Facelift - Low Brake Fluid Pressure at One Caliper

I recently tried to refurbish my front brake calipers. The rubber boots on the pistons were in terrible shape. They must have been original to the car and after 135,000 miles, they owed me nothing more.

Unfortunately I was knee deep in the drivers side caliper when I realized the replacement parts I ordered were wrong. I’m usually good about checking before starting work, but I missed it. I had to reassemble the caliper without any boots…they were shredded upon removal. I ordered refurbished calipers from RockAuto for $50/ea. (after core return) Figured that would be the easiest way to proceed.

So this past weekend I finally went back in there and replaced the calipers. Went smoothly, and easily. There was a little bit of brake fluid leaking out from at least one of the pistons. I happened to have one problem. I could not bleed the passengers side brake. I literally left the bleeder open for 30 minutes. Nothing. The crazy thing is that the brake works, but I couldn’t bleed it, so I took it to a shop.

They managed to bleed it and everything works well now…except that they noted that the brake fluid was coming out very slow in that one caliper.

No lights, or codes are present. The car doesn’t know anything is wrong with the brake fluid delivery. The steering wheel remains straight when braking. I would literally not know anything is amiss…if I didn’t know something was amiss.

Any recommendations on where to start? I don’t have a garage, so this might be something I don’t want to tackle, as I am concerned about brake fluid getting on surfaces it shouldn’t get on.

Thanks for reading.

Did you replace the brake hoses? Common for them to swell up on the inside. Cheap and easy to change. If yours are original, just change them.

On your year car, is there a proportioning valve for the front brakes - wondering, if there is, if the valve is partially closed to the side that will not bleed - Tex.

They would most likely be originial…

Thanks for the tip. Found a replacement for less than $17!

Will report back.

Thanks for the response. I don’t know if my Teves IV ABS system has a proportioning valve…will check JDHT.


Checked, and I don’t believe there is. There is a pressure delay valve, but that’s for the rear brakes.

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Okay - just curious what may be the cause of the reduce flow of brake fluid to that side - you stated you did not get any fluid, and your mechanic stated that he did get a small flow to bleed - very strange since not the same flow as the other side - again just very curious - Tex.

No idea, that’s why I came here.

The other side…no problems.

I’ve ordered a new rubber line hoping that’s the cause of the issue.

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I would probably replace both side’s lines. It sounded like you only ordered the one. If one has gone bad with age the other may not be far behind

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Yeah….I guess I should have ordered 2….

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Maybe test the flow before you connect the new line to the hard line. Could be a restriction in the hard line coming from the mc?

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As stated …. The flexible brake lines are the problem. If they are not replaced one will eventually jam the brakes on.

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Will not get to replace the hose this weekend, but will get to it no later than end of next week, possibly sooner. Once replaced, I’ll see if I can gravity bleed it.

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Hope it’s the hose, but I wonder.
If it’s a hose that’s Compromised on that side, to the extent that little or no fluid exits the bleed nipple, would not the that caliper see less fluid volume, thus less pressure to the brake pad?
Yet vehicle does not pull but stops straight?
BTW, changing the hoses absolutely the correct first step.

I agree, it makes little sense. I was shocked to see the pads engage the rotor, yet no fluid came out?

Brakes work absolutely fine.

I’ll replace the hose this week and report back. After that I would agree that things get more complicated. The steel lines all look in good shape with no rust or dents anywhere.

You may find replacing only one new rubber brake line, those brakes will now work 100%, but they will now pull because other side was not perfect.

Replace both (such an easy job), and bleed plenty of fluid, those lines are not totally clean, probably bits of rubber gunk in them.

I replaced all three (front/back) rubber brake lines, and power bled three pints! A few months later, i was still getting black gunk in brake reservoir. Another bleed, and it has all stayed clean since.

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Replaced the rubber brake line. Had fluid coming out of the metal hose coming out of the engine bay, so I know it’s clear from there.

New hose on, and I successfully attached it to the other end and I still have the same problem.

Either the caliper is bad, or that last little bit of metal tubing between the (new) rubber hose and the caliper is blocked.

When I crack that connection, from the hard pipe to the caliper, I get plenty of brake fluid. Unfortunately, I can’t tell what direction it’s coming from, the caliper or the line.

I pulled a vacuum at the caliper bleed valve but get nothing.

Remove rubber hose to caliper, take bleeder screw out of caliper, squirt a lot of brake cleaner in there. Hopefully that unplugs it. If not, put some air compression on it afterwards.

OK. I’m concerned about a blast of brake fluid, but at this point… I’ll place a rag loosely over the bleeder hole.

It was a refurbished caliper I put on recently.

Swap bleeder screw side to side to determine if the screw is blocked. Maybe part of a shipping plug where the hard line connects to the caliper? Put old caliper back on and get an exchange from Rock Auto; they have a painless warranty process and split cost of shipping to return (and cover shipping on replacement).

I pulled off rubber hose to the hard line into the caliper and I tried blasting with compressed air.

No dice.

I removed the short length of hard pipe from the caliper to the rubber hose, all clear.

So then all that was left was pushing air through the caliper. It was difficult to run compressed air nozzle into the hole where I removed the hard pipe, but I did the best I could and couldn’t get air out through the bleeder screw.

I then blasted air from the bleeder screw hole and I was able to feel air come out through the other hole…but only if I slowly pressed air and waited for the pressure to build up in the caliper. I couldn’t get it to work the other way, no matter what I did, but I also couldn’t get as good a seal from my air compressor at the inlet (not the bleeder screw) hole.