Finally bought a gx 470 and she's glorious. It's an 2005 with 130,000 miles on it. Everything runs smooth except the brakes.

I have had the gx now for about 3 months or so. With pre-purchase test drive being sounded. Even the 8 plus hours of driving the vehicle back was fantastic.

However, I then started to notice a weird feeling in the brakes after about a three or four days. As a side note, the seller whom I purchased this vehicle from primarily works on these types of vehicles (4runners, gx, land cruisers, etc). He informed me that the front calipers were replaced with a used set along with new pads and rotors. Feeling that the brakes were fine when I test drove the vehicle....I never thought anything about them.

I'll do my best to describe the issue: say I'm coming up to a red light and I slowly compress to come to smooth stop... the brakes will start to bite, but with in milliseconds I will lose brake pressure and have to press the petal even further to regain braking pressure to slow the vehicle. This will continue until the petal is floored. Basically stair-stepping on the petal until the vehicle stops.

In addition, when I do lose braking pressure...I have found that stepping off and then back on to the petal helps to regain braking pressure to slow the vehicle down.

However, say I need to come to a quick stop and I quickly press on the petal, the braking pressure stays consistent until the vehicle comes to a halt. In this instance, the petal is only about 35 percent compressed with ample pressure behind the petal.

I've bled my brakes and I honestly think it made no difference or it made the problem worse. A garage which I have taken the gx to have serviced and fluid filmed states they could try upgrading to a 460 caliper to possibly fix the issue (which I also eventually want to do also). I have watched a lot of videos but have yet to come across anything in the forums similar to my experience.

Could this be the solenoid failing to provide pressure for the brake booster? Or is there really that much air in my lines to cause such variable braking pressures. When I switch the vehicle on, not started and compress the brakes, I can hear the solenoid kick on when the petal is held firm at about 40 to 50 percent. Does the same thing when I start it up too. Side note (even when I'm parked, if I ease on the brake petal, it will sink all the way to the floor).

Questions I have currently:
1. solenoid sound = working?
2. Are the used 4runner calipers actually trash and needs replaced?
3. Is the solenoid not activating soon enough to provide pressure?

At this point the problem has worsen. I only half the time regain pressure after stepping off and pressing the petal again (have to repeat three or four time). Most times I'm floored to get the vehicle to come to a stop.

I'm frustrated and I truly don't want to spend money just to fix something that isn't causing the issue. I love this vehicle and I want to maintain her for years to come.

Here a picture of my GX for the long post.

 

Get the truck flat-bedded to your mechanic. You don't want it to totally fail while in traffic!

I'm thinking brake booster. But a mechanic familiar with these systems will be able to tell you for sure. Someone who works on the GX, LX, the FJ Cruiser, etc.

Chip H.