89 HJ61 Calipers seizing in unison! (1 Viewer)

[Blueberries]

Hi everyone!

I started having problems this summer with my brakes. I was away a lot, so, I thought that my calipers seizing was due to not being used much. The strange thing is that they both seized at the same time! I'll be driving along and suddenly the truck will brake to a halt without me applying the brakes! I've never experienced anything like this, so I replaced my calipers and pads and still the same thing happens.

Is this related to a vacuum problem that I've heard people on this site talk about?

Would it be my brake booster for sure, or should I be looking somewhere else?

Thanks, in advance.

Tim

 

[MatS]

I would be looking more towards your master cylinder and brake booster as opposed to a caliper issue.

I've had master cylinders after the vehicle warms up keep the brakes applied but that's only after they are applied. I don't know what causes the brakes to apply themselves... seems awful suspect.

 

[raevenzero]

Do a full flush. It sounds to me like there is water in the system. When things warm up, water expands and locks the brakes.

What releases them? If it releases after sitting for a bit and cooling off, it's likely water.

 

[Christian]

Mine did the same thing, actually ended up with wheel well fires on the German Autobahn! The master is probably the issue, the front piston might not be returning to zero position, and this means any pressure in the system can't vent to the master. When driving the heat from the wheel bearings starts to expand the fluid in the calipers, which starts to press the pads against the discs creating even more heat and... you get the point...

Change the master and flush...

 

[Blueberries]

Thanks so much guys! I've been away for awhile so haven't had a chance to check this thread.

I suppose that flushing the system and refilling would be the first check. It that fails, then, Master cylinder replacement which I'm sure there is a thread on mud somewhere describing the process of changing out the master?

Thanks!

 

[roscoFJ73]

Maybe try the 60 series forum. This forum was set up for diesel and 24 volt queries.

 

[too tall]

If your booster gets a hole in the diaphragm the brakes will sometimes apply from vacuum alone . might be worth unhooking the vacuum line to the booster and see if they still lock up .