Brake Master Questions (1 Viewer)

[dekuiper]

I have searched for "Brake Master" but did not find what I am experiencing.

My '91 FJ80 has soft brakes. When I press the pedal, it goes nearly to the floor but it does stop the vehicle. If I press, release, and press again, I have firm pedal with only a couple inches of travel (max) and the vehicle stops much more effectively. I have had a brake shop look at it, bleed the lines (twice) and adjust the brakes he put on. Same issue. He thinks the MC may be going bad.

Is that correct? Would I need a new MC or just a rebuild kit. Or is it something else?

TIA

 

[LX_TREME]

I had same problem before and replaced the master cylinder (need about 2 -2.5 brake bottles of brake fluids) and If you decide to replace new master cylinder i suggests to get new one.Personally i wont get rebuild master cylinder and wont play around with the brakes, maybe for rebuild alternator yeah but not on the MC, and remember to bleed all 4 lines real good after.

Good Luck

 

[Jim_Chow]

I swapped in a new Aisin FJ80 MC a couple years ago. They're only like $130 from places like MAF. I got mine from a cruiser shop in NC. Don't forget to flush the LSPV last if you have one. Old fluid hangs in there, even after flushing the rear brakes.

 

[robbie]

First thing I would do is make sure the rear drum brakes are adjusted properly. With them out of ajustment you could have the same symptoms. Later robbie

 

[corbs]

I had same symptoms and a new Master cylinder (and one slave in the rear that was leaking) solved the problem. . .

 

[Seminole]

I agree with checking your rear drums first. I had the same problem when I first got mine (it's a 91). I flushed and bled the system first(including LSPV), still had the problem. I then did the booster test (it's in the FSM, Haynes and here in past posts), that was okay. I then pulled the drums to find that the RR WB oil seals were gone and the drums were full of grease. After cleaning and replacing the seals, I found both wheel cylinders shot. After a rebuild w/ new springs and hardware, it stops on a dime. Although it seems like it is starting to get mushy again so I now suspect my MC. WTH, it's only $$$.

 

[robbie]

Rear drums will go out of ajustment sooner than you think. I would readjust the brakes or if slightly loose then back up a dozen or times and hit the brakes to adjsut them or with the truck in park pull the parking brake handle up and down until you get about 8-10 clicks on the handle. The last method using the P- brake handle only works if your adjsutment is close. If your P-brake handle is pulling to the end of the throw then you will need to adjsut at the drums. There is always the chance that you will adjust only one whick could also give mushy brakes. later robbie

 

[dekuiper]

Looks like I better check on the rear adjustments as my P brake doesn't work at all. If that doesn't do it, I'll go the MC route...Thanks

 

[Kalawang]

If you're not losing fluid, check your master for scratches inside. Your pistons are probably gone, but their reason for being damaged would likely be a scratched master. If the master is OK, look elsewhere, but be sure first. Even what seems an insignificant scratch can and does wreak havoc.

You can also look carefully at the rubber collars of the pistons for damage.

Most times replaceing the pistons is enough. However, with the cost of labor in the States, it's normally simpler and more sure to just replace the entire assembly. Whatever you saved on parts wouldn't be worth the cost of labor if you had to do it again.


Kalawang