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BobinDenver
03-24-2010, 09:11 AM
Howdy gang!

I was up camping this past weekend and sometime during the weekend the brakes started acting up. The normally responsive brake pedal wasn’t responding without significant applied pressure. There is an inch or two of travel at the top then it hits a "wall" where I have to practially stand on the pedal to get the vehicle to stop.

My actions / thoughts:
- The brake fluid was a little low so I topped it off with no effect.
- It seemed rather sudden and there is no sound/vibration issues so I’m ruling out pads/rotors (though I know they are just around the corner).
- The pedal doesn’t drop and pumping the brakes doesn’t work (though…ABS) so I’m thinking it’s not the master cylinder.

Sooo… power brake booster… which is connected to the ABS, correct? No codes.

Noting that leisurely deceleration has always been an issue for the 80...has anyone had a similar experience?
If it’s the booster, is that a job I can do with a plug and play part? Or are brake items always saved for the professionals?
Thoughts on reconditioned / used boosters?

And just in time for the snow! :thumb:

Thanks in advance! :cheers:

Bob

nakman
03-24-2010, 09:51 AM
Bob how new is your brake fluid? Sounds like water or air could be in the lines, and if it got cold that water can freeze and would feel exactly how you described. Bleeding is pretty cheap/easy, I'd probably start there.

powderpig
03-24-2010, 10:29 AM
As Nak man said, bleed the brakes. Then if it is still happening, I would pull the ABS fuse to see if it is in the ABS system or the mechanical systems. Do you have a FSM or other service manual you can follow the trouble shooting diagrams(toyota's FSM is some of the best to find the problem).
If all is well after you bleed the brakes, then you might of found your problem. If not ask more questions.

SteveH
03-24-2010, 10:31 AM
Without sounding like a 'unintended acceleration' deal, my '95 FZJ did this a few times for my wife (who is pretty perceptive of vehicle behavior) and so I pulled the ABS fuse and it has never come back. I once reinstalled the fuse, and it did it again. She doesn't mind driving w/o ABS. There are no ABS codes set, and all systems are in good working order. This is a statistical sample size of '1', so your mileage may vary. All I can conclude is that on occasion, the ABS kicks in for no real reason. I may be nuts, but the non-ABS brakes behave nicely 100% of the time, which is all I require. I tested the master cylinder, and have regularly replaced pads and the front rotors. I bled the brakes - so there's no physical issue I can find. I hope you figure it out!

thefatkid
03-24-2010, 11:02 AM
Sounds more like the brake booster is out. The 80s have a issue with the port on the manifold getting plugged with carbon. I'd inspect for correct vacum at the booster. Some 80s also had in issue with water freezing in the booster hose.

The ABS should have no effect on the braking system when not in activation. If you have an unintended activation it should have a motor and soleniod sound. In a case like SteveH I would perform a resistance check on the sensors and inspect for metal contimination (common if you have broken a birf). A stuck soleniod should set a code on startup, as the vehicle would fail the self check.

One thing I have noticed on braking performance is when the wheel bearings get very loose the pedal gets very low and braking performance is odd.

sno bored
03-24-2010, 11:40 AM
Was this first thing in the morning and how cold was it? My Truck will do this first thing in the morning when it is cold, 10 degrees or colder. I thought it might be water in my brake fluid. There was a thread on mud where others had similar problems at cold temps. A couple of people had recently changed their fluid and were still having this problem.

It seems as though the brake check valve freezes up and it takes a few pushes on the brake pedal to free things up. When I start my truck up I push on the brake pedal a few times until the brakes feel normal and then I start driving. I didn't feel as though I needed to replace the check valve because the only time I have this problem is first thing in the morning at cold temps.

corsair23
03-24-2010, 12:00 PM
I'm with Tim if the fluid is old, flush it and bleed the brakes first. I'd also suggest checking the soft lines for any signs of bulging - I'm pretty sure at least one member has discovered poor braking performance was due to old soft lines that would buldge when pedal pressure was applied. Sounds like your pads are close to needing replacement so now would be a good time to replace the pads all around, flush the fluid, bleed the brakes, and check the lines for bulging.

Another simple thing to do/check is to pull the ABS sensors and clean all of the little metal shavings that are surely to be there, off.

I'd start there 'cuz that is the kind of stuff I can do myself now...After that I'd probably be calling one of the experts :)

BobinDenver
03-24-2010, 01:02 PM
The morning I noticed it (Saturday) it was single digits. There were a number of temporary conditions that I examined but since it has continued doing it I ruled them out.

Excellent idea re: bleeding the brakes. It's at the top of my exploration list. Occam strikes again! :doh:

For posterity, how much brake fluid does an stock 80 brake system hold?

nakman
03-24-2010, 01:12 PM
One large jug will do it, I believe they're 32 oz? And you won't use all of it.

And that my be the first Occam's Razor reference in forum history.. well played! hope you're right. ;)

SteveH
03-24-2010, 03:58 PM
Brian C - thanks for the suggestions. I wish this would happen to me, so that I could be sensitive to the ABS motor sound. I know it didn't happen on sub-freezing days. I'm sure an inspection of the vacuum lines and check valves to the booster isn't a bad idea, as a variety of vehicles eventually have problems like these, as they age.

TIMZTOY
03-24-2010, 11:22 PM
Regardless if changing the fluid fix's the issue at hand the brake fluid should be changed ever few years or when it gets dark/black in color. Really it should be changed before it's black.

Uncle Ben
03-25-2010, 06:24 AM
Regardless if changing the fluid fix's the issue at hand the brake fluid should be changed ever few years or when it gets dark/black in color. Really it should be changed before it's black.

In completely agree! Moisture is what causes it to get black and moisture will pit and wear out brake components.

BobinDenver
03-28-2010, 11:04 AM
Good news: I bled the brake system and there was very little black fluid. It took about 16 oz- 32 oz will guarantee that you'll be covered and have some left over - besides, it's cheep.

Bad news: The brakes are still wonky. I'll be visiting Oleg for a booster. Since I've heard of few booster failures I'm reasonably comfortable with a used part rather than a reconditioned one. And for the price, I could replace them 4 times over. :)

Thank you all for your input; I'll let you know the outcome of the booster efforts.

TIMZTOY
03-28-2010, 01:36 PM
I would get a free brake inspection from a shop Instead of throwing parts at a problem, and hoping to fix it. almost every shop does FREE brake inspections. Just tell them in detail what happened so they know what to look for. Hell even go to 2 or 3 shops and get diffrent diagnioses. Free beats guessing in my book any day.

S**t swing by my shop in littelton I'll take care of ya, won't test drive too hard :hill:

powderpig
03-29-2010, 08:51 AM
Well Bob, you did not state if you pulled the fuse or not to see if the problem is mechanical or ABS system. I have only replaced one VB on a 80 in over ten years of working on them. It looks like you have only done part of the diagnosis of this. While the VB is some what easy to replace, it can be a bear to set up properly. Do you have a FSM to diagnosis this problem and to show you how to replace it? Or are you winging it?
If so, I would do what Tim as suggested, have a diagnosis done by a shop that will give you the labor for free. Not all shops will do this, but some will.
It is better to know what the problem is, then to throw parts at it. It cost more when you do it this way.
Good luck with your choice.