Stuck bolt on a brass part

[Dave Sherman]

Specifically, it's the brake failure warning switch on my MG Midget. It's a brass part with a shuttle valve in it that pushes one way or the other if there's a pressure loss in the front or rear brakes and trips a switch. There are two small O-rings sealing the piston, and apparently one of them failed and emptied the master cylinder after sitting for a week. Years ago I bought a rebuild kit for it when I overhauled the rest of the brake system, but I couldn't get the threaded part (the big hex bolt) off easily, mainly because there's no good way to get a grip on the rest of it. Any ideas on how to remove it safely? It's not a readily available part, so I don't want to damage it. I'm afraid of gripping it in a vice for fear of twisting it or breaking off one of the fittings. There are two fittings opposite the ones on top you see.

 

[default]

Delete it? You'll know if a brake circuit fails all on your own

 

[Kool1]

When working with parts assembled with dissimilar metals, it is almost always a scary challenge. I like to use flare nut wrenches when a metal tube is involved and a penetrating lubricant to help cut through some of the rust buildup. Pray like he!! when wrenching on the part and make sure the wrench gets a solid grip.

 

[The_Jeff]

Go for a crow's foot on a long extension.

If that fails, cut the line and put a 6 point socket on it.

If you cut the line where you can cut it, you can metal fatigue it off down at the line nut.

 

[Dave Sherman]

Ok, the problem isn't the line fittings, it wasn't that long ago I replaced all the brake lines and I had no trouble removing the old ones. It's the large hex thing I've circled in yellow. The flare fitting circled in red I just haven't removed yet. I need a way to grip the body once I've removed the lines. The hex piece I would have no trouble using a deep socket or closed end wrench, I just need a way to hold the body once I get it out of the car. The car's inboard fender is pretty flimsy and would surely bend if I tried to wrench it while it's in place.

 

[doitmyself]

If you are already removing the lines, why not just remove the entire unit and mount it in a vise to hold it while you remove the end piece?

Oops, just saw your vice comment in the OP. I don't have an answer. Other than you might have to use some wood shims in the vice to hold it in a manner not to apply stress to any breakable part. Heat often helps get things unlocked, if you have new internal rubber parts for replacement.

 

[JHZR2]

Can you remove all the lines safely, then remove the part entirely, rebuild it on a bench, and install it all?

Since apparently the lines come off easily, and you can safely do them with a flare nut wrench, Id go the route of doing that and working in a better space. Given dissimilar metals, you may well be looking at needing to use heat, icewater, wax, solvent, and a lot of time...

Good luck!

 

[05LGTLtd]

Use wood to make a shallow box the part fits in, then epoxy putty to form around the part which is slathered in Vasoline and use plastic wrap or foil to make a separating layer. One pour for one side then another pour for the other side and you have custom clamshell you can put in the vice...

 

[oldhp]

Put it vise, use heat from propane torch and then put icecube on it. Should unscrew easy, if not, repeat.

 

[Rand]

kroil is pretty amazing too..

I had a neighbor with a wheel so corroded on I couldnt beat it off the rotor safely.. and i was really trying..

I sprayed just a few sprays on it and.. about 10s later the wheel FELL off.

I usually try Kroil,>>> some gentle heat,>>> then more aggressive heat/ice.

 

[The_Eric]

Stick it in a vice, warm it up and give it a few sharp raps on a long wrench. It'll come apart. I know you're concerned about the vice thing, but it's about your only realistic option.

 

[wings&wheels]

Arrgghh..the dreaded PDWA..

The brass body is tough, you should be able to free the plug/fitting using a vice w/ wood or other cushioned jaws mostly to protect the cosmetics, a lot of penetrating fluid and maybe some gentle heat. Try not to damage the body or round off the plug as the replacements are usually made of cast iron and look different, rust, etc.

The TR6 uses a similar piece. When it all goes back together I coat all of the threads with either a silicone brake grease, one compatible w/ rubber, or Lucas/Girling rubber grease. PBR also makes a rubber grease if Lucas/Girling is unavailable.

Good luck, fun car.