Brake Problems - The 1947 - Present Chevrolet & GMC Truck Message Board Network

sparky69 · 08-09-2004, 05:21 PM

I am having problems with the front disc brakes on my 72 c10.
After pressing the pedal the caliper stays compressed to the rotor.
I replaced the calipers and hoses and still the same.
Does this indicates that the master cylinder is bad???
Or maybe the valve thing below the master???

Gordo · 08-09-2004, 07:45 PM

Be sure the brake pedal is returning all the way back. Reach down and pull up on the pedal to see if the brakes release or not. If the pedal is hanging up for some reason it can hold pressure on the brakes.

walker · 08-09-2004, 07:56 PM

The calipers never return away from the rotor, they always drag a little as there is no return spring inside the caliper. In fact a lot of disk brake conversion kits include a 2lb RPV(residual pressure valve). If you mean that it won't release the caliper at all, and it won't turn, then I would look at your M/C first (cheap replacement, $15 new), then your proportioning block, then your lines. You may have a piece of crud in there plugging the works.

sparky69 · 08-09-2004, 09:14 PM

I just got back in for the night. I replaced the Master Cylinder and bleeded the front and still no go.
Yes Walker they are camped down on them pretty tight and only way I can get them loose is open the bleeder valve and push the piston back and expelling some of the fluid.
I guess tomorrow I'll look at the P valve and see if any fluid will flow back from there.
gee's not much more I can replace on this thing.

**68 Stepside** · 08-09-2004, 09:39 PM

I've heard somewhere on this site about the rubber brake lines collapsing on the inside over time, just an idea. Good luck.

sparky69 · 08-09-2004, 09:51 PM

Yeah I read that yesterday. I replaced the rubber lines when I replaced the calipers today.

Any other ideas wouldn't hurt

68C15 · 08-09-2004, 09:53 PM

here, try this. step on pedal real hard, then start to open one fittong at a time going from caliper back to MC. bleeder then hose @ caliper, then line @ combo. valve, then line @ MC. when you open a fitting & wheel turns freely that is where the problem is. hope this makes sense. only do one at a time.
BTW, with caliper piston pushed all the way in does the caliper slide freely on the pins?

sparky69 · 08-09-2004, 10:01 PM

68c15
I can move them but they are not loose though

Longhorn Man · 08-09-2004, 10:22 PM

Does the pedal stay down, or is it returning properly?

elk hunter · 08-09-2004, 10:42 PM

i have had the booster cause the same problem you are talking about. press the brake pedal and see if you can turn the wheel, if not unbolt the master from the booster. if the wheel turns, it is either the booster or the pedal assy.

Longhorn Man · 08-09-2004, 10:49 PM

That's where I was headed lk...the Longhorn was like that too when I first got it.

sparky69 · 08-10-2004, 08:27 AM

The pedal worked normaly. When I had the M/C off the wheels where still locked up.
Elk hunter, if it was the booster the rear brakes would be locked up too wouldn't it? My rear brakes works fine for right now.

I'll tinker around with it some more today and see what happens.

thanks for the imput.

sparky69 · 08-10-2004, 03:42 PM

Well, More and more surprizes.
Last night my front disc where locked up and now this morning they were working normal.
Now I have another problem. As I was pumping the brakes to see if the fronts will lock up again I heard a strange noise coming from the rear.
It appears to be back brake line next to the frame sprung a leak.

Could this been the problem all along? Could the proportioning valve been sensing the leak and that what caused my fronts to lock up?

elk hunter · 08-10-2004, 03:46 PM

sparky, the front will lock up easier because of the volume (and pressure) of fluid moved by the master. i beleive it is something like 90% to the front and 10% to the back. did you opt for a rebuilt master? if so, i would bet it is a bad rebuild. ALWAYS buy a NEW master. why take a chance? press brake pedal,if wheel is stuck, break line loose at the master. if it frees up and you have eliminated the booster/pedal assy. from the equasion, then it is the master. if it does not free up, then check for defective rubber hoses or crimped hard lines. never seen a combo valve cause this problem but not out of the question. you can test this by doing the same thing as testing for a bad master.

Longhorn Man · 08-10-2004, 03:47 PM

No, it's just another problem. Either you have a messed up line/hose prop valve, or the calipers you bought are bad.
But first you have to fix the bad line out back.

With a bad booster holding the pedal down, the rear wheels could still turn easily becouse the rear drums are often out of adjustment.

sparky69 · 08-10-2004, 04:07 PM

Yeah I'll have to wait and get that rear line replaced before I do any more testing.

I did drove the truck from my back yard to my driveway which has more solid ground to work on. I had the booster disconnected and the front brakes did not lock up. I'm pretty sure the back brakes wasn't doing anything while I was moving it.

elk hunter · 08-10-2004, 04:09 PM

did you say that one or both calipers were stuck? if you opened the bleeder and pressurized fluid came out, and the wheel turned free, its not a caliper problem.(if it were the calipers they would not free up)

sparky69 · 08-10-2004, 04:18 PM

Yeah Both of them. The old ones and the new rebuilt ones. I put new hoses on them also.

But it appears to be working now but I can't confirm that till I get the rear line fixed.
Also if its anything, The brake light was on during this whole thing.

Longhorn Man · 08-10-2004, 04:48 PM

Your brake light is controlled by the brake pedal...you sure it was coming up all the way?

sparky69 · 08-10-2004, 09:40 PM

Sorry Longhorn man, I ment the brake warning light which is controlled by the switch on the proportioning valve.

Longhorn Man · 08-10-2004, 09:49 PM

Ahhh, OK. Have you looked at all the lines in the front of the truck? A pinched line could do this.

elk hunter · 08-10-2004, 10:41 PM

the brake light on the dash tells you that there was a loss of pressure to the front or the rear brakes(like you couldnt tell by the fact there is no pedal left right?). the switch in the combo valve slides back and fourth when this happens. it is possible that it was stuck and would let fluid under master cylinder pressure pass but not return,and when the rear line went the switch lost pressure to the rear letting the switch move back to the neutral or rear loss position.

08-09-2004, 05:21 PM	#1
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Brake Problems I am having problems with the front disc brakes on my 72 c10. After pressing the pedal the caliper stays compressed to the rotor. I replaced the calipers and hoses and still the same. Does this indicates that the master cylinder is bad??? Or maybe the valve thing below the master???

08-09-2004, 07:45 PM	#2
Gordo Registered User Join Date: Jan 2001 Location: Killingworth, CT. USA Posts: 3,378	Be sure the brake pedal is returning all the way back. Reach down and pull up on the pedal to see if the brakes release or not. If the pedal is hanging up for some reason it can hold pressure on the brakes. __________________ 1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist.

08-09-2004, 07:56 PM	#3
walker Registered User Join Date: Jul 2003 Location: north of Phx AZ about 30 miles Posts: 698	The calipers never return away from the rotor, they always drag a little as there is no return spring inside the caliper. In fact a lot of disk brake conversion kits include a 2lb RPV(residual pressure valve). If you mean that it won't release the caliper at all, and it won't turn, then I would look at your M/C first (cheap replacement, $15 new), then your proportioning block, then your lines. You may have a piece of crud in there plugging the works. __________________ Andy,Phx AZ '67 C-10 (Ahhh, done at last. Well there is that disk front end I want to put in and...) "23 C-Cab-sold '48 Ford 8N tractor(still working) '67 Scout(Now on the road) '70 MG B.-sold

08-09-2004, 09:39 PM	#5
68 Stepside huh? Join Date: May 2000 Location: Washington, Illinois Posts: 5,692	I've heard somewhere on this site about the rubber brake lines collapsing on the inside over time, just an idea. Good luck. __________________ Someday when I'm lonely, Wishing you weren't so far away, Then I will remember Things we said today. RIP El Jay

08-09-2004, 09:53 PM	#7
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	here, try this. step on pedal real hard, then start to open one fittong at a time going from caliper back to MC. bleeder then hose @ caliper, then line @ combo. valve, then line @ MC. when you open a fitting & wheel turns freely that is where the problem is. hope this makes sense. only do one at a time. BTW, with caliper piston pushed all the way in does the caliper slide freely on the pins? __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

08-09-2004, 09:14 PM	#4
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	I just got back in for the night. I replaced the Master Cylinder and bleeded the front and still no go. Yes Walker they are camped down on them pretty tight and only way I can get them loose is open the bleeder valve and push the piston back and expelling some of the fluid. I guess tomorrow I'll look at the P valve and see if any fluid will flow back from there. gee's not much more I can replace on this thing.

08-09-2004, 09:51 PM	#6
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Yeah I read that yesterday. I replaced the rubber lines when I replaced the calipers today. Any other ideas wouldn't hurt

08-09-2004, 10:01 PM	#8
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	68c15 I can move them but they are not loose though

08-09-2004, 10:22 PM	#9
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Does the pedal stay down, or is it returning properly?

08-09-2004, 10:42 PM	#10
elk hunter Registered User Join Date: Dec 2003 Location: oregon city, or Posts: 164	i have had the booster cause the same problem you are talking about. press the brake pedal and see if you can turn the wheel, if not unbolt the master from the booster. if the wheel turns, it is either the booster or the pedal assy. __________________ yeah, but how's it wheel?

08-09-2004, 10:49 PM	#11
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	That's where I was headed lk...the Longhorn was like that too when I first got it.

08-10-2004, 08:27 AM	#12
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	The pedal worked normaly. When I had the M/C off the wheels where still locked up. Elk hunter, if it was the booster the rear brakes would be locked up too wouldn't it? My rear brakes works fine for right now. I'll tinker around with it some more today and see what happens. thanks for the imput.

08-10-2004, 03:42 PM	#13
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Well, More and more surprizes. Last night my front disc where locked up and now this morning they were working normal. Now I have another problem. As I was pumping the brakes to see if the fronts will lock up again I heard a strange noise coming from the rear. It appears to be back brake line next to the frame sprung a leak. Could this been the problem all along? Could the proportioning valve been sensing the leak and that what caused my fronts to lock up?

08-10-2004, 03:46 PM	#14
elk hunter Registered User Join Date: Dec 2003 Location: oregon city, or Posts: 164	sparky, the front will lock up easier because of the volume (and pressure) of fluid moved by the master. i beleive it is something like 90% to the front and 10% to the back. did you opt for a rebuilt master? if so, i would bet it is a bad rebuild. ALWAYS buy a NEW master. why take a chance? press brake pedal,if wheel is stuck, break line loose at the master. if it frees up and you have eliminated the booster/pedal assy. from the equasion, then it is the master. if it does not free up, then check for defective rubber hoses or crimped hard lines. never seen a combo valve cause this problem but not out of the question. you can test this by doing the same thing as testing for a bad master. __________________ yeah, but how's it wheel?

08-10-2004, 03:47 PM	#15
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	No, it's just another problem. Either you have a messed up line/hose prop valve, or the calipers you bought are bad. But first you have to fix the bad line out back. With a bad booster holding the pedal down, the rear wheels could still turn easily becouse the rear drums are often out of adjustment.



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08-10-2004, 04:07 PM	#16
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Yeah I'll have to wait and get that rear line replaced before I do any more testing. I did drove the truck from my back yard to my driveway which has more solid ground to work on. I had the booster disconnected and the front brakes did not lock up. I'm pretty sure the back brakes wasn't doing anything while I was moving it.

08-10-2004, 04:09 PM	#17
elk hunter Registered User Join Date: Dec 2003 Location: oregon city, or Posts: 164	did you say that one or both calipers were stuck? if you opened the bleeder and pressurized fluid came out, and the wheel turned free, its not a caliper problem.(if it were the calipers they would not free up) __________________ yeah, but how's it wheel?

08-10-2004, 04:18 PM	#18
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Yeah Both of them. The old ones and the new rebuilt ones. I put new hoses on them also. But it appears to be working now but I can't confirm that till I get the rear line fixed. Also if its anything, The brake light was on during this whole thing.

08-10-2004, 04:48 PM	#19
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Your brake light is controlled by the brake pedal...you sure it was coming up all the way?

08-10-2004, 09:40 PM	#20
sparky69 Registered User Join Date: Feb 2003 Location: Terre Haute, IN Posts: 94	Sorry Longhorn man, I ment the brake warning light which is controlled by the switch on the proportioning valve.

08-10-2004, 09:49 PM	#21
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Ahhh, OK. Have you looked at all the lines in the front of the truck? A pinched line could do this.

08-10-2004, 10:41 PM	#22
elk hunter Registered User Join Date: Dec 2003 Location: oregon city, or Posts: 164	the brake light on the dash tells you that there was a loss of pressure to the front or the rear brakes(like you couldnt tell by the fact there is no pedal left right?). the switch in the combo valve slides back and fourth when this happens. it is possible that it was stuck and would let fluid under master cylinder pressure pass but not return,and when the rear line went the switch lost pressure to the rear letting the switch move back to the neutral or rear loss position. __________________ yeah, but how's it wheel?

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