Brake bleed/bad MC?

[scottyg]

I brought home my M37 last weekend. 1954 with 14000 original miles. The left front WC was blown so I installed both front WC's to be on the safe side. I am having trouble bleeding the brakes. I have a vacuum system bleeder kit and went arount the truck twice from farthest away from the MC to closest. The pedal goes to the floor on the 1st pump. If I pump it 6-8 times, it gets hard and will hold the pressure. As soon as I let off, the next pump goes to the floor. What is the valve and line coming off thetop of the MC? Should it be open or closed? It made no difference in the bleeding. Could my MC be bad? Any help would be great.

Thanks,

Scottyg

[Charles Talbert]

I brought home my M37 last weekend. 1954 with 14000 original miles. The left front WC was blown so I installed both front WC's to be on the safe side. I am having trouble bleeding the brakes. I have a vacuum system bleeder kit and went arount the truck twice from farthest away from the MC to closest. The pedal goes to the floor on the 1st pump. If I pump it 6-8 times, it gets hard and will hold the pressure. As soon as I let off, the next pump goes to the floor. What is the valve and line coming off thetop of the MC? Should it be open or closed? It made no difference in the bleeding. Could my MC be bad? Any help would be great.

Thanks,

Scottyg

Most likely what happened:

If the M/C was not already bad, it is now as a result of pushing the pedal to the floor. By doing so, you forced the M/C piston past its normal area of travel within the cylinder bore. This will ruin the piston cups. Never push the pedal farther than 3/4 of its total travel distance during bleeding, even if it is new. The best option is to simply replace the unit, as rebuilding has a very high likelihood of not being sucessful. In fact the best option for you is to go ahead and replace the rear wheel cylinders and the Master cylinder. Good idea to check the drums for roundness and the shoe linings while you are into it. It isn't that expensive to renew the whole system, by far the best policy to do so.

Your question concerning the valve and line on the M/C reservoir cap, it is simply a vent line. All M/C's of this type must have an open air vent into the reservoir in order to work properly. The line is routed back into the engine intake air system so the M/C can be vented during water fording activities without the worry of taking on water.

[scottyg]

Charles,

I understand about the MC travel issue going to the floor. Actually, I read your conversation with another individual on another thread/website before I started the brake job. So... I bled the brakes using s vacuum bleeder kit. I just replaced the front WC's and the drums and shoes are like new. Only 14000 original miles. So all that being said, looks like a MC is recommended? Do you offer them? I am also interested is discussing a power steering conversion with you. I understand that you can supply all the parts as a kit?

Thanks,

Scott

[scottyg]

Charles,

Good call on the rear WC's and brakes. I just took them apart for inspection. Not confidence inspiring. The MC was original. Going to change it and the rear WC's. Can you supply the parts?

Scott

[Charles Talbert]

Charles,

Good call on the rear WC's and brakes. I just took them apart for inspection. Not confidence inspiring. The MC was original. Going to change it and the rear WC's. Can you supply the parts?

Scott

We can supply all the brake parts, can also offer the hydraulic power steering conversion. Give me a call at the shop tomorrow if you would like, 704-474-4683.

[scottyg]

Will do. Thanks.

Scott