Issue after tundra brake upgrade
 

Hey all, so I just completed the tundra brake upgrade with the Callahan rotors/calipers. I've bled the system (passenger rear-driver rear-passenger front- driver front, with DOT3) and the front caliper pistons are just not engaging.

There is crystal clear, new brake fluid continuously coming out, with no air bubbles. But neither of the front brakes are engaging at all. The brake pistons don't even look like they are trying to move. The install really couldn't be any more straight forward so I'm not sure how I could have overlooked anything, but it's possible! I have watched Timmy's tundra upgrade install video like 5 times and read through several writeups on here and the other forum.

Anything anyone can think of before I tow it to the shop next week?

By any chance are you bleeding with your engine running? As if the pistons are not moving in fluid is not pushing them. I just did this last week on a 1998 sr5 with rebuilt calipers that I rebuilt. I had no issues bleeding mine but I always seal off my lines and dont loose the fluid out of my master cylinder and abs.

To me its sounding like you have air in your brake lines from what you are explaining.



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Yeah were your lines capped or just dripping endlessly? If you have air in the master cylinder it's a difficult job to bleed it back out. Air is the enemy when it comes to brake lines.

What does the pedal feel like?

Calipers mounted correctly?

Recheck the hardline connections from the calipers and into the rubber/braided line. I just did the upgrade and I had a hell of a time getting the lines to seal completely.
The pistons wouldn’t move and the pedal would go to the floor.


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If you bled them properly and really are getting clean no air fluid out of the bleeders I wonder if you somehow got unlucky with two seized calipers. Were they new?

Like someone else asked, how does the pedal feel?

Curious to hear if this issue gets resolved! I was looking into doing the Tundra upgrade to my 2002 Limited, but every shop I spoke to refused to do it. Only a specialized Toyota shop agreed to do it, but they're booked out until December.

My very unofficial observation shows that people with the 01-02 modern brake pump system vs the older vacuum driven brake booster system tend to have more complications with the larger calipers. Doesn't mean it's not possible to do it right, just might run into more soggy pedal issues than those of us with the older brake system.

I did my brake upgrade in June to the 231mm, the caliper’s I bought had a small seal leak so every time I would push the pedal brake fluid would just come out the seam where both halves of the caliper meet, make sure you’re not losing brake fluid from anywhere. I got new calipers after that and worked like a charm. Hope its that “simple”.

Here's the OEM bleed procedure for the 96-00 4Runners:

https://i.imgur.com/BFS1dvk.jpg

Take careful note of the procedure to 'bench bleed' the master cylinder before doing the rears, then the fronts. This would be necessary if the master reservoir ever got at all low (it is internally split, so you can get an air pocket even if the fluid looks about half full).

Also possible that you just hammered the seal in the master cylinder and you are loosing pressure internally there.

-Charlie

Do you have the calipers on the correct side? Are the caliper bleeders at the top? How do you know the caliper pistons aren't moving?

So tonight I tried my hardest to get all the air out, rebleed all the brakes, even attempted to bleed the master cylinder, and that didn't work out so well, the Dorman master cyl bleed kit is garbage. I am going to remove the MC tomorrow night to bend bleed it, reinstall, bleed the hell out of the brakes again, and if that doesn't work, to the shop it goes wednesday.

I did not have the engine running. I have a 1999 so as far as I'm aware the engine does not need to be running. The key was on though. For sure seems like I have lots of air in the lines, I did not cap off the lines and it sat overnight, but the reservoir was never empty.

Feels good actually, not spongy.

Yup, bleed nippled up top.

I'm not leaking anywhere, I've triple-checked all connections.

I hope not, man that would be unlucky as hell, hoping it's just air.

The install is easy as heck, took me an hour total for both sides. I just got a ton of air into the system I think.

Yeah, I have looked everywhere for leaks and nothing, so I think I'm good there.

This seems like the likely culprit, I did not cap the lines and they sat overnight, most likely lots of air in the system, dangit. I tried bleeding the master cylinder tonight while it was still installed, and it was a huge pita. I am going to remove it tomorrow and bench bleed it, hopefully, that will solve things, if not it's going to the shop on Wednesday.

When I first installed them I did have them on the wrong side! But before I bled them I swapped them, so glad they were as easy as heck to install.

I used some 1/4 id (I think) clear rubber hose, threaded into the master cylinder holes and routed back into the reservoir to bench bleed cuz I didn’t have a bleeder kit... worked like a charm.

You might want to grab a MC to booster gasket before you take it apart, mine was shot and had to make a new one cut out of a butter carton


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My quick and dirty MC bleed method is to just crack the fittings on the MC while it’s under pressure and let the air and fluid leak out around the threads. Messy though.