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RTV sealant - curing time, temperature????

I'm going to be using Permatex RTV Ultra Blue for the first time in a week or two, under a differential cover on a Dodge RAM 1500 truck. People are giving me opposite stories about how long to wait before filling it up and driving:

Some say you MUST wait 24 hours before refilling the differential, because it has to cure to be fully oil resistant.

But others say, in so many words, "nawwww." I know of one technician who has fixed hundreds of differentials, and he said you just put it around the seam, put it together and torque down the bolts, and by the time you've cleaned up your tools and put them away, you can go ahead and pour in the oil and take off. He's done this for years, and has NEVER had a "leaker."

Which is true?

Another item is that the instructions on the RTV container say it takes 24 hours to cure at 70 degrees temperature. Well, it happens to be February, and the temp around here is 30-50. Will that really have any effect on anything?

I'm just trying to find out the facts here; I don't want my rear end to grenade out in the middle of nowhere!

Ron M.

Reply to
Ron M.
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I learned and finally followed the damn directions and now have a leak free Jeep!

Except for my rear diff cover!!!!

That was recently put on by a shop using RTV when they put new bearings in for me.

They did not wait for 24 hours for it to cure, they just put it on, waited a few minutes if any and filled it up.

That is the only leak on my Jeep and I have had everything apart for servicing in the last few years.

Actually that leak ticks me off. I had my Jeep nice and dry under and am quite proud of that.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

"R>

Reply to
Mike Romain

Oh, in the cold I leave a light bulb or space heater on the area. The stuff goes jelly if it freezes and won't set strong at all.

Mike

Mike Roma>

Reply to
Mike Romain

I'd wait a bit. BTW, if you didn't know, RTV stands for "Room Temperature Vulcanizing". Most of them have an acetic acid based cure (the kind that makes your nose sting if you get a whiff). This requires moisture to catalyze the cure. Therefore, cure time is a function of humidity and temperature.

-Jeff Deeney-

Reply to
Jeff Deeney

"Ron M." wrote

If you have the time to let it dry for 24 hrs, that's good. But for those of us that don't have that kind of time (I work as a tech, flat rate, and there is no such thing as allowing an RTV'd diff gasket to set up for 24 hrs) RTV works quite well even if you fill the diff up within 5 minutes of installing the RTV. The more important thing is to make sure both the cover and the axle are spotlessly clean and "dry". Not just dry, "I wiped it with a rag", but dry because you use a brake cleen type of cleaner on the surfaces. You want to make sure there is no oily residue of any kind.

I'll add my voice to the tech that you talked to. I've done literally 100's of diff covers with RTV and have filled them with 5-10 minutes...no leakers.

Ian

Reply to
shiden_Kai

Just a heads up.

He stated he is using the 'ultra' line of Permatex which is not an acetic acid cure, it uses something else.

The older ones used that and those fumes don't just sting your nose, they kill the O2 sensor in an instant.

The 'Ultra' line is called 'sensor safe'.

If it smells like vinegar, keep it far far away from newer vehicles. Even using it on the diff has killed it on some friends vehicles.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's
Reply to
Mike Romain

People often get by with wetting an RTV-sealed joint quickly after the sealant has been applied, but it's safest to wait a while. I've obtained the best results by waiting overnight for RTV to cure. It'll seal diff covers and transmission oil pans successfully that way. Even installed some early Chevrolet valve covers with no gasket but RTV, and they were oil-tight for over 60,000 miles. Follow s. kai's advice to clean every millimeter of BOTH surfaces with something like Brakleen, or acetone. ABSOLUTE cleanliness is a must.

Reply to
the fly

I have a good bit of experience with this blue goo for sealing cooling systems.

Where hot water and pressure is involved, you'd better let it cure the recommended 24 hours.

I tried to push the time and ended up with leaks every damn time, but doing it right, it sealed perfectly

Reply to
HLS

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