So I'm another victim to seized piston. Front passenger wheel does not rotate smoothly when I jacked up the truck. I plan to replace the caliper with one from Advance Auto parts. I'm decent at working on my own vehicle, but never bleed the brake. How hard is it? And I need to bleed all 4 corners after I replace the front caliper? Tips and advice are greatly appreciated. If any member from Long Island NY willing to help, then even better. Thanks.

Yeah, you ought to bleed the whole system. You'll need two people. Start at the right rear, go to left rear, then front right, then front left. I'd actually do a bleed on the one you're working on first just to get the major air out. You can also set the piston to where you need it, fill the caliper reservoir, then start your bleeding procedure.

For any given caliper, have someone slowly push the brake pedal while you crack the bleeder. Close the bleeder before the brake pedal hits the floor. Repeat until no bubbles are seen. I use a clear length of hose to direct the brake fluid into a container on the ground. It keeps the fluid off the truck/driveway, and lets you see the bubbles coming out. Keep an eye on the fluid level under the hood so you don't bleed it dry and have to start over.

Fullboogie is right, no matter what when a line is opened when working on the brakes they must be bled. Start RR, LR, RF, LF.

It has been a little while, but given the electro-hydroboost setup the 4Runner's have, I believe the last time that I bled the brakes on mine all I had to do was hold the pedal down while my friend opened the bleed. The system automatically pumped the fluid through as it was trying to build pressure in the system until he closed the line again. I recall this having been super easy to do. The pedal was firm as the day as it was new after this.

Hopefully @BlackWorksInc can confirm this.

Do you have too? No, as long as your reservoir does not go dry. Only the point of the separation will introduce air. It is good practice to bleed all 4 corners any time you are doing this 'just in case'. It is also a good time to flush the system by running old fluid out and adding new fluid to the reservoir.

One thing I like to do when replacing calipers is to pre-fill the calipers with fluid before I put them on. It helps speed the bleeding process.

You should also bleed the LSPV if you have one, and it would be the last thing.
Also, with ABS you should completely bleed the system with the engine off, then again with the engine running, and again with the engine off.
If you have the system where the ABS is part of the Master Cylinder, it's way more complicated.

I replaced front calipers yesterday and bled on the front and the truck drives fine. That being said it would be a good idea to do all 4. My pedal is a little softer than it should be and I suspect I didn't quite nail it last night at 11pm when I wanted to finish the job

this. you don't have to bleed all 4, only the ones changed. but if done correctly, it wont hurt anything to bleed them all.


also, I suggest changing both calipers, not just the one.

The system will push fluid through to the rear, but not the front. I don't know why.

I don't think the 4th gens have a load sensing proportioning valve. It's all electronic. Dynamic Rear Proportioning (aka EBD)

The service manual makes no mention of bleeding with the engine off then running then off. It's done with the ignition on, and the engine can be running or not. As long as the ignition is on the ABS pump will operate, but you might want to run the engine if you are concerned about running down the battery. It's not complicated as long as you don't get air in the ABS unit.

If the fluid gets too low (but before the reservoir is dry), I think it will beep at you. But it's better not to let it get that low. It's also good not to let the pedal go to the floor if you can avoid it, or you may damage the seals inside the master cylinder.

A length of clear tubing is nice to prevent air from getting sucked back into the caliper. I used 2 feet of 3/16" ID flexible transparent plastic fuel line ($2.99 at the auto parts store).

When I remove any caliper, I always try to put a clamp on the brake line (flexible hose) before disconnecting it from the caliper. This prevents too much fluid from leaking out of line, and helps to prevent excess air from traveling up the line to the master cylinder. I leave the clamp on the line until the line is secured back on the caliper. This makes bleeding the system much easier. As long as you keep the master cylinder full (so it doesn't draw air in from above), I have had good results with just gravity bleeding one corner at a time. I follow the pattern suggested in earlier posts, but I use a clear plastic tube over the bleed screw to observe the fluid condition as it drains. Checking for air bubbles and fluid color. If I am doing a flush, I wait until the fresh fluid shows in the tube before shutting the bleed screw and moving onto the next corner. I have done it this way for many years, and never had a problem, as long as the master cylinder NEVER gets too low.

just finished replacing my MC unit with a used unit i bought off a forum member, got my brakes working ok now, but need help in understanding my brakes better.

1. the mc motor was still hot after about 30mins of driving [remember i have complained about this in a previous thread , together with the drivers side fender - you feel a heat surge on the drivers side when you open the engine bay after driving for a while, this is less pronounced on the passenger side], my worry is - am trying to understand what is generating the heat, could it be the mc motor assy?- going by the 40amp fuse that powers it, the bugger might be consuming lots of electrical power - thus generating the heat, if it is kicking in too often....................could you help me check the tempreture of yours after driving for a while

2. with ignition off, 1 tap on the brakes, the mc pumps kick in, 2nd tap..nothing happens, 3rd tap. the mc pumps kick in again. pls some1 should confirm if their mc pumps act this way too

3. after sitting a while - upwards of an hour without engaging the brake pedal, if i turn the ignition on,,, the mc motor kicks in represurizing the system, am wondering if this is normal..cos its supposed to be a closed system, and was pressurized completely [ie abs motor pumped and stopped], so why does the abs motor still represurrize the system after that?..the bad mc sill acted like this prior to failing, could you pls confirm if yours does the same,

After sitting, turning ignition to "on" will cause MC to start and run for about 5-8 seconds. After initial charge every 3rd depression of the pedal will cause the pump to run again for about 5 seconds. If I pump the pedal 40 times with the key in "Off" position it will take about 20-30 seconds total with 2-3 cycles during that time to full charge again. Hope this helps.

This is a bit off topic for the thread, but I'll answer anyway.

2. Yes, mine does this. It comes on every other time I press the brakes, even if I press them lightly.

3. I don't know about an hour, but the pump usually comes on when I turn on the ignition. I don't usually pay attention to it, so I can't say if there is ever a time when it doesn't come on. It's a closed system, but I guess pressure will make its way past the seals over time. The seals aren't perfect, and if the pressure is very high maybe it's difficult to store it for a long time. Even if that's not the case, it might top off the pressure just to be safe, like it does every other time you press the brakes, no matter how lightly. I think the service manual procedure for checking the fluid level says to pump the brakes 40 times with the key off to get all the pressure out, so there must be a lot more reserve capacity than two pumps of the brakes.