95 Blazer brakes went to the floor almost

[Dave186]

Coming home today and pulled up to stop and the brake pedal went to the floor almost, still stopped but scared me LOL. I checked because I thought I had busted a line or caliper or wheel cylinder. No visible leaks and Ive pumped and pumped the brake pedal to see if it would. You think its the master cylinder??? It has all that crap under the hood I suppose for the antilock brakes that I have NO clue about. Thanks in advance for the help.

[old_master]

Did the red "BRAKE" light in the instrument cluster come on? If so, there's a hydraulic fluid leak somewhere. If not, it might be the power brake booster, master cylinder, or a problem with the ABS unit. Usually if there's a problem with the ABS, the orange "ABS" light will come on.

[Dave186]

The only time the red brake light came on was when I was pumping it to see if there was a leak. I cant find any visible leak. The ABS light did not come on either. Im assuming its the master cylinder although I hate to blow $60 bucks and that not be it. Thanks for the reply.

[Dave186]

I decided to put a master cylinder on it today. Did NOT help. Pedal when pushed goes slowly to the floor. ABS light did not come on so Im assuming its ok. HELLLLPPP!!!!!

[old_master]

Before you installed the master, did you bench bleed ALL of the air out of it? If not, the ABS unit will have to be bled. The ONLY way to bleed the ABS unit is with an ABS capable scan tool.

[Dave186]

Yes I bench bled it very well to make sure it had no air. Its doing the same thing as before. The brakes work but if you sit and hold them the pedal slowly goes down. Its not that its goes quickly at all just very slowly. Thanks for your replies I have no clue what to do to it now. As I said before the ABS light has never come on other than when you turn on the key initially then it goes out.

[old_master]

An internal leak in a master cylinder can cause what you're experiencing, but to have 2 leaky ones??? Better buy a lottery ticket the odds are astronomical. Probably NOT the master cylinder. The only other thing that can cause the pedal to sink is an external leak. Might want to pull the wheels and drums in the rear and have a close look. Could be a leaky wheel cylinder.

The rear brake system that is used on your vehicle has been used since 1978 with very few, (minor) changes. There are 6 places, (lands) on each backing plate that the shoes rest on. If those lands are not lubricated with each rear brake job, the lands will wear down. When they wear down, it allows the shoes to move inboard. If they move too far, they will lose contact with the wheel cylinder pistons which will allow the wheel cylinder to blow apart when the brakes are applied. If the backing plates are not replaced along with the blown wheel cylinder, the new cylinder will also blow out. This is a very common scenario with this brake system. Basically there are two reasons a wheel cylinder will blow out: Worn backing plate lands and oversize drums.

[Dave186]

Would the backing plates have to be gotten from the dealer?? Im going to pull the rear wheels and drums today to see if I can see any leaks. I have no clue other than to try what youve said. I appreciate the responses. Hopefully I can see something obvious. Wanna buy a good Blazer?? LOL.

[Dave186]

I pulled the rear wheels, and left side was a little damp ( I mean it is just very slightly wet and looks like its been like that for awhile) but no obvious leakeage like I would think for the problem Im having. Would that be the cause???? I have no clue where to go from here other than that slight possiblility that Ive gotten a bad master cylinder. HEEELLLLPPPPP again LOL.

[old_master]

It's very doubtful that the little bit of seepage you're seeing at the wheel cylinder is causing the pedal to sink. Have you noticed the fluid level going down, either before or after replacing the master cylinder? That would be a clue if there's an external leak. Have you traced the hydraulic lines from the master cylinder to each wheel looking for a leak?

[Dave186]

Ok, on the wild assumption and against the probability I took the other master cylinder back and told them I thought it was bad. Put the new one on (bench bled very good) and still have the same problem. I bled all 4 wheels starting with the farthest away. When I got to the right front there was no fluid coming out of the caliper and I mean NONE whatsoever. So I broke the line loose before the rubber hose and had fluid there. Could a collapsed rubber hose cause it to do what its doing?????? Im on my last resort before setting fire to it LOL. Thanks again for the replies.

[Dave186]

OOPS I forgot to answer that yes I have traced the brake lines from the master cylinder to each wheel along the frame and there are no visible leaks. Also there was no fluid loss in the master cylinder resevoir (not sure I spelled that right) I forgot to answer in my previous post.

[old_master]

YES, a restricted or collapsed flex line could cause the pedal to sink. It's extremely rare for a flex line to do what yours is doing. Normally what happens is the hydraulic pressure will get past the restriction when you apply the brakes. The pressure then gets trapped in the caliper causing the caliper to remain applied. When the pedal is released, the pressure slowly decreases, (equalizes) getting back past the restriction, and the caliper releases. If you have a problem with one flex line, it's best to replace both of them, along with the rear flex line(s). Keep us posted as to the results.

[Dave186]

Thanks, I am going to try and replace it tomorrow bad storm here this evening and pouring rain and I dont have a place to work on it. Ive had the other problem with the caliper staying applied but never this way. I appreciate the advice and will post if that cures the problem.

[Dave186]

Ok I tackled that thing again today. When I took the brake line loose from the caliper I found out that it had fluid up to the caliper but would NOT bleed. SO I replaced the caliper bled it and the brake pedal still slowly goes down. Im at a loss here with no clue what to do next. So far Ive replaced the master cylinder (twice). Replaced a rear wheel cylinder that probably didnt need it. Checked the lands where the rear shoes rub against and now replaced a caliper. At this point Im totally lost. If you have any ideas please tell me. I do appreciate your help.