those at all. 3 years in PA with inspections was enough for me.

Patrick

[Terry M.]

Re: 1972 350 exhaust leaks at the middle joint (transmission hanger)

No such thing here in Michigan - though the car is licensed in Illinois.
I don't mind avoiding those at all. 3 years in PA with inspections was enough for me.

Patrick

No such thing in Illinois either and you should see some of the POS Hoopties dead on the side of the road here.