Cracks In Exaust Manifold

[Humbla]

Hi gurus,can anyone tell me why I have to replace my exhaust Mani every 3 or 4 years due to cracks,getting a bit boring now.Coming up to my 4th one this year,any way of sorting this I know I do a lot of ks every year 30000 plus but its mostly long hwy trips pissing me right off it is. :-)

[Impulse-NL]

Reweld it ?

Or buy a good one ...

[Ben C34]

Reweld it ?

Or buy a good one ...

Rewelding it id a waste of time and money considering how cheap another stock one is..

Its the heat cycles that kill them.

Do you get in the car and give it a hard time straight away or let it warm up first? If you even give it a hard time!

[Humbla]

They have all been replaced with good ones,but after a couple of years they crack.

I just want to know is there a way of sorting this out.Not to sure how welding would

work on these. :-)

[Trex]

Reweld it ?

Or buy a good one ...

He asked why it cracks.

I can only imagine it's getting hot possibly because always on boost on the freeway and it's tuned? Everyday on boost for hours would take it's toll on a lean tune. Only speculating though.

[Humbla]

Rewelding it id a waste of time and money considering how cheap another stock one is..

Its the heat cycles that kill them.

Do you get in the car and give it a hard time straight away or let it warm up first? If you even give it a hard time!

Ha ha,I never thrash a cold engine on any car,I warm up for 20 seconds then drive sedately till it gets to operating temp,

then drive it like I stole it , :-) :-)

[Humbla]

He asked why it cracks.

I can only imagine it's getting hot possibly because always on boost on the freeway and it's tuned? Everyday on boost for hours would take it's toll on a lean tune. Only speculating though.

Safe PFC tune 220 at the rears for many years now perfect afrs. PS me lady lil ol lady. :-)

[colourclassic]

Where is it cracking? What gaskets are you using? Are you torquing fasteners to spec or by feel?

[Trex]

Sorry. Didn't mean it's bad lean. But leaner than they intended for DD freeway use. That's the only way I see it cracking a few times

[Humbla]

My mechanic is the one doing the work I assume he uses a torque wrench to the right specks.

[zebra]

Peak EGT is at stoich (14.7:1 for petrol)

Richer or leaner results in lower EGTs

So being lean on the highway isn't the issue.

Id say the issue lies in how the exhaust is supported.

[colourclassic]

My mechanic is the one doing the work I assume he uses a torque wrench to the right specks.

I'd be speaking to him then; don't assume. Check what gaskets you're using too - those cheap cardboard-ish ones don't transfer heat well, and like to leak.

EDIT:

Also, check that you have the front exhaust hanger installed at the gearbox cross member, it's the only real form of support the turbo has. Even without it, it shouldn't really cause cracks on the manifold.

Edited April 27, 2015 by colourclassic

[Humbla]

Thanks heaps guys,my 33 is serviced every three months,and up on the hoist as well I like to be safe,I'll chat to him when I get back from brissy in a couple of weeks.Far as I know exhaust supports are all there in good condition.I'm just thinking there must be a reason for the Mani to crack have to find out why. :-)

[KiwiRS4T]

Just to confirm you are talking about a stock factory manifold?

[Humbla]

Yes it is .

[boostn0199]

Are you running a flex pipe in your dump and has your dump got a solid mount to the body near its flange like the std ones do? they play a big part in saving manis, gaskets, loose bolts etc.

[scotty nm35]

Are you running a flex pipe in your dump and has your dump got a solid mount to the body near its flange like the std ones do? they play a big part in saving manis, gaskets, loose bolts etc.

^^ This. The exhaust is a 5m long breaker bar, and your manifold is very soft at that temperature. A flex join in the front pipe isolates the forces caused by your muffler swinging around.

[zoomzoom]

^^ This. The exhaust is a 5m long breaker bar, and your manifold is very soft at that temperature. A flex join in the front pipe isolates the forces caused by your muffler swinging around.

I used a few of these as exhaust mounts:

http://www.ebay.com.au/itm/Toyota-Landcruiser-HZJ80-HDJ80-Series-Exhaust-Mount-Rubber-Set-3-/201205416170?pt=LH_DefaultDomain_15&hash=item2ed8c700ea

Had to fabricate my own brackets, but they make a great semi rigid mount. The exhaust cant swing around anymore.

[scotty nm35]

I used a few of these as exhaust mounts:

http://www.ebay.com.au/itm/Toyota-Landcruiser-HZJ80-HDJ80-Series-Exhaust-Mount-Rubber-Set-3-/201205416170?pt=LH_DefaultDomain_15&hash=item2ed8c700ea

Had to fabricate my own brackets, but they make a great semi rigid mount. The exhaust cant swing around anymore.

My exhaust grows in length by 1 1/2 inches at the track, I would be surprised if those would give enough movement to last long term, unless the bracket can bend...

Later model Nissan cars have a fixed rear bracket to stop the muffler swinging around, but they still run a flex joint stock.

[AngryRB]

I had a bracket made to bolt the dump at bell housing, then at the gearbox mounts, not sure how long it would of lasted but looked legit...