Last September (2003), I started hearing a ticking from the engine compartment of my 97 Tahoe. Took it to the dealer (as I was new in MA and didn't know who else to go to) and turns out that the exhaust was cracking around the flange that connects to the manifold. They said it's unweldable and must be replaced. OK, no problem, the truck is ~120K miles at this point, so we replace it.

By early November (2003), the new one has sheared completely off the flange. It was replaced under warranty.

Between then and now, I've had to have the exhaust bolts tightened repeatedly.

Today, I take it in again for the now familiar noise of escaping exhaust in the engine compartment. They tell me it's cracking at the flange.

Yes, I know I have a 138K Chevy Tahoe. Predijusts aside, what could be causing the repeated problem here? I had the truck with NO exhaust problems for over a year in NC.

Coincidentally, I think, the problems started when I towed one of the Miatas up here to MA when I moved. Just prior to moving, I replaced the old tires with new Michelin M/S tires. I don't think either of these could have triggered the exhaust thing, but thought I'd mention it in case there's something I don't know.

The 2nd issue was after towing the SM car up here.

There has been no towing since Sept 11/12 though, so I can't tie this instance to a tow.

The only thought I've had is broken motor mounts? Thus causing extra engine movement and extra stress on the mounting point. Any other thoughts? I've never considered an exhaust as a "wear-item". Muffler yes, pipes no.

Thoughts? Questions I should ask?

Thanks,
Diane

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by r2x &raquo;</TD></TR><TR><TD CLASS="quote">The only thought I've had is broken motor mounts?</TD></TR></TABLE>

My thought is this is probably the right thought. I'd check both the motor and trans mounts. If it ends up being one or the other smart money says do both. Other that, I've got nothing for ya

 

Apart from engine movement like you suggested, high cylinder head temps come to mind. Think of the THSCC bus...running at high RPMs, and high temps, all the time, it goes through exhaust systems rather rapidly. Maybe this is the same/similar?

 

well, it is colder in MA than NC, but that shouldn't be a problem..

all i can say is that it's a chevy... hehehe. j/k..

as far as i know, pretty much all fords have this happen, and all v6 nissans have this problem. the trucks, that is. i don't know why, but my 2000 frontier had it happen.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by E-AT_me &raquo;</TD></TR><TR><TD CLASS="quote">and all v6 nissans have this problem. the trucks, that is. i don't know why, but my 2000 frontier had it happen. </TD></TR></TABLE>

I work at Nissan and I have not once seen that happen. Not doubting you, just stating my observations.

r2x - Check the obvious things. Check the joint at the downpipe to the y pipe. Check the motor mounts, manifold brackets, etc. Anything that is directly related to the manifold, that could cause extra movement, or cause restricted movement, both of which could cause the weak link of the system to go (the welds in this case)

 

maybe add a piece of flex pipe into the exhaust line to take the stress off this point? apparently it is the weakest point..

 

Is this the same Tahoe that Karl Schultz Rode in

 

Along with the engine mounts, as already suggested, I would look at all the exhaust hangers. Make sure they are all intact and correctly mounted. Make sure they check the trans mount too, it mounts way under the truck and can get saturated with oil and crud with time and the rubber separates. The front mounts can fail enough to let the motor move around, but appear to be OK with the motor just sitting still.

 

Just a wacky idea,

Any chance you're getting water on your exhaust manifold in the rain? Missing any gasket that goes around the hood?

Wonder about EGT's too. Bad O2 sensor could cause it to go lean, or ignition timing could be too retarded. Or a couple of fuel injectors could be getting clogged.

I'd DEFINITELY be looking at oddball-temperature issues like these, because normally you could hit the exhaust manifold with a hammer and not crack it. Probably true even under normal operating conditions.



-Chris

[Edit, I thought it was the manifold cracking, not the downpipe thingy... anyhow I say temperature issue )

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 743power &raquo;</TD></TR><TR><TD CLASS="quote">I work at Nissan and I have not once seen that happen. Not doubting you, just stating my observations.

r2x - Check the obvious things. Check the joint at the downpipe to the y pipe. Check the motor mounts, manifold brackets, etc. Anything that is directly related to the manifold, that could cause extra movement, or cause restricted movement, both of which could cause the weak link of the system to go (the welds in this case)</TD></TR></TABLE>

we'll, i've had it happen to me and so have a lot of other people on nissanoffroad.net just fyi.. it's only the passenger side manifold on the 3.3 v6's, though. not the drivers side.

 

get good nuts.....the locking kind

 

I am thinking about getting these for my tahoe......

http://cgi.ebay.com/ebaymotors...%3AIT