jus what the title says... can u use high temp silicone for gaskets?? like for the dp, hf cat, and exhaust...?? is this good or bad any info would be great.

 

dont be shy now, speak up...lol

 

Check the temp specs. I seriously doubt it can stand up to the heat at the downpipe connection. The cat might be too hot, too. It might hold up at the cat-back connection, at least for a while. You would be much better off just using the metal gaskets and making sure the surfaces are flat and mate up well for a good seal.

-Max

 

Permetex copper gasket is rated up to 600 degrees IIRC. I'll double check to make sure.

 

Why would you be wanting to use this stuff when there is a right way to do the job. I understand if you have to make flanges or something and they don't make a gasket for it, but is it worth all the headaches and removing/ replacing the exhuast components if the silicone fails when you know stock gaskets work, and work quite well?

 

i dunno i was just wondering because some1 mentioned this too me...but right now im in need of gaskets for the pettit dp i got along wit the hf cat and the exhaust...and im just trying to get my hands on some rite now

 

I know if you use silicone grease or sealant before the motor and part of it gets combusted, the gases emitted can ruin your O2 sensor which might cause your engine to blow, so i would at least not use it before your O2 sensor, but i wouldnt use it at all. Just my 2 cents from what i picked up at UTI.

 

Hi temp silicone doesn't work for **** on our cars. I used it to hold the gaskets on place while putting the car back together. After I got finish it didn't leak but after 2 days it did. So as soon as I get home from this deployment I will repalce all the gaskets in the exhaust. So to make it short; nope, it doean't work

 

You should NEVER use any sort of gasket sealer on exhaust components. All you need are 2 clean, flat surfaces and a quality gasket. Adding a layer of silicone will just give a weak spot - the silicone will blow out and you'll have an exhaust leak.

Most of the exhaust gaskets (if they're quality parts, like the stock Mazda gaskets) are re-usable MANY times.

Dale

 

It's when the surfaces are mismatched or not flat that life begins to suck.

I recently installed some gaskets (dp/cat, cat/cb) that I made from Mr. Gasket gasket material. Due to heavy flange warping, I had to make them 2 layer and insert fitted shims of the gasket material to provide compression the whole way around the pipe. I used the 600F Permatex copper RTV to hold the layers together, but it is not used to do actual sealing. I think it's safe in this role, but alone I wouldn't trust it.

Someone did provide good advice once on the RTV alone: make the bead and let it sit for a full 24 hours before clamping it. Otherwise, the clamping process will just make a mess and it won't seal.

Dave

 

Does that advice hold true for making a gasket around the oil pan? I followed the instructions of FSM and installed the gasket within 10 minutes of laying the bead of gasket around the pan.

Thanks!

 

No. For parts like an oil pan or transmission case I've used a different gasket which takes a few minutes or so.

Dave

 

How did the flanges get so warped? I've never seen flanges THAT warped on an RX-7. Would a stock Mazda gasket with the metal ring in the middle not seal up?

I have seen problems where people get exhaust "cocked" to one side where the flanges wouldn't line up well. Usually happens when you tighten one exhaust flange slightly misaligned, which pulls the whole system out of line. I always assemble everything loosely, then snug up all the bolts, then tighten everything.

This is also why I don't like muffler shop exhaust - it's VERY hard to get the flanges to be properly lined up if you're making an exhaust system. A quality system will line up and fit properly.

I chased my tail big time on exhaust leaks on my first '87 turbo - I learned lots on that car .

Dale

 

For all exhaust gaskets after the manifold: just brush them and re-use them.

 

Dale, I have no idea wtf happened to the flanges on mine. To start, both faces of the cat flanges were well corroded and not too flat. The muffler pipes are plain steel and they weren't doing too well either. I suspected warpage.

So I took them to a shop who put them on the belt sander to clean the faces - possibly a mistake since I think he didn't sand the faces so they are now not flat. Unfortunately I didn't inspect for that until they were all bolted in. Doing the fitted gaskets works, but I don't know how long it will last. I also think for some reason the exhaust hangers don't line up well - to get it all bolted in, the exhaust is pushed back about 1", stretching the hangers a bit. I'm sure that only gets worse when it heats up and expands.

So I may remove the dp, cat, and cb all again and test clamp them off the car. Inspect which faces aren't flat using a flat plate and feeler gauges, and have them resanded (or milled? or ground?) or cut them off and new flanges welded in. With new flanges I can make sure they all line up perfectly. I think I'll also bolt it together and use a tape measure to figure out if the hangers are located in the right places too.

So anyway, I've been chasing my tail too. It just shouldn't be this hard.

Dave

 

What exhaust are you running - stock parts, what brand aftermarket parts, etc. ?

Dale

 

Stock cat, old style RB dual in plain steel, and Pettit SS dp.

Dave