brake question

[dwlambert1701]

Ok here we go again. Got a 1963 C10 with drums all around. New dual disc/drum MC power booster, PV. Yes I will be added disc brakes to front soon. But for the time being this is what I got. Question is I've got brake pressure when the truck is shut off, but pedal goes to floor when the engine is running. First road test was short I could stop going up hill but not much going down hill. Can I just disconnect the vacuum hose from the booster until I can find the problem. just so everyone knows the other end the hose is in the.back the carb

[gofastnut]

It sounds like the booster is working; making it easier to press the pedal.
First, do you have any external leaks in the brake system(master cyl, hoses, wheel cyls)?
Not trying to be a smart alec, just trying to get the basics out of the way.
Second, if you pump the pedal, does it build pressure? If so, does it fade?
Third, If you slam your foot down on the pedal does it seem firm? If do, does it fade?
Trying to determine whether you have problems with the master cylinder or not.
Let us know and good luck!
Jeff

[dwlambert1701]

Originally Posted by gofastnut

It sounds like the booster is working; making it easier to press the pedal.
First, do you have any external leaks in the brake system(master cyl, hoses, wheel cyls)?
Not trying to be a smart alec, just trying to get the basics out of the way.
Second, if you pump the pedal, does it build pressure? If so, does it fade?
Third, If you slam your foot down on the pedal does it seem firm? If do, does it fade?
Trying to determine whether you have problems with the master cylinder or not.
Let us know and good luck!
Jeff

pretty sure Their aren't any leaks but going to double check. To be able to stop it did seem like I had to pump the pedal.

[gofastnut]

If you push hard on the pedal and hold it down, does it bleed down on ya? or stay firm?
Iyou pumped and the pedal got more firm, that's air in the lines (bad wheel cylinder, lines, or master cylinder), or most likely a master cylinder issue--internal leak.
If it's not an external leak, then I think the master cylinder is going ka-put.
Also, Since it's drums, do you have any fluid coming out of the bottom of the drum(inside of wheel) on any wheels?

[MARTYZ]

Just my opinion but I would get the disk brakes on to match your MC and PV setup and proceed from there. May fix your issues!
Booster with no vacuum will just give you a very stiff pedal with slow brake response, wouldn't suggest it.

[jtrichard]

also check your adjustment if the master is for disc then it wont like to move much fluid ...pumping is air or adjustment or both

[Wrenchbender Ret]

If its not air in the system then you may not have the shoes adjusted up good.
You will need check valves in each system as disc brake master cyl. don't have check valves.

[luvbowties]

...agreeing with Wrenchbender Ret. Actually, first you need to buy a correct mc for drum-drum brakes----only cost about $18. Save the disc/drum mc for later use when you have added disc brakes.

After verifying leaks are non-existent, adjust brakes; but 1st read all you can about how to adjust YOUR brakes. Use the method that tells you to tighten a drum to where it will not turn, and THEN back off the adjuster to where the drum turns but has a slight drag to it--other methods will drive you crazy & may never get the adj. correct.

Then, bleed the brake system beginning with farthest from mc & work your way closer and closer. When these 2-3 things are done, drive it--BE CAREFUL-- & see how brakes respond. If still not correct, reply again with what you've done/verified, and get further instructions.
Sam

[Improbcat]

Luvbowties is right, it will never work correctly with the wrong MC. Drum brakes need residual pressure or they retract too far, disc brakes don't. So without the residual pressure you are using most of the pedal travel just to get the front shoes to touch the drums, never mind actually start stopping the truck.

[66Submarine]

Originally Posted by Improbcat

Luvbowties is right, it will never work correctly with the wrong MC. Drum brakes need residual pressure or they retract too far, disc brakes don't. So without the residual pressure you are using most of the pedal travel just to get the front shoes to touch the drums, never mind actually start stopping the truck.

Drum brakes don't work like that; you adjust the shoes out with the star wheel adjuster. The return springs pull them all the way back against the anchor pin when you release the pedal. There is no "residual pressure".

[luvbowties]

Originally Posted by 66Submarine

Drum brakes don't work like that; you adjust the shoes out with the star wheel adjuster. The return springs pull them all the way back against the anchor pin when you release the pedal. There is no "residual pressure".

I've never added res. pres. valves; but my neighbor could never get his brakes correct until he added them, to which end, I do not recall--HOWEVER, his mc & booster were below the level of all his brake lines AND all wheel cylinders: it was under the cab and much of his frame. [I always attributed his need for those buggers to that "below-level" scenario; maybe bleeding some wc-lines back into the lower level mc when parked(?: all just my theory).] He has a cabover, approx. 1951 Jeep pickup, w/a Regal front suspension, eng. & trans. **BTW: his license plate reads something like "UGLYTRK", quite befitting!**

He swore I'd need the same when I added power disc/drum brakes to my 1966 Chev--wrong...and I bought what looked like in the parts book that it'd bolt on, that it would pump the extra juice I wanted on each pedal pump, and that I could totally adapt with a minimum of trouble. So mine is a hodgepodge mixture/combo of parts whose description and original application I kept a record of, somewhere?!

Good luck to the op on your troubleshooting and correcting.
Sam

[gofastnut]

It appears I didn't read your first post correctly, dwlambert. I didn't catch the DISC brake master cyl. And the guys bring up a good point about making sure the drums are properly adjusted. As far as the proportioning/hold off valve, I think you need 5 or 10 lbs residual pressure for the drums.

[truckeroy]

I don't mean to hijack this thread, but i have a problem doing my power brake conversion. I put a reman booster from an early 80's Chev pu. The master cyl is the one is saw recommended on this website- 10-1363 for a 70's Buick/Pontiac. The problem I'm having is fluid seeping around the threads in the outer most port. I put in an adapter to get the 1/4 line attached. I first thought the fitting was too short to seat properly. I found a longer threaded one but it still leaks when I push on the pedal. The seat looks OK in the MC port. Is it possible that the internal seat in the reman MC is bad? I know once I have used it, it is mine (I bought it online), so I would have to buy another one (locally this time), but I don't want to do that and end up with the same problem. Does anyone know what I can do to fix this? Thanks, Roy

[Captainfab]

It sounds to me like either the flare on the end of the tube is mis-shaped, or cracket, or the seat in the master port is damaged. I would inspect the end of the tube first. Do you have a double flaring tool to put a new flare on the end of the tube?

Originally Posted by truckeroy

I don't mean to hijack this thread, but i have a problem doing my power brake conversion. I put a reman booster from an early 80's Chev pu. The master cyl is the one is saw recommended on this website- 10-1363 for a 70's Buick/Pontiac. The problem I'm having is fluid seeping around the threads in the outer most port. I put in an adapter to get the 1/4 line attached. I first thought the fitting was too short to seat properly. I found a longer threaded one but it still leaks when I push on the pedal. The seat looks OK in the MC port. Is it possible that the internal seat in the reman MC is bad? I know once I have used it, it is mine (I bought it online), so I would have to buy another one (locally this time), but I don't want to do that and end up with the same problem. Does anyone know what I can do to fix this? Thanks, Roy

[truckeroy]

The master cyl is a "new" refurbushed and the adapter fitting and the brake line is new also. The leak is coming from the adapter threads to mc. I have put a longer thread length brass fitting to see it the threads were not long enough, and the brass being softer I thought it might seal better, no difference. It is not leaking between the fitting and the tube. the seat in the mc "looks" good, but it is hard to tell. The edge around actual hole in the mc port seems to be sharp edged, but the cone around the hole seems smooth and consistant. I'm afraid it's going to be a new mc. I've never had this problem before. I doubt if any "hard" sealant would seal very long, I know tape won't work. It only leaks when I pump the pedal a lot, but I'm sure with even normal use it would continue to leak over time.

[TJ's Chevy]

I just learned a ton about brakes! lol!

[Captainfab]

In recent years I have experienced a few brass fittings that would not seal, with either the threads on NPT or against the seat on inverted flare. IMO this is to be expected considering where most of these parts are made now days. I would try a different fitting, before switching the entire master cylinder. Preferably from a different manufacturer.

[truckeroy]

The first fitting I tried was a steel one from O'Reilly's. It had less thread length, so I found a brass one from ACE hardware with longer thread length. Both still leaked. Also, when I bench bled the mc with the blue plastic plugs sent with the mc, I noticed this port was seeping around those theads also. At the time I just thought it was because of the plastic being of poor quality. I have another steel fitting I could try, but at about $5 a fitting, I can buy another mc for $20. HA. Thanks, Roy

[truckeroy]

OK, I think I finally go the leak stopped at the mc port. It was a crude method. It looked to me like the bore inside of the port had a rough and jagged edge around it. Most ports have a little flat surface around the hole. I took a flat bar and tapped the surface and created a flat area around the bore. I also wondered if the brass port assembly inside was seated into the mc because the fluid seemed to be coming from around the conical area, not just the hole. After doing this I cranked the brass fitting in real tight. It seems to have worked. Now for the next problem. I have pedal, but not a lot. (haven't looked at the shoes yet, they may be worn). When I start the truck and hit the brakes the pedal goes down to the floor. The fronts have a slight drag when turned by hand. I still have to check the rears for adjustment. Still wondering if this MC is at the root of my probmems and since it was seeping at the port, did I get all the air out of the mc when bench bleeding? I just love working on these old vechicles, it keeps mind mind active and my blood pressure up.

[tincan1966]

As someone mentioned before, I believe, you do not need a proportioning valve for drum/drum brakes.

I also agree with others that you should be using a drum/drum MC and a distribution block.
On my '65 I am using a '68 C10 manual master cyl with a block from a '67-'68 Camaro with manual drums. This provides the correct pressure to both front and rear brakes.
This is basically the same setup most of the aftermarket vendors use.

[truckeroy]

I guess I'll give an update on my "brakescapade". Even though I thought I had stopped the leak in the mc, I still see a little dampness at the port at times, so I sent and email to the company where I bought the mc. They sent me another one without wanting the old one back. Can't beat that. The first one had an old painted pitted cap on it. this one has a new cap. I still couldn't get much pedal so I started to adjust the shoes. I just touched the right rear adjuster and it fell apart inside the drum! Trying to get drums off with the brakes still adjusted out is not fun along with the center hub rusted. I built a puller and after all day I got both drums off. Inside the right one I found the tension spring that holds the adjuster together wedged between the shoe and drum. I was a little bent and worn. Maybe that is why it took so much effort to remove the drum. HA. I also discovered 2 studs borken off on the right rear. The other side seemed to be ok inside but it was still hard to remove because of the rust around the center hub. So I decided to rebuild them even though the shoes had a lot of liner left the right side had a few skid marks due to the spring and the drums were grooved. Also the wheel cyl were weeping a little. Someone had rounded off the bolt heads on the cyl, I broke one, chisled 2 and got one out the intact. Also the threads on the line going into the right rear were a little rounded. Someone sure had a time with that right rear and they sure cause me more problems than I wanted. Tommorow I hope to get everything back together. I haven't looked at the fronts yet. Do I dare? Happy Holidays.

[E.TexasTwister]

Well did you get it working correct?

[truckeroy]

Got everything back together. I haven't looked at the front brakes yet, but they seem to be OK. I don't like the amount of pedal travel, but other than that, They are stopping very well. Thanks, Roy