C-1 Brakes

[Bwmurph]

Hi All,
I've recently become unhappy with the brakes on my '59. Several years ago I had a Studley's IFS with non-power disc brakes installed. My mechanic at the time used DOT 5 (silicone) brake fluid. The car seems to be increasingly hard to stop and i have to really stand on the pedal to "lock up" the wheels. Its to the point where its uncomfortable to drive.
So ... I thought I would bleed the brakes and see if that helps; went to get my Motive Power Bleeder and the nipple on the pressure block broke off as well as all the hoses cracking. Hoses were fixed easily but tried putting a brass nipple in the pressure block using JB Weld - unsuccessful. So I'm just going to order a new one from Motive.
Here's my dilemma: I haven't liked the silicone fluid from Day 1 and today I notice on the Master Cylinder cover that it says use DOT 3 fluid only. I would like to switch back to glycol, but I understand that is a real PITA. I've read that you will have to disassemble everything (master cylinder, calipers, etc..) to properly clean all the silicone out of the system. Is this true ? Can I just run alcohol or some other solvent through the system to cleanse it ? I REALLY don't want to take everything apart if I don't have to.
Any suggestions will be appreciated.

Also, if anybody is interested, I still cant get my drivers side seat to go back far enough to suit me !
Bernie O

 

[Tom Bryant]

When I was in GM Parts we had a GM brake system cleaner in quart or larger cans on the shelf. It was a system cleaning solvent. I'm not sure if it was alcohol or not but something similar. You cleaned out the master cylinder reservoir then poured the solvent into your pressure bleeder or master cylinder. Then opened the bleeders until there was no trace of old brake fluid coming out. Next step was to put new brake fluid into your bleeder and repeat until all of the solvent was gone and only clean brake fluid comes out. There is an element online that runs in circles panicking about even a trace of Dot 5 in a brake system while spouting all sorts of claims of doom and disaster. My wife's 81 has had Dot 5 in it since it was new without any performance related problems yet.

I found a gallon jug of Blue Mountain Brake System Cleaner online that sent me to a dead end at Ebay That sounded like the brake system flush cleaner we used to use. I'm not sure if the auto parts stores or GM dealers have the system cleaner on the shelf or not. I'm confident that a thorough flush with cleaner and a refill with Dot 3 will do the trick. Back to the 81, two years ago I put on new Bendix carbon ceramic pads and flushed/bled the system with fresh Dot 5 and the brakes on that car have never been better. When you go under to bleed the brakes have someone pump the pedal to verify that all of the caliper pistons are moving. It also could be a problem with the proportioning valve.

Tom

 

[Bwmurph]

Thanks Tom ! I figured you would be the one to reply and also to have some extensive knowledge on the subject!
I’m out of country right now but will attempt to bleed the brakes with my Motive Power Bleeder when I return home next week.
If I can get a nice hard pedal and a decent stopping distance with the DOT 5 I will leave things as is. I’m also going to look into upgrading to power brakes.
Stay tuned. Thx again !
Bernie O

 

[Bwmurph]

Thanks Tom ! I figured you would be the one to reply and also to have some extensive knowledge on the subject!
I’m out of country right now but will attempt to bleed the brakes with my Motive Power Bleeder when I return home next week.
If I can get a nice hard pedal and a decent stopping distance with the DOT 5 I will leave things as is. I’m also going to look into upgrading to power brakes.
Stay tuned. Thx again !
Bernie O

OK I definitely decided to go the power brake booster route. I think I read somewhere that you need at least 18 in/Hg to operate the booster correctly. I just checked my car ('59, GM Crate, 350/300, original WCFB dual quads), and I have 20-22 in/Hg at idle and differing readings depending on RPM, but all above 20 in/Hg, So, unless anyone tells me different I think I'm fine in that regard.
I think I'll also go back to DOT 3 brake fluid at that time as well. Again, unless anyone can convince me otherwise.
Any and all comments, suggestions, etc...are welcome.
Bernie O

 

[Tom Bryant]

Sounds like you will be fine with that. I don't know what pad compound you have on your car but you might try a new carbon ceramic to see how that feels.

Tom

 

[Bwmurph]

Sounds like you will be fine with that. I don't know what pad compound you have on your car but you might try a new carbon ceramic to see how that feels.

Tom

Here we go again ! Been a lot of stuff going on in my life since this topic was last raised, but ready to get back at it.
I've received my new master cylinder/brake booster for the '59. I've spent the last 2 days flushing the entire brake system with alcohol; went through almost 3 quarts of alcohol. Now I'm planning on flushing the alcohol with Dot 3 before I mount the new mc/booster.
My question is about bleeding the brakes: Everyone says to start the bleeding process at the furthest brake cylinder or caliper from the master cylinder, which would be the right rear wheel. However, the brake lines run from the master cylinder to the left front, then the right front, down the right side frame rail to the right rear, then across the axle to the left rear.
Wouldn't that make the left rear the farthest from the master cylinder ? Shouldn't I start the bleeding process there ?

A couple of other things I'm thinking about on this project: I'm wondering if I go back to Dot 3 and get the brakes bled correctly if I'll be satisfied with my current non-boosted master cylinder. The boosted mc is really long and fairly heavy - a lot of weight hanging off that firewall, although I suppose the brake lines running to the mc would offer some support. (I wonder what their return policy is? I haven't even taken it out of the box yet). Also, I know NOTHING about proportioning valves - not sure if i have one or where it is or how to adjust it. Wondering if that could be my problem all along.

And while I'm at it, how about speed bleeders and/or gravity bleeding ? Do they work ?

Thanks for letting me rant and any and all responses are appreciated.

Bernie O

 

[Tom Bryant]

I don't think that the DOT 5 is causing poor braking. You do need a proportioning valve on a front disc/rear drum system. The attachment below from the CPP web site explains it in detail better than I could. When I did the front disc conversion on my 69 Chevy C10 I used all 1971 brake parts. I bought the proportioning valve from CPP and it is similar to the picture below. This type is also referred to as a combination valve as both front and rear systems flow through them and are balanced to the needs of the braking system. These factory valves are not adjustable and mount to the booster right beside the master cylinder. There should be one in your system. If it isn't close to your master cylinder look on downstream. If there isn't one, Call Studley's and ask what their recommendation is for their IFS that they sold you. CPP might be able to recommend a factory type valve also. If they recommend an adjustable proportioning valve, here's a link to a good read on the topic from Wilwood. ​ A Proportioning valve is required on vehicles that have disc brakes on the front wheels and drum brakes on the rear wheels. Disc brake pads are normally in contact with the disc, while the drum brake shoes are normally not in contact with the drum. If the pressure was not proportioned the disc brakes would engage before the drum brakes when you depress the brake pedal. The Proportioning valve compensates for this, allowing the drum brakes to engage first before the disc brakes. The Proportioning valve does not allow any pressure to the disc brakes until a pre-determined pressure has been reached. The pre-determined pressure is low when compared to the maximum pressure in the braking system, this allows the drum brakes to engage before the disc brakes engage.

Having the rear brakes engage first provides the control and stability needed to stop your vehicle safety. The proportioning valve reduces the pressure to the rear brakes. Whichever type of brakes your vehicle has, the rear brakes require less pressure than the front brakes. If equal braking force were applied to all four wheels during a stop, the rear wheels would lock-up before the front wheels. The proportioning valve only lets a portion of the amount of pressure to the rear wheels thus preventing rear wheel lock-up. I hope this helps get you headed in the right direction. Let me know what you find. Tom

 

[Bwmurph]

Tom,
I believe this is my proportioning valve. It is mounted on the frame directly under the master cylinder. I assume it’s working correctly, but …… I don’t know how to, or even if, you can test it.
I’ve run almost 3 qts. of alcohol through the system, and now almost a quart of Dot 3 and I’m still seeing silicone seep back into the master cylinder. Guess I’ll run another quart of Dot 3 through it.
What do you think about speed bleeders ? It’s difficult for me to get some help on this with the amount of time involved.

Thanks for your help !
Bernie O

 

[Tom Bryant]

That's it. It looks just like the one I put on my C10. I have never tried speed bleeders. They might work well if you are doing them by yourself. I've come to rely on my Motive pressure bleeder since I bought it to use on the '81 when I replaced the rear calipers. I couldn't get all of the air out no matter what I did. The Motive bleeder fixed that quickly.

Is it both the front and rear sides of the MC that has silicone still showing up? It seems like it would be well flushed out by now with that much alcohol ran through it. Does it float on top of the DOT3 or settle to the bottom? You might be able to suck the silicone out of the mc reservoir with a syringe after it has set for a while and settled. It must be getting trapped in the mc bore, or calipers somewhere.

All of my driving life I have checked my brakes on a gravel drive or road by going about 15-20 mph and firmly braking. It's easy to tell if you have one wheel or front or rear pair that aren't working right. If the rears slide but the fronts don't or the fronts slide but the rears don't, you have a proportioning problem. Rears have to reach a pre-determined psi before the combo valve allows flow to the front discs, so the rears will grab slightly before the fronts. This should quickly transition to even 4-wheel braking. I found this video that explains how to reset a proportioning valve and how the type you have works. Probably not your problem since you got plenty of flow out of front and rears when you flushed and bled the system. But it is a problem that can pop up while you are bleeding.

Tom

 

[Bwmurph]

That's it. It looks just like the one I put on my C10. I have never tried speed bleeders. They might work well if you are doing them by yourself. I've come to rely on my Motive pressure bleeder since I bought it to use on the '81 when I replaced the rear calipers. I couldn't get all of the air out no matter what I did. The Motive bleeder fixed that quickly.

Is it both the front and rear sides of the MC that has silicone still showing up? It seems like it would be well flushed out by now with that much alcohol ran through it. Does it float on top of the DOT3 or settle to the bottom? You might be able to suck the silicone out of the mc reservoir with a syringe after it has set for a while and settled. It must be getting trapped in the mc bore, or calipers somewhere.

All of my driving life I have checked my brakes on a gravel drive or road by going about 15-20 mph and firmly braking. It's easy to tell if you have one wheel or front or rear pair that aren't working right. If the rears slide but the fronts don't or the fronts slide but the rears don't, you have a proportioning problem. Rears have to reach a pre-determined psi before the combo valve allows flow to the front discs, so the rears will grab slightly before the fronts. This should quickly transition to even 4-wheel braking. I found this video that explains how to reset a proportioning valve and how the type you have works. Probably not your problem since you got plenty of flow out of front and rears when you flushed and bled the system. But it is a problem that can pop up while you are bleeding.

Tom

Well, I finally sorted out my brakes and sent the new master cylinder and power booster back to the vendor.
Here’s what happened: I was starting to disassemble the current m/c in order to install the new one w/booster. While doing this I noticed a lever connected to rod on the m/c was just kind of flopping around and didn’t seem to do anything. I stuck my finger in the opening to move it and it fell on the floor. A quick examination and it appeared to be some kind of fulcrum (?). After re-attaching it with a c-clip (top) and a bolt (bottom). I decided to test the brakes and the now work great !! I don’t know how long this thing has been disconnected but it’s been a long time because I have not been happy with my brakes forever.
You learn something new ever day !

 

[Tom Bryant]

I guess it's sometimes the simplest things. You just have to find them. I'm glad that you found it and, except for the time spent, it was free.

Merry Christmas