ecosse
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| posted on 8/11/06 at 04:09 PM |
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Repairing cast manifolds
Has anyone any suggestions for how best to repair a cracked exhaust manifold?
I've read about the various ways to weld one i.e. cast rods, MIG, brazing, all while heating the manifold and none of them seem to guarantee
success (although all seem to guarantee to distort and further crack said manifold!) I've tried various exhaust putties, all of which just crack
and fall off so has anyone found a method or paste or anything that actually works (before I gas myself  ) ?
Cheers
Alex
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smart51
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| posted on 8/11/06 at 04:21 PM |
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Cast alloy or cast iron?
cast aluminium can be done with technoweld or lumiweld. Its a bit like soldering with a blow torch. more tricky but should be just the job.
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iank
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| posted on 8/11/06 at 04:23 PM |
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Is it rare? If not getting an uncracked one from the scrapman probably easier and cheaper than repair.
Alternatively make a tubular steel one.
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ecosse
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| posted on 8/11/06 at 04:23 PM |
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Sorry, should have said, it's for a cast iron manifold.
Cheers
Alex
Its for a jag, and the problem is that they all do it so getting a good one from a scrappy is difficult, and new ones are £400+!
[Edited on 8/11/06 by ecosse]
Thought about making one but it wouldn't be the easiest to do due to the space available to do it in
[Edited on 8/11/06 by ecosse]
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nitram38
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| posted on 8/11/06 at 04:36 PM |
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The problem with gas welding with cast rods is that the manifold tends to bend so as soon as it is bolted on it will crack.
The place I used to work, the guy uses a bronze type rod and tig welds it.
I use to use it when I welded manifolds, but he keeps the materials a secret!
This is a softer material and allows some give. Not sure what it actually is, but it definitely looks like bronze in colour.
We also 'V' ed the cast out before applying.
[Edited on 8/11/2006 by nitram38]
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SeaBass
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| posted on 8/11/06 at 05:59 PM |
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The Audi Inline 5 Turbo manifold on Ur Quattros tends to crack rather often and many people offer repairs.
Most use the brazing technique but drill a hole at the start and end of the crack to stop it 'creeping' after repair.
Thanks
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lexi
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| posted on 8/11/06 at 06:24 PM |
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Had it last year on Accord coupe. Got the cast rods and Arc welded it after pre heating.........failed after 1 wk. Took it off did it again without
heat..same result. Only found one manifold in breakers and it was cracked. Paid £300 from Honda
Alex
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MikeRJ
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| posted on 8/11/06 at 07:16 PM |
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A while back fixed a cast iron volvo manifold for a friend. I explained there were no guarantees that it wouldn't crack etc. but I vee'd
out the crack, stuck it in the oven for an hour (wound up to max), and then quickly MIG'ed it using normal mild steel wire. That was probably
6 months ago and it's held up so far...
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zzr1100rick2
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| posted on 8/11/06 at 07:40 PM |
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dont forget to stress releive it as in hit it with a hammer
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gazza285
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| posted on 8/11/06 at 08:14 PM |
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Get the mating surface reground on a surface grinder or machine back to flat after welding as this relieves the problem of warpage. Other than that
good luck, cast iron is very hard to weld with any sort of success and what works once doesn't have to work next time.
DO NOT PUT ON KNOB OR BOLLOCKS!
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mark chandler
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| posted on 8/11/06 at 08:14 PM |
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Deep V, heat in a forge and ideally tig with special cast rods or gas weld.
I have however successfully heated in an oven and mig welded a couple of times, you need to play a blow torch over the work and cool gently.
Regards Mark
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Mark Allanson
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| posted on 8/11/06 at 08:18 PM |
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quote:
Originally posted by SeaBass
The Audi Inline 5 Turbo manifold on Ur Quattros tends to crack rather often and many people offer repairs.
Most use the brazing technique but drill a hole at the start and end of the crack to stop it 'creeping' after repair.
Thanks
I have done several of these, you need to make really sure that no scale is left on the inside of the manifold as this would then pass through the
turbo - not good!
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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907
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| posted on 8/11/06 at 08:57 PM |
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Hi
Cast Iron is one metal where the gas bottles still remain "king".
Vee out, all the way through, and use a bronze rod.
Heat all round slowly to preheat.
A matchstick laid on the ground surface should char light brown if it is hot enough.
Weld, and cool slowly.
It's important to heat the casting opposite the area to be welded so that
it shrinks evenly on cooling to prevent distortion.
hth
Paul G
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ecosse
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| posted on 8/11/06 at 09:11 PM |
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Thanks for all the advice, I think I'll try and borrow some Oxy/Acetylene bottles and have a go at brazing it.
Plan:
Drill holes in the ends of the crack, heat as hot as I can, braze, peen with hammer and keep heating, gradually allowing to cool over time, when done
get faces re-machined flat.
I think i'll try and find a second hand pair first, even if cracked, as the car is my daily ride so needs to be on the road 5 days a week
Cheers
Alex
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iank
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| posted on 8/11/06 at 10:07 PM |
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Be careful, CO poisoning creeps up on you.
If you start to feel woozy, light headed or you lips feel 'fuzzy' wind the windows down and stop.
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