2004, 4.7 brake issues

1

1sam16

Member
Thanks for the replies to my sons 4runner question yesterday! I think we're much better prepared to solve our serpentine belt/idler/tensioner issue.

The next big problem with this rig is the brakes. The woman we purchased it from has not driven the truck for the past year. She had the whole brake master cylinder unit replaced- I think she said it cost $1200? But she said shortly after the repair the warning signal came back and had no low/no brake fluid in the master cylinder. Someone told her she had blown a brake line. I filled it up last night, and the pedal doesn't push to the floor nor is the master cylinder seeming to lose fluid. But the warning signal is blaring, and I have all the the Brake-VSC Trac-ABS lights on. I know the Master cylinder was replaced because the old part is in a box in the back. Was thinking about going through and bleeding all the brakes this afternoon to see if that solves the problem? Your advice would be really helpful! My son is so excited about his new truck:)

Thank you
1sam16
 
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Bleeding the rear brakes is done with engine on, Crack open bleeder valve and have brake pedal depressed and it will pump a steady stream of fluid out. Front brakes are done the "normal" way. However, since you have a dry(?) MC there may be a bit more involved. Someone with that experience will chime in I'm sure.
 
There are several pieces/parts of the ABS/master cylinder assembly, please post a few photos of the old part so we know exactly what pieces/parts were replaced.
 
The truck is parked across town until we can limp it home. Going back over this afternoon/evening. We'll take some pictures... but the unit that was replaced looks like the picture I hopefully attached:)
 

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A picture of his truck.
 

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The engine doesn't need to be on to bleed the rear brakes. Open a rear bleeder valve (I do one side at a time and attach a rubber hose to the valve and have a water bottle to catch draining fluid), turn the key to ignition (but don't start) then depress the brake pedal. Be sure the MC is full when you start and be careful not to run it dry. Have someone watch it or check it every 5-10 seconds, fill it up when needed. If you hold the pedal down too long the alarm will go off. Stop, turn the key off, check the MC level, start again.

As said, the front lines are bled the normal way.
 
Nice truck! My son Gabe would've loved to have a 4runner with a hood scoop... Maybe we'll stumble onto one in the future? But first, we need to get it to stop/replace some idlers/tensioner pulleys, and do a quick patch on the frame. The previous owner kept a file on all the things that she had fixed. We're glad she got as much done as she did but unfortunately, I think she got ripped off- lots of high dollar parts replaced.

Thanks for all your help!
 
1sam16 said:
The truck is parked across town until we can limp it home. Going back over this afternoon/evening. We'll take some pictures... but the unit that was replaced looks like the picture I hopefully attached:)
Click to expand...

perhaps the replaced unit is bad?.
start the truck and have someone depress the brakes, while you hold the silver cylinderical part /motor in your hands...if it pulses/actuates....thats a clear sign that the brake assy is halfgood, if it doesnt actuate. check the abs brake fuse in the fuse bay if its blown - i think its a 40 amp fuse.
 
OK- here is the picture of the brake master cylinder unit that was replaced-
the whole unit was replaced. The core is in the trunk... maybe if some parts are bad I could swap with parts off of the core? She seemed to think that they replaced much more than was needed for whatever problem she was having.

Once the battery is charged back up I'll turn the vehicle on depress the brake and check for vibrations indicating the brake booster is working.

I did find at least one area that brake fluid is leaking... hoping this is helpful in diagnosing the problem and moving towards a fix.

Again thanks,
1sam16
 

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BTW- It did look like the leak was at the coupling. Looks like theres a shroud that has come apart on the RT/leaking coupling?
 
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Does the removed master cylinder have the black ABS control ECU on the driver's side?

This is why I wanted to see a few photos of the one they removed, it's not what's on the new one but what is still on the old one that will tell us what all was replaced.

That fluid leak could well be your issue.
 
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Got it- heading over one more time tonight- will get a couple pictures of the old unit. I shot that leaking area with some PB blast and will tear it apart and see whats up.
 
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Followed ur directions- the brake unit does vibrate/buzz but not necessarily in conjunction with brake pedal use. With the ignition on, the unit would vibrate/shut off/vibrate/shut off in a pattern. I made a quick video, but can't seem to upload it.
 
OK, it shows that they did indeed replace the entire assembly.

Usually the only parts that need replacing are the electric motor, the accumulator and sometimes the ABS pump, but usually it's only the electric motor that wears out for the most part.

Most all Toyota dealerships and I would assume smaller garages will only replace the entire assembly because by the time you purchase the motor, accumulator and possibly the pump it will cost you more than buying the entire assembly plus more labor as well.

By the way the previous owner paid the going discounted price for the new assembly, so she didn't get ripped off, unless it was on the labor to install it.

My best guess is if you fix the leak you found and get all the air out of the system it should work as it should.

That all being said if I were you I would plan on replacing all the metal brake lines at some point, just looking at the "leak" photo tells me the rest of the metal brake lines are very rusted and could at some point burst and leave you without brakes again and most likely when you least expect it, it could be a very dangerous event!!

For the most part replacing these brake lines is not that hard to do, the hardest ones to get too are where they run behind the gas tank, to remove the old ones you need to remove the gas tank, but I wouldn't brother removing them just fish the new lines in that area and leave the old ones in place.
 
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1sam16 said:
Followed ur directions- the brake unit does vibrate/buzz but not necessarily in conjunction with brake pedal use. With the ignition on, the unit would vibrate/shut off/vibrate/shut off in a pattern. I made a quick video, but can't seem to upload it.
Click to expand...

When operating normally the motor should come on for about 10 to 15 seconds when you turn on the ignition after being off for several hours or overnight, and then again about every 3rd depression of the brake pedal when the vehicle is running.

What is likely happening is the leak you discovered is for the rear brake line and is losing pressure causing the pump motor to operate to build up pressure again.
 
"I filled it up last night, and the pedal doesn't push to the floor nor is the master cylinder seeming to lose fluid. But the warning signal is blaring, and I have all the the Brake-VSC Trac-ABS lights on."

You're saying here the brakes are functioning correctly right?? With all the dash lights on. After replacing that entire unit the VCS module that controls all your traction control and vehicle stabilization needs to be calibrated (zero point calibration). Those functions will be disabled until then.
 
Fayetteville, Arkansas! I lived in Little Rock for four years:) When we first began to tear into this truck on Saturday- the brake master cylinder was completely empty- but the truck still had a fairly firm pedal. We added brake fluid and slowly drove it up and down the street. When we checked the brake fluid level there was not a noticeable difference. But this afternoon the levels were down and I noticed the small leak at a brake line junction point over the back of the fuel tank. I think this leak is the main brake issue. I'm hoping that once we figure out a way to safely fix this/these leaks. The alarm noise will go off and some of the Christmas tree of lights will turn off on the dash... here's for hoping:) Thank you
 
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