Changed the brakes pad and calipers several months ago, but the brakes feel spongy. One of my friends stated the problem could be the brake lines are expanding making the brakes feel that way. The car is 86 GT with less than 41 K miles. If I have to replace them I will, but could it be another problem?
You have air in the lines, the pedal is out of alignment, or one or more of the flexible lines between the calipers and hard lines are bad.
Air in the lines can be caused by the flexible lines being bad, or the master cylinder or one or more of the calipers having a tiny leak (which could let air in, but not fluid out).
Another possibility is that moisture is seeping in through the lines and getting in the fluid, or the fluid is just bad, and it boils when some heat gets into it. If the spongy feel only happens after a bit of driving and the engine has warmed up, this is probably happening. If always spongy, look into the other possibilities first.
spongy sounds like air in the lines, did you bleed the brakes after replacing the calipers?
never heard of brake lines expanding but I suppose its possible, not probable though. lines usually just rot and brake.
when you hold the pedal down does it slowly drop? if so it is definitely air in the lines, these things can be problematic to bleed, number one because the lines are routed differently than most cars, the rears run down the passenger side and the line the furthest from the master cylinder is the drivers side rear, so you have to start there, then the passenger rear, then passenger frt and then drivers side frt.
it could also be a bad master cylinder, bad vacuum booster. but start by bleeding the brake properly.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
Bleed the three times with some help after the first time they felt good but we did it several more times to be certain. Your input is noted and I will try it once more, thanks.
Originally posted by 84fiero123: never heard of brake lines expanding but I suppose its possible, not probable though. lines usually just rot and brake.
The internal section of the flexible lines that the fluid actually travels through can rupture, and the fluid will be pushed out into the area around the line but inside the rubber, causing it to expand. If the original lines are still on the car, it's a possibility, but it's rare to happen, and not the first place I'd look. I'd look for incorrectly bled brakes, or leak in the master cylinder, first.
The internal section of the flexible lines that the fluid actually travels through can rupture, and the fluid will be pushed out into the area around the line but inside the rubber, causing it to expand. If the original lines are still on the car, it's a possibility, but it's rare to happen, and not the first place I'd look. I'd look for incorrectly bled brakes, or leak in the master cylinder, first.
forgot about those, they usually just rot inside and don't expand, on those you would see it right away I would think just looking at them if they are expanding.
I forgot to ask, you are bleeding them the right way, right?
I have a friend who thinks he knows everything there is to know about working on cars and went to help him bleed brakes on one of his vehicles one day and he was letting the brake pedal back up before I had tightened the bleeder, spent about ten min and he said he had no pedal still. I tried to explain to him he had to hold the pedal down until I had the bleeder closed and he said no you don't. well we argued for about another ten min and I said you have a manual for this van, go look it up. well I was right, he was wrong but never admitted it just did it the right way after that, no longer take his word for knowing how to do anything. the pedal went right up after the first time we did it right and kept going up each time after that I no longer help him without first going over what we are doing and if I ain't familiar with the vehicle I consult the manual myself.
Steve
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
I had a similar spongy/low pedal after doing all pads/calipers on my 86 GT, power bleeding several times did not help. They felt ok but not right, too much pedal movement compared to other cars. I found this (ogre's cave rear caliper adjusting) - fixed my pedal problem. The rear caliper pistons had to travel a little to far when stepping on the brake causing a spongy/low pedal.
[This message has been edited by AL68 (edited 09-27-2013).]
