Troubleshooting a brake system

jlogan

I have a B2200, 1989, five speed. All of a sudden I have decreased braking performance, fluid levels are good, does not decrease, don't see any obvious leak...when stopping, pedal goes much lower than before. Pumping does help a little, but only with pedal height from floor, not increased brake performance...it "feels" like maybe only one set of brakes are working (fronts or rears) but so far can't determine which with certainty...my impulse is use the parts cannon approach and replace all brake componenets, but would feel better if I could use a more methodical approach,

Any ideas/experience appreciated. Need to go get my Christmas tree ! Thanks...

MazdaMitch

jlogan Honestly if the truck has never been touched, after 30+ years, it's probably time to remove the calipers and rear wheel cylinders, flush the metal lines with brake clean, replace the front two calipers along with new rubber lines, and the rear wheel cylinders and I think there is one rubber line at the rear.

Also a good time to replace the master cylinder. Use new synthetic brake fluid.

All in all the brake booster is probably tired and needs to be replaced too.

Troubleshooting is on page 4
https://mazdaminitruckin.com/wp-content/uploads/2024/09/P-Braking-System.pdf

jlogan

Thanks MItch...appreciate the link and advice....Its had some work done on it over the years, but now it sits in storage mostly except for a few times of the year...so less than 200miles most years....I got all new pieces for the back, a new master cylinder and of course will flush and bleed the brakes...fronts look like they are working from the polish on the discs and no noise...pads were replaced some years, but not that many miles ago...I'll let you know what I find as I work on it...

Is it possible the proportioning (?) valve is faulty? I see that some just work around that...

MazdaMitch

There IS a proportioning valve on the firewall, but over never had to work on one of those yet.

Cusser

I'd jack up the back on jack stands, have helper push down on brake pedal, and see if the rear wheels can be turned by hand. Second would be to open the rear bleeder valve (on left rear wheel cylinder) and see if fluid pumps from there. Also while under there, look for brake fluid leakage. It would be a good idea to pull the rear drums to check for fluid leakage and verify thickness of the brake linings. I like to manually adjust the brakes after installing the drums.

If all OK, then go to the fronts.

bjzman99

To your point on proportioning valve, I have been looking for a replacement and have not been successful on finding a new part.