The Stovebolt Site Forums The Parking Lot Big Bolts 51 gmc brake master cylinder

Due to rust, I couldn't get my cylinder filler top off my reservoir so I took it out from under the truck thinking I could drill into it and put a tap into it and
back it out. That didn't work so now I have a master cylinder with a hole in the filler top that still won't come off. I am not sure if the cylinder is bad or not,
but from the previous owner I was led to think it was ok. Anyway, I'm not sure what to do now. I don't think the top will come off as it is rusted on so badly and a shop
has tried with no luck. Does anyone have any ideas for me ?

Thanks

Heat from the top, need to be willing to sacrifice top, might have to split and peel off.

Ed

Thanks Ed, I will try heating one more time. I appreciate the response !

Troy

Since you have it out, why not soak it in rust remover for a day or two, then try again? 🛠

I will try that too. I’m sure open to all suggestions at this point.

Thank you sir

If all else fails consider mig welding a nut to it. Between the heat and additional torque using a wrench???done similar with the lock ing lugnuts that need a key.

Thanks tlm for the suggestion, I appreciate it !