Strange Brake Problem...

[Meaux]

While backing down the driveway in the AM, the rear brakes come on partially. I understand this is the ABS setting itself and normal. Sometimes it's really bad, the car will hardly move, but not allways...What I do is put the car in drive and pull forward, stop, and then back up, sometimes this stops the rear brakes from actuating, but not allways.

After driving however, this does not happen again... till the next morning.

I'm glad I'm not trying to get to a Hospital... :-)

Thanks...

[Q45tech]

Please understand the ABS works by removing brake pressure.

Traction control works by engaging brake pressure on the rear.

[Meaux]

Hummm....So, If I don't have Traction Control, (and I'm sure I don't) why is this happening?

1994 Q45, 80Kmi., 1 TPS.

[Q451990]

That is odd... so you're saying that the brakes are engaging enough to keep the car from moving? The ABS self test should almost feel like the brake pedal is "dropping out from under you" as it pulsates. I always notice that it's extra harsh if you're backing down a steep hill. Also seems to be harder to get the car out of park and in gear if you don't set the parking brake heavily...

Heath

[Meaux]

No, they (rear brakes) do not stop the car from moving.

What happens is this:

Start car, brakes engaged, shift to "R", foot off brake pedal, car moves backward in normal fashion, after about 10ft. the brakes seem to barely come on slowing the car down...Increasing RPM's to over 2000 dosen't feel like it's doing the car any good, and the braking seems to increase, so, I stop the car, shift to Neutral, pump the pedal, and shift back to R. Sometimes this works, sometimes not. eventually I get down the driveway and it dosen't happen again...till the next morning...

I noticed the other day when I had the TPS misadjusted, I had to move the car backwards and it did not do it, I thought "Hey, I'm fixin' something"... Heck, it might be the transmission and not the brakes...sure feels like the brakes though...If I had a short driveway, I may never experience it.

[texasoil]

I can not think of any way the main(hydraulic) disc brakes would engage themselves. However, the 'parking brake' shoes might 'jam' when backing if they are rusty/gummed up and not releasing fully for some mechanical reason.

[Q451990]

And you're sure it's not the ABS self-test? It should feel like a "bump" or vibration in the brake pedal. Many times passengers think I ran over something...

Heath

[Meaux]

I don't feel anything in the brake pedal because my foot is not on the pedal, she just slows down after 10 feet, kinda like backing over a speed bump, but never getting over it.

This morning I engaged the emer. brake and released it a few times, in drive and reverse to see if it made any difference. The emer. brake seems to be normal...after all that, it still did the same thing.

Oh well.............I reckon I'll have to get used to it till I do the brakes, maybe I'll find something then.

Thanks

[elwesso]

My Q does the same thing expect when its cold, im not sure what it is.... however i dont think its the brakes because it doesnt do it when its been warmed up for a little bit... See if letting it warm up for 5+ mins helps

[texasoil]

since you have eleminated emergency brake possibility (admittedly a remote possibility), that leaves the auto transmission as probable ssource. try a good fluid flush and new filter. It's possible its mostly plugged and colder oil is too thick to flow through it. Newer Dexron III has much better 'low temperature' flow characteristics than previous Dexron fluids.

[1990Q45'r]

I had a similiar problem with one of my other cars (71 Mustang.)The power brake vaccum booster was leaking and made the brakes apply by themselves while driving. Once replaced all was fine.

[Meaux]

texasoil, I think you're on to something there...It may well be the transmission...cold.