Soft brake pedal
- Thread starter mwrohde
- Start date
This is the master cylinder for my truck. I don't think it has an accumulator. But I don't jack about it.
BRAKE MASTER CYLINDER. Fits: 1998 TOYOTA 4Runner LUXURY(-0008),LIMITED(000
3400CC EFI, AUTOMATIC 4-SPEED | Village Toyota Parts
BRAKE MASTER CYLINDER. Fits: 1998 TOYOTA 4Runner LUXURY(-0008),LIMITED(000
3400CC EFI, AUTOMATIC 4-SPEED | Village Toyota Parts
jeremyc74
Banned
Is the float switch inside the reservoir moving up and down freely? That's not going to solve your overall problems, but it might be what's causing the brake light to stay on.
Yea, I did.
I'm going to go home after work and jack with it some more, then take it to a pro. This is my 16-year-old son's first car and I need it working better sooner. Can't have The Boy sitting in the driver's seat making engine noises. Need him driving.
nevada
Senior Member
how are the rear brakes? are they adjusted properly?
does the pedal pump up at all? engine off, pump the brake a few times, does it get better? any change at all?
rear drum brakes being out of adjustment will cause a low pedal, which many people incorrectly describe as a spongy pedal.
I was pretty careful with the rear brakes. I think they are properly adjusted. My test for that was the fact that the e-brake holds the truck on a hill.
I'll do the other tests shortly. About to go back out to the garage and starting stirring around.
Pedal is more firm when the truck is off, but it will still slowly sink to the floor.
I fixed the "Brake" light. It just took more fluid. It looked fine to me through the reservoir, but I guess the sensor wasn't happy. Stupid me.
I jumpered E1 and Tc to pull ABS codes. It's flashing an 11 and a 51. I *think* the 51 is "ABS Pump Motor Lock", whatever that is. I don't have a clue what the 11 is. Still googling.
I fixed the "Brake" light. It just took more fluid. It looked fine to me through the reservoir, but I guess the sensor wasn't happy. Stupid me.
I jumpered E1 and Tc to pull ABS codes. It's flashing an 11 and a 51. I *think* the 51 is "ABS Pump Motor Lock", whatever that is. I don't have a clue what the 11 is. Still googling.
nevada
Senior Member
master cylinder is bad.
What do you base that on? It's a brand new master cylinder.
I've now cleared the ABS code, and it doesn't return. Found codes and procedures here: MR2 ABS error code check How-To
The internet and idle hands can be very dangerous.
nevada
Senior Member
you either have a leak somewhere, or the MC is bad.
based on the pedal dropping to the floor. fluid doesn't compress, that volume is going some where. if you had that severe of a leak, you would have noticed it. but the MC will bypass the fluid internally, and you cant see it.
it being new doesn't mean much, I have diagnosed, and replaced many new brake master cylinders for this very same problem.
just last week, I was test driving a car for a different problem, and the MC went out. pedal dropped to the floor. it was fine when he drove the car down, and it was also a new master cylinder....
My thought process has been very similar to that. Can it be bypassing internally at one of the wheels?
I've also read that something the abs system can bypass internally. Yes?
jeremyc74
Banned
I could for sure, but the system is separated into two circuits, front and the rear, so a failure on one end doesn't kill the whole system.
When you pump the pedal up till it's hard, and then hold it, does it still eventually go to the floor even with the new master cylinder?
In many cases a failure in the system will damage an old master cylinder. There's a buildup inside the cylinder that creates a step where normal travel stops. So if something is leaking and the master exceeds it's normal travel the seals get cut and you now have a bad master where you didn't have one before. This is why you always see people recommend putting a block under the pedal when bleeding brakes on an old vehicle.
I suspect you damaged your original master by bleeding the system, but that wouldn't explain why it's still going to the floor if it is. Something else is likely bypassing.
Yes, it does.
I suppose it could have traveled further than it was supposed to. I didn't realize that was possible from the brake pedal.
jeremyc74
Banned
Something is still bypassing somewhere then. Tricky to diagnose, because there are still a few possibilities. I might start disconnecting lines and plugging ports to see if I could get it to stop and narrow down the possibilities.
Yea, it's actually really common. When I was a kid I went to the parts store for a set of calipers and the counter guy asked me if I wanted a master cylinder too. I told him it was fine. Went home and replaced the calipers and the master failed. I walked back into the store and he slid one across the counter to me. Later I read about this same situation in a Popular Mechanics and they made the suggestion about putting a block of wood under the pedal. Next time I was in the parts place I gave the counter guy a piece of my mind. He knew exactly what was about to happen and just let me do it. I was 16 and poor, and the extra $20 hurt. :ybrick:
I took it to my mechanic. He's in the same camp as y'all - bad master cylinder.
He says that I probably bought a bad one, rather than screwed it up myself. But, he may be being nice to me. I give him money, after all.
He did his pre-purchase inspection (after I bought it) and found quite a bit of other things, too. So, I'm on Rock Auto buying parts. I'll work through the list and my son will have a vehicle that'll run for year.
Thanks for your help and support. I'll check back after I get the parts installed and let you know the results.
He says that I probably bought a bad one, rather than screwed it up myself. But, he may be being nice to me. I give him money, after all.
He did his pre-purchase inspection (after I bought it) and found quite a bit of other things, too. So, I'm on Rock Auto buying parts. I'll work through the list and my son will have a vehicle that'll run for year.
Thanks for your help and support. I'll check back after I get the parts installed and let you know the results.
LittleCaesar
New member
Good to hear, well at least you know where the problem lies. Of the 50 MCs I have replaced over the years at least 1 out of 5 "new" ones have been bad right out of the box. The feeling of "did I just buy a new piece of crap" sets in real fast.
For sensors and the like these 4runners like OEM or OE manufactures for replacement parts.
For sensors and the like these 4runners like OEM or OE manufactures for replacement parts.
Explain that to me. How could that cause the pedal to sink to the floor? There's not fluid in that at all, right?
