Fixed that dratted stud, still leaking

[BlueStag]

And the dreary tale goes on;

 

I have been fighting a leaky throttle shaft on my front SU, so I purchased from Ztherapy a pair of throttle bodies.

 

While I was wrestling with that, I decided it was time to tackle the leaky manifold to exhaust flange gasket.

 

Of course, I sheared off a stud in backing off the nuts. Wadda surprise.

 

And I decided to clear out the manifold heating and the remnants of primitive emissions hardware. I even got my mitts on an early balance tube to replace the 260 tube that I have been running.

 

I got the broken stud resolved with a helicoil. I set it loosely on the head studs and ran on a few flange nuts just enough to keep it from falling off.

 

And I fought like hell to get the exhaust pipe to fit over the three studs. So much so that I released the manifold from the head and struggled to get the manifold to fit up with the pipe. The gasket had a rough time of it. Eventually I got them tied together and loosely nutted, then the manifold to the head.

 

Got everything tightened up and the carbs on.

 

Fired it up.

 

Damned thing leaks from the manifold to exhaust flange, again. Worse than ever. Kill me now.

 

One element that might illuminate the question: this is all in my Triumph Stag.

 

The Stag has a rear suspension not unlike a ZX: semi trailing arms, which pivot on a subframe. Factory Stags were V8s, and two exhaust pipes passed thru holes in the subframe. My rig has a single pipe passing thru the subframe.

 

I wonder if my exhaust suffers from being too "tight", not having any ability to twist with the engine.

 

I might be looking for some flex pipe. Anyone care to tell me where I am wrong? God knows I am ready to accept being wrong about some damned thing,

[beermanpete]

Flex pipe or flexible hangers should help. On our '73 240Z the whole exhasut system (appears to be OE or equivalent) is solid but hangs on flexible rubber mounts. Generic rubber hangers are available at most auto part stores.

[BlueStag]

Flex pipe or flexible hangers should help. On our '73 240Z the whole exhasut system (appears to be OE or equivalent) is solid but hangs on flexible rubber mounts. Generic rubber hangers are available at most auto part stores.

 

Got the flexible rubber hangers, but the hole that the exhaust passes thru is pretty tight. I think it is bound up there.

[NewZed]

When you mate the flange to the manifold and tighten the three nuts, do the two surfaces come together parallel and flat? On the Zs, typically, everything hangs below the mounts so you can tighten up the flange before flexing the pipe whatever small amount is necessary to get it on to the hangers. There's enough wiggle room to make sure the gasket is seated and everything comes together right. The first hanger is back on the tail shaft of the transmission, which moves with the engine as a unit anyway. The only attachment to the body is the rubber hanger way back at the rear bumper.

 

It sounds like your system is too bound up to get the flange and manifold mating surface parallel and tight.

[BlueStag]

 

 

It sounds like your system is too bound up to get the flange and manifold mating surface parallel and tight.

 

I'm thinking that you are right, that my exhaust is not quite lined up to the manifold. Definitely thinking of fitting in a flex pipe if I can find one.

[beermanpete]

Adding a flexible section should help. Or see if you can bend the pipe a bit to get the basic alignment closer.

 

Summit sells the flex-pipe. Here is an example: http://www.summitracing.com/parts/WLK-42216/

[Leon]

Also, check your flanges for straightness. I've seen them warped enough to never seal.

Edited March 10, 2012 by Leon

[BlueStag]

Also, check your flanges for straightness. I've seen them warped enough to never seal.

 

You might well be onto it.

 

I did as I described above: cut out a section, replaced with a flex pipe (near where the pipe turns horizontal beside the trans) took off the carbs and heat shield, tightened up the flange before tightening the flex pipe, put the carbs back on, and

 

DAMN!

 

It still leaks. At the back side by the block, a substantial leak. Where there is no stud to tighten.....Kill me now.

 

If I have to take off the whole manifold again I am just going to burn the damned thing down to the ground.

 

Any chance that I can just bung in two gaskets and get a seal? Please?

[NewZed]

I had a similar problem with my first 280Z exhaust flange. I cut the metal rings out of one gasket and doubled up with a complete new gasket. I wrapped them both in crinkled up aluminum foil to hold the rings in place and to add some filler for the gap. The reason I cut the metal rings out was to concentrate pressure in the area that needed sealing (which probably put more bending on the flange, but it wasn't working anyway).

 

My flange and mating surface both looked flat but I couldn't get the leak to stop, like your situation, until I took these "hack" like measures. It was a small leak before but you could still hear it with the hood open and see the carbon trail it left. The hack job did well and lasted ~10,000 miles until I got another down pipe. On disassembly, there were signs that it was starting to breakthrough, but you couldn't tell from outside.

 

Edit - that ceramic muffler sealer you can get at the auto parts store might help also. It's designed for high heat.

 

Any reason you can't unbolt at the anti-resonator and replace just the down pipe or is yours gone?

Edited March 10, 2012 by NewZed

[BlueStag]

 

Any reason you can't unbolt at the anti-resonator and replace just the down pipe or is yours gone?

 

Ain't no such part to be found on my rig.

[BlueStag]

Also, check your flanges for straightness. I've seen them warped enough to never seal.

 

Leon WAS going to get the award, and might yet.

 

I took down the exhaust pipe and inspected the flange, duh, why did I not look at that earlier?

 

The "ears" were distinctly distorted.

 

A bit of heat, a large hardened steel rod and a mallet straightened them out. And a large flat file smoothed off the small high points.

 

Put the blasted thing back together, and it still freaking leaks at the back of the flange, toward the block.

 

It may be time to start drinking.

[Leon]

Leon WAS going to get the award, and might yet.

 

I took down the exhaust pipe and inspected the flange, duh, why did I not look at that earlier?

 

The "ears" were distinctly distorted.

 

A bit of heat, a large hardened steel rod and a mallet straightened them out. And a large flat file smoothed off the small high points.

 

Put the blasted thing back together, and it still freaking leaks at the back of the flange, toward the block.

 

It may be time to start drinking.

Damnit.

 

Did you put in a new gasket once you straightened the flanges? Check both flanges with a straight-edge? You can also try to use some of that copper gasket spray to see if it will help seal up once everything is true.

[BlueStag]

Damnit.

 

Did you put in a new gasket once you straightened the flanges? Check both flanges with a straight-edge? You can also try to use some of that copper gasket spray to see if it will help seal up once everything is true.

 

 

Yer really working for that blasted prize.

 

No, I am fighting with the same damned gasket for days now. I'm in Burbank CA, and what do you know? None of the local shops bother to keep this sort of gasket on hand. Give them three days, and they will have a new one for you.....I may need to drive a few miles tomorrow for a fresh one.

 

Some copper gasket spray, you say? I will need to look into that.

 

And no, I did not put a straight edge against the cast iron manifold. I did, the other day, run a file over the surface to knock down any obvious high points.

 

I am getting distinctly annoyed......

[BluDestiny]

If I was still in Burbank I would just give you one. I think I have 2 laying around and an almost complete gasket set for the bottom end.

[BlueStag]

 

Edit - that ceramic muffler sealer you can get at the auto parts store might help also. It's designed for high heat.

 

 

Tell me more about this stuff.....

[BlueStag]

If I was still in Burbank I would just give you one. I think I have 2 laying around and an almost complete gasket set for the bottom end.

 

If you were still in Burbank I'd ask you to crawl your skinny young butt up under the car and work the ratchet on the flange nuts......

 

I'm buying two of the nasty things when next I buy any of them.....

[NewZed]

Tell me more about this stuff.....

 

It might not be durable enough for the heating cooling cycles of the exhaust manifold, at the flange, but who knows. Here's one example - http://www.autozone.com/autozone/accessories/VersaChem-3-oz-Inferno-metal-repair/_/N-25hw?itemIdentifier=30671&_requestid=765970

 

Since you're trying to save an existing system, and can't get reasonably priced replacement parts, maybe a custom copper washer would be in order. Cut a couple of rings from soft sheet to size to fit around the pipes in to the manifold, and let them deform in to the defects.

[BlueStag]

It might not be durable enough for the heating cooling cycles of the exhaust manifold, at the flange, but who knows. Here's one example - http://www.autozone.com/autozone/accessories/VersaChem-3-oz-Inferno-metal-repair/_/N-25hw?itemIdentifier=30671&_requestid=765970

 

Since you're trying to save an existing system, and can't get reasonably priced replacement parts, maybe a custom copper washer would be in order. Cut a couple of rings from soft sheet to size to fit around the pipes in to the manifold, and let them deform in to the defects.

 

I'm dubious....I certainly don't want to GLUE the mess together, but I doubt very much that anything outside of NASA would.

 

I like the idea of some soft copper, perhaps a sheet on either side of a fresh gasket.....with some spray copper adhesive.....

[Tony D]

Take your studs off and stone the entire surface. I've seen stock manifolds where the rust has made them rough, and old adhered gaskets were 'piled up' and leaked against the block. Tighten in the proper sequence and if necessary use a double gasket and some Red RTV. That drastic measure has stopped the worst leaks...which were eventually traced to debris on the mating surface once they were cleaned and straightened they sealed just fine.

 

Of this I speak of the manifold to headpipe gasket.

 

If this is manifold to head...then use a graphoil composite turbo gasket. They seal stock manifolds with considerable warpage without any sealant whatsoever. Flat paper gaskets just don't cut it, and the later graphoil gasket is 'universal' if not somewhat expensive. Then again how many other gaskets have you bought.

 

Speaking of being in LA, you can go simply BUY graphoil gasket in sheet form. Worst case is you go online to McMaster.com and order some before 9 AM with a credit card. Usually if I do that it will be delivered UPS Ground by 6PM that SAME evening at my place out by Moreno Valley for typical UPS Ground charges...meaning CHEAP!

[BlueStag]

Take your studs off and stone the entire surface. I've seen stock manifolds where the rust has made them rough, and old adhered gaskets were 'piled up' and leaked against the block. Tighten in the proper sequence and if necessary use a double gasket and some Red RTV. That drastic measure has stopped the worst leaks...which were eventually traced to debris on the mating surface once they were cleaned and straightened they sealed just fine.

 

Not a chance of getting the third stud out. It is rusted in there fast and would certainly snap off if I attempted to get it out.

 

I did clean up the surface pretty thoroughly, gave it a good scrape and filed down with my largest mill file.

 

I am frustrated if the whole point of this is that the two surfaces must be perfectly smooth and flat to achieve a seal.....I just cannot accept that. I have managed over the years to close up a few flanges without nearly this much effort.

 

I am going to buy a fresh gasket today and ask for some sort of glop to add in there. I live in hope.