Exhaust manifold leak..not where I expected!

[P38 4.6 Timmy]

G'day all.

I've had a small exhaust leak for a while now, somewhere on the driver's side manifold. I checked all around the manifold to head and manifold to down pipe flanges, but couldn't see any tell-tale soot marks nor feel any puffing with my hand.

So, dreading that it might be the flex bellows, I removed the heat shield for a better look. Still couldn't see any signs, so with the engine idling, I ran my hand around the manifold (trying not to burn myself) and discovered the leak was from the collector where the header pipes converge into 1, that was a bit of a surprise! After removing the manifold, this is what I found....

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And this is after a quick sand blast. You can see the crack goes through the weld then runs along the tubing.

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On to the repair next.

[P38 4.6 Timmy]

Even though I had soaked the down pipe flange studs & nuts with CRC a few times over a couple of days, 2 of the studs still snapped..

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So I decided to drill them out and use bolts instead.

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[P38 4.6 Timmy]

I did a braze repair on the crack, decided not to risk arc welding it and blowing away the thin walled tubing! Unfortunately I don't own a TIG, so that wasn't an option..

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Turned out pretty good, it's been back on the car for a couple of days now, and so far so good....haven't been off-road yet though, so time will tell

[P38 4.6 Timmy]

I was wondering if anyone has seen these stainless tube headers crack like this before?
The down pipe flange lines up perfectly, so there's no stress on the manifold from there.

Maybe I'd better take it a bit easier on the Ol' Girl when we go bush

Cheers, Timmy.

[Keithy P38]

I do recall hearing stories about the drivers side header pipes cracking at the collector.

Someone who has experienced it for themselves or with more P38 knowledge than I might be able to expand on it a bit.

Cheers
Keithy

P.S. Nice weld!

[P38 4.6 Timmy]

Hey Keithy, thanks mate! Hopefully it holds up

That's interesting, I just had a look at a thread on RR.net and quite a few people had the exact same cracking at the collector on that r/h manifold.... The blokes who had welded it up said they had no further problems, so that's promising.

Well, hopefully the crack has relieved the stress and now the header won't need to visit the pschychiatrist.

Cheers, Timmy.

[benji]

Both sides of mine had numerous cracks in them.
I took them to a guy (known good welder), and he patched them up with a mig.
That was roughly 4 years ago, and they've been fine.

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[P38 4.6 Timmy]

Good to know Benji, that once repaired, they seem to hold up well.

I've always been a bit concerned about the exhaust cross over pipe. It's silly how it sits lower than the chassis cross member and cops a bit of a beating off road. Mine's got numerous dents and scrapes etc, it must transfer a fair strain to the manifolds when it's getting bashed around. It's a pity LR didn't tuck it up out of harms way a bit better.

Cheers, Timmy.

[benji]

I've been trying to find a way around that for a while. I've got a dent in mine from the high country.

Unfortunately you've still got the handbrake and fuel tank to make a clean undercarriage though. ....

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[P38 4.6 Timmy]

Yep..true about the fuel tank, mine has copped a bit of a hiding. Heaps of scrapes in the steel bash/mounting plate and some decent ones in the plastic at each side as well.

In deep muddy stuff and ruts etc., small stones and other muck gets jammed in between the tank and the plate. This can't be good, I imagine a sharp stone being trapped in there and "drilling" it's way through the plastic So I dig out what I can with a flat screwdriver. Probably just being paranoid though!

I've thought about making up a bash/slider plate that attaches to the front cross member (weld mounting tabs to the cross member), then comes downwards at a 45' angle to clear the exhaust cross over pipe, then goes rearward and fixes to a custom removable cross member just aft of the hand brake drum.

I must get around to it one of these days; lots of other stuff higher on the to-do list though!

Cheers, Timmy.