Hi all,
heres my story. About a month ago one of the caliper pins that holds the caliper to the body fell out while i was driving. not a huge problem, it caused the caliper to fall on the rotor, lots of grinding noises and some small grooves in the caliper itself. i replace the pin on the caliper—sans the aluminum spacer/bushing cause it fell out and they don't sell them—never even removed the caliper. After replacing the pin all was well in my truck again. yesterday it happened again but this time it was the opposite pin. So I figured ill just put the pin make sure the pads are positioned ok and be on my way. BUT NAY!!!!. After i repositioned my caliper I now have spongy brakes. Brakes are firm when engine is off but spongy once it is fired up. replaced master cylinder. bled front brakes. drop kicked a wall, yelled, cursed, preyed to the Blazer gods. Still nothing. those gods are not merciful are they?
91, S10, 4.3, ABS, 4X4,

that was my situation here are the key points for those who refuse to read a novel.

• caliper pin fell out
• after i repositioned my caliper brake pedal depresses to the floor when on but firm when off.
• bled front brakes even though this made no sense
• took it to a snake in the grass mechanic they told me they would charge me 500 bucks to replace the master cylinder
• I replaced my master cylinder myself
• same problem occurs and now I am out of ideas.

now for my speculations(tell me if im offbase)

I think maybe something happened to my caliper. maybe the piston is not traveling far enough. maybe somehow it is stuck. I tried pumping the caliper in question without the rotor to see if the piston was traveling. it was but not very fast or far, but I have never tried that before so I'm not sure what is normal or not.

it could be air in lines. still think this is strange being that i never exposed the lines or cylinders until I became desperate enough to change the cylinder.

help me out please!! until then i will bleed all my brakes cause I'm sure you are all going to tell me that is the problem. But before you do remember that this problem only occured after my caliper pin fell out, and even then only after i replaced the pin.

Thanks in advance LOOK, THINK, COMMENT,

 

Here's my take. Firm pedal truck off is normal since the brake booster assists there. I would rule out the booster being a problem or the master. It sounds like air in the lines to me. Did you bench bleed the master cylinder first? If you buy and replace the calipers they will come with the slide bushings more than likely. Here a semi loaded calipers will run about $20+core a piece. If you do decide to change the calipers now would be a good time to change the rubber brake lines as well. Then you will need a good brake bleed. I just did a bunch of brake work on my truck and my pedal is spongy. Once it hits a certain point they work ok, indicating air in the system. So I will be building a pressure bleeder to try and get as much air out of the system as possible. Or take it to a place that can pressure bleed it for you.

 

First thing, it doesnt say anything about bench bleeding the master cylinder with the little hoses that it comes with before you put it in, this is a must do, and it came with instructions on how to do it that I hope you read and followed. This is a must or you will never get the air out of it from driving. Take if off and bleed it properly if you havent done it before installing.

Second, you CANT just bleed the front brakes, you have to do the farthest brake to the closest when you have the master cyl lines open, no exceptions... And you have to make sure you didnt get any air into the ABS module... Like when you have your caliper off, pinch off the line so it cant drip dry while you work, or keep topping up the fluid as it leaks out, or work fast and get the system closed ASAP. If you had the master off, and a caliper at the same time, I almost promise you that you ran that module dry. Take off the master, bleed it, put it back on THEN take off the caliper and replace, THEN bleed in proper order...

Third, calipers are cheap, and you have a damaged one now from the rotor rubbing and missing parts, and when you had it off and pushed the pedal (which BTW is a big NO-NO) you should have had the piston pop right out of it and make a real mess, not just move a little, so you have one buggered caliper. Pull out your wallet and take your old caliper in to the store so you dont have to pay the core charge, and get a new one. It should also come with the parts you are now missing, and plug the line so it doesnt drip dry on you or you are never going to get the ABS system bled out properly.

Go around your truck and do the bleed again, RR, LR, RF, LF in that order, and message us back. And check the level of the brake fluid every 10-15 bleeds, if you run out of fluid you have to do it all again. There is at least a whole litre bottle in the brake system, so you will have to get at least half a litre from the 2 rear brakes to know that you got all the lines purged from the front to the back. And dont go putting in any fancy fluid, it says DOT3, use DOT3.

 

Actually you can buy the bushings and the little seals that you somehoe lost. Brake Best makes them. O'reilly has them on their website. Check it out. Like $2.00
http://www.oreillyauto.com/site/c/se...994&vi=1060580
The best way that I know to n;eed brakes is with a hand held vacuum pump with the brake bleeder attachment. One person operation but it does go easier with two. If you got air in your ABS system you need to get it out and need a couple of the little special tools to compress the high pressure accumulators in the brake module. They run anywhere from about $6.00 each to like $30.00 each (for the exact same tool mind you). Don't get ripped off. Here is where to get them. I bought three. Two for the ABS module and one for the combination valve.
http://www.carparts.com/PERFORMANCE-...2206_10618.car
Ohsofly is right on the money for the rest.

 

You guys are just well … just awesome.
you send me in a direction that usually works thanks for the fast reply calipers are cheap. as for some of your concerns:

yes i did bench bleed my master before installing it.

no i havnt taken out my caliper yet, and i sure wouldnt have it off with my master c. too many holes = bads news.

thank you for explaining the importance of the piston in the caliper only coming out a tiny bit. i figured that was abnormal. ill replace the caliper next.

 

I have a question I replaced my caliper and got ready to bleed my brakes but the rear wheels have some sort of clip over the bleed screw. I have never bled the rear brakes before how do i get the clip off so I can get access to the screw? please help again

 

 

Got me a trade ticket for this stuff years ago, 2 months a year for 4 years sure beat college however I looked at it... However I only really did brakes and suspension and driveline stuff in my 9 years on the job, so when it comes to engine diagnostics Im still fairly green... I took that stuff in school, but aside from the odd tune-up and intake gasket I never really got the chance to mess with the engine tech on the job, which makes these forums a valuable resource for me now that Im getting into the engine stuff on the side at home for some extra coin.

FILTYSANCHEZ, you dont need to take that clip off, you shouldnt ever be using open end/box end wrenches on bleeder screws to loosen them, put a 1/4 drive socket on that bleeder and open it... Then stick your finger over the hole while someone else pumps the pedal. You dont need to close the bleeder when the pedal is to go back up, just the finger over the hole will keep air from getting back up when the other person lifts the pedal. Then when all is bled, have them hold down the pedal while you tighten that sucker back up. You might want to invest some bucks in a set of line wrenches, they have a 5 sided box end and are so you dont strip those bleeder heads. The little clip you are talking about is to hold the brake cylinder onto the backing plate, I wouldnt go taking that clip off if you dont have to, and its kind of a one use thing, it gets mangled removing it and new ones come with the wheel cylinder usually. But if you want to take it off, you bend the tangs that point into the center back, then you will have to bend them back in before putting it back on, and you will need the wheels and brake drums off so you can push on the wheel cylinder while you try and snap that ring back on. Just try getting your 3/8 size 1/4 drive socket onto that bleeder to loosen it, and WD40 that badboy before you go trying to break it loose cause if it snaps off you are buying a wheel cylinder.

Also if you ever go dipping into that ABS module, be careful cause those round things that look kinda like batteries have a ****load of pressure inside them at all time and can seriously hurt you if not taken apart properly. In school they taught us that those "Accumulators" can have over 1000psi in them when the vehicle is off and parked, and can remove a finger with a squirt of brake fluid like a hot knife into butter.

 

thanks for the reply, but i have 1/4 socket and it doesnt fit there either. the walls of the socket are too thick it rubs against the side, so not too sure what im doing wrong ill try again

 

Ok found a thinner socket got it done and finished.
What I did:
• replaced the master cylinder (Bench bled <---- a must saved a bunch of time)
• replaced the caliper (cheap and super easy)
• did a full bleed of all the breaks and master cylinder (a pain in the *** cause you have to crawl under the car, but not hard with a cheap bleed kit)

so far so good i havn't gone highway yet but the brakes are much more firm then they ever were, making me think that this was a problem long before this whole mess. my cars wheels don't lock up so easy now which is good cause i always felt that to be a problem, now it does its job.