After 6 visits to have our brakes repaired they still don’t work. Pedal was slowly going to the floor so we took our 96 Voyager to our local independent mechanic who replaced the master cylinder. Seemed fine for a few days then brake pedal got soft again so we took it back and he bled the mc. Fine again for a few days. Hard to say how many miles as it was holidays and we were off work. Visit 3 he replaced the mc again. Visit 4 he bled the system, again. For visit 5 we went to Midas,(they replaced pads 2 yrs ago) they bled the mc. A few days later we returned and got a third replacement mc. That was yesterday and today the brakes went soft after maybe 20 miles of driving on our first trip out after picking the car up. Each time the pedal seems fine initially then, we assume, air gets into the line and it slowly goes to the floor. They have checked and found no leaking fluid. Both parties seem mystified and have offered to return our money. Any ideas?
The problem might be with the front caliper piston seals.
These seals can fail where when hydrualic pressure is applied to push caliper pistons out to apply the brake pads no brake fluid leaks out. But when the brake pedal is released and the caliper pistons move back into the calipers, in doing so it draws air back into the calipers thru the seals. This would explain why the hydraulic pressure is restored once the brakes are bled, but shortly falls off after the brakes have been operated several times.
Thanks. Looks like they replaced the calipers when they did the brakes 2 yrs ago. We’ll run this by them tomorrow.
I hope Midas gave you a lifetime guarantee on the calipers. Their brake jobs are usually very overpriced. I love it when someone gets to make a “chain store” fix a problem at their expense.
They have to be overlooking something very simple. Anyone who replaces a master cylinder 3 times and leaves a customer with the same problem may be on shaky brake knowledge ground.
Wild guessing, maybe they’re simply not bleeding the system properly or there’s a fault with the rear brakes if the vehicle has drum brake rears. Worn or out of adjustment rear drum brakes can mimic a faulty master cylinder.
Hope that stab in the dark helps.
There is definitely a leak allowing air to enter the lines when the brakes are released.
Calipers and wheels cylinders are prime suspects.
Replacing the master cylinder 3 times smacks of ignorance.
Here we go again.they(midas)say that another guy was coming to look at it and that the A.B.S system has to be bled also. This is a older van with some rust - the first shop didnt want to mess with this system because there hasn’t been a plate covering the system for what looks to be sometime and has some rust. I told the guys at Midas everything that I was told by the first mechanic and everyone’s advise here. All I know is I have about 700 dollars into this and have been without reliable brakes 5 or six times while driving…please someone help
Make sure the MC is fully retracted when the brake pedal is released.
There is a pushrod the goes from the brake booster to the MC. There must be a little free play there.
When the MC is retracted valves open and allow the reservoir to refill the system.