Miata exhaust leaks? Options

[Dave H]

https://www.youtube.com/watch?v=nR1Ht_pGWcc

The video isn't the greatest, but trying to get the bugs out of the miata before next sunday. Currently it appears I'm getting an exhaust leak... the gasket is new, everything is tightened down pretty well, is it possible I have a bad gasket? Or do I have something else going on?

[SteveAshcraft]

https://www.youtube.com/watch?v=nR1Ht_pGWcc

The video isn't the greatest, but trying to get the bugs out of the miata before next sunday. Currently it appears I'm getting an exhaust leak... the gasket is new, everything is tightened down pretty well, is it possible I have a bad gasket? Or do I have something else going on?

Sounds like an exhaust leak. What is the smoke coming from the area near #4? If it is something burning off the header then it has probably stopped already. If not, I'd bet on a crack in the header. Hope not but they are weld-able.

I'm sure I'm just telling you stuff you already know but
Can you feel hot gas coming from some place
like the gasket between the header and the head or
where the header connects to the next section of the exhaust

With an exhaust leak of that magnitude I would expect you to be able to feel hot gas some where.
If you get someone to block the tail pipe does it change what it sounds like?

[Dave H]

My guess is on an exhaust leak as well.... it smells like exhaust, and as far as I can tell, there's nothing on the header that would be causing that kind of burn off, and this was right after I started the engine. I guess I'm pulling the header tomorrow...

[Dave H]

Oh, and the rattling is the hood stand, it was right next to my phone, that's why it's so loud.

[SMeyers]

Squirt a little oil in the intake, see if any blue smoke exits near the noise.

Did you tighten the header bolts from middle > outward? In weird cases if tightened just randomly it can pinch a gasket a little wrong.

New header, or used? Is it straight? Are you sure?

All I got. Good luck.

Edit..... Are you sure both mating surfaces were completely clean? No old residue?

[Dave H]

The head was new, so that surface was clean. Pretty sure the header was clean when I put it on, but I'll check that as well when I have it off. It was tightened from center outward, but I wouldn't put it pass me to screw that up. And I can't say that I checked if the header was straight or not... another one to check tonight. Grabbing a new gasket today, hopefully it's just a problem there, I'd rather not have to replace the header

[DaveM]

Hi There!

It has always surprised me how much smoke you can get from something as small as an oily fingerprint! But that smoke is very close to the EGR pipe that is welded to the No. 4 header close to the mounting flange, if you don't see a problem with gaskets you might check for a crack in that weld. Fingers crossed its okay ....

[Jahoney]

Possible warped manifold, where it mounts to the head. Had that same issue with our 1990 Miata with the stock manifold. Replaced it with an aftermarket header and the issue was resolved.

[Dave H]

Yea, I'll be sure to check that as well.... Before I pulled the motor there was no issue, but it was sitting for a year and a half on a shelf in my garage before it got put back on. I'll pull it apart tonight and see if I can get a better idea of where the issue is at. Thanks for all the suggestions!

[SMeyers]

You do realize that you are now obligated to report back to all of us, right?

[Dave H]

Well, if you see a smoking miata at the event on sunday, you'll know what's going on at least

[SMeyers]

I think I’ve got it now.....

Smoking Miata.......Dave H

Miata with squealing belt or sketchy wiring..... Steve A.

And the Miata with eight co-drivers...... Kevin V.

Thx.😂

[Dave H]

I think I’ve got it now.....

Smoking Miata.......Dave H

Miata with squealing belt or sketchy wiring..... Steve A.

And the Miata with eight co-drivers...... Kevin V.

Thx.😂

Kevin only has 7 co-drivers now.... I bought my own

[Dave H]

So put a new gasket in there, still leaking. Used a metal ruler and tried to get a gauge if the manifold is warped or not. Was hard to tell, but my guess at this point is it's warped. So probably going to look at the replacement route. If I do go with a race header, what happens with the tube that runs over to the intake manifold? I don't assume anyone has an extra header for a miata laying around they'd want to part with, do they?

[SMeyers]

Couldn’t a local machine shop easily handle the warpage issue? For not a lot of money?

Or was this just a cheapie/older/dented model header?

[Dave H]

So yup, a bit of a warp there... https://youtu.be/zBe3AZ3A-Ek First couple machine shops I called said they couldn't do anything with it, found someone in Mesa who said they might be able to fix it. But considering that I can get a used one from ebay for under $100, it might be cheaper. We'll see what machine shop rates are though

[Jahoney]

The warp doesn't look extreme, but if a machine shop will do the work, the process of grinding it down to eliminate the warp is going to obviously thin the metal, which in turn will make it even more susceptible to warping again. I'd recommend a new or used one. If you want to go with stock as a replacement, I'd try the U-Pull salvage yards first. If you can find one, it's super cheap. Just look at the head where the manifold connects and look for signs of carbon build-up to reduce the possibility of getting another warped manifold. Otherwise, eBay is a good choice. Just watch the feedback of the seller (if you're not a regular eBay buyer, this is just a tip).

You might also contact Dave Lahey. He's not racing any longer, but I know he still lurks here around the forums from time to time and hes always got Miata parts laying around.

[Dave H]

I did find a machine shop that said they can fix it.... only charging me $45, so I'm not going to complain, and he'll have it back to me tomorrow. Did see one on ebay for $80 plus shipping, but I'll probably just keep this one and save the money to go with a race header eventually