4th Cracked Exhaust Manifold

[OnSafari]

Hi all,

I am the original owner of a 1999 3.5L Sport with about 165,000 miles on it. As mentioned in the below thread, I recently discovered my right side exhaust manifold is cracked for the THIRD TIME

msport97.proboards6.com/index.cgi?board=general&action=display&n=1&thread=3060

I have also had the left manifold crack once about 40K ago which was replaced and so far is fine.

I'm curious to know if anyone else, either 3.0 or 3.5 owners, have had this problem. If so, please list what year vehicle, engine, which side cracked, at what appx mileage and how many times.

I recall this was practically an epidemic on the old Starion Turbo but for it to happen on a normally aspirated engine as often as I have seen it seems very odd.

Thanks!

[Joel_CA]

Wow.. i havent seen very many of them myself. Are they cracking in the same general area?

Joel, CA

[OnSafari]

Joel,

I don't recall where the left manifold cracked as I never saw it but the right side manifolds all cracked in basically the same place which is through the main manifold between the 2nd and 3rd exhaust ports (the front most port being the 1st and the back port nearest the firewall being the 3rd).

I have pix of the most recent incident. I'll get them sized and posted somewhere in the next couple days. I'll post the link here when they are up.

Thanks!

[OnSafari]

Okay, got a couple pix posted here:

www.supergtusa.com/ex_manifold/

The location of the crack in these photos is the same basic area of the cracks in the previous two right side manifolds that I had replaced.

Any ideas?

[Joel_CA]

That's one helluva crack! I'm not sure what to tell you at this point since you're more than likely going to have to replace it with a factory part. When ordering from the parts department- ask the parts guy if there is a superceded part number for the manifold. If so, the newer part number is more than likely an updated part which should be better. It's also possible for the item to have the original part number and still be an improved part. If you still have the old manifold- perhaps you can take it to an exhaust shop and have them fabricate some custom headers using the stocks as a template/guide. Good Luck!

Joel, CA

[OnSafari]

Thanks for the input Joel. This crack is actually quite a bit smaller than the last one. This one is relatively new though. If I let it go for awhile, I'm sure it will get bigger like the last one.

I actually requested a check for a part update or supersession the last time this happened, which was only about a year ago, but the part I got was the most recent.

I know Mitsu manifolds are generally a high quality ductile cast iron so if that isn't holding up, I suspect any common type of fabricated tublar material wouldn't either. It must run pretty lean to get this hot.

Anyway, I will just replace it again but I still wonder if this has anything to do with my failed pre-cat code, whether it's legit or false. Seems there must be a connection.

Anyway, thanks again for your input.

[Joel_CA]

Yes, the crack can trick the PCM into a number of things. I'd replace the manifold 1st and see what happens.

Joel, CA

[byrdman]

Wow. Just to throw some more ideas out, since replacement hasn't done the trick yet...

High temps - Plugged or failing Cats/PreCats... Bad fuel distribution (injectors), burned/bad exhaust valve (do compression leak-down test) -- all this stuff you'd likely have noticed a general loss of power

Sudden temp change - Do you wash your engine hot? Water crossings? Is there a missing heat sheild that covers the manifold here?

Mechanical damage - Exhaust stressed by knocking into stuff (frame members, trail damage, excessive motor movement)... check all ex. hangars, motor mounts, flex joints...

If you go tubular, there are lots of materials that will take the higher temps, but oddly you may be best off going with something that is softer and that will give instead of crack. Check out www.burnsstainless.com (look for tech articles) they have a good info on materials...

Good luck. I'm gonna go look at mine right now!

[labedra]

FYI, mine cracked also, passenger side. I wonder about getting another one since yours cracked so many times. Also is it possible to have a good welder weld it ? Should it holdup ? Is there an aftermarket part made ? I really don't want to get it from the dealer since i think this might be factory fault of poorly developing this header.

[diverdawg]

Well, add me to those with a cracked exhaust manifold. I have a 2000 with 70k miles, 3.0 V6. At first I thought it was the muffler or pipe, then realized the noise was coming from the engine compartment. it would quiet down after Monty warmed up. That was the manifold expanding from the heat and the crack closing up. It was on the passenger side. Dealer is replacing. I have always treated my vehicles with respect and must admit this is the first manifold cracking I have ever run into.

[byrdman]

Just a question, might all you folks have California emission vehicles? 2 pre catalysts and 1 main catalyst?

[OnSafari]

I was thinking the same thing. Yes, my 3.5L is a California vehicle with the precats.

[byrdman]

My 98 is 3.0 and non-CA, so I'm not familiar with the exact setup on the precats. Is there any flex pipe with that setup? I only can tell you my exhaust failed at the front flex pipe, which is just after the Y pipe joins (no precats), so that engine/exhaust moves around a good bit during normal use.

My other thought (especially if you already have flex pipe after the Y pipe) is that there may need to be an expansion joint or added flex pipe so that both halves of the Y pipe (or wherever the two downpipes w/ precats join) can expand/contract with temp changes without putting stress on the manifold. The precats heat up much faster than the manifold does. Sounds like a PITA to try, as I'm sure space to add anything is tight. I think you can get a flex pipe section down to about 4" length, but you'll need at least 6" with legs to weld into the splice would be more realistic.

There is a test for excessive exhaust back pressure too (this would raise temps) I think they say 2psi max measured at the O2 sensor, but I don't know at what RPM/load, etc... Joel?

[ggroth]

My 99 3.0 V6 102k miles has the same exact crack... I thought it was a hole somewhere in the exhaust system till I was replacing the A/C belt and had the car running with the hood up... I will probably just live with the loudness since replacement didn't seem to work... A/C belt just tore off again, gonna replace the A/C clutch and put on another belt... crossing fingers hoping the compressor isn't the problem...

[byrdman]

Is anybody else missing the heat shield from the manifold? i.e. you shouldn't be able to see the bare cast iron like in the pics here...