97t4r81
New member
Not what I was hoping to hear. Oh well I love my rig enough to deal with it
Seemingly never ending sinking brake pedal issue
- Thread starter m0ist
- Start date
Not what I was hoping to hear. Oh well I love my rig enough to deal with it
I have had similar experiences with my 96 almost from day 1 when I bought it with 89k. Even with all new rotors, calipers, pads, drums, shoes, hardware, fluid, etc I still get times where the pedal is very soft. If I come to a light and it is soft, once I stop if I lift up and push again it becomes hard and feels normal. Last time through I replaced the rear line with a Wheelers stainless line and bought a Motive Power bleeder as well. Still have the same issue.
My next steps are to replace the Master as it is original as far as I know. May look into a slightly larger bore T100 master. Will also due front stainless lines (although they are newer rubber replacements). Even thinking about swapping my front calipers again just to see if it helps.
My runner still stops well, but the soft pedal at times makes me a little leery..
My next steps are to replace the Master as it is original as far as I know. May look into a slightly larger bore T100 master. Will also due front stainless lines (although they are newer rubber replacements). Even thinking about swapping my front calipers again just to see if it helps.
My runner still stops well, but the soft pedal at times makes me a little leery..
OP, tell us exactly what is your method of bleeding the brakes.
Not the order of bleeding, but rather - how exactly do you bleed the brakes ?
2nd:
If you apply the parking brake, can you move your car by pushing it ?
(Careful, don't do this on an uphill/downhill road. Leveled surface only. )
Also, for future readers: Having a soft pedal and moving ahead with replacing friction parts - rotors, pads, shoes, drums - is not the most likely solution to the problem.
Not the order of bleeding, but rather - how exactly do you bleed the brakes ?
2nd:
If you apply the parking brake, can you move your car by pushing it ?
(Careful, don't do this on an uphill/downhill road. Leveled surface only. )
Also, for future readers: Having a soft pedal and moving ahead with replacing friction parts - rotors, pads, shoes, drums - is not the most likely solution to the problem.
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PO told me the brakes needed to be replaced and bled. I just took his word on it and replaced everything then bled. Pads looked fine and shoes were gone. Replaced them all anyway.
Bled the brakes the way I bleed any car.. Two person job, as I don't own a pump. Have a bleeder canister or whatever you want to call it, which has fluid in it so air can't be sucked back in.
Handbrake is non functional. Bell crank is seized.
I haven't read the whole thread, so I'm sorry if I'm repeating information here -
In normal driving conditions, The rear (drum) brakes - get adjusted by actuating the handbrake.
If your bell cranks are seized, there will be no adjustment (i.e movement of the shoes towards the drum), at all. It will stay as you have adjusted it when installing the brakes, or by using the service hole and clicking the star adjuster.
I understand that you make the adjustment manually, and don't expect to get such far travel of the pedal, however - in your place, I'll take care of the bell cranks (not a hard job), due to the handbrake being a critical part of the brake system's operation.
From this point on, it's just my wild theory:
If you're not adjusting the shoes tight enough (which I'm sure you're doing right), then simply driving the car and using the handbrake a couple-three times a day, would have solved the issue for you, - the shoes get adjusted a few fractions of a mm any time you'd pull the handbrake lever, but - being the handbrake is not working at all, such adjustment never takes place.
Just a wild assumption, I'm sure you're doing everything right when adjusting, and it's only my mind running wild.
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1st gen 4runner brake problems
If I press my brake pedal slowly for a normal stop the pedal will go to the floor and the brakes won’t grab. At this point I have to release the pedal and press it again quickly. Then I can stop. When I go to Stop regularly as long as I push the pedal like I want to do a quick stop it will work. I don’t appear to be losing brake fluid from a leak I can see. I have bled the brakes, but that didn’t do anything. What’s my next step?
89 4runner 3.0 v6
If I press my brake pedal slowly for a normal stop the pedal will go to the floor and the brakes won’t grab. At this point I have to release the pedal and press it again quickly. Then I can stop. When I go to Stop regularly as long as I push the pedal like I want to do a quick stop it will work. I don’t appear to be losing brake fluid from a leak I can see. I have bled the brakes, but that didn’t do anything. What’s my next step?
89 4runner 3.0 v6
AZBub
New member
Take a good hard look at the brake booster. Likely there is a small tear in the membrane which causes this exact issue. I had this issue and everyone kept saying it’s the MC so i replaced it, twice, then they said it’s air trapped in the ABS, had that bled out twice as well. then they said air in the lines, I bled over a gallon of fluid out each line. Then, out of desperation i got a used brake booster and popped it in. problem solved instantly.
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So I had a sinking pedal issue as I previously posted as well. At some stop lights the first pump would go very low with mediocre (at best) brake performance. At the stop I would lift the pedal and the next pump was firm like normal brakes.
After replacing most items in the system (most wear items were due) pads, rotors, shoes, drums, rear braided line (front lines arent very old), adjuster rear's tights (e-brake works as it should) and running a power bleeding through the whole system (after gravity bleeding and a normal pump-pump bleed procedure) Nothing really seemed to reduce or correct the sinking pedal. Up until last weekend I have just lived with it thinking the master and booster would be next.....
Well last weekend I finally got around to replacing most of my vacuum lines with the Silicone kit people have been ordering. I replaced every line I could see with silicone with the exception of some HD rubber lines (back of intake in 3 places and the booster line). There were also a few small lines I haven't done yet due to time. (one line running towards drivers side headlight, some lines towards the frame rails/possibly ADD)....
After replacing the vacuum lines with silicone I now have a firm brake pedal and have not had a sinking pedal for a week. So it seems as though my issue with a possible vacuum leak, weak line that may have been collapsing or one that was cracked that I could not see. Wanted to give this a week before reporting in, but these lines have helped my brake pedal issue.
So how do your vacuum lines look?
After replacing most items in the system (most wear items were due) pads, rotors, shoes, drums, rear braided line (front lines arent very old), adjuster rear's tights (e-brake works as it should) and running a power bleeding through the whole system (after gravity bleeding and a normal pump-pump bleed procedure) Nothing really seemed to reduce or correct the sinking pedal. Up until last weekend I have just lived with it thinking the master and booster would be next.....
Well last weekend I finally got around to replacing most of my vacuum lines with the Silicone kit people have been ordering. I replaced every line I could see with silicone with the exception of some HD rubber lines (back of intake in 3 places and the booster line). There were also a few small lines I haven't done yet due to time. (one line running towards drivers side headlight, some lines towards the frame rails/possibly ADD)....
After replacing the vacuum lines with silicone I now have a firm brake pedal and have not had a sinking pedal for a week. So it seems as though my issue with a possible vacuum leak, weak line that may have been collapsing or one that was cracked that I could not see. Wanted to give this a week before reporting in, but these lines have helped my brake pedal issue.
So how do your vacuum lines look?
T4R2014
Elite Member
I think the ABS pump needs to be investigated further. 2/3 of my 3rd gens have funky pedal feel accompanied by over-reactive ABS. I think the ABS pumps on these are one of the achilles heels that has shown up over time.
Beaumont67
New member
My brakes (front & back) are fairly new (premium NAPA/UAP line) & I seem to get a soft brake peddle feel, only when I slow down enough to turn into my driveway, off the main highway....kinda weird.
- pedal always seems momentarily soft, unless I pump the pedal once / making the turn
- which should not be necessary / because my breaks are not hot, from normal drive home
I'm just driving home, and as I turn into my drive...I get the feeling, my ABS might be playing a trickery (on me).
- @ a certain point in lower mph braking
- been like this since took ownership, 7,500 Km / 5K miles ago
- rest of my driving, the pedal feel is adequate & firm enough / Gen3 like
- I know its gonna happen, when turning into drive / just bugs me though...doesn't make any sense
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Buckaroo
Member
I think this could be normal. ABS is designed to kick in when the wheel speed sensors detect the wheels are turning at different speeds. If you have any slight wheel slippage when you are turning (gravel?), the ABS could kick in. When you do the turn, you must be on the brake pedal pretty firmly to feel the pedal sinking...(down hill?). Normally, I am braking ahead of my turn and then letting off pressure as I go around a corner. Also, maybe if you are making a very tight turn with brakes applied, the difference in speed between the outside and inside wheels could set off the ABS.
Buckaroo
Buckaroo
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Did you ever find a solution to this problem? I’m having the same issue!
I replaced the MC, gone thru about 2 gallons of brake fluid bleeding the lines. I haven’t messed with the spinner in the rear brakes yet.
I disconnected the abs connectors and pumped the brakes, no change. So maybe it’s not the abs pump?
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You may have hit on something here. I know this thread is older than mask wearing (not quite as old as sheep) but your words here gave me pause for this exact same problem I am having. 1988 4runner DLX 4x4 - new booster, mc, new rubber lines all around, new rotors and pads, no apparent leaks anywhere.....it doesn't make sense that the pedal goes to the floor like it does. I cannot stop the rig like I know I am supposed to. I maybe need to look into the vac lines to the booster. It's even been looked at by not one but TWO brake techs and they have fixed NOTHING. Anyone please help.
A master cylinder can leak into the brake booster without and external leak visible. The seals in a master cylinder can also go bad causing pressure to bypass the piston and not be forced to the calipers. A booster that isn't getting enough vacuum or that isn't operating correctly will give you a very stiff pedal. If you haven't replaced the master cylinder then that would be my suspect.
During the first push of the brakes, doea the brake pedal hit solid at the bottom stroke and slowly sink to touching the floor?
Or is your brake pedal just low and not touching the floor as you hit solid at the bottom on the stroke?
Hate to be that guy to revive an old thread but man I’m getting desperate. Same issue but my 95’ 2nd gen has 4Wheel ABS which seems to a bit uncommon, i unplugged it, same thing. Replaced the MC, power brake booster, bled the system using every method possible, adjusted rear shoes. New pad and shoes, and rear wheels cylinders. The only thing someone mentioned was a possibility of vacuum leak. Tried spraying some brake clean around all the possible areas for leaks but still Nothing! This “cheap” off road project is getting pretty expensive… any help would be greatly appreciated.
