exhaust keeps breaking!!

[joey71]

I have a 97 sierra, 4wd, 5.7 w/195000 miles on it. I had the manifold back to cats replaced, now the exhaust keeps breaking on me. Sat. after getting off of the highway it cracked just after the downward bend on the passenger side, just before the o2 sensor. Took it back to shop and they welded it back together and took out the flange that fastens the front half to the cats back. Now I get off of the highway tonight and it cracked right where it comes out of passenger side manifold. Is there a reason for this and what kind of alternatives do I have. The shop says that there is not much he can do with it except for keep welding it-- (does not sound like an permanent fix!!) The front half of this darn exhaust costed me 315.00 and to have it installed was another 165.00, and I was wondering if this is common among Gmc and chevy-- (that is what the exhaust shop tells me. Thank you for any suggestions--

[joey71]

Originally Posted by joey71

I have a 97 sierra, 4wd, 5.7 w/195000 miles on it. I had the manifold back to cats replaced, now the exhaust keeps breaking on me. Sat. after getting off of the highway it cracked just after the downward bend on the passenger side, just before the o2 sensor. Took it back to shop and they welded it back together and took out the flange that fastens the front half to the cats back. Now I get off of the highway tonight and it cracked right where it comes out of passenger side manifold. Is there a reason for this and what kind of alternatives do I have. The shop says that there is not much he can do with it except for keep welding it-- (does not sound like an permanent fix!!) The front half of this darn exhaust costed me 315.00 and to have it installed was another 165.00, and I was wondering if this is common among Gmc and chevy-- (that is what the exhaust shop tells me. Thank you for any suggestions--

does anybody have a clue-- This damn thing broke again-- engine and tranny mounts are all in place and the pipes are nice and sturdy-- cant keep welding the damn thing-- FRUSTRATED!!!

[98SilvyKid]

Sounds like just a badly made manifold. Must have some manufacturing defects. This isn't really common for GM trucks, so this might make sense if you have a different brand header (aftermarket). I'd just get it replaced.

[kenny-1907]

It almost sounds like they do not have flexable hangers for the exhaust system. Have a look around under the truck around the exhaust system for the hangers, they should have a tab that bolts to the exhaust and one tab that bolts to the frame and a piece of rubber between them and if there is not , that is what is causing it to brake. Just a thought.

[frosty12345]

I know this discussion is incredibly old, but I was hoping you had found a solution seeing as i am now having this issue. Any suggestions?

[Schurkey]

Start by verifying that the engine and transmission mounts are in acceptable condition.

Next, how is the pipe attached to the manifold--is there a joint that allows some rotation?

How are the pipes attached to the vehicle--some kind of rubber straps to allow for movement?

[rhandwor]

Originally Posted by joey71

I have a 97 sierra, 4wd, 5.7 w/195000 miles on it. I had the manifold back to cats replaced, now the exhaust keeps breaking on me. Sat. after getting off of the highway it cracked just after the downward bend on the passenger side, just before the o2 sensor. Took it back to shop and they welded it back together and took out the flange that fastens the front half to the cats back. Now I get off of the highway tonight and it cracked right where it comes out of passenger side manifold. Is there a reason for this and what kind of alternatives do I have. The shop says that there is not much he can do with it except for keep welding it-- (does not sound like an permanent fix!!) The front half of this darn exhaust costed me 315.00 and to have it installed was another 165.00, and I was wondering if this is common among Gmc and chevy-- (that is what the exhaust shop tells me. Thank you for any suggestions--

Its very hard to weld cast iron properly. It has to be good grade and heat treated. Most weld shops aren't capable to do a proper weld.
Your better to go to a scrap and purchase a good used unwelded manifold.

[j cAT]

Originally Posted by rhandwor

Its very hard to weld cast iron properly. It has to be good grade and heat treated. Most weld shops aren't capable to do a proper weld.
Your better to go to a scrap and purchase a good used unwelded manifold.

This is a 10 year post that does show the muffler shops do cause problems when then weld up all the piping and replace the pipe hangers with welded steel rods to the frame.

the engine and tranny mount is an easy check if they are cracked. , esp. the tranny and driver side mounts.

the manifold was not mentioned as being the problem but the pipes the shop installed are cracking. the weak point would be the piping in the O2 sensor area if the exhaust pipes are too rigid. since this occurred shortly after the pipe replacing it must be the muffler shop screwed up and with what they said this is common means that THEY screwed up a lot of these vehicles...

exhaust manifolds can be welded if removed and the welder is certified. this would be with old GM vehicles not anything made in the last 20 years or so.. manifolds today are to thin .
It would be a surprise if the poster replies to this ...

[DeltaP]

Even though this is 10 yrs old there's something to be learned here.
Today's manifolds aren't worth the trouble it takes to re-weld. Although cast iron handles heat really well, (absorbs it like a sponge), today's manifolds are pretty flimsy. Used to be you'd weld 'em up with Nickel rods and mill 'em down flush to the head. Today they burn away and become boat anchors.
Most of these gas wrench jockeys in today's muffler shops I've seen only know how to cut and clamp parts together and occasionally wire weld... well they're practicing anyway.
You need to find yourself a really good muffler shop that bends their own pipe and does top notch welding. They're still out there.
Sounds like a good time for headers and revamp the entire exhaust system. After replacing some engine, tranny mounts and proper hangers of course.

[Bove]

How many times have you brought it back to be welded over? hopefully your repair man is grinding down the previous welds before going at it again. Welding over the old welds is no good. There would be no penetration and would just add to the problem. Give it a look and check that out because i know there are many people in garages who are not familiar with welders but know how to pull the trigger or touch the electrode

[strmn94]

to weld cast iron you have to heat it up and then you braze it, then keep it heaated up then bring the temp down slowly. my grandfather could weld cast iron, but it was a pain.