Brakes: Master cylinder lid will not turn on 62 GT

[Jimmie]

I want to check the fluid in the master cylinder on my 62 GT and cannot turn the cap even with lots of pressure on the handled of my ratchet. Should I just put more pressure. I am concerned about destroying something. It has been over 4 years since I had the brakes redone. Thanks for any suggestions you can give.

[Mike Van Veghten]

First, I'd use a 6 point socket.
Hold tight pressure against the socket to the cap, and pull, or push the wrench handle.
Make sure that when it breaks loose, your hand and face wont crash into anything solid..!
As long as the socket doesn't slip, you aren't going to hurt anything.

Mike

[skyway]

Those "?zink?" caps can be pretty tight sometimes; corrosion is often involved.

In addition to what Mike said above, consider using some penetrating fluid & giving it time to work.
Maybe even doing some gentle tapping all the way around the outer edge of the cap above the threads.

[2R5]

It will come off but I question that you don’t check this a couple times a year

[studegary]

I would tap the cap around the edge, with something like a chisel, in the unscrewing direction, then try to turn it.

[Harryhawk]

Sometimes nipping bolts and other things up a bit ( with an accompanying crack sound ) and then loosening works. Cheers Harryhawk

[PackardV8]

On any stuck fastener, I use a socket on an impact gun and begin by bumping it in the close/tighten direction, then keep lightly bumping and increasing the pressure until it loosens.

jack vines

[345 DeSoto]

What HE said^^^^^^^^

[TX Rebel]

Apply heat to the top of the cylinder, then break it loose with a 6-pt. socket & ratchet. It will save breaking the aluminum cap.

[Studebakercenteroforegon]

As inexpensive and readily available as this particular master cylinder is - I would just buy a new one and be done with it. I suspect that even if you did succeed it getting your cap off, the threads will be damaged enough to make you not want to use it.

[Blue 15G]

Not pertinent to your dilemma, but I've noticed that some of these cylinders are coming through with plastic caps on them now.

[Jimmie]

Thanks for all of the suggestions. Hope I can have an opportunity to help others sometime. Jim

[DEEPNHOCK]

Dissimilar metals. Electrolytic corrosion.
Newer caps are plastic, so this condition disappears.

If you want to keep your original cap, lightly wire brush the cap threads and then buff the cap threads like you are polishing it to look good.
Then use a light film of non-metallic grease (not anti seize).

[rocket1]

When you do get it off you might want to install a new copper gasket.