Dear friends,

I want to replace header pipe. The three nuts are seized. Looks like nuts and flange became one metal piece. I have used PB blaster for 7 days. Heated with my
home depot torch(not oxy-acetylene torch).


Please help me.

Thanks

It will be very rough to release the nuts by heat using a propane torch. The idea is to get the nuts red hot before the studs start absorbing heat - for that you need oxy-aceteline. A 5/8 inch six point socket may fit better than the 15mm. Differences in socket brand is a factor too, as has been suggested. Use 1/2 inch extensions and ratchet to reduce flex. You have to work quickly getting the nut to cherry red and then make an attempt. An extension with a "wobble" drive end may be useful for getting on the nuts directly. Watch your knuckles. -- Dave

Thanks

The main problem is thick corrosion bond between flange and surrounding of nut's bottom. PB blaster could not break. I am afraid too much force will make nut rounded and break the stud.

Thanks again.

Anil

Poster kturri and I are of the same mind. I've seen many very badly corroded nuts come off with oxy-acet. You need to heat the nut only - if you heat the stud along with the nut-it will expand with the nut-deafeating the purpose of the heat. A propane torch can not get the nut heated to cherry red fast enough. In a previous note you said you had heat on it for 20 minutes. To do it properly with an oxy-acet torch--maybe 30 seconds--at most. -- Dave

Just did this on my 940, but in my case the exhaust manifold cracked. I tried all the tricks, but had to grind the 3 nuts off. You will unlikely be able to do this without damaging the studs. It just might be easier to have a local shop do it and pay them the admittedly high price of 100 bucks.

Removing exhaust mani is dicey, in my case, I had it off 2/3 years back for a leaking head gasket. A stud them snapped on torque up, so again, dicey, wouldn't go there, unless I had to.

Drive the car until the engine is well warmed up. Squirt nuts with PB (or mixture of 1/2 acetone 1/2 ATF). While everything is still stinking hot, use a socket that just fits over the end of the studs. Add a couple extensions and give the nuts a series of whacks with a medium sized hammer. Repeat as often as you care to. Find a 6 point socket that will drive on to the nuts (imperial or metric) and give them a try. I have found the studs are pretty good material and have never broken one. Unfortuneately, your mileage may differ.

Greg

without an acetylene torch you will need some luck if you plan to leave the exhaust manifold attached to the cylinder head.

you might be able to remove the nuts even if they are no longer fully hex and the proper size due to rust by using one of these

http://www.amazon.com/Irwin-Industrial-Tools-394001-Bolt-Grip/dp/B0000CCXVZ

if these come off using an extractor and the underlying studs are not overly eroded you dodged a bullet and are good to go.

if the studs are in poor rusty condition you will have to remove the exhaust manifold and replace them.

if it was me doing this job not having a torch to heat the 3 header nuts i would be planning on removing the exhaust manifold and separating them on the bench where access and control is optimal.

"i would be planning on removing the exhaust manifold and separating them on the bench where access and control is optimal."

I wouldn't suggest it. Because, considering how long the manifold has been on the head, there is a very real possibility that a manifold stud or more will snap. And that is far worse a problem.

I'd suggest trying to cut the nuts off possibly with a Dremel.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

if you have ever actually done that job, on your back, in the driveway with the car on jackstands you know how awkward it is and how little clearance you have with your arms outstretched upwards.


a dremel, at that angle, with virtually no clearance for at least one the nuts.......you must be kidding!

Thanks to all for input.

This morning I tried to bang the nuts with chisel and hammer, the bond between
3 nuts and flange is so strong, I could not break the bond between the nuts and flange, it looks like one piece of strong metal. The nuts are fully hex and studs are in good shape. I tried to make red hot with propane torch and sprayed cold water. The bond is still strong. Today I sprayed the manifold 8 nuts and studs with PB blaster.

Thanks again

"I tried to bang the nuts with chisel and hammer"

The nuts can be sacrificed, that is why I suggested trying to cut them off with a Dremel. If you can reach the nuts with a chisel and hammer, you may be able to reach it with a rotary tool. http://www.harborfreight.com/catalogsearch/result/index/?p=1&q=dremel

Try a different 15mm socket, some will fit tighter, if you want to turn the nuts off.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.

"I could not break the bond between the nuts and flange"

I think you may have one-piece flanged nuts. I seem to recall some that were made that way.

--
Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

if the flange and nuts are one piece how was the header assembled with the manifold if the studs are protruding from the bottom of the manifold?

for 23 years corrosion rust bonded nut bottom part with flange.

you might try a tight fitting socket attached to 1/2" extensions ending in a 1/2" drive breaker bar with a cheater pipe. 3/8" will likely not be enough heft to break it loose.

this presumes you do not have a compressor and GOOD impact gun.

a good 1/2 drive impact gun will likely spin them off.


it is an awkward position to loosen them.

15 mm socket is loose and 14 mm does not fit. If I make the stud and nut red by heating with propane torch(20 minutes),than immediately use what you described with 1/2 in breaker bar, I am afraid if stud breaks?

Thanks,

Anil

Try to put the heat on the nut, NOT the stud, with the heat you are trying to expand the nut, not both.
If a 15mm is to loose, try imperial sockets to see if you can get a tight fit.

I suggest heating the nut to cherry red, but don't be concerned about the stud getting hot or the speed to wrench the nut. The purpose of getting it hot is that iron oxide has a lower melting temperature than iron. Once hot enough, even if quenched, the rust is gone.