seized Flathead screws

[OUTFXD]

still working on the master cylinder.    Got the floor pan out, Cut the hoses,  Got the pedals removed. 

 

cleaned off all the muck and now the flathead screws that hold the dust boot collar in place wont come loose.  Used an impact hammer until the the heads started to deform,  sprayed down the threads with PB blaster. sadly the collar prevents me from getting a good grip on the screws with vicegrips. 

 

Short of cutting off the heads and drill and taping the master cylinder,  what can I do? 

 

Just kinda looking for tips and advice while I let my head decompress.

[Doug&Deb]

Mopar certainly wasn’t thinking that nuts like us would be wrenching on their stuff 70 years later or they would have used different fasteners. Try heating them if possible. I know they’re for a boot so be careful. Let them cool down. Try tightening with your impact first then loosen. Slotted screws are a bear when they get stuck.

[52ismine]

Take your screwdriver and place the tip in the slot and hit the top of the screwdriver with a hammer. Sometime this will jar the rusted threads loose. Also try tightening the screw then loosening it.

[Ivan_B]

I think these are too small to work with. If you've got to the point of deforming the heads and they would not move, using vice grips would just tear those heads off completely. I would cut and drill them out. Using heat would fry the rubber parts of the cylinder. If you do it now, rather than trying a lot of other useless things, you'll probably save yourself some time

 

[Dave72dt]

What you need to be concerned about are the parts that aren't readily replaceable, like the collar and stop.  The rubber parts should come in the rebuild kit, don't know about the boot rubber.  shear the heads off the screws if need be, at least you can salvage the collar and stop as well as remove any internal parts and then work on getting the remains of the screws out using whatever means at your convenience.

 

If a fresh boot is available, get the old one out of the way, remove as much as possible, apply heat to the master where the screw threads are and try again. You can also try a little impact hammer, flat punch action on the master itself where the threads are.  Sometimes a little vibration there can loosen them up.