Brake problem – cant lock them up

[tekno62]

Im having a brake problem’s on my 72

The first one I think I have fixed. The back brakes would loose fluid and I could not find any leaks. The PO had installed dual exhaust and the passenger side was riding tight on the brake line. I think that the fluid was just being boiled out. I have bent the brake line with about 1/ 2” clearance.

The other problem is that I can’t lock up my brakes. This is the one that’s bothering me right now. I put in a new master/booster from Kragen as well at new cylinder in back and new pads all around.

Anyone have any ideas why I cant lock up my brakes - front or back

I need to pull a trailer and like to have the brakes 100%

[VDOG]

Kragen Master Cylinder, im doing the same thing. Im on my second one in 3 days, could not a full stream of fluid to the rear. Bought a new one from CPP, still have the same problem. Did you bench bleed your MC?
Also I bought a vacuum bleeder from Harbor freight, other than my problem it bleed the front in seconds.

[tekno62]

no I didnt bench bleed. really glad I didn't as the pipe connectors where different then the original I had to get adapters. I had the master cylinder for a few months with no problem ( fist time the rear reservoir has been empty )

Originally Posted by VDOG

Kragen Master Cylinder, im doing the same thing. Im on my second one in 3 days, could not a full stream of fluid to the rear. Bought a new one from CPP, still have the same problem. Did you bench bleed your MC?
Also I bought a vacuum bleeder from Harbor freight, other than my problem it bleed the front in seconds.

[VDOG]

you have to beench bleed, dont worry Kragen will still take it back. Dry it off and take it back, thats what I will be doing tomorrow. In fact the first one I got was wet.

[tekno62]

what is bench bleeding? that where you put fluid in the master cylinder before you install it? it came with the booster

[lyrikz]

Originally Posted by tekno62

what is bench bleeding? that where you put fluid in the master cylinder before you install it? it came with the booster

If you have to ask what bench bleeding is, you shouldnt be doing your brakes. Thats between life and death there you not stopping.

Basically when you buy the mastercylinder you lock it in your vise. Have someone help you and what you do is fill it full of fluid and then put your fingers over the 2 outlets. Nowhave someone push the cylinder in and before they let it back out, cover the outlet holes so that it sucks fluid down. You will do this quite a few times and eventually when you press down on the plunger you will get no air just fluid out of the outlets.. They do sell bench bleed kits that make it easier and less messy...

Do a quick google search and you will find a ton of articles to help you out. And just because you didnt bench bleed it doesnt mean its bad. It just takes that much longer to bleed the brakes. Just easier to take the MC out and bench bleed it, and reinstall and then bleed the brakes in the correct order.

[tekno62]

why cant I do that when its installed in the truck... my dad and I have bleed brakes for years, and have had no problem removing the air from the system.

Originally Posted by lyrikz

If you have to ask what bench bleeding is, you shouldnt be doing your brakes. Thats between life and death there you not stopping.

Basically when you buy the mastercylinder you lock it in your vise. Have someone help you and what you do is fill it full of fluid and then put your fingers over the 2 outlets. Nowhave someone push the cylinder in and before they let it back out, cover the outlet holes so that it sucks fluid down. You will do this quite a few times and eventually when you press down on the plunger you will get no air just fluid out of the outlets.. They do sell bench bleed kits that make it easier and less messy...

Do a quick google search and you will find a ton of articles to help you out. And just because you didnt bench bleed it doesnt mean its bad. It just takes that much longer to bleed the brakes. Just easier to take the MC out and bench bleed it, and reinstall and then bleed the brakes in the correct order.

[lyrikz]

Originally Posted by tekno62

why cant I do that when its installed in the truck... my dad and I have bleed brakes for years, and have had no problem removing the air from the system.

You absolutely can bleed it in the car. Just messy. Bolt it in place and then have someone with their foot on the pedal. Depress the pedal and then before they lift up their foot, put your fingers over teh 2 outlets and when they lift the pedal it will suck fluid into the MC...

And give the brakes 100 miles or so to break in fully and you should be able to lock them up. If you cant, then id figure you have a booster problem...

[tekno62]

no ones ever said I was afraid of making a mess.

I'll keep any eye on the brakes. may re-bleed them later this week.

Originally Posted by lyrikz

You absolutely can bleed it in the car. Just messy. Bolt it in place and then have someone with their foot on the pedal. Depress the pedal and then before they lift up their foot, put your fingers over teh 2 outlets and when they lift the pedal it will suck fluid into the MC...

And give the brakes 100 miles or so to break in fully and you should be able to lock them up. If you cant, then id figure you have a booster problem...

[cdowns]

clamp pin on combination valve to bleed brakes

[tekno62]

Sorry - I dont understand your post.

Originally Posted by cdowns

clamp pin on combination valve to bleed brakes

[lyrikz]

Originally Posted by cdowns

clamp pin on combination valve to bleed brakes

I dont understand your post either..

Do you mean were the wire goes to the prop valve???

[cdowns]

Originally Posted by lyrikz

I dont understand your post either..

Do you mean were the wire goes to the prop valve???

get service manual read service manual step by step instructions on proper way to bleed brakes//AFTER ALL it is the difference between life and death to have a brake system working properly

[lyrikz]

Originally Posted by cdowns

get service manual read service manual step by step instructions on proper way to bleed brakes//AFTER ALL it is the difference between life and death to have a brake system working properly

Ok, sense the smartassness there. I have never heard it called a combination valve. Are you talking about the proportioning valve that is located just off the mastercylinder??? We are talking about bench bleeding the master cylinder.

Is there another valve that im missing somewhere???

[Arad68]

Originally Posted by cdowns

clamp pin on combination valve to bleed brakes

He is talking about the button on the end of the combination valve. If you hold this button (usually covered by a rubber disc) in place with a clamp, it will keep from offseting the combination valve piston illuminating the light on the dash. It also makes it easier to bleed the brakes.

[cdowns]

Originally Posted by lyrikz

Ok, sense the smartassness there. I have never heard it called a combination valve. Are you talking about the proportioning valve that is located just off the mastercylinder??? We are talking about bench bleeding the master cylinder.

Is there another valve that im missing somewhere???

little bit of smartass but if you read the service manual you'd know what a combination valve is and it's full function is //you WRONGLY call it a proportioning valve

[lyrikz]

Originally Posted by Arad68

He is talking about the button on the end of the combination valve. If you hold this button (usually covered by a rubber disc) in place with a clamp, it will keep from offseting the combination valve piston illuminating the light on the dash. It also makes it easier to bleed the brakes.

Ok, so this is what you are calling the combination valve?


I thought they were called proportioning valves. Either way, your talking about that rubber disc located on the front right? Clamping that off isnt necessary it just makes it easier to bleed the rear brakes?

[Arad68]

Originally Posted by lyrikz

Ok, so this is what you are calling the combination valve?


I thought they were called proportioning valves. Either way, your talking about that rubber disc located on the front right? Clamping that off isnt necessary it just makes it easier to bleed the rear brakes?

yes!

[lyrikz]

Originally Posted by cdowns

little bit of smartass but if you read the service manual you'd know what a combination valve is and it's full function is //you WRONGLY call it a proportioning valve

I deal with newer cars all day at my shop and they call them proportioning valves. And CPP calls them proportioning valves also.
http://www.classicperform.com/Store/...uck/7172PV.htm

And my technicians call them that. I just want to know if we are talking about the same thing is all? It might just be old school terms your "combination" valve. Never heard em called that. That is if we are talking about the same valve. lol.

[cdowns]

Originally Posted by lyrikz

I deal with newer cars all day at my shop and they call them proportioning valves. And CPP calls them proportioning valves also.
http://www.classicperform.com/Store/...uck/7172PV.htm

And my technicians call them that. I just want to know if we are talking about the same thing is all? It might just be old school terms your "combination" valve. Never heard em called that. That is if we are talking about the same valve. lol.

chiltons motors haynes and GM service manuals all call them combination valves //reading service manuals is very old school

[lyrikz]

Originally Posted by lyrikz

I deal with newer cars all day at my shop and they call them proportioning valves. And CPP calls them proportioning valves also.
http://www.classicperform.com/Store/...uck/7172PV.htm

And my technicians call them that. I just want to know if we are talking about the same thing is all? It might just be old school terms your "combination" valve. Never heard em called that. That is if we are talking about the same valve. lol.

Back on topic, what cdowns and i were talking about is the hydraulic control valve (ie combination or proportioning). On that valve there is a metering section on it that must be disabled so you can bleed the front brakes. They do make a tool for that. Part #J23709 for general motors.

Also, just so you know for 1965-1969 brake bleeding procedure is
RR, LR, RF, LF.

Now if you have a 1970-1974 the bleed procedure is.
LF, RF, LR, RR.....

[lyrikz]

Originally Posted by cdowns

chiltons motors haynes and GM service manuals all call them combination valves //reading service manuals is very old school

I dont really care what its called, you could call it a boombom clang valve for all i care. I just wanted to make sure there wasnt something i was missing.

That is old school. Now its all on the net..

I can honestly say that i did NOT disable the metering valve like they say. My brakes bled fine and are rock solid. I also went with the old school way of doing the brake that is the furthest away first. From what it says in the vintage manual, in a 70-74 its completely different....

[lyrikz]

Originally Posted by tekno62

no ones ever said I was afraid of making a mess.

I'll keep any eye on the brakes. may re-bleed them later this week.

back to your main issue. If you still have a soft pedal, id bleed the master cylinder, then when your bleeding the brakes disable that valve that cdowns is talking about and try that again...

LET US KNOW THOUGH. ahah

[tekno62]

thanks - I didnt disable the little rubber covered pin. I'll re bleed the brakes this week and let you all know.

Originally Posted by lyrikz

back to your main issue. If you still have a soft pedal, id bleed the master cylinder, then when your bleeding the brakes disable that valve that cdowns is talking about and try that again...

LET US KNOW THOUGH. ahah

[lyrikz]

Originally Posted by tekno62

thanks - I didnt disable the little rubber covered pin. I'll re bleed the brakes this week and let you all know.

I would try that....

Mine feel fine, but i didnt do what cdowns said. Im going to go back and redo them and use his method... I have a feeling they will feel even better...