Brake problem (1 Viewer)

[Hamachi]

I recently replaced my all brake lines, brake booster (FJ62), and MC (FZJ80) on my 1978. After bleeding the system, my brake pedal goes half way and feels like its hitting something. I bled the lines again and checked front and rear for leaks and other problems (all OK) and the brake pedal still feels the same.

Can anyone shed some light on this?

Thank you.

 

[tornadoalleycruiser]

picture of the of the master cylinder. If there is a little bolt possibly on the bottom, then whomever rebuilt or put together the master might not have put the piston in the correct spot thus not allowing it to go the full stroke.

 

[Picz34]

Yes I agree. Had the same thing happen to me. See picture below. If this bolt has been removed the piston on the side may not be in the correct place.

 

[Hamachi]

My MC is a brand new FZJ80. I will check it when I get home.

Thx guys!

 

[Hamachi]

Looks like this.

 

[Picz34]

Looks like that bolt I refer to might be on the bottom of this one. There is a piston in there that moves back and forth with the pressure from the pedal. If that Piston is out of position it would feel like you are hitting something with the pedal before you get all the way to the floor.

 

[Hamachi]

I forgot to mention that when I open the bleeder, the pedal does go to the floor. It only stops half way after bleeding.

 

[Hamachi]

Anyone got any other thoughts on this problem?

 

[Hamachi]

picture of the of the master cylinder. If there is a little bolt possibly on the bottom, then whomever rebuilt or put together the master might not have put the piston in the correct spot thus not allowing it to go the full stroke.

It goes full stroke when bleeding it...

 

[tornadoalleycruiser]

Do u have brakes? If they are bled properly and you have a firm pedal not sure what the prob is. They will go to the floor when bleeding. Or maybe you are not describing the problem in a manner I can understand.

 

[Hamachi]

Do u have brakes? If they are bled properly and you have a firm pedal not sure what the prob is. They will go to the floor when bleeding. Or maybe you are not describing the problem in a manner I can understand.

This is the situation -

I just installed a fj62 bb and a new fzj80 MC on my 1978 fj40 with all new brake lines. Front disc and rear drum.

When I bleed the brakes, the pedal goes to the floor when each wheel is bled.

After the complete bleeding process, the pedal only goes down half way , is harsh and feels like it is hitting something.

After a thorough inspection, there is nothing mechanical to cause this... My question is - what could be causing this?

 

[bikersmurf]

Is the brake booster working properly? It almost sounds like youve got no assist.

Have you adjusted the rear brakes? It sounds like you have little resistance till the shoes hit the drum then it's solid without any assist.

 

[tornadoalleycruiser]

Is the vehicle running? Booster operating? Check valve in booster hose installed correctly. If after it starts does the pedal drop slightly once vacuum is applied to the booster? And do you have brakes? Stock 78 master was like 7/8 bore. If u kept stock front calipers and stock rear drums then yes you will have a firm pedal when using a 1" master from a newer cruiser and it will require more foot effort.

 

[Hamachi]

Is the vehicle running? Booster operating? Check valve in booster hose installed correctly. If after it starts does the pedal drop slightly once vacuum is applied to the booster? And do you have brakes? Stock 78 master was like 7/8 bore. If u kept stock front calipers and stock rear drums then yes you will have a firm pedal when using a 1" master from a newer cruiser and it will require more foot effort.

 

[Hamachi]

Yes it's running.
Yes valve is in properly.
The pedal does not drop when started.
I have brakes, but kinda spongy then hard when it hits halfway point.
I have stock front disc and rear drums.
I have an fj62 booster.

Would a proportioning valve help?

 

[tornadoalleycruiser]

I'm running a fj62 booster and that master on a grafted in 78 firewall and pedals on my 64. But I have larger piston calipers up front and rear disks so they balance out. A prop valve is only applicable once you have determined you have brakes or not and the rear is locking hard compared to the front. I test in a gravel lot with a spotter. Do you have brakes that are functioning or are you concerned you have a firm pedal without the vehicle running and without vacuum? Cause if that is the case then yes you will have a super firm pedal. Just stepped on mine and they are rock hard till I start it. I did connect my booster hose backwards upon initial startup and it was an eye opener once I got that darn check valve installed correctly.

 

[Hamachi]

I'm running a fj62 booster and that master on a grafted in 78 firewall and pedals on my 64. But I have larger piston calipers up front and rear disks so they balance out. A prop valve is only applicable once you have determined you have brakes or not and the rear is locking hard compared to the front. I test in a gravel lot with a spotter. Do you have brakes that are functioning or are you concerned you have a firm pedal without the vehicle running and without vacuum? Cause if that is the case then yes you will have a super firm pedal. Just stepped on mine and they are rock hard till I start it. I did connect my booster hose backwards upon initial startup and it was an eye opener once I got that darn check valve installed correctly.

My brakes work, but the pedal only goes down half way, then bottoms out and brakes stop abruptly.

How did you connect the booster hose incorrectly?
Can you send pics of right way?

Also the check valve on the fzj80 is built in..

 

[snaggletto]

Are you bleeding brakes with a vacuum device, or is someone pushing the brake pedal manually?

I have tried a couple vacuum bleeders and they work to a point, but I have found that having someone actuate the brake pedal always gets it done the best.

You also have to realize you are running a Frankenstein setup and it may never feel normal. Caliper size and volume displacement and how it matches to your master and booster may not be a good match.

You may even experiment with a proportioning valve on the front and/or back to see if you can get the feel you are looking for.

 

[tornadoalleycruiser]

There is a booster check valve. One way air hose valve inline with the hose. You have too large a bore thus firm pedal. There is a happy medium area when brakes are balanced. What you have is a 1" master on a system designed for a 7/8" master thus more volume with no place to push it. If you were to go to larger bore pistons in the front it will take some of the pedal throw by filling the larger volume of space in the larger pistons. If you instal rear disks it may also help. Or you can install a master designed for that system which was a 7/8 " bore . Or just know you will have a firm pedal and have brakes. Did you use a master designed for rear drums? There is a lot of math in a brake system or a lot of trial and error. I do not run stock calipers thus my system needed more volume. JimC has some posts with the math if you really want to figure it out.

 

[Hamachi]

Thanks for the information. I appreciate it.