I have had one [censored] of a time fixing an exhaust leak from my crossover pipe. First it was the gasket, now after getting a used crossover it’s coming from the joint where the flange meets the pipe. I won’t tighten it any more due to warping of the flange so I went the JB weld high heat epoxy putty route.
It’s my first time using it so I didn’t actually knead it into a ball, I flattened the stick out and kept folding it over on its self until the two parts were mixed and a nice grey color. I prepped the surface prior with engine degreaser followed by brake kleen, then used 60 grit sand paper to rough up the surface.
As I was pressing and molding the putty in place it began snowing. By the time I was done it was in the low 30s and still is 16 hours later. I fired it up this morning and I could still hear the exhaust leak, and after 30 seconds the putty patch went from solid rock consistency back to putty and was malleable.
I’m reading online it needs double cure time in temps lower than 50 degrees F. However after 16 hours, 8 of which I used a work light which burns your hands after being on 30 minutes to try and quicken the curing process, some areas are still malleable.
So did I knead incorrectly or is it too cold for this stuff to cure?
First time using JB Weld: User Error or too cold?
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I dunno, but please post results of further attempts TIA
Years ago I had a’79 L82 Corvette I desmogged by having a Midas shop put an earlier model big block exhaust on the car. They did a great job on the install and I noticed they brushed every joint with furnace cement before assembling. The owner told me it was a common practice. Drove that car for 12 more years and never had an exhaust leak. I never forgot the furnace cement thing and it’s easy to come by too. It sure worked for me and it might work for you. Just a thought. HD and Lowes both carry it.
Can’t copy and paste for some reason but Home Depot has “Rutland Furnace Cement in tub black -64c” for $6.29. The pictures show a caulk like tube. Might be your answer.
None of this will help you but I gotta "vent it".
1) I've only used the original JB Weld and it's been PERFECT every time.
Your grey color being uniform HAS to be OK.
2) I checked to see what your "High Heat" version packaging looks like. I wasn't aware they made that.
3) Were you able to partially disassemble your system (to get a better bite) or did you just apply it superficially?
An "up-side-down pyramid" of putty stuck in a hole likely will blow out. 'Know what I mean?....no shoulder.
4) The temperature was likely your problem. I wouldn't think a bad batch came down the pike.
But you did say a hardened sample went back to being putty, no?
5) At first you don't succeed.....
I recently used JB Weld in Florida summer, mixed it properly, and it still hadn't hardened after 24 hours. Methinks the formula has changed.
Temperature. Epoxy setting time is related to temperature. We have epoxies at work that require elevated temperature to set. That stuff goes in an oven. At lower temperatures it can take the epoxy a long long time to set, or it might not even set.
Mixing is also critical. I've had epoxies fail to set due to inadequate mixing. My rule of thumb is mix it well, then mix it some more.
When using epoxy, keep the little pan or whatever of waste mixed epoxy. Then you can check the setting of the epoxy in the waste, without disturbing the patch. In other words, you can poke and prod the waste, you wouldn't want to poke and prod the patch.
My bet is on the low temperature. Even with localized heating, the exhaust pipe would tend to draw off the heat and remain cool.
I haven't had much luck with patching exhaust systems. The patch tends to be very temporary.
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I use high temp rtv on exhaust joints. (Permatex orange or preferably red). It's been a while since I've done that type of repair, so Permatex may have changed their colors on their hi-temp rtv. It works long-term although you may not think it would.
And I’ve tried copper rtv to no avail. The gap has to be paper thin to seal properly. This gap is 1/8 inch.Originally Posted By: Kira
None of this will help you but I gotta "vent it".
1) I've only used the original JB Weld and it's been PERFECT every time.
Your grey color being uniform HAS to be OK.
2) I checked to see what your "High Heat" version packaging looks like. I wasn't aware they made that.
3) Were you able to partially disassemble your system (to get a better bite) or did you just apply it superficially?
An "up-side-down pyramid" of putty stuck in a hole likely will blow out. 'Know what I mean?....no shoulder.
4) The temperature was likely your problem. I wouldn't think a bad batch came down the pike.
But you did say a hardened sample went back to being putty, no?
5) At first you don't succeed.....
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What about thick gasket material you can cut to fit?
Trying rtv once more. I noticed that latest crossover pipe is slightly smaller in diameter than the old one, which makes no sense given its the same make and model, 3 year difference. If the rtv blows I’m gonna take it out and haul [censored] then come back and tighten the compression gasket while it’s still hot. I’m just hoping it doesn’t shrink upon cooling.
I also ordered that furnace cement as a back up. 😀
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3M Scotchweld or Devcon.
Add a hot air gun to your tool kit. They're very handy for heat shrink tubing, flame less warming of things, whatnot.
Originally Posted By: DoubleWasp
I recently used JB Weld in Florida summer, mixed it properly, and it still hadn't hardened after 24 hours. Methinks the formula has changed.
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