I have a crack in my exhaust manifold that i am getting replaced in a couple weeks here....i just want to put a lil bandaid on it

will jb weld do the trick?

if so, how long will i be able to go with the jb weld on it?


also-how long do i have to let it cure?

if i let it sit for 12 hours, then turn my car on just to move it out of the garage, to the driveway, would that damage it?

+ for all helpers

thanks

well, theres a few things to keep in mind about jb weld... first, its an epoxy base, and epoxy is a thermoset plastic, meaning that it cures once, and does not melt down again very cooperatively, so if it gets too hot it would likely catch fire instead of melting away....

having said that, i know that west system epoxy used in boat building wont actually reach a flame point until about 500 degrees, and i believe i read that it gets softer before that point, becomes kind of a charred, coagulated mess... so i think it may be pushing the limit, if i were to do that i would use jb weld and wrap the spot in some fiberglass to firm it up a little since fiberglass doesnt burn or melt till well beyond 500 degrees.

maybe give jb weld a call and ask them if anyones ever done it before.

midnightcarving I must type slow or something. You message wasnt here when I started this post.

Couple quick things I thought of about using JB Weld on an exhaust.

1) What is its operating temp?
2) What is its expansion characteristics in comparison to the surrounding material?

With that being said JB Weld is very strong. After it cures it can be machined like a normal piece or metal. I have used it several applications but I am not sure it would hold up to the heat your exhaust will produce. If you want to try a temp patch you will need to make sure the area you are repairing is completely clean of rust or any other foreign material so the JB Weld can attach to the surface properly. Allow it to sit at least 4-6 hours for full curing. After that you should be golden.

Make sure you check out the above before doing the repair. It would be bad to find it on fire after 10 minutes of drive time!!! or a larger crack in your exhaust because it expands much quicker than the material you are repairing.

[This message has been edited by NeoNot (edited 12-06-2007).]

If you get the industrial strength version of JB weld it says right on the package that it has been used as a piston patch, head patch, ect. ect. I dont actually know the number to tell you how the heat inside the engine in certain places compares to the exhaust but I would assume that they are comparable.

JB Weld will cook itself (smoke, fire, etc.) I tried it on an exhaust manifold once.

If you want to repair a crack on an exhaust manifold go to NAPA and buy the Hi-Temp Metal Repair Compound.
It is made by Permatex and it looks like this:



You can read more info on it here:
http://www.permatex.com/pro..._Repair_Compound.htm

When it dries it feels like cast metal and can be ground down and sanded. I used it to fix a crack on an old Pontiac 400 exhaust manifold and it is still holding strong.

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[This message has been edited by Oreif (edited 12-06-2007).]

it says right on the back of the jb weld box: holds up to 600 degrees F.

doesn't my engine only run up to 240, if that

if my engine temp on my car shows it's between 180 and 240, could the manifold really be twice to 3 times as hot as the engine?

If I am not mistaken the temp reading is the temp of the coolant or oil? And the manifold doesnt have a cooling system other than air that blows by. Not to mention all the hot gas goes through it after being burned.

If the manifold can glow red then it is definately hotter than 240 degrees.

Sounds like the stuff from napa is made for this kind of thing so I would go with that

ok

plus for you!

I used a exhaust sealer from Autozone to double seal the joints on my test pipe, I'd use that over JB weld. I can get you a pic of it later, its in the exhaust section near the muffler tips, cost like $4.99 and works great.

I dont mean to hijack the thread but just a quick question? How much torque can JB weld handle? As I was tightning my water pump bolts a piece of engine block broke off exposing half of the bolt thread consequently creating a coolent leak. I really dont want to pull my engine to weld cast iron so I though I'd try JB. Thanks.(You can have your thread back now)

quote Originally posted by 5speedsup: I dont mean to hijack the thread but just a quick question? How much torque can JB weld handle? As I was tightning my water pump bolts a piece of engine block broke off exposing half of the bolt thread consequently creating a coolent leak. I really dont want to pull my engine to weld cast iron so I though I'd try JB. Thanks.(You can have your thread back now)

I would use the Black Hi-Temp RTV. Remove the bolt and coat the threads with the RTV and then screw it in. This is the same stuff you are suppose to use on the head bolts that screw into the water jacket.

As for exhaust manifold temps, They run a lot hotter than the coolant in the engine. The JB Weld will turn black and start smoking within a few minutes of the engine running. As I said we tried it once and it does not work. The compound I posted is good for 2000*.

quote Originally posted by Oreif: JB Weld will cook itself (smoke, fire, etc.) I tried it on an exhaust manifold once. If you want to repair a crack on an exhaust manifold go to NAPA and buy the Hi-Temp Metal Repair Compound. It is made by Permatex and it looks like this: You can read more info on it here: http://www.permatex.com/pro..._Repair_Compound.htm When it dries it feels like cast metal and can be ground down and sanded. I used it to fix a crack on an old Pontiac 400 exhaust manifold and it is still holding strong.

I just tried this stuff and it will blow right out of the hole the first time you accellerate. It does get plenty hard and will hold up to the temp but it doesn't stick unless you could secure it somehow. Perhaps a worm screw hose clamp? I'm not trying to debunk you Orief, just relaying my personal experience also. I will add, my problem was a hole and you mentioned yours was only a crack. That could have meant less pressure for yours.

Jim

quote Originally posted by shermdizzle: it says right on the back of the jb weld box: holds up to 600 degrees F. doesn't my engine only run up to 240, if that if my engine temp on my car shows it's between 180 and 240, could the manifold really be twice to 3 times as hot as the engine?

Exhaust gases can get up to 1400*F in the chamber. I think when it hits the manifold it is atleast around 800-1000* still, so yup, it'd cook.

JB Weld is the absolute best epoxy that I've ever used. Strong as steel but not for exhaust work. I've fixed radiators with it and they held for years, I've used it as a permanent threat sealant and it lasted, fixed stripped threads and even used it to seal transmisson lines and block leaks. Although the label indicates otherwise I'll say that its only good for 300*F though.

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87GT - with 3800SC Series III engine, 4T65eHD
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

quote Originally posted by jimbolaya: I just tried this stuff and it will blow right out of the hole the first time you accellerate. It does get plenty hard and will hold up to the temp but it doesn't stick unless you could secure it somehow. Perhaps a worm screw hose clamp? I'm not trying to debunk you Orief, just relaying my personal experience also. I will add, my problem was a hole and you mentioned yours was only a crack. That could have meant less pressure for yours. Jim

For a hole, you would need to fill the hole with something and the compound would act like the adhesive. As an example for an exhaust manifold that had the old A.I.R. pump holes in it you could cut a small circular patch out of steel then use the compound to hold the patch down. I would never expect the compound by itself to fill in a hole.

Just for reference, I measured my exhaust manifold temperatures with a thermocouple measuring device and the typical surface temps ran from 800-900°F on average up to 1,100°F under certain conditions. No epoxy-base material that I know of will handle that without combusting.

JazzMan

to answer my own question...i went on JBwelds website

and it clearly states: do not use on exhaust manifolds!!!

lol, there's my answer

Man... I love POR-15 products... have used many of their kits on random things...
You might investigate this. It is complete, and idiot proof. I say this because I am an idiot, and this stuff has not failed me.

Now I have not used the manifold kit... but if experience matters, this should be a quality product.

http://www.por15.com/prodinfo.asp?grp=MRK&dept=11

Keep in mind that if you ever get a vacuum leak, your manifolds will get hot enough to glow red. So your fix has to be good enough for that heat.

Use furnace cement from a hardware or muffler patch and before it dryes wrap it with manifold tape! Should get you a week or two.

Thermoweld from Car Quest - has a much higher temperature rating than JB Weld. About six bucks for a small jar. Only drawback is that once you open it, pull off the seal and stir it up well (liquid on top) you have to use it then. In other words, you have to buy a new little jar each time you want to patch something.

the only way to fix a cracked exhaust manifold is to either replace it (best bet) or to weld it. JB weld will either crack and chip off, or burn up. the manifold fix stuff napa sells will work for a while, but it'll eventually blow out and you'll be right back to the drawing board. I've patched a few manifolds on my old chevy truck, and nothing works except doing it right.

with my old 2.8 the rear E man was cracked, i used "thermoweld" i used jb, i used that stiff oreif talked about, non worked, i even wrapped it with allumnim foil over each compound, none worked., i will say tho, the jb lasted the longest when i wrapped it with foil. (3 or 4 days) this pic is after i got fed up, blew the stock 2.8, and replaced it with a 3400., and new logs...

Not sure if this was mentioned but the stuff in the exhaust aisle called "Thermosteel" it is little metal super fine bits that look like they are in oil. They are separated most of time unless someone shakes/stirrs them. Anyways it works for exhaust cracks, just put it on thick.

Not on exhaust man, it'll just burn up. otherwise it will withstand just about anything you can throw at it. I used it to put a fitting into a stripped out brake proportioning valve and it has never leaked-that's alot of pressure!

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Muffler tape/ bandage is the only thing that I know of that may hold up to the temperatures. I have used it on tail pipes, mufflers in the past but not on my Fieros. It works best to give it a couple of wraps and back it up with metal (tin can, light steel) and secure it with hose clamps. As stated in the above posts, the Fiero manifolds get incredibly hot and those like to crack in the most inaccesible spots, muffler tape may only last long enough to get the car to your repair facility. Can you get a spot weld on it as a temporary measure?

This thread may come in handy when you're ready for the repairs.
https://www.fiero.nl/forum/Forum2/HTML/065384.html

Let us know what works best on the crack, ok?

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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"