Brakes

J

john nicholls

New member
Aug 18, 2010
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Started to a rally in July, got about 20 miles and stopped to check wheel temps. Three of four rear drums were above 350d. There was no issue with
front discs. I have never before seen over 150d. I returned home and rears seemed to be adjusted to tight (don't know how or why). I am pretty anal
about checking and no prior indications have been noted.

I pulled one, RRF, and it seemed to be opening and closing as it should. I backed off all adjusters until just barely a scrape could be heard. I did
a test run today, 11/7,. Initial readings were ok. On returning home, I checked them again and got the following readings: LF -500d, RF - 500d, RRF
- 200d, RRR - 113d, LRF - 260d, and LRR - 200. Current mileage is 96836.

History:
Mar. 2016 at the Dothan GMC rally, I found out that my master cylinder to booster plate had been flattened out. Removed it and replaced with the
correct one with a bend in it. Pedal was higher.
Sept. 2013 at 88400 miles, I replaced the master cylinder, the boogie flex lines, and installed 80 mm calipers and new hoses.
Sept. 2012 at 85285 miles, I rebuilt rear drum brakes with shoes, cylinders and spring sets.

I would appreciate any ideas on what is going on.
--
John Nicholls,
78 Royale w/455
Pensacola, FL
 
I would suggest that you check the pin that goes from the booster to the master cylinder. If it is too long (no clearance at the end) then it could be closing the port that allows the brake fluid to return to the master cylinder when releasing the brake pedal.
This could cause constant pressure on the rear wheel cylinders that could cause drag and overheating.

If you find this is not the problem then you should probably replace the master cylinder.

Emery Stora
77 Kingsley
Frederick, CO

>
> Started to a rally in July, got about 20 miles and stopped to check wheel temps. Three of four rear drums were above 350d. There was no issue with
> front discs. I have never before seen over 150d. I returned home and rears seemed to be adjusted to tight (don't know how or why). I am pretty anal
> about checking and no prior indications have been noted.
>
> I pulled one, RRF, and it seemed to be opening and closing as it should. I backed off all adjusters until just barely a scrape could be heard. I did
> a test run today, 11/7,. Initial readings were ok. On returning home, I checked them again and got the following readings: LF -500d, RF - 500d, RRF
> - 200d, RRR - 113d, LRF - 260d, and LRR - 200. Current mileage is 96836.
>
> History:
> Mar. 2016 at the Dothan GMC rally, I found out that my master cylinder to booster plate had been flattened out. Removed it and replaced with the
> correct one with a bend in it. Pedal was higher.
> Sept. 2013 at 88400 miles, I replaced the master cylinder, the boogie flex lines, and installed 80 mm calipers and new hoses.
> Sept. 2012 at 85285 miles, I rebuilt rear drum brakes with shoes, cylinders and spring sets.
>
> I would appreciate any ideas on what is going on.
> --
> John Nicholls,
> 78 Royale w/455
> Pensacola, FL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
John

It's fairly easy to check

Put the rear up on jack stands so you can spin the tires.

See how they spin.

Start it. Engage brakes a few times and see if they spin.

You can remove the MC to get to the pin without breaching the hydraulics. Just remove the bolts.

You can then clay off the pin for the right length

JWIWD.

Dolph Santorine

DE N8JPC

Wheeling, West Virginia

1977 ex-Palm Beach TZE167V100820
1-ton, Sullybuilt Bags, Reaction Arms, 3.70 LSD, Manny Transmission, EV-6010,

>
> I would suggest that you check the pin that goes from the booster to the master cylinder. If it is too long (no clearance at the end) then it could be closing the port that allows the brake fluid to return to the master cylinder when releasing the brake pedal.
> This could cause constant pressure on the rear wheel cylinders that could cause drag and overheating.
>
> If you find this is not the problem then you should probably replace the master cylinder.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>

>>
>> Started to a rally in July, got about 20 miles and stopped to check wheel temps. Three of four rear drums were above 350d. There was no issue with
>> front discs. I have never before seen over 150d. I returned home and rears seemed to be adjusted to tight (don't know how or why). I am pretty anal
>> about checking and no prior indications have been noted.
>>
>> I pulled one, RRF, and it seemed to be opening and closing as it should. I backed off all adjusters until just barely a scrape could be heard. I did
>> a test run today, 11/7,. Initial readings were ok. On returning home, I checked them again and got the following readings: LF -500d, RF - 500d, RRF
>> - 200d, RRR - 113d, LRF - 260d, and LRR - 200. Current mileage is 96836.
>>
>> History:
>> Mar. 2016 at the Dothan GMC rally, I found out that my master cylinder to booster plate had been flattened out. Removed it and replaced with the
>> correct one with a bend in it. Pedal was higher.
>> Sept. 2013 at 88400 miles, I replaced the master cylinder, the boogie flex lines, and installed 80 mm calipers and new hoses.
>> Sept. 2012 at 85285 miles, I rebuilt rear drum brakes with shoes, cylinders and spring sets.
>>
>> I would appreciate any ideas on what is going on.
>> --
>> John Nicholls,
>> 78 Royale w/455
>> Pensacola, FL
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
John,

I too frequently check bearing and brake temperatures.

You say the first check was OK, but give no data. Engineers hate that. We want all the data, even if you think it doesn't matter. It would matter
in this case because if the master cylinder is not a real OE (with 1/2 thick ears), then there is a lot that can be wrong. Having it not release is
one. It may have taken the first stop to build the pressure in the system.

If you want to see if the pressure is releasing, that is easy but messy. With the coach cold, crack the lines loose at the master cylinder. They
might seep, but should not drip. Start the engine, lean on the brakes a good time or two and shut down. By the time you get back up front, there
should be no line pressure in the front brakes (the rear of the master cylinder) and maybe very little in the rear.

One of the things that does cause brake problems with the drum rear is that the self adjusters are never exercised. They can work. You have to make
them work by stopping hard in reverse (and rearranging everything in the cabinets). Many people never stop hard enough in reverse to make this
happen.

Matt

> Started to a rally in July, got about 20 miles and stopped to check wheel temps. Three of four rear drums were above 350d. There was no issue with
> front discs. I have never before seen over 150d. I returned home and rears seemed to be adjusted to tight (don't know how or why). I am pretty anal
> about checking and no prior indications have been noted.
>
> I pulled one, RRF, and it seemed to be opening and closing as it should. I backed off all adjusters until just barely a scrape could be heard. I
> did a test run today, 11/7,. Initial readings were ok. On returning home, I checked them again and got the following readings: LF -500d, RF -
> 500d, RRF - 200d, RRR - 113d, LRF - 260d, and LRR - 200. Current mileage is 96836.
>
> History:
> Mar. 2016 at the Dothan GMC rally, I found out that my master cylinder to booster plate had been flattened out. Removed it and replaced with the
> correct one with a bend in it. Pedal was higher.
> Sept. 2013 at 88400 miles, I replaced the master cylinder, the boogie flex lines, and installed 80 mm calipers and new hoses.
> Sept. 2012 at 85285 miles, I rebuilt rear drum brakes with shoes, cylinders and spring sets.
>
> I would appreciate any ideas on what is going on.

--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
When was the last time you replaced the rear rubber hose and is your
parking brake cable loose?

> Started to a rally in July, got about 20 miles and stopped to check wheel
> temps. Three of four rear drums were above 350d. There was no issue with
> front discs. I have never before seen over 150d. I returned home and rears
> seemed to be adjusted to tight (don't know how or why). I am pretty anal
> about checking and no prior indications have been noted.
>
> I pulled one, RRF, and it seemed to be opening and closing as it should. I
> backed off all adjusters until just barely a scrape could be heard. I did
> a test run today, 11/7,. Initial readings were ok. On returning home, I
> checked them again and got the following readings: LF -500d, RF - 500d, RRF
> - 200d, RRR - 113d, LRF - 260d, and LRR - 200. Current mileage is 96836.
>
> History:
> Mar. 2016 at the Dothan GMC rally, I found out that my master cylinder to
> booster plate had been flattened out. Removed it and replaced with the
> correct one with a bend in it. Pedal was higher.
> Sept. 2013 at 88400 miles, I replaced the master cylinder, the boogie flex
> lines, and installed 80 mm calipers and new hoses.
> Sept. 2012 at 85285 miles, I rebuilt rear drum brakes with shoes,
> cylinders and spring sets.
>
> I would appreciate any ideas on what is going on.
> --
> John Nicholls,
> 78 Royale w/455
> Pensacola, FL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>

--
Jim Kanomata
Applied/GMC, Fremont,CA
jimk
http://www.appliedgmc.com
1-800-752-7502
 
Gentlemen, I thank you for the input.
Since the last thing done was the bracket (mc to booster)and since it now appears to be affecting both front and rear, I will start with the pin. The
mystifying part there is that the only trip since Dothan was to Bean Station (1000 miles) with no problems noted. I can't believe that I didn't check
the temps. Guess I should start keeping records.

Dolph, please expand on the clay method or link me to it.
Matt, first readings were RRF 175, RRR 115, LRR ?, LRF 225. Dumb me didn't think the front was involved and didn't check.
JimK, I never use the parking brake for fear they won't release. Rear flex lines were replaced Sept. 2013.
--
John Nicholls,
78 Royale w/455
Pensacola, FL
 
John:

Ken’s gizmo is brilliant, and worth the time.

If you know the clearance you want, you put a piece of clay in between the pin and the MC.

If it’s pressing, the pin displaces the clay completely.

You then take the length of the pin down in small increments until you have the clearance you want, and you’ll be able to measure the clay.

Here’s how it’s used on engine assembly:

http://www.enginelabs.com/engine-tech/engine-blueprinting-how-to-check-piston-to-valve-clearance/ http://www.enginelabs.com/engine-tech/engine-blueprinting-how-to-check-piston-to-valve-clearance/

The other gizmo is worth the time on the lathe.

Dolph

DE N8JPC

Wheeling, West Virginia

1977 26’ ex-PalmBeach
1-Ton, Sullybilt Bags, Reaction Arms, 3.70 LSD, Manny Transmission, EV-6010

“The Aluminum and Fiberglass Mistress"

>
> Gentlemen, I thank you for the input.
> Since the last thing done was the bracket (mc to booster)and since it now appears to be affecting both front and rear, I will start with the pin. The
> mystifying part there is that the only trip since Dothan was to Bean Station (1000 miles) with no problems noted. I can't believe that I didn't check
> the temps. Guess I should start keeping records.
>
> Dolph, please expand on the clay method or link me to it.
> Matt, first readings were RRF 175, RRR 115, LRR ?, LRF 225. Dumb me didn't think the front was involved and didn't check.
> JimK, I never use the parking brake for fear they won't release. Rear flex lines were replaced Sept. 2013.
> --
> John Nicholls,
> 78 Royale w/455
> Pensacola, FL
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
 
Your symptoms match what mine were when the pin was too long.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
> Gentlemen, I thank you for the input.
>
> Matt, first readings were RRF 175, RRR 115, LRR ?, LRF 225. Dumb me didn't think the front was involved and didn't check.

John,
I have had reaction arms on the rear for enough years to forget the spread front/back before that, but the the side to side was never 50°. Maybe
30°, and the spread at the other pair was similar.

Go for it guy, when you get the brakes pulling right, they are good.

Matt
--
Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
'73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
Now with both true Keyless and remote entry
SE Michigan - Twixt A2 and Detroit
 
My first thought is just what Jim K said - the rubber brake lines. Am I late to the thread - has this been fixed already?

Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
Howell EFI + EBL + Electronic Distributor
 
> My first thought is just what Jim K said - the rubber brake lines. Am I late to the thread - has this been fixed already?
>
> Larry Davick
> A Mystery Machine
> 1976(ish) Palm Beach
> Fremont, CA
> Howell EFI + EBL + Electronic Distributor

He stated that the rears were already replaced.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
 
Somehow the 1 got dropped in my address book? Got er changed..

> No sir, it is johnrita1

--
C. Boyd
76 Crestmont
East Tennessee
 
Progress Report
The pin is not too long. On to master cylinder replacement. Is there any way that the combination/proportioning valve could be involved with this
problem?

FYI - The capture nut holding the upper bracket bolt spun. Believe it or not one can get vice grips behind the radio and grip it in order to get the
bolt out. Takes two people. Fred made it happen.
--
John Nicholls,
78 Royale w/455
Pensacola, FL
 
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