Calipers not working - The 1947 - Present Chevrolet & GMC Truck Message Board Network

70 GMC 4x4 · 03-23-2002, 04:27 PM

Just did the drum to disc swap and I can not get the calipers to work. I have brake fluid to the bleeder screws. Is there anything special you have to do? There is a rubber thing on the porportioning valve that is stuck in, is that right?

Thanks,
Tim

slam33 · 03-23-2002, 07:35 PM

did you use the right master and prop valve?

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71 basic C-10 350. The only option is the rust.No nothing on it, but thats all about to change. <A HREF="http://www.geocities.com/stevemau/slam33page.html?1004806705410

" TARGET=_blank>http://www.geocities.com/stevemau/slam33page.html?1004806705410

</A>

72futuresweet2wd · 03-23-2002, 08:23 PM

I also completed a disc to drum conversion but I cannot seem to get any pressure when I bleed the lines. I called Early Classics and was told it sounded like there was air in the lines. I have bench bleed this damn thing multiple times and started at the first fiting after the porportioning valve and it still has hardly any pressure. WTF?

------------------
1972 2wd Blazer (Project)
1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck
2002 Chevy Trailblazer (Wifes)

fleetimus · 03-23-2002, 10:53 PM

There are a few things that can be the problem. I already went thru this. Make sure the rod into the master is long enough. Disc brakes take a longer rod than drum. Bleed the master first. Then go to the right rear, then the left rear, right front and the left front last.

Nobody mentioned what year or what master you were using. It all has to work together.

I can be reached at (530) 889-1104. I converted my 68 fron 4 wheel drum to 4 wheel disc.

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68 Chevy l/b, 4 whl disc in the foothills of No Calif

70 GMC 4x4 · 03-23-2002, 11:15 PM

Fleetimus,

I am using the master cylinder and brake booster off a 72 GMC, also the porportioning valve. I know the calipers sat a while before I put them on, could they be rusted in place? Do I need to replace them? I have fluid at all for wheels.

Thanks

72futuresweet2wd · 03-24-2002, 06:52 AM

fleetimus

I bought everything new from Early Classics and I don't know what year they use. I have done things in the order you mentioned I was wondering if the new master cylinder or the porp valve could be screwed up. The only thing I did not replace is the lines and the rear drums.

------------------
1972 2wd Blazer (Project)
1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck
2002 Chevy Trailblazer (Wifes)

woodmancfh · 03-24-2002, 08:18 AM

70 GMC 4x4,You say you're getting fluid to all four wheels-you don't by chance have the calipers switched from left to right?Look at the bleeder valves-they should be at the highest point on the caliper.

------------------
70 Chevy C/20
72 GMC 1500-SWB/For Sale
72 GMC K/2500

fleetimus · 03-24-2002, 10:21 AM

I'm thinking!?!?!? I am still wondering about the push rod. If you are using the drum push rod for the master, it does not have enough throw for the disc brakes. Make sure the rear brakes are adjusted. Is the dash brake lite on? If so, you may have to reset the proportioning valve. Some have the small button on the end that has to be pushed in while bleeding a rear line. Make sure the lines are hooked up to the right resevoir on the master. If one resevoir is larger, it should be supplying the disc brakes. ( I don't mean to offend anybody with these suggestions) I am just throwing out possibilities.

------------------
68 Chevy l/b, 4 whl disc in the foothills of No Calif

70 GMC 4x4 · 03-24-2002, 11:52 AM

The push rod, master cylinder, brake booster all came from a 72 3/4 truck with disc brakes. One thing is the button on the porportion valve does not move, seems like it is pushed all the way in, is there suppose to be movement?

Thanks

72futuresweet2wd · 03-25-2002, 09:01 AM

fleetimus

My prop valve has the small button on the front of it and I did not know it must be pushed in for the rears. It moves when you pump the brakes I will try holding next time I get a chance. Also the brake light in the dash is on. Rear brakes are adjusted and the chambers are equal sizes.

Thanks

------------------
1972 2wd Blazer (Project)
1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck
2002 Chevy Trailblazer (Wifes)

Alex Hayley · 03-25-2002, 10:38 AM

This is the first time I have heard anything about the button on the proportioning valve being related to bleeding the rear brakes. Can you tell me what needs to be done with the valve as it applies to bleeding the brakes? Does it need to be pushed in the entire time while bleeding the rear brakes? Does it need to be used when bleeding the front brakes? Thanks...

[This message has been edited by Alex Hayley (edited March 25, 2002).]

Alex Hayley · 03-26-2002, 09:40 AM

ttt

tom hand · 03-26-2002, 11:05 AM

Any service manual shows how to make a simple tool to hold the button in on the prop valve but I have never had to do it to get the brakes bled. One thing that no one has mentioned is free play on the pushrod. You need to check that there is free play when the pedal comes back or the master cylinder will not return fully. If the Master cylinder does not return fully you will never get the brakes bled.

------------------
72 GMC Sierra SWB almost finished---- 84 Softail
Olive Branch MS

03-23-2002, 04:27 PM	#1
70 GMC 4x4 Registered User Join Date: Apr 2001 Location: Marion, Iowa Posts: 126	Calipers not working Just did the drum to disc swap and I can not get the calipers to work. I have brake fluid to the bleeder screws. Is there anything special you have to do? There is a rubber thing on the porportioning valve that is stuck in, is that right? Thanks, Tim __________________ 70 3/4 GMC 4x4, 400sb

03-23-2002, 07:35 PM	#2
slam33 Registered User Join Date: Aug 2001 Location: Long Beach, Ca Posts: 1,432	did you use the right master and prop valve? ------------------ 71 basic C-10 350. The only option is the rust.No nothing on it, but thats all about to change. <A HREF="http://www.geocities.com/stevemau/slam33page.html?1004806705410 " TARGET=_blank>http://www.geocities.com/stevemau/slam33page.html?1004806705410 </A> __________________ 71 LWB 350/350still working on it but it's going tp be sweet. www.geocities.com/stevemau/slam33page.html " TARGET=_blank>http://www.geocities.com/stevemau/slam33page.html?1004806705410 </A>

03-23-2002, 08:23 PM	#3
72futuresweet2wd The face of my 69 c10 Join Date: Jan 2001 Location: Central Indiana Posts: 171	I also completed a disc to drum conversion but I cannot seem to get any pressure when I bleed the lines. I called Early Classics and was told it sounded like there was air in the lines. I have bench bleed this damn thing multiple times and started at the first fiting after the porportioning valve and it still has hardly any pressure. WTF? ------------------ 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck 2002 Chevy Trailblazer (Wifes) __________________ 2002 Harley Davidson VRod 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) 2002 Chevy Trailblazer (Wifes)

03-23-2002, 10:53 PM	#4
fleetimus Registered User Join Date: Jul 2000 Location: Auburn,Ca USA Posts: 369	There are a few things that can be the problem. I already went thru this. Make sure the rod into the master is long enough. Disc brakes take a longer rod than drum. Bleed the master first. Then go to the right rear, then the left rear, right front and the left front last. Nobody mentioned what year or what master you were using. It all has to work together. I can be reached at (530) 889-1104. I converted my 68 fron 4 wheel drum to 4 wheel disc. ------------------ 68 Chevy l/b, 4 whl disc in the foothills of No Calif __________________ 68 Chevy l/b, 4 whl disc in the foothills of No Calif

03-23-2002, 11:15 PM	#5
70 GMC 4x4 Registered User Join Date: Apr 2001 Location: Marion, Iowa Posts: 126	Fleetimus, I am using the master cylinder and brake booster off a 72 GMC, also the porportioning valve. I know the calipers sat a while before I put them on, could they be rusted in place? Do I need to replace them? I have fluid at all for wheels. Thanks __________________ 70 3/4 GMC 4x4, 400sb

03-24-2002, 06:52 AM	#6
72futuresweet2wd The face of my 69 c10 Join Date: Jan 2001 Location: Central Indiana Posts: 171	fleetimus I bought everything new from Early Classics and I don't know what year they use. I have done things in the order you mentioned I was wondering if the new master cylinder or the porp valve could be screwed up. The only thing I did not replace is the lines and the rear drums. ------------------ 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck 2002 Chevy Trailblazer (Wifes) __________________ 2002 Harley Davidson VRod 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) 2002 Chevy Trailblazer (Wifes)

03-24-2002, 08:18 AM	#7
woodmancfh GMC RULES Join Date: Feb 2001 Location: Central Ohio Posts: 154	70 GMC 4x4,You say you're getting fluid to all four wheels-you don't by chance have the calipers switched from left to right?Look at the bleeder valves-they should be at the highest point on the caliper. ------------------ 70 Chevy C/20 72 GMC 1500-SWB/For Sale 72 GMC K/2500 __________________ 70 Chevy C/20 72 GMC K /2500

03-24-2002, 10:21 AM	#8
fleetimus Registered User Join Date: Jul 2000 Location: Auburn,Ca USA Posts: 369	I'm thinking!?!?!? I am still wondering about the push rod. If you are using the drum push rod for the master, it does not have enough throw for the disc brakes. Make sure the rear brakes are adjusted. Is the dash brake lite on? If so, you may have to reset the proportioning valve. Some have the small button on the end that has to be pushed in while bleeding a rear line. Make sure the lines are hooked up to the right resevoir on the master. If one resevoir is larger, it should be supplying the disc brakes. ( I don't mean to offend anybody with these suggestions) I am just throwing out possibilities. ------------------ 68 Chevy l/b, 4 whl disc in the foothills of No Calif __________________ 68 Chevy l/b, 4 whl disc in the foothills of No Calif

03-24-2002, 11:52 AM	#9
70 GMC 4x4 Registered User Join Date: Apr 2001 Location: Marion, Iowa Posts: 126	The push rod, master cylinder, brake booster all came from a 72 3/4 truck with disc brakes. One thing is the button on the porportion valve does not move, seems like it is pushed all the way in, is there suppose to be movement? Thanks __________________ 70 3/4 GMC 4x4, 400sb

03-25-2002, 09:01 AM	#10
72futuresweet2wd The face of my 69 c10 Join Date: Jan 2001 Location: Central Indiana Posts: 171	fleetimus My prop valve has the small button on the front of it and I did not know it must be pushed in for the rears. It moves when you pump the brakes I will try holding next time I get a chance. Also the brake light in the dash is on. Rear brakes are adjusted and the chambers are equal sizes. Thanks ------------------ 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) http://community.webshots.com/user/69chevytruck 2002 Chevy Trailblazer (Wifes) __________________ 2002 Harley Davidson VRod 1972 2wd Blazer (Project) 1969 Chevy C10 (Driver) 2002 Chevy Trailblazer (Wifes)

03-25-2002, 10:38 AM	#11
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	This is the first time I have heard anything about the button on the proportioning valve being related to bleeding the rear brakes. Can you tell me what needs to be done with the valve as it applies to bleeding the brakes? Does it need to be pushed in the entire time while bleeding the rear brakes? Does it need to be used when bleeding the front brakes? Thanks... [This message has been edited by Alex Hayley (edited March 25, 2002).]

03-26-2002, 09:40 AM	#12
Alex Hayley Registered User Join Date: Jul 2000 Location: NC Posts: 987	ttt

03-26-2002, 11:05 AM	#13
tom hand CCRider Join Date: Feb 2000 Location: Olive Branch,MS,USA Posts: 2,232	Any service manual shows how to make a simple tool to hold the button in on the prop valve but I have never had to do it to get the brakes bled. One thing that no one has mentioned is free play on the pushrod. You need to check that there is free play when the pedal comes back or the master cylinder will not return fully. If the Master cylinder does not return fully you will never get the brakes bled. ------------------ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS __________________ 72 GMC Sierra SWB almost finished---- 84 Softail Olive Branch MS



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