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Kahoona · 08-27-2019, 07:53 PM

Our 1996 Geo Tracker has a problem. After a period of driving the car begins to feel like the brakes are on. The pedal is solid at the top of the range and can't be pushed down. The car has to be forced to move. After some time, about ten minutes function returns for a while. Has anyone encountered this? I checked the wheel temps and found one front about 30f hotter than the other so I freed up the stiff caliper but the same thing still happened.

Possible contributors
Towed a thousand miles + with a brake buddy doing the stopping. I understand that these can exert a lot of force.
We had to add a lot of fluid once but it stopped leaking. I could find no drips. Might be master cylinder or unrelated.

farmerstu · 08-27-2019, 08:03 PM

possible brake booster valve. it may be leaking vacuum to the booster and that slowly applies the brakes. does it do it only after a period of driving without applying the brakes? also probable your lost brake fluid went into the booster which damages and swells the diaphram.

cfowler55 · 08-27-2019, 08:12 PM

Possibly the rubber cups on the master cylinder pistons are swollen/distorted. This will block the return to the reservoir , which will result in having residual pressure in the system. Look at the seal on the bottom of the cap and see if it looks to have been contaminated.
Charlie

Kahoona · 08-28-2019, 05:17 AM

Thanks. I'll check and get back. I can probably take the hose off the booster and see if it happens but I need a booster and MC anyway sounds like

kdauto · 08-28-2019, 04:02 PM

Quote:

Originally Posted by Kahoona

Our 1996 Geo Tracker has a problem. After a period of driving the car begins to feel like the brakes are on. The pedal is solid at the top of the range and can't be pushed down. The car has to be forced to move. After some time, about ten minutes function returns for a while. Has anyone encountered this? I checked the wheel temps and found one front about 30f hotter than the other so I freed up the stiff caliper but the same thing still happened.

Possible contributors
Towed a thousand miles + with a brake buddy doing the stopping. I understand that these can exert a lot of force.
We had to add a lot of fluid once but it stopped leaking. I could find no drips. Might be master cylinder or unrelated.

If you have a stiff caliper it needs replacing, not "freeing up". Ideally they'd be replaced as a pair per axle.

Sticking calipers can get REAL hot. Hot fluid can gas and exert pressure back to the master and pedal. This is worse with old (3+ year) fluid that has absorbed moisture.

Kahoona · 08-29-2019, 08:02 AM

Quote:

Originally Posted by kdauto

If you have a stiff caliper it needs replacing, not "freeing up". Ideally they'd be replaced as a pair per axle.

Sticking calipers can get REAL hot. Hot fluid can gas and exert pressure back to the master and pedal. This is worse with old (3+ year) fluid that has absorbed moisture.

PS Freeing up was only a temp fix to see if it was the problem.

That could be part of it. I have a new one ordered arriving today along with a master cylinder,and rear shoes. It is only sticking a small amount and produced a disc temp of 135f when it happened but I will replace. I did have too much fluid in the res but reducing did not help. Can't get a booster for a while.

It is an interesting problem.

atroph · 08-29-2019, 08:26 AM

I'd also suggest replacing the hoses that go to each of your front calipers.

Your vehicle is a 1996 and over time the hoses will swell on the inside giving the indication that the brakes are not letting off.

There is engough hydraulic pressure to force fluid through the hose, but not enough opening to allow it to freely flow back to the master cylinder when letting off the brake pedal.

Mojim · 08-29-2019, 12:44 PM

Quote:

Originally Posted by atroph

I'd also suggest replacing the hoses that go to each of your front calipers.

Your vehicle is a 1996 and over time the hoses will swell on the inside giving the indication that the brakes are not letting off.

There is engough hydraulic pressure to force fluid through the hose, but not enough opening to allow it to freely flow back to the master cylinder when letting off the brake pedal.

yep I had that happen change your …. front brake lines

Waiter21 · 08-29-2019, 12:52 PM

I can't speak about the Geo Tracker specifically, but what you described is a classic symptom of bad brake hoses.

The inner rubber liner the hose starts to separate. This acts like a one way valve, when you press on the brake pedal, fluid flows through the hose to the caliper, but when you let up off the brake, the one way valve prevents the fluid from flowing from the caliper back to the master cylinder.

My recommendation: replace the brake hoses and then do a full flush/bleed to get all the old fluid out of the system.

Kahoona · 08-30-2019, 03:07 PM

Quote:

Originally Posted by atroph

I'd also suggest replacing the hoses that go to each of your front calipers.

Your vehicle is a 1996 and over time the hoses will swell on the inside giving the indication that the brakes are not letting off.

There is engough hydraulic pressure to force fluid through the hose, but not enough opening to allow it to freely flow back to the master cylinder when letting off the brake pedal.

Quote:

Originally Posted by Waiter21

I can't speak about the Geo Tracker specifically, but what you described is a classic symptom of bad brake hoses.

The inner rubber liner the hose starts to separate. This acts like a one way valve, when you press on the brake pedal, fluid flows through the hose to the caliper, but when you let up off the brake, the one way valve prevents the fluid from flowing from the caliper back to the master cylinder.

My recommendation: replace the brake hoses and then do a full flush/bleed to get all the old fluid out of the system.

Yes. I was warned that this could be the problem. The hoses were OK. The brakes are fine now. They returned to normal when I bled the system. The MC had deteriorated in the only 2 years since it was installed (by previous owner) and leaked, then stopped leaking. When I bled the system it returned to normal. This morning I had the MC replaced along with the passenger side caliper just to be sure. I will do the other side when I get home along with the rear break pads, drums, booster and hoses. She is now ready to chase surf on the otherwise inaccessible parts of Hatteras and Ocracoke islands.

An odd fact for you all. Only three wheels have bleeder valves on the Tracker.The passenger rear side has none and the fluid passes through it and goes to the drivers side which has the bleeder. Never seen that. Thanks for all of the help.