bamayote

this is a 99 tacoma 4x4 with 202k miles. i replaced the brakes about a month ago. here's the deal.

i've never ever had this problem in any vehicle i've owned. my dad is a pretty good wrench head from way back, but he says my truck is possesed!

when i leave the house i've got a pedal that's pretty good. just a little spongy. but after about 10 minutes of drivin the pedal is very high and tight.

i've never had a pedal 'rise' like that. i can understand if a brake pedal gets weaker and softer, but not higher and tighter.

any suggestions as to why this is happening?

thanx all!
brad

Maj

Can you be more specific on what was replaced/repaired? Pads, calipers, master cylinder, vacuum booster? Generally speaking, anytime the pedal firmness improves from pumping the pedal (or driving the vehicle in your case) you have air in the lines.

Potomacduck

I had the exact same problem on a VW Jetta about 10 years ago.

Here's what was wrong on that car: One of the calipers was bad (sticking). When you step on the brake pedal the caliper piston is compressed. When you took you foot off the pedal, the piston would not completely release. So in effect the brake pads were still under some compression and dragging on the brake disk.

This produced a lot of heat and in turn expanded the brake fluid ever so slightly and increased the hydraulic pressure in the brake lines, hence the high and tight brake pedal.

Even if the calipers seem to be working, it only takes a few hundreths of an inch for them to be compressing those pads, even slighty, so this can be difficult to diagnose.

bamayote

good point. i guess i'd kinda focused on a prob with the emergency brake cause i'd changed the drum pads about a month ago. i've been readin most of the night and i'm gonna bleed the brakes this afternoon and look into the proportioning valve as well.

thanx for the reply all!

Anthology

yeah this happened to me a couple times in my 00 Cougar.

bamayote

it seems i was lookin in the wrong direction. i finally took the truck to my local mechanic. he checked the brake system from bumper to bumper. said when he experienced the "hanging brake" problem he put it on the rack and discovered it was the front brakes that were hanging.

he checked both calipers as mentioned before and checked the master cylinder, said all was fine with those components.

he thought he'd narrowed it down to the load sensor. replaced it. i drove it for two days without any probs, but today they hung up so bad i could barely limp it on the side of the road. i mean these things are tight!
this seems to happen when the truck is cold, or the first time i'd driven it today. i was behind a tractor and the slower i went the tighter they got! all the while my brake pedal got higher and higher.

so while i was on the side of the road waiting on my dad to bring his trailor i heard a "clank" ( after they front rotars and calipers cooled down ,, assuming), then when i got back into the truck to move it onto the trailor i barely had a brake pedal and they'd freed up.

good news is that it was a beautiful day and my mechanic adjusted the emerg brake while he had it and i've got a great emerg brake now......lol

anyone else had this prob? or got any other directions to look in? i've got the truck at the mechanics now. hopefully he'll find something.

good thing i've got a '86 yota truck to drive!
thanx all for looking!
brad

terryjmatthew

Sounds like your rear brakes are adjusted too tight and when they heat up and expand, they start dragging.

bamayote

yeah i thought that was the problem i was having, but when they locked up this afternoon. the rear brakes didnt smell at all and the front brakes were popping like they were hot. and they defenitly smelled hot.
another reason i'm quite sure it's the front brakes...... i was tryin to pull out on back on the road and the back tires where on gravel..... front tires on the pavement. the rears were throwing gravel all over the place.
i surely hope i'm not sounding argumentative!