Master Cylinder gave up?

B

btruong25

New member
Hi,

I was just wondering if someone could help me diagnose my brake problem. with the car off and if you pump the brakes multiple times, the brake usually get stiffer with pressure till you cannot pump it anymore. However, i have pushed it over 50 times and it remains the same.

I checked the brake fluid level and it still is full. Sears did a brake fluid flush for me a while back. Could they have not done it right? i brought it back to them and they couldn't figure it out and told me to take my car back or pay for another brake fluid flush.

While driving too, there is a lot of travel and i have to push it almost to the floor to start to brake.

Does this sound more like air in the system or the master cylinder decided to give up on me.
 
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btruong25 said:
Hi,

I was just wondering if someone could help me diagnose my brake problem. with the car off and if you pump the brakes multiple times, the brake usually get stiffer with pressure till you cannot pump it anymore. However, i have pushed it over 50 times and it remains the same.

I checked the brake fluid level and it still is full. Sears did a brake fluid flush for me a while back. Could they have not done it right? i brought it back to them and they couldn't figure it out and told me to take my car back or pay for another brake fluid flush.

While driving too, there is a lot of travel and i have to push it almost to the floor to start to brake.

Does this sound more like air in the system or the master cylinder decided to give up on me.
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sounds like a lot of air! unless they screwed up the cylinder somehow??
 
It sounds like you have air in your system and need to do a THOROUGH bleeding..... and I mean THOROUGH!!!! I would bleed till at least 10 pumps of pure fluid (no spattering/air) through each wheel's bleeder valve. It sucks to have to do that much, but the 4Runner's brake lines are finicky. If the pedal still hits the floor, than yes, you should address the master cylinder. Have you ever rebuilt a brake master cylinder before? If not, you can PM me.
 
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preacher35 said:
It sounds like you have air in your system and need to do a THOROUGH bleeding..... and I mean THOROUGH!!!! I would bleed till at least 10 pumps of pure fluid (no spattering/air) through each wheel's bleeder valve. It sucks to have to do that much, but the 4Runner's brake lines are finicky. If the pedal still hits the floor, than yes, you should address the master cylinder. Have you ever rebuilt a brake master cylinder before? If not, you can PM me.
Click to expand...

Where did you get the O-Rings/Rebuild kit for the 4th Gen 4Runner's Hydraulically Assisted Master Cylinder Unit? I've got my old one that failed due to an o-ring so if can get replacements its a good used unit I'd like to keep around.
 
I had the same issue and it was because my brake were bled improperly. You just have lots of air in the lines and will need to be rebled like the others stated.
 
BlackWorksInc said:
Where did you get the O-Rings/Rebuild kit for the 4th Gen 4Runner's Hydraulically Assisted Master Cylinder Unit? I've got my old one that failed due to an o-ring so if can get replacements its a good used unit I'd like to keep around.
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Well, the short answer is, I have not rebuilt my T4R brake master cylinder. While I have rebuilt a few for other vehicles in the past, my Runner's MC is good. However, in answer to your question, I went on an online hunt for a rebuild kit. Couldn't find one. I suppose that's because you can purchase a remanufactured MC for $23.00 at Advanced Auto.
 
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preacher35 said:
Well, the short answer is, I have not rebuilt my T4R brake master cylinder. While I have rebuilt a few for other vehicles in the past, my Runner's MS is good. However, in answer to your question, I went on an online hunt for a rebuild kit. Couldn't find one. I suppose that's because you can purchase a remanufactured MS for $23.00 at Advanced Auto.
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I absolutely doubt that, I haven't found a single credible aftermarket supplier for the 4th Gen's system. I checked Advanced Auto's website and while they list a master cylinder, I have a feeling its not the correct part.

I could be wrong, but I don't think I've seen any aftermarket support for the Toyota system on the 4th & 5th gens yet.
 
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blackworksinc said:
i absolutely doubt that, i haven't found a single credible aftermarket supplier for the 4th gen's system. I checked advanced auto's website and while they list a master cylinder, i have a feeling its not the correct part.

I could be wrong, but i don't think i've seen any aftermarket support for the toyota system on the 4th & 5th gens yet.
Click to expand...

ok....
 
preacher35 said:
ok....
Click to expand...

Sorry, I came across a bit more rude that I intended.

I meant it more as I haven't found anyone that sells replacement parts for this other than Toyota.

http://www.toyota-4runner.org/4th-gen-t4rs/120125-hydraboost-brake-assembly.html

Not to mention I don't know if any auto parts store wants the liability of selling just the master cylinder section as that still requires owners/end users to tear apart something Toyota does not consider "Serviceable."
 
Help getting access to Master Cylinder test section 39-28

paco1038 said:
Is there a way to gain access to 39-28 “checking the master cylinder”?
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?? Paco1038 did you ever get an answer or find a way to access the section on testing The Master Cylinder? Our 4R is acting weird and we were told it’s the master cylinder. Hear almost a whistle like vacuum leak when pressing brake pedal, but when pumped it goes away. My son had a caliper replaced and they said they couldn’t bleed rear brakes by using vacuum pump or p(moping with bleeder opened, so they told him it’s the Master Cylinder is bad. I prefer to test it first if possible.

Thanks.
 
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