Spongy Brakes: Solved

In mid-December I made this post https://www.tacomaworld.com/threads/2008-trd-brake-master-cylinder.405847/#post-11507115 which noted my brakes were very spongy. I figured this was likely the master cylinder, which I replaced with no impact on the problem. Eventually I remembered I had done a rear brake job a few months prior and then not use the truck due to surgery.

I was so sure the problem was associated with the rear brakes I took them apart, reassembled, and adjusted them several times. In that thread, DoorDing suggested I could pinch off the hoses with vice grips (being careful not to damage them) and this would help in diagnosis.

Well, three weeks after that suggestion, I decided to try it. Since I KNEW it was the rear brakes, I closed them off first. To my astonishment I had no brakes (except the emergency brake). Just to be sure I opened and closed them a few times: absolutely no doubt my front brakes were no longer working!

I removed the vice grips from the rear brakes and shut the driver side front and presto: almost all my braking was back. When I pinched the passenger side front I had spongy brakes, but left front almost perfect brakes.

It turns out I had a bad caliper and even though my problem started after the rear brake job, the left caliper was essentially killing my front brake action. There was never any fluid loss and the rotor looks normal (no rust as you would expect from non-functional brakes). I have no idea what was wrong but I replaced both calipers and the problem is now solved.

So, if you have spongy brakes remember DoorDing's suggestion.

 

Unconventional perhaps, but useful info.

 

Did you try bleeding the old caliper before replacing it? Not much to go wrong in a fixed caliper other than leaks or seized pistons.

And yes, @DoorDing is a good $#*!, and gives out good advice.

 

Yes. I bleed the system, replaced the master cylinder, re-bled the system, adjusted the rear brakes, bled the system again. I think I went through a total of 1 quart of brake fluid I bled them so often.

I have never seen a caliper fail like this: no leak but no pressure on the brake.

 

Perhaps two pistons on one side of the caliper were seized, so rather than the pads being squeezed against the rotor evenly, only one pad was pushing, flexing the rotor and/or caliper bracket causing the spongy feel. Since the truck was parked a whole year, it almost makes sense, but still quite unusual.

One good thing though, all that bleeding was not in vain - 1 quart is about enough to do a full fluid flush, so your brake's hydraulic system will thank you.

 

I’ve been chasing this problem for over a year now and this just solved it. I can’t how relieved I am to fix this bc I’ve spent so much time and a little money on it. Thanks dude. My problem lies in the back drum brakes unfortunately but at least I know where it’s at.