Cracked Exhaust Manifold - Suggestions ?

[pixola]

Hey folks,

After 9 years, looks like the exhaust manifold has showed up some metal fatigue.

I'm wondering if its possible to repair a cast AVO manifold or am i up for a new one ?

IMG_0232.jpg

[mx52nv]

Andrew,
Just give them a ring for a replacement one would be far better than trying to fix the cracked one. Nine years is pretty quick though. Mine is 12 years young without any issues.

Only time will tell how long the FM BP manifolds hold up for.

Les @ MX5 Shop

[kazjim]

if you Cant get another one economically, you have two choices ....
three are specialists who do 'cast iron brazing' - not sure of the process
OR you can go to your welding supplier and ask for NiFe Rods for your stick welder ...

Put manifold on BBQ until it is HOT .. (not red, but just below)
Rig up your welder to it and repair the crack (A little bit at a time, allowing it to warm up again on the BBQ between each 20/30 second blast with the welder
Knock off slag and wire brush between welds too - cleanliness is KING here ...
once you have a nice clean weld, grind and check - wear a mask and goggles because cast iron is a bitch in the eyes and is a fine powder in the lungs . . .
it wont spark from the grinder either ..
when you are happy (and re-welded the manifold again, just in case ) you need to cool it down very, very slowly ....
like in the oven and turn down the temp every hour or so until it is around the 100' mark...
then wrap in hessian bags (if you have them) and put under a bench or out of the way - let it cool overnight ..

next morning check for cracking and repeat if necessary !

cast iron is a little scary to weld at first due to the whole destressing technique required, but it can be easy and cheap repair !

Oh, BTW - I've made several turbo manifolds using this technique, so i know it works !

Good luck
JB

[pixola]

I got quoted $1000 for a Manifold from AVO (incl. Ceramic Coating).

Yowsers.. same thing from FM in US is AUS$700 landed.

[sprx3]

I got quoted $1000 for a Manifold from AVO (incl. Ceramic Coating).

Yowsers.. same thing from FM in US is AUS$700 landed.

Just wondering did you tell them your situation & that fm do it cheaper?

i would have thought that they would look after previous customers & i am a little shocked that the cast manifold cracked.... were you running standard avo specs or a bigger heaver turbo? or different cooler piping?

[pixola]

Yeah I gave em the whole story..

I mean, they sell kits for $4800.. will hunt around for another solution but it's kind of like this:

1. Buy the AVO manifold at a rip off price ( last resort )

2. Buy a FM manifold and then pay the $$$ to redo part of the plumbing if the spacing/offset of the turbo changes

3. Find a cheaper source of the AVO manifold ( 2nd hand or other seller )

[Sean]

Pixola,

It may be easier to weld then people expect, I'm pretty sure they are not iron, but another metal that is more reasonably and easily welded. I know of a few people who have welded sensors into the cast downpipes on AVO systems.

In terms of buying one - I may have a contact for AVO gear, will look into it for you if you like?

[pixola]

Thanks Sean,

Ordered one from AVO. Given the amount of effort to take the old one off and replace.. I'll just get a new one and expect a few more years out of it.

AW

[buz 138]

AVO are just plain rip off pricks!! ...in every way possibly imaginable!...and border line retarded im pretty sure.. (waits for shop fan boy flaming..)
you should have got in contact with 6boost. custom manifolds, life time warranty, no more expensive

just my 2.5 cents though

[pixola]

The way I look at it..

I could have got an FM manifold for half the money or so.. but then I'd have to relocate my down pipe.. exhaust.. intercooler hoses if there wasn't a perfect fit.

Grimace.. bear it.. get the car fixed and back on the road.

[buz 138]

thats the whole point of it being custom. put everything exactly where you want it....
1) send the AVO manifold off...
2) say "replicate this. i need everything in the same position please"
3) pay the man for his time
...and probably the biggest bonus of all..
4) no dealing with AVO!!

anyway it done and dusted now so good luck with it all mate

[Sean]

While I've had a fair bit of exposure to 6boost gear before (particulary on toyota engines) and find it to be top notch, for this situation I'd still be going with the AVO gear.

This is the first AVO manifold for an MX5 I've ever heard of problems with, back in the day when I was doing my first conversion I found Lee and other at AVO very helpful and keen to offer advice. The cast manifold looks almost like a factory fitted item and the structure and materials lend themselves well to packaging a turbo unobtrusively into the confines of an MX5 engine bay.

As good as Kyle is, I reackon he'd be pushing pretty hard to replicate the AVO manifold and placement with a reliable tubular manifold at a similar price. There may also be complaince and insurance hurdles for a car that had previously been approved and engineered as an AVO based conversion.

[Dave]

if you Cant get another one economically, you have two choices ....
three are specialists who do 'cast iron brazing' - not sure of the process
OR you can go to your welding supplier and ask for NiFe Rods for your stick welder ...

Put manifold on BBQ until it is HOT .. (not red, but just below)
Rig up your welder to it and repair the crack (A little bit at a time, allowing it to warm up again on the BBQ between each 20/30 second blast with the welder
Knock off slag and wire brush between welds too - cleanliness is KING here ...
once you have a nice clean weld, grind and check - wear a mask and goggles because cast iron is a bitch in the eyes and is a fine powder in the lungs . . .
it wont spark from the grinder either ..
when you are happy (and re-welded the manifold again, just in case ) you need to cool it down very, very slowly ....
like in the oven and turn down the temp every hour or so until it is around the 100' mark...
then wrap in hessian bags (if you have them) and put under a bench or out of the way - let it cool overnight ..

next morning check for cracking and repeat if necessary !

cast iron is a little scary to weld at first due to the whole destressing technique required, but it can be easy and cheap repair !

Oh, BTW - I've made several turbo manifolds using this technique, so i know it works !

Good luck
JB

Great advice there JB... the only thing I would add is that if you use an angle grinder to prep a cast-iron surface, you should follow it with a file to remove the smear of carbon that the grinder brings to the surface of the casting.
I have tried brazing old exhaust manifolds before with usually poor success. The constant high temperature the manifold operates at (and possibly the gases running through them) makes it a PITA compared to engine blocks and the like. The more you chase the edge of poorly adhering braze, the more heat you put into the casting - adding to the likelyhood of fresh cracking as it cools...
Pixola - Seeing you are getting a new one you should have a "crack" ( ) at welding the old... at the prices you are quoting, surely a successfuly welded manifold would still have a reasonable value? If Sean is right about it being cast steel rather than iron, it would be an even stronger repair.

Cheers,
Dave

[Okibi]

Should have just borrowed mine until you could find exactly what you wanted.

[pixola]

The hassle of taking the manifold / turbo apart.. lost time/travel was part of my decision to buy a new one,
pay a mech to put it on properly and not have to take it off again.