Hello Everyone,

So I am having issues with my brakes on an 08 sr5 v6 4unner. The steering wheel is shaking when braking mostly at freeway speeds, but it is also shuttering/bouncing the brake pedal like there is air in the system. I bled the brakes the other day and a bunch of air came out. I bled it by putting the ignition to on and had a friend pump the brakes. The pedal feels better but the brake pedal still shutters/bounces. I looked at the brake pads and they all look fine except the rear drivers side is wearing unevenly.

I looked at the guide rods and they have flat spots on them, but they look like they are machined to have flat spots. Are they supposed to?

Also from my research it seems at least one my calipers is probably frozen. I am thinking they are all probably the original ones maybe not. I have had the vehicle for 4 years and not replaced any of them. They all move though, to see if they are frozen I am not sure how much to push them out and in to see though, I will research that more. When you replace calipers do you do the two fronts or two backs at the same time? Or just only do whatever is bad?

First and foremost you need to find out why you're getting air in the system and correct it, that shouldn' be happening for that to be happening the system has a break or other leak, etc. that's causing the system to suck air.

I think brakes pads and or calipers and or rotors should be replaced in pairs, i.e. both fronts together, etc. but it can be done singularly, I just wouldn't recommend it.

The air in the system is from when I did it wrong earlier this year. I have not checked to see if there is more air. The brake fluid level is not changing though. Ok sounds good, do you know if the rear caliper guide pin is supposed to have flat spots on it?

Thank you

No I don't know since I haven't done any brake work on my T4R yet, but I wouldn't think so, pins on many other brakes I have done over many years have been round, but others will have to confirm this for you.

Some of the guide pins on the calipers can have flat spots, I think it's to help retain/move grease around in there? I've seen them also have an o-ring on one guide pin and not the other on different models (not sure why).

As for air in your system, at this point it's in the solenoid pack and the ABS system. I'm not sure if the "manual method" will work for you in this case as the usual thing I have to do is get the scantool to actuate the ABS system and get all the air bubbles out of the system. I would say at this point you may need to take it to a dealer or shop that has a scantool that can actuate the ABS system properly (the TIS Techstream has an automated function, most aftermarkets do not and requires a bit of understanding of which solenoids and for how long to actuate because too long and you risk burning them up, not sure if newer tools have timeouts like the TIS does, been a while since I played in the aftermarket tool realm).

My guess is that due to air in your systems and possibly however you did your brakes prior (did you install new rotors and follow break in or did you just slap pads on old non-turned rotors?) you've glazed the rotors and they'll need to be machined and at the bare minimum the pads sanded if not replaced.

I had my rotors turned and put new pads in earlier this year. I think I got all the air out of the system as it only bounces/shudders when lightly pressing the brakes and usually at high speed. I see some other threads about rebuilding and checking the calipers so I will see if one is seized that way. Also I need to check if a rotor is warped probably as well. Do you think this is the right way to go? Or should I bring it somewhere and have them purge the system with the tool first?