About to take out the leaf springs on the old XJ and I've spent a couple weeks now heating the bolt heads with propane and soaking in PB before I start in on em. I'll spend like 5 mins or more a bolt just heating right on it but it still doesn't seem like it gets the thing hot all the way through. It never does get close to red hot. Is propane gas hot enough? The MAP/PRO stuff only gets like 150F hotter so it'd hardly be worth it specially since it costs 3x more.

 

I usually use MAP gas, I don't remember it being that much more expensive for the small bottles you find at Home Depot, but a quick google search told me that;

S o not sure if an additional 130*F is really that big of a difference but it seems to get the bolts hot enough. More important is having a good quality torch head - I have a fairly simple Bernzomatic one that has 4 "jets" vs the 1 "jet" on my smaller crappy one and it really helps with the flame intensity

 

It's the heating and cooling that makes the rust let go.

You're probably fine.

 

+1 for the MAPP gas. I made the switch years ago and won't ever go back.

Try to rapidly heat the nut and NOT the bolt to maximize the heat expansion benefit.

 

Propane will work fine, but MAPP is better. Heat and quench with water. Rapid expansion/contraction is more effective at breaking the bonds.

 

I've heated plenty of nuts and bolts with propane, no need to get red hot, and i usually spray with PB when hot, quenches it and helps draw the penetrating oil into the joint. Seems to work for me almost every time.

 

^^^THIS^^^
I just changed leafs/coils and didn't break a single nut (except my own)

 

The factory bolts had red Loctite on them. Red Loctite releases at 550° F. Propane ought to get hot enough.

 

When I did my leaf springs I used MAPP, which was more convenient and faster. But getting it red hot was not necessary. Either would work.

 

MAPP gets hotter much faster. Definitely use it for sweating copper pipe. I use propane all the time on bolts. A quality tip is important. A combination of propane, penetrating oil of your choice and tapping with a hammer is my method of choice and it always works fine.

 

Get some CRC freeze-Off.

 

Thanks for all the good advice. Have a lot better picture now of how heating works...with rapid cooling/quenching.

Was afraid though quenching with PB would set it AFIRE! I guess that doesn't happen though?

Also, I could see how a good torch tip would concentrate the flame better, but I'm not sure if mine is good or not as I only have one I got from probably HD.

Can anybody point me to a picture of what a good torch tip is, or maybe model / brand name?

 

Oh yeah what's this CRC freeze-off? First I've heard of it.

 

This is what I use. They usually say like turbo tip or similar.

 

No, but that is exactly why I mentioned using water. Many times I use more than one heat/cool cycle. Reapply heat to a bolt you've quenched with oil, and it will catch fire. I don't really buy the theory that PB gets drawn into the threads after heating, nor have I seen evidence that it does.