darkglass

I have a 98 4runner that has started to misbehave in the brake department. Im hearing and feeling a weird grinding like noise that is intermittent. Here one day and gone the next. I believe this is coming from the front brakes. The real scarry part is it feels like I cant stop the truck when this happens. It acts like something is freezing up. I thought brake lines, rotors, .... What do you guys think?


btw: doing a search on this I discovered that the culprit could be something in the rotor or brake pad, ABS system kicking in (this is hard to believe because it is suppose to help stop the vehicle... I almost rear ended someone yesterday), or ???????

dusty98

Have you checked your pads? You can check them w/out pulling the wheel.
Crawl under & look at the brake caliper. You'll see a square hole that you can see the pads & rotor through.
If they're really thin, they'll need to be replaced.

I'd find something else to drive till you figure that out. It's only going to get worse & we all know how well other people drive.

afonda

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I found this thread and it sounds just like my problem...
I don't know what "GEN" 4runner I have, but it is a 1997 4x4 3.4 liter engine.
Anyway... my brake problem comes and goes almost every other time using the brakes. the problem is a loud noise when breaking sort of like a wooooooooooooooooo, with swoooooooosh thrown in too and also a rubbing feeling and sort of like the pads are grabbing only on the passenger side most notably at slower speeds. also some high pitched squeeling sounds like the pad wear indicator.

The real time data... Just replaced the rotors (genuine toyota rotors and not the cheap aisan stuff), and pads about 2000 miles ago. replaced the calipers about 10,000 miles ago along with the flex break lines.

I also just bled the front break lines and took the truck for a test drive and the breaks worked great... a day later back to the usual with the rubbing sound and noise with the grabbing sensation...

What is going on!!!! it is driving me crazy. this has been going on for over a year or more. please help...

hross14

This may sound like a stupid question--but were the pads put in correctly. Meaning friction material towards the rotor and metal towards the calper pistons. Just asking because i have brake pads installed this way before. Funny as hell....

Ron Helmuth

afonda -you have a 3rd gen 4Runner (1996-2002 model years)

sorry guys I just had my front rotors and pads replaced but am not able to tell what you are describing.

Any Midas shops near you?-they do free brake checks...

afonda

yes the pads are installed correctly with the pad wear indicator on the outside.

What is this proportioning valve??? and does it affect the front breaks?

afonda

I could really use some input here fella's...

Thanks.. Andy

BoulderFrost

I think I may be having this same problem...

bwhyit

Have you actually taken your wheels off and looked at your brakes? It may be something abvious.

I'd also look at the backing plates to see if they were bent and not touching the rotors. Also pull your rear drum and clean all the dust out with some brake clean. Either of these could explain the noise. The performance problem may be related or may not.

afonda

ok... sorry but you guys are not helping.... a bit!!

Yes I have freakin' looked at the breaks... I have installed them from the calipers up to the flex break lines. and bled them as well.

May be time for the toyota techs at the local toyota dealer.

JGrauman

i think i figured out your problem. you're looking at your breaks, not your brakes. you'll have to check out your brakes to find the problem just messin' with you.

seriously though, i just bought my 98 in december and have had this same issue. i did as you did and after i replaced the rotors i thought the problem was fixed, but a week later it's back! it comes and goes and drives me crazy. i'm going to try a different pad, probably tomorrow, and see if that helps. it's like the pads are "skipping" on the rotor rather than sliding smoothly. hoping to not have to replace the calipers, possibly one is sticking pushing the pads unevenly against the rotor. guess it's going to be a trial by fire problem.

afonda

You d'man!! You absolutly nailed my "brake" problem.

yes.. its like the pads are skipping and sometimes the caliper does not "squeeze" evenly or something of the like.

I dont think new pads are the answer.

What is the proportioning valve? I dont think its the calipers since I just replaced them last year and I had the prob. prior to that.

Also... can the antilock system have an influence on the problem??

At one point I was considering that there may be an air bubble trapped in the anti lock system. not sure, but I did bleed the fronts and the problem went away for about 48 hours and then came right back. Could be air getting in somehow but I have no idea how!!

It's a mind scrambler.

SteveO

All the brake lines go through the ABS pump. Maybe you're having an issue with the pump.....don't know, just a sugguestion.

hross14

you can Unplug the ABS pump and your system will work as a regular brake system.

Ok this is what i would do--maybe this would help you with Trouble shooting.

Pull off calipers and compress one piston at a time--do the others move freely. If not rebuild, clean or replace.

And i think i know what the provblem is your residule valve--follow the logic

When you pump your brakes it pushes on the rotor--then barely backs away once you release the brake pedal. but if the residual valve wasnt working right--when you released the pedal the brake pad could come back into their bores farther than they should. ERGO--the pump (MC) volume is not enough to go the extra distance required--Hence, they seem like they are skipping and not stopping because they are barely touching the rotors

What i would do to trouble shoot--rig up some connection drectly to the MC and with a pressure gauge in line and see what happens--I am not sure of the exact pressure it should maintain--but i think it is like 2lbs. or just see if it bleeds off.

afonda

found out today... that if I pump the brake pedal real hard the problem goes away temporarily (like 5 mins or so).

Wierd.

Thinking of taking it to local toyota dealer for diagnosis.

JGrauman

i'm guessing that i could possible still have air in the lines. upon startup and making my first turn out of the driveway, the right caliper is not fully released. i pulled the pads yesterday and checked the individual pistons, each moved freely and held pressure, pushing out the others. i will bleed the system and hopefully this will help.

I just had my trans flushed last week at the dealer, so my visit to them for the month is up! good luck and keep us posted

BoulderFrost

Don't know if this will help you or not, but I am convinced that I have your same problem and I will be avoiding a mechanic by upgrading my whole break setup with the Tundra mod which can be searched for on YotaTech. I figure rather than pay a mechanic to diagnose the problem and then charge me an arm and a leg to fix it, I may as well upgrade my whole setup to a performance setup for less than $400. I'm not positive this will work but feel confident nonetheless...

RacerX

This might seem obvious but I used to run into it VERY often on peoples cars (ex-shop manager among other things)

Any area that needs to slide requires anti-seize or high temp grease, such as the guides on the calipers (metal pins/rods that retain the pads)

In the case of the 4runner/tundra the slide pins, and outer edges of the pad (contacting the caliper) should be coated. If not the pads can get wedged and create all kinds of issues. Think of this surface much like a bearing, if there isn't lubrication is will bind and be very inconsistent.

Also make sure the pins are straight by pulling them out and rolling them on a flat surface, if they are rusted, replace them.

It is possible that you may have a warped piston in a caliper but if you changed the pads it would be apparent as it would not retract when inserting new pads.

Hope this helps out...

Ron Helmuth

any updates? I am a curious sort of guy..... was it a caliper sticking?

BigBallsMcFalls

if you have to think about your brakes THAT MUCH then step away from the
vehicle and bring it to a toyota dealer and just get it fixed.

brakes are simple, and if you don't know how to set them up,
and also diagnose any problem,
then you shouldn't be in there friggin with them AT ALL.

























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