- Thread starter
- #21
I've replaced the brake booster, and still have the issue. I'm thinking the seized caliper may be the problem. What is the seized rear slide pin you refer to?
Help Me Diagnose My Brake Issue - 97 FZJ80
- Thread starter ColoradoLC
- Start date
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The rear calipers use slide pins to control the movement when you use the brakes. They can seize and then the calipers don’t work as intended.
Did you also replace/function check the valve on the brake booster that pulls vacuum from the intake manifold?
are you getting vacuum to the booster? your new booster came with a new check valve right?
A very hard pedal with reduced braking is brake booster/vacuum related.
A soft pedal with reduced braking is a fluid leak or master cylinder issue.
If the pedal feels normal and you have reduced braking, I'd be looking at calipers.
Brake fluid should be almost water clear. The darker it is, the more contaminated it is. It should be flushed every 2 years or so.
Calipers should be rebuilt with OEM kits. If the pistons are corroded, replace them. They're still available new.
If the cylinder walls are corroded, then replace the calipers with OEM rebuilds.
All of the bits and pieces for the calipers are available new.
I have 2 sets of calipers that I rotate every 2 years or so. Both sets have been powder coated and get a complete rebuild with all new OEM parts when off the truck. Amsoil moly grease on everything.
Vacuum sealed and sitting on a shelf ready to be installed.
A soft pedal with reduced braking is a fluid leak or master cylinder issue.
If the pedal feels normal and you have reduced braking, I'd be looking at calipers.
Brake fluid should be almost water clear. The darker it is, the more contaminated it is. It should be flushed every 2 years or so.
Calipers should be rebuilt with OEM kits. If the pistons are corroded, replace them. They're still available new.
If the cylinder walls are corroded, then replace the calipers with OEM rebuilds.
All of the bits and pieces for the calipers are available new.
I have 2 sets of calipers that I rotate every 2 years or so. Both sets have been powder coated and get a complete rebuild with all new OEM parts when off the truck. Amsoil moly grease on everything.
Vacuum sealed and sitting on a shelf ready to be installed.
- Thread starter
- #27
Yes for both. I now have a new booster, so that's is a part I won't have to replace for a while!
- Thread starter
- #28
I do change the brake fluid every couple of years and it is enough that it is usually barely discolored by the time I replace it. No air in the lines and just to be sure this wasn't the issue, I've probably run nearly 2 gallons through all of my brake lines.
You bring up good points about pedal stiffness. I'm now back to thinking it is my calipers and I like your approach to this, so I have ordered a new set of fronts for both sides. Once I get those one, I'll rebuild the old ones and have those as spares.
You can also have an internal leak, from the proportioning valve bias or the ABS pump, which won't appear at any of the fittings. I suspect for most people, it's the latter. I have thre 80s and only one of them has factory–like braking. I'm planning to rebuild a spare pump and change it out on one to see what, if any, difference it makes.
One thing I forgot to mention, when swapping calipers I often have the truck up on 4 jackstands in the driveway. After changing calipers and bleeding, I put the tires back on and run the truck in gear. A mix of slow and fast application of the brakes activates ABS and cycles the fluid through the system. I do this 5 or 6 times and it keeps things working properly.
- Thread starter
- #31
Hi folks, I am happy to report that I did indeed have a bad caliper. After replacing both, I found one of the old ones was sticking a bit and that didn't turn up when I did some manual tests with the wheels on, but front of the truck up. I've done a little ABS activation in a gravel parking lot near me and plan to bleed one more time to stiffen up the pedal feel. I've always been able to maintain my brakes with the help of this site, but this one was a bit frustrating since I felt like I had to pull the part cannon out at one point.
The silver lining is that I got in there and really tuned up the parking brake and that is holding better now that it ever has. I feel like I could park my 80 on a wall.
Thanks for all of the suggestions you made. There was some really good troubleshooting detail and some good suggestions made here. Hopefully this thread will help someone else that had a difficult to diagnose brake issue in the future.
The silver lining is that I got in there and really tuned up the parking brake and that is holding better now that it ever has. I feel like I could park my 80 on a wall.
Thanks for all of the suggestions you made. There was some really good troubleshooting detail and some good suggestions made here. Hopefully this thread will help someone else that had a difficult to diagnose brake issue in the future.