Brake Problems - 76FJ40 Need Expert Advice.

[firemanj92]

Ok, she stops but there’s a loud woosh of air coming from the booster and the pedal definitely goes down further than it used too. Could this mean my booster is bad? I made a video but not sure how to post it.

above post.

To check if MC is bad is a simple test:
hold brake pedal (motor off) then turn motor on-pedal should sink. If it doesn't=either master check valve/grommet or master is bad.

 

[chubot]

Ok, so I just did the booster test and everything works as described. I’m going to order the motive pressure bleeder or see if I get one at my local parts store. When I put a clamp on the soft line going to the rear the pedal like TexLX450 said, it was rock solid so I know my calipers are good. That leads me to think that I must have a fair amount of air in those rear cylinders.

 

[45Dougal]

The movement will be greater if the rear isn't as tightly adjusted as before - didnt you tighen them right up in order to bleed though?

 

[rainingagain]

I’ve been on vacation and haven’t posted in a while. I swapped out the synthetic brake fluid for some conventional and noticed a considerable difference in brake pedal. Is there any problem with using synthetic brake fluid in an old rig that any of you guys have noticed?

You only get into trouble when you mix glycol based and silicone based fluids. They won't actually "mix". Technically you can mix DOT ratings but you shouldn't put say DOT-4 in a DOT-5 vehicle. There's other differences but the big one is boiling point - DOT-5 is higher than DOT-4.

Ok, she stops but there’s a loud woosh of air coming from the booster and the pedal definitely goes down further than it used too. Could this mean my booster is bad? I made a video but not sure how to post it.

Is it a constant whooshing noise or just an initial sound when you press the brakes? Old boosters make some noise when you engage the diaphragm but constant is a problem.

To post the video, you'll have to upload it to some site like youtube and link it, "Insert Media".

 

[chubot]

Ok I’m good on the fluid and the woosh sound is just when you press the brake pedal. It’s stopping good but the pedal is definitely not where it used to be and my brake light switch is not working consistently. Does anyone know if the brake lights are tied to the pressure switches? Like, if there’s not proper pressure in the braking system then the brake lights don’t come on. It doesn’t make sense they would engineer something like that but just curious if anyone knows.

 

[chubot]

The movement will be greater if the rear isn't as tightly adjusted as before - didnt you tighen them right up in order to bleed though?

I did tighten the cylinders up pretty tight. Just enough so I couldn’t turn the wheels by hand.

 

[charliemeyer007]

The brake light switch that controls the rear brake lights is on the pedal. The light on the dash is activated by the sensors on the brake master cylinder/emergency brake lever.

 

[chubot]

Ok I just need to replace the brake light switch then. It’s been working intermittently.

 

[Mr. Green]

I’ve always found the buddy system is better than a pressure bleeder.
Doing it solo sucks but a 2x4 or correct length stub from seat to pedal after pumping it up works as a “temp” buddy also. Just have a lot of laps to do!
Also, a shortcut I’ve used previously especially when cylinders are locked up tight is to use a c clamp over the cylinders to isolate and then bleed normally remove air. The travel is limited so it reduces volume consumed and when your pumping pressurizing the fluid you can open bleeders quick and shut and the fluid jets thru the lines to help remove air. the Adjustment is just volume from reservoir anyway. Good luck you’ll get it soon!

 

[chubot]

I got my brake light switch replaced and the brakes are working great. I guess you really have to work to get the air out of those wheel cylinders. Tapping on the rear brake line that runs across the rear axle seemed to work pretty good. Now it’s time to replace some suspension bushings.