How do you apply heat to a stubborn bolt?

Agree. And, make sure the heat is applied away from any combustibles - your engine compartment is full of petroleum products, fanbelts, insulation on wires, etc, that would love to burst into flames. If you do go with the propane torch, you want to heat the nut, not the bolt (remember that heat makes things expand, and expanding the bolt is NOT what you want).Apply a little heat, so it's sizzling hot (lick your finger and just barely touch it), not red hot or anything like that.

There is no bolt to reach so I should not heat it at all.  How can I find out reverse threaded?

Try turning the ratchet to the right instead of to the left.  If it is still tighter than you can move, then I would recommend getting a Chilton or similar book for your make/model of car and see what it says about removing the fan.  You can also just try searching on the internet for your make/model and the phrasing "removing fan" and see what comes up.

Check a service manual. You might be able to find an after-market one in a library near you, or browse the pages you need at a Barnes and Noble or similar bookstore.

Just talked to a mechanic at Mercedes that said it is not reversed threaded. 20 gorillas put it on during the assembly line.  I REALLY don't want to strip this thing as it's starting to. He told me WD-40 won't reach the threads. Any suggestions or should I just go for it and write you guys back for instructions once it strips?

My recommendation is still to get a Chilton Manual for the make/model.  If you are trying to avoid taking the car to a mechanic for the work, then don't continue and strip the head, because that will be about the only option you're left with at that point.

I agree - look at / get the manual. As an added note, often vibration will help when force alone will not. Put your wrench on the bolt, and tap it a number of times with a hammer - tap, not pound it off. The idea is to break loose the rust or whatever holding it, not to use the force of the hammer to turn it.

And beyond that, there's always drilling it out, but that's a real pain, so you want to avoid going there if possible.

You could also post some pictures here of what the assembly looks like.  Maybe there's something else that needs to come lose before the bolt you're working on will come lose...

What make/model is the car anyway?

All good advice.  I did mis-speak.  It is not a bolt..rather a flat, allen wrench screw. A real challenge in a hiddious location. I have purchased a Hayes manual but the removal instructions were vague.

Taking a guess, I search for "mercedes fan screw" and found this:

http://www.ehow.com/how_2198001_replace-fan-clutch-mercedes-e.html

Looks like it requires a special tool, so maybe it's not a regular star head.  That could be why it's stripping out on you.

1993 Mercedes Benz 190 E 2.6  chasis 201  engine 301

I have ready removed the radiator wich gave me more room, used the clutch fan pulley holding tool so the fan doesn't turn.  There is nothing in the way. It just doesn't want to budge right now

I bought a special star socket by part number from a manual. (18 bucks) I'm using a 2 foot torque wrench.

http://www.baumtools.com/pdf/Mercedes_catalog_2008-sm.pdf

I'd try the vibration method - remember, you aren't trying to hammer the screw loose, just to send enough vibrations to break it loose from where it's been locked in place for all these years.

I will try this and comment back for an accepted solution.  Thank you! - Art

Thanks for staying with me on this, guys. It finually came off with a vengence! Vice grips...nothing. Socket....nothing. Vibration and socket worked. I ahve taken off many a screw and bolt in my life. THIS one was the worst! I just thought I was doing something wrong.  I'll post another question about this car shortly. Thanks again. Art