CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Continuous air in brake line no leaks found

OK, bear with me as it’s a long story…
Had my van in the shop for when many brake pedal. They found air in left front caliper. Also leaking wheel cylinder. Bled lines and new cylinder. A week later I’m back in the shop for the same problem. They bled lines again. Air in same Spot. 3 days later I’m there again. This time they replaced master cylinder. 3 days later I had car towed back as I couldn’t even pump them to get a good stop. Ok so, now I’ve returned back 7 times since 11/27/2017. Still finding air in the left front caliper. So this past Monday, took it to another shop that specializes in brakes. This guy bled the brakes, replaced the other wheel cylinder (which was not working), machined the rear drums, cleaned and lubricated adjusters, clean and lubed caliper housings replaced the pins.
The next day, SAME PROBLEM. with mushy brakes. Literally NO ONE seems to know what is wrong with the brakes. And I’m driving it needed to pop it in neutral to slow down enough to stop as it is down to the floor. No leaks. Just air

The brake caliper piston seal is leaking when you release the brake pedal.

When you apply the brakes, the hydraulic pressure forces the seal to expand and prevents any fluid leak. But when you release the brakes, the piston in the caliper is drawn back into its bore along with seal, and this is where a slight amount air can leak past the seal into the caliper.

Replace both calipers, and that will fix your brake problem.

Tester

4 Likes

Concur w/Tester above, replace the calipers. It’s sort of odd the shop hasn’t came to that conclusion already, given the symptom is always air getting into the one caliper. Calipers aren’t overly expensive. $120 or so each for the oem part probably. They can be repaired too, the repair kit usually costs around $30/caliper. But there’s a labor fee involved for that, so most folks just replace the calipers and have done w/it. I’d replace the flexible hoses going to the calipers and rear wheel cylinders too if it were my car.

I wouldn’t have expected a Caravan to have rear drum brakes. Is that really so? You mention “wheel cylinder” and that part goes w/drum brakes. What year is it?

3 Likes

Me too.

2 Likes

@George_San_Jose1
Thank you. It’s a 2002. Yes Drum brakes.

@Tester
Did I mention no leaks found anywhere, which is why they can’t figure it out? They repaired the calipers, are you saying just completely change them instead?? Not that I’m second guessing you

I would say you’re done with this shop. If it takes a shop more than twice to figure something out, it’s time to give another shop a chance. 7 times is downright inexcuseable. I hope they haven’t been charging you each time.

I agree with the others, it’s most likely the caliper. And any shop that takes 7 tries to diagnose a brake line issue probably sucks at rebuilding calipers too, y’know?

1 Like

I suspect the problem is in the master cylinder.

@shadowfax
I did take it somewhere else. They couldn’t fix it either. I’ve used the same shop for years. They are always good and fair. It isn’t just this shop, no one that I know can figure it out.
Appreciate your response tho (:

Master cylinder has been replaced

Did they replace the pistons and seals? Sand blast the rust away? It is easier to install remanufactured brake calipers.

@Nevada_545
I don’t really know if they did all that. Honestly.

So replace calipers? How about Abs unit?

1 Like

I concur with @Tester but I have a couple of other suspects. One is the bleed valve, especially if someone put one of those one man bleed valves in there. Annother is the copper seals where the brake hose is attached. They should never be reused. The rubber hose itself could be bad as well.

I would also look closely at the brake lines but usually if they develop a pin hole leak or start weeping, it is pretty obvious, but it should be looked at.

1 Like

@keith
There’s something no one’s mentioned yet. I’ll have them checked as well.
Thanks for the input!

You might be able to get away w/just replacing the left front caliper, and leaving the right front in place. I’m not sure what pro mechanics recommend when replacing calipers, if only as a pair of individual is ok. For suspension parts its usually done in pairs, but not sure for calipers.

1 Like

@George_San_Jose1

I appreciate your response. Thank you