71-72 Front Brake Calipers...Sticky Pistons? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chewed 71'er · 06-26-2003, 04:00 AM

Has anyone ever experienced stuck or sticking pistons in their brake calipers? From the amount of rust I cleaned out of the bleeder valves, I think the calipers in my 71 are original. In everyday driving, it stops okay. But stopping in a hurry is a problem, as truck wants to continue rolling, and brake pedal seems solid (but not bottomed out). Sometimes rear brakes lock up stopping hard, doesn't pull left or right. Have plenty of lining on front pads and rear shoes. Recently replaced master cylinder and proportioning valve (for leaks), throughly bled all 4 wheels. Power booster is working properly. I guess there's the possibility of worn rotors?

Lippyp · 06-26-2003, 05:14 AM

Standard mineral brake fluid is Hygroscopic (this means that it absorbs water) If the fluid has not been changed for a long time the fluid can become waterlogged and this can lead to the boiling point of the fluid reducing leading to increased fade under heavy/prolonged braking and can also attack any iron or steel components in the braking system. This happens more if the vehicle hasn't been used for a while so I would imagine that it is possible that you have rusted calipers.

It's not worth taking risks with brakes so I would consider replacing them. Also check the flexible hoses on the front, it is possible for them to weaken and balloon when you step on the brake so losing pressure to the calipers. You should be able to get any brake shop to check your rotors to see whether they are still in tolerance.

**jerry moss** · 06-26-2003, 10:05 AM

hard pedal and still rolls, sounds like a bad booster. also check the caliper slides and make sure everything moves freely.

**CPNE** · 06-26-2003, 10:28 AM

Like Jerry said. Check the caliper bolts, chances are they are in pretty sad shape. These are the slides Jerry is referring to.

*Piston* · 06-26-2003, 10:41 AM

I would lean more towards low vacuum or leaking booster, both will have the same affect. during slow application the booster is able to assist but in a panic stop it doesnt have the capacity to assist that quickly.

jimfulco · 06-26-2003, 10:10 PM

Some brands of pads are just that way. I put Raybestos semi-metallics on my 72 Nova & they fade almost as bad as the OEM pads did. Anything over 70mph is scary. I've used Delco & EIS pads on that car in the past & it would stop so fast from 3-digit speeds that your ears would pop. My daily driver is an 88 Tbird, & it has Albany semi-metallics from Auto Zone & they work quite well, considering the car weighs nearly 4000 lbs. & has the little 10" discs.

06-26-2003, 04:00 AM	#1
chewed 71'er Registered User Join Date: Mar 2002 Location: KC, NW Missouri Posts: 144	71-72 Front Brake Calipers...Sticky Pistons? Has anyone ever experienced stuck or sticking pistons in their brake calipers? From the amount of rust I cleaned out of the bleeder valves, I think the calipers in my 71 are original. In everyday driving, it stops okay. But stopping in a hurry is a problem, as truck wants to continue rolling, and brake pedal seems solid (but not bottomed out). Sometimes rear brakes lock up stopping hard, doesn't pull left or right. Have plenty of lining on front pads and rear shoes. Recently replaced master cylinder and proportioning valve (for leaks), throughly bled all 4 wheels. Power booster is working properly. I guess there's the possibility of worn rotors?

06-26-2003, 05:14 AM	#2
Lippyp English Chevy Owner Join Date: May 2002 Location: Shropshire, UK/ Lot, France Posts: 1,848	Standard mineral brake fluid is Hygroscopic (this means that it absorbs water) If the fluid has not been changed for a long time the fluid can become waterlogged and this can lead to the boiling point of the fluid reducing leading to increased fade under heavy/prolonged braking and can also attack any iron or steel components in the braking system. This happens more if the vehicle hasn't been used for a while so I would imagine that it is possible that you have rusted calipers. It's not worth taking risks with brakes so I would consider replacing them. Also check the flexible hoses on the front, it is possible for them to weaken and balloon when you step on the brake so losing pressure to the calipers. You should be able to get any brake shop to check your rotors to see whether they are still in tolerance. __________________ Phil '67 C10 long fleet. 350/TH350, 4 bbl Carter, K&N, Dual exhaust, loads of stuff coming soon 2001 S10 Blazer Daily Driver, bone stock 4 door 4x4 with manual transmission

06-26-2003, 10:05 AM	#3
jerry moss Born Psycho Join Date: Feb 2001 Location: brentwood,cal,usa Posts: 4,852	hard pedal and still rolls, sounds like a bad booster. also check the caliper slides and make sure everything moves freely. __________________ jerry moss 72 cheyenne super K20- tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,tow hooks,bumper guards,toolbox,aux. fuel tank,posi front and rear,plus other goodies!!! SOLD 69 suburban K20-tilt,tach,vacuum,speedwarning,buckets,shoulder belts,am/fm,4 inch all spring lift,4 speed, 14 bolt full floater, dana 44 HD,warn winch,posi front and rear,tow hooks,plus other goodies. 73/80 chevy/gmc K20 SB400,turbo 400,205,tilt,a-c,gas hog. 77 K/5 cheyenne blazer-daily driver/beater. SON HAS IT NOW BRENTWOOD,CALIFORNIA

06-26-2003, 10:28 AM	#4
CPNE Resident Curmudgeon Join Date: Dec 1999 Location: NH Posts: 6,664	Like Jerry said. Check the caliper bolts, chances are they are in pretty sad shape. These are the slides Jerry is referring to. __________________ Currently on or near the homestead: 67 Chevy SWB 2WD stepside 350/3 on tree (Pat's) 67 GMC SWB 2WD Fleet 402/auto (Brian's under construction) 67 Chevy 3/4 ton 2WD 402/auto (Business Hauler) 67 Chevy 1 ton dually 2WD 396/4 speed (Former business hauler, Needs TLC) 68 Chevy 1/2 ton Suburban 2WD 250 six/3 on tree (Brian's Needs TLC) 70 Chevy 3/4 ton 4WD 350/4 speed (Pat's - Disguised as a 68 GMC) 71 Chevy SWB stepside (Crushed by tree - parts donor) 72 Chevy 3/4 ton 4WD (Parts donor) 72 Chevy 3/4 ton 4WD Suburban (Parts Donor) 72 GMC 3/4 ton 4WD 292 six/4 speed (Mine - Disguised as a 67 GMC) 81 GMC 4WD Dually Dump Body 350/4 speed (Business Hauler) 82 Camaro Z/28 355/Super T-10 (Pat's toy) 93 Caprice 9C1 (Brian's Cop Car) 02 Toyota Camry (Reliable but a souless steel and plastic hulk) 2011 2SS RS Camaro M6 Factory Hurst Shifter Maybe I need to sell some of this crap Yet another Bozo with a sawz-all

06-26-2003, 10:41 AM	#5
Piston Account Suspended Join Date: Oct 2002 Location: Olathe, KS Posts: 2,301	I would lean more towards low vacuum or leaking booster, both will have the same affect. during slow application the booster is able to assist but in a panic stop it doesnt have the capacity to assist that quickly.

06-26-2003, 10:10 PM	#6
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Some brands of pads are just that way. I put Raybestos semi-metallics on my 72 Nova & they fade almost as bad as the OEM pads did. Anything over 70mph is scary. I've used Delco & EIS pads on that car in the past & it would stop so fast from 3-digit speeds that your ears would pop. My daily driver is an 88 Tbird, & it has Albany semi-metallics from Auto Zone & they work quite well, considering the car weighs nearly 4000 lbs. & has the little 10" discs.



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