Hi and thank you for allowing me to join this group.
I am trying to sort out a 1963 3.8 FHC for my 82-year-old father. I have had to do a lot of work to the car because it has sat since 1978. It is a dry California 2-owner car with only 45,000 documented miles but needed all new complete brakes including master cylinders soft lines, bridge pipes, 8 calipers(pistons), and pads, clutch master and slave, radiator, distributor, weather strips, water pump, all new hoses, fuel pump, complete rebuilt fuel system including the carburetors, and much more.
The car runs out great but it has an issue that I can’t seem to repair.
After the first test drive the brakes stayed on and the pedal was very hard. I was able to finally get the brakes to release but not sure how this happened. I then checked the adjustments again and test-drove the car again. It did it again and this time I cracked the left front caliper bleeder and the rear banjo fitting on the master cylinder and this released the pressure and the brakes freed up. I drove the car back home with the e-brake. I have now taken the servo apart and checked it and rebuilt it as needed. I have also checked the vacuum and it is good. I have now purchased a new vacuum valve and will replace the old one at the tank. After I rebuilt the servo I tested the car again and it did it again. This time I used a screwdriver and wedged it in between the front and rear master cylinders and moved it back and forth. It compressed both cylinders on the fulcrum and the brakes freed up. It is as if it is “cammed over” (this is a semi-truck term when the brakes are out of adjustment or the shoes are badly worn the brakes “camm over” and they are lock-up so that the trailer can not be moved until the linkage is released. Please help me with a suggestion of why this might be happening. I really appreciate it. Sorry for the long explanation.
Welcome to the forum.
It sounds like you may not have the brake pedal free play adjusted properly as it sounds like when you cracked the line at the MC pressure was released. Adjust the MC push rod at the pedal for some clearance.
Tom
Welcome to the community…… as a starting point try running without servo and see what happens
Yeah, what Tom said. I’m not familiar with the earlier E-type brake setup but had the problem you describe with my XK120 when I first got it back on the road. In my case I didn’t allow sufficient freeplay between the push rod and the end of the main piston in the tandem master cylinder. Heat from braking caused the brake fluid to expand and lock the piston toward its rearmost position, jammed into the push rod, locking the brakes and rendering the pedal rock hard and immovable. I had to ensure the m/c piston was all the way against the stop and then adjust the push rod to allow a small bit of clearance.
Thank you Tom. I will give it some more free play. I had the rod backed off to the point that it was hitting the clevis pin. I then added a washer on each side of the master under the bolting flange to the pedal assembly to give t a bit more free play or adjustment. I will see how much more I can give it. I may need to shorten the push rod. I bought the master cylinders from SNG Barrett. Have you had any experience with the rod being too long? Thank you again. Regards Andy
Thank you Nicholas for the help. I responded to Tom and will try to give it more free play. Regards Andy
On the last two 3.8 master cylinders I rebuilt I had a very difficult time getting the correct seals. Typically the ones supplied were way too tight. In searching the archives, you will see this has been a problem for others also. The last time, I ended up sending the master cylinders to Apple Hydraulics who had the correct seals. Not saying this is your problem, just has been an issue in the past.
Welcome to the forum Andy!
I own a 63 FHC and just for the record, your master cylinder and booster assembly should look like this-
First, as suggested, break the problem down into 2 parts. Get the brakes to lock. Pull the vacuum supply hose (will be connected where the blue tape is in my picture). If that releases the brakes, then the vacuum booster is likely your problem. If that does not release the brakes, then the problem is in the actual hydraulics. Report back and we can go from there.
Also, where is the car located? A forum member may be right around the corner.
It’s looking good Harvey
Thank you. Mine looks like yours, the configuration is the same but yours is a bit more tidy and new looking. LOL. I have disconnected the vacuum and it still persists.
Last night I removed the master cylinder and shortened the length of the pushrod by about 3/16". I reinstalled the master and it is better but it is still applying brakes by itself. I don’t even need to press the brake pedal. It was good on the first 5 mile run this morning but then I went again and this is when it started to drag the brakes. I pulled over when I felt the resistance and put a flat screwdriver in the linkage and moved/pried the top master cylinder towards the front of the car and then the brakes released. It seems to be heat related too. I feel that there is still not enough free play and again I have about 3/16" more that I can shorten the rod before the rod is bottomed out. All of the hydraulics are new.
Hi Andy
I had to shorten the rod on my new master to get it to release properly.
Mike
let me add a bit more. When the brakes are applied (by themselves) the button on the booster can be pressed but it hardly compresses the bellows because it is locked up ( I guess the master cylinder). Once it is freely moving again the button can be pressed and the booster collapses as it should.
I really think that this is the problem with mine. I am going to cut a bit more off of it today and try it again. I have also stacked 2 washers under the master to give it even more but it still isn’t enough. Thank you.
I know just enough about this to be dangerous but when I was putting mine together I noticed that the Spare Parts Catalogue listed 2 separate part numbers for the two MCs. I did some research and convinced myself that having 2 MCs with the same part number, which in my case is what I had, would be OK. But mine is not operational now so maybe trouble is coming for me too. Anyway, I recall a really long passionate article/thread that I found by a guy who went into great detail on how this sytem worked and I do believe he had a lot to say about the length of the rods. I really can’t recall where I found the article but generally I find stuff like this using Google searchs. Maybe someone here has a link to the article. I think it was pretty contentious at the time.
I had a similar problem once on my '62 and traced it to the eccentric barrel nut on the arm that presses the button on the servo. As it was, it was adjusted too tight and wasn’t allowing the pressure to be released. this is all explained in the original factory manual. The part is item 18 on the exploded view.
I had had similar problems due to aftermarket seals and cured those by re-using the original seals. The masters were the originals that I had rebuilt after getting them sleeved by White Post.
Andy, when I said to check for brake pedal free play, I did not mean to simply cut off the rod and see what happens. I meant to check how much free play and then adjust/cut rod so that you have the specified amount. I do not have the spec here, but I would suspect about 1/16in at the rod would be fine. Once you have the specified free play, and have that ruled out, then you can continue troubleshooting elsewhere if the problem persists.
Tom
Is this the one?
https://forum.etypeuk.com/viewtopic.php?f=4&t=4120&p=27776&hilit=master+cylinder+vbm#p27776
Yep, that’s it!!!
I don’t know if any of this will help the OP but there is certainly a lot of food for thought there.
