DISC Brake problem

[Ed ke6bnl]

My boy and I were working on installing a new set of mufflers and when were ready to lower the truck we noticed that the front wheel with disc brakes were extremely hard to turn. We removed one caliper and pushed in the caliper puck and they freed up, but after the first pump you can hardly turn the tire and wheel. We lubricated the allen bolt with silicone grease but still have the problem. Since we were not involved with the work prior to my boy getting the truck I have concern on the arrangement of the dual master cyl. lines. the front reservoir(closest to the grille) lines go to the front disc brakes and the rear reservoir nearest the fire wall go to the rear drum brakes. Any help is appreciated. I never ran into this type of problem and the manual does not get into the brake line set up in any detail. Thanks Ed and Jim

This is a 70 chevy shortbed

[jhow66]

You may have a 4 drum master cyld.--they have a check valve in the outlet ports to keep a certain amount of pressure on the drum brakes so the shoes will stay extended. The only way to check is to remove the line to front brakes at master cyld.If there is one (brass looking) take a sheet medal screw and put in the opening and with a pair of pliers pull it out. Reinstall line . Also if it had one when you disconnect the line both wheels should free up.

[vcrazy8]

It sounds like the caliper is sticking. The piston can stick and not release. Rebuilt calipers are pretty cheap or you can get a rebuild kit

[Ed ke6bnl]

Originally posted by jhow66
You may have a 4 drum master cyld.--they have a check valve in the outlet ports to keep a certain amount of pressure on the drum brakes so the shoes will stay extended. The only way to check is to remove the line to front brakes at master cyld.If there is one (brass looking) take a sheet medal screw and put in the opening and with a pair of pliers pull it out. Reinstall line . Also if it had one when you disconnect the line both wheels should free up.

I did notice that both bowls of the master cyl. are the same size and recall that others I have worked on had a small and a large bowl. I will look for a check valve. Do you think there is a problem with using this master cyl. for these aplication with front disc and rear drums??

[jhow66]

One of my buddies changed his truck to front disc and used his power drum setup. He had the same problem as you--front brakes dragging--removed check valve --no problem since. If you have good stopping power now leave as is. If not get a power disc master cyld and porp. valve.

[nitor]

I would suggest you make sure the master cylinder you have is for a disc brake setup, get a porportioning valve and also, because the calipers are so inexpensive, I would replace both of those. It's not a good thing when you cannot stop . It's better to spend the little bit of cash and make sure everything is correct and working properly than have problems. If those brakes are dragging, the rotor will warp, and you will probably end up replacing those as well.

Just my $.02

[JoetheMobster]

Brakes Smakes!!! Brakes are overrated anyway!

LOL!

Just kidding, but I agree, stopping is good! I've had a few personal experiences with lack of brakes! Good thing it was a Ford (78 Fairmont SW) that I experienced it in!

[Ed ke6bnl]

We will check out the brakes Monday we had no signs of any problem with braking but noticed this condition when working on an unrelated job on the truck thanks so much for all the useful help and we will check and replace all the parts that need it. Great group and hope to be able to add some input when I feel I can of help thanks Ed ke6bnl

[Iron-Butt]

I put two new rebuilt calipars on at 13.00 each from the autoparts store.

[Southpa]

You have the wrong master cyl. and likely the wrong prop. valve. Drum brake trucks use equal pressure all around, hence, the same size wells in the m/c. Disc brake m/c have the larger well up front as more "brakage" is applied up front than the rears.

If you are replacing the m/c and prop. valve just ask for one for a 71 or 72 truck. And I would get the kind that has the 2 hold down clips rather than the single hold down clip. I've been thru 2 remans of the latter kind and both leaked out the cap, they suck.

[spinning wheels]

I'm currently in the process of changing the booster, master cylinder and proportioning valve on my 3/4 truck. You do need to run the correct proportioning valve for disk brake setups. 1/2 ton and 3/4 use the same one. None of the local auto parts stores could find a proportioning valve. Chevy dealers told me that it was a discontinued item. I did find what I was looking for at CPP (classic performance products). Check them out at classicperform.com. Or call 1-800-522-5004 They are great folks to deal with. Good luck

[Ed ke6bnl]

Well we got the check valve out of the m/c it wasn't wanten to come out so we resorted to the suggestion in the thread to put a screw in and pull it out. we pulled and pulled and it finally came out, I quess it would not have been so bad if I new what was exactly going to be remove then again with out your help I would not have gotten this far. The brakes are free after releasing the pedal and we will check into the others suggestions as to the follow up. Thanks again you guy are a wealth of knowledge. Ed and son Jims truck thank you.

[72addict]

I have had the front brake hoses swell up before. Once swollen the fluid cannot leave the piston are when you let off of the brake pedal. To check for this, crack the bleeder and see if the caliper releases. If it does release, remove hose at caliper, and check for fluid flow out of the brake hose. If no flow, remove hose from brakeline and check it there. Can also try blowing thru hose once it is off vehicle. Good luck

[Big69C20 Toy]

hmm i wonder why i never had this problem with my c20.... i switched over but dont have this problem.... or perhaps i do but just never noticed cuz of the BB pushing the truck ...

[Stout72]

If I'm not mistaken, the front reservoir serves the rear drums, and rear reservoir serves the front discs. At least, that's the way it's plumbed on my truck. I just went thru a major brake job earlier this year which included replacing the Bendix M/C with OEM. Is this the wrong arrangement? Truck seems to stop OK, better than before, but the front discs tend to get a little squeaky sometimes.

[Ed ke6bnl]

Originally posted by Stout72
If I'm not mistaken, the front reservoir serves the rear drums, and rear reservoir serves the front discs. At least, that's the way it's plumbed on my truck. I just went thru a major brake job earlier this year which included replacing the Bendix M/C with OEM. Is this the wrong arrangement? Truck seems to stop OK, better than before, but the front discs tend to get a little squeaky sometimes.

That the way I remember it to be. I plan to plum my truck with a checkvlave to the rear drums (m/c is under the floor) and to use a adjustable proportioning valve inline to the rear brakes, can be set to the best braking comonations. Ed ke6bnl

[Alex Hayley]

Resurrecting a thread from the dead but this is the closest description I can find to the issue I am experiencing. I replaced my master cylinder, lines, hoses and calipers on my 72 C10. The front driver's caliper sticks even after pushing the piston back and then applying the brakes. The replacement master cylinder has two reservoirs of the same size but is listed at Autozone for front disc.

Master Cylinder link

Looking at the outlet ports, both are brass flares. Does the check valve look any different than the brass flare? Do I have a master cylinder for drum brakes?

Originally Posted by jhow66

You may have a 4 drum master cyld.--they have a check valve in the outlet ports to keep a certain amount of pressure on the drum brakes so the shoes will stay extended. The only way to check is to remove the line to front brakes at master cyld.If there is one (brass looking) take a sheet medal screw and put in the opening and with a pair of pliers pull it out. Reinstall line . Also if it had one when you disconnect the line both wheels should free up.