jstluise

It's been years since I've had any exhaust work done, but my leaks are getting annoying enough that I want to get a new system put on. Anyways, years ago when I had everything from the manifold back replaced, I pretty quickly developed a crack in the collector pipes...basically where the two small pipes join in a Y into the larger pipe. I had it worked on a couple more times after that to fix the leak (I'm assuming they just welded up the crack) but it always came back. So, I've just dealt with it up until now.

So my question: is this crack developing at the collector common? Or was the shop I took it too just incompetent? All I can think of is that some residual stresses developed from welding and through the heat cycling a crack developed. Do they ever heat treat exhaust welds to remove residual stresses?

I just want to know if there is anything in particular I should mention to the new shop to make sure it is done correctly. Is there anything special that should be done to prevent it from cracking?

Thanks!

wyoming9

iTrader: (1)

Most times cracks are from the exhaust system not supported like it should be .

as the exhaust system hangs putting pressure on that part of the system

Bad Engine and Transmission mounts could cause this as well .

In this case the engine is moving not the exhaust.

I have never had one crack.

When new these trucks had support on the down pipe the first time that pipe is taken off that support is gone unless at the Toyota Dealer.

I am sure if you ask the shop to stress relieve your weld you will get a blank stare .

Also till you were done paying for the extra labor you could buy a brand new Virgin piece and then some. .

jstluise

I do have the support on the downpipe...I believe it attaches to the bell housing or somewhere near there. So, the pipe is rigid from the manifold to this support and moves with the engine/trans. Beyond that the exhaust system is supported by the rubber dampening hangers. So, I could see a crack developing after the support due to the exhaust system moving, but the crack at the collector is between the manifold and support...an area where nothing should be moving.

I thought maybe if the support is too close to the collector and there is any flexing in the pipe when clamping down the support, this could cause some stress and a crack to develop.

Or, they were just crappy welders and had too large of heat affected zone...

I suppose I can just take it to a shop and hope for the best. I would love to do it myself because I'm an experience MIG welder, but bending pipe is a different story.

87hoerunner

X2 on engine and transmission mounts

rustypigeon

Mine cracked twice in that spot. I decided to remove the bolt that clamps the pipe to the bellhousing to allow it to flex as it heats up. I just took the bolt out, but left the metal band that wraps around the pipe and the bracket to allow some flex. That was about 16 years ago and it hasn't cracked since.

I think the ridgid clamp in close proximity to the manifold connection creates stress every time it heats up and cools down.

wyoming9

iTrader: (1)

I tend to agree with that because none of mine ever cracked..

Then welding on exhaust parts the thermal cycle who knows the wire they used might not have been the best choice.

Find the certs for the exhaust pipe steel and get the wire that matches the closest

I just go to Napa and get the exhaust parts that fit simple to change and it does not need anything fancy.

highonpottery

iTrader: (1)

Mine cracked in the same spot but i've only driven it maybe 15k miles since repairing it 5 years ago. I have no idea about the quality of the replacements available. I always had the trans mount in-place so it's pretty rigid up there between the CAT and the exhaust manifold. Always though the crack was due to heating/cooling rather than movement - mine had thick weld seam but the pipes are pretty thin.

jstluise

That's good to hear. That was my initial thought as well...the clamp is causing too high of stress in the welds, possibly from installation but most likely from heating/cooling.

I'm thinking right now I might just try to salvage what I have as an experiment. Weld up the crack (if possible) and install without the clamp. Just to see what happens. Another possibility is seeing if there is a way to clamp it farther downstream (maybe on the trans) to reduce the stress on the pipe, but I'll have to get under there and take a look. I guess as long as the motor/trans mounts are in good shape and the exhaust hangers are good, then any movement in the exhaust system induced by the engine will be okay.


Wyoming, does that mean you don't have the clamp installed? Trying to figure out what you mean.


IIRC mine had a pretty thick weld as well which could contribute to the problem. Basically the thick weld, thin pipe, and heat affected zone introduces a big stress concentration.