Need help with my Brakes...'57 Chevy 3100

Hello -

Finished converting my '57 Chevy 3100 to a 4spd and took it on it's inaugural ride. Everything seemed to be working fine, although it truck seemed a bit sluggish. Whatever, I though, I'm not used to the gearing yet, and I have 2.73s in the rear.

But it kept getting worse...like I was pulling a heavy trailer.

Then I started to smelled something burning.

Uh oh.

Got out of the truck, and ALL 4 brakes were smoking, and the brake lights were stuck on. Pedal seemed a bit firmer than usual.

Limped the truck home, and got it up in the air. This morning, all the wheels spun freely, so I pulled the tires, got under the truck, and inpected all the lines, thinking maybe I damaged one when I was getting the tranny in place. No kinks anywhere that I could find. MC full of fluid. Parking brake wasn't engaged. Brakes lights worked like they should. Pumped the brakes for a minute with the car up in the air. Brakes released as they should, and the brake light worked as it should.

Here's the setup I've got: The PO installed a dual well MC with front discs, looks like a Speedway kit. Both lines from the MC feed into a non-adjustable proportioning valve, and the brakes lights are actuated by a pressure switch that's plumbed into the lines feeding the front brakes. Rear end is stock with drums from a 72 - 73 full size Pontiac. When I got the truck, the brakes were shot, so I did a full brake job including cutting the front rotors, new front pads, complete new hardware on the rear, new shoes, cut the drums, and a new wheel cyl on the pass side (leaking). Brakes bled out fine and worked as they should. Previous owner did not have any of the e-brake hardware installed, so I reinstalled the complete ebrake system, including all new cables and hardware. Ebrake works as it should, holds the truck on a hill and disengages smoothly.

The only thing that I can think of that's bad is the proportioning valve. This one one of those solid brass units that you can get on Ebay that has a provision for a pressure switch. Can proportioning valve go bad and cause the brakes to lock up?

When I did the brake job, the MC well feeding the rears was empty because of the leaking wheel cylinder. Any chance some moisture could have gotten in there are corroded the inside of the proportioning valve?

If not, any ideas what would cause all 4 brakes to lock up? Everything seems to be in order, so I'm stumped.

Thanks...

Chris

 

Chris, Do you have power brakes ? If you do ,There needs to be one eight inch clearance between the rod going to the booster and the master cylinder. tex1935

 

Tex - Sorry, should have mentioned that...

No, I have manual brakes with the original under-floor mc.

Chris

 

More than likely this is the cause. Your brake pedal should have a return spring on it as well so it won't cause the brakes to possibly drag.

Go an initial 1/8" and see what happens, you may need to go more.

Bob

 

Bob - You must have posted right before I replied. Anyway, the manual brakes that are in place worked before, albeit not very well because of the leaky wheel cyl. I didn't change anything on the MC, linkage, or pedal, and the PO had the truck running and driving, so I doubt that there's anything wrong with the linkage and clearances.

Chris

 

my first thought would be, like said, there is not enough play in the pedal to master rod. my second thought would be if the brake system was near anything hot?

 

TB - Just took the truck for another ride and the same thing happened. I got the truck in the air again, and no part of the brake system was warm, other than the rotors, which were starting to stick. It seems as if brakes start to stick as I drive and it gets worse the more I drive. The brake lights were stuck on again, but I cracked a front bleeder and they went off again, so I'm building pressure in the front lines.

Still a mystery to me.

Chris

 

Sounds like the fluid is expanding and increasing the pressure in the system, as evidenced by the brake light, and the sticky brakes. I know I know, I'm a rocket surgeon, right? lol.

The return port on the MC might be wonky, or not drilled through.

 

Post #2 should cover it. Make sure you have play in the pedal, there still should be a (hopefully) adjustable rod that enters the back of the master.

Bob

 

Initially you stated all 4 brakes were dragging, and if that's still happening then the master could be building pressure because of the pedal not staying fully returned.

If only the fronts are dragging, check for a residual valve, internal in the master or external (aftermarket) and then only a 2 lb. external if the master is floor mounted.

A proportioning valve only affects the rear pressure, and I've not seen any fixed value PVs that have a provision for a pressure switch, so maybe a picture of your setup may be of help. Normally these brass units are GM style OE combination valves that include a fixed value prop valve, differential pressure switch and sometimes a metering or hold off valve to the front discs, identified by a rubber covered button or pin. The combo valve could be defective, and if you decide to remove it, replace it with just an adjustable prop valve. These are available with a provision for and sometimes include a brake light pressure switch.

 

I just checked...there is 1/8" play in the brake pedal, so that's not it.

Chris

 

When is the last time the brake fluid was replaced?

 

Ba - Not since I've owned it, don't know how old it is. The rear fluid is all new because it all leaked out through the bad wheel cyl.

Here's a pic of the proportioning valve. I was wrong...it's not brass, it's steel 'cause it's rusting.

Chris

 

You really need to pitch that old combo valve, as it dates back to the late '60s/'70s! Curious though where your brake light switch is?
Do you know the age and application of the master cylinder?

 

Bob - My sense is that the work on this truck is at least 20 years old. The brake light switch is plumbed into a "T" thats plumbed into the front pass side brake line, the one coming off of a 45 degree angle from the upper right hand corner of the valve.

I'm planning on chucking it and using the original mechanical style switch that mounts near the brake pedal.

I have no idea of the age or application of the MC. I was looking at Speedway, and it doesn't match the ones that they offer. I'll post a pic tomorrow.


Chris

Chris

 

I'd have to agree with V8Bob. When I was building my truck the brakes locked up after we bled them and we couldn't release them. The stuff was all out of the 74 Camaro that was the donor for suspension and drive train and had been sitting in my shop for over 15 years. Had to put in a new MC and proportion valve. Now she works fine.

 

I'm almost thinking the same way as VooDoo... it sounds like your fluid is expanding. Are any brake lines near your exhaust? Also, if for any reason, atf was used, or a silicon based fluid, you will have these issues. I'd drain the system completely and replace with DOT3. It is a pain in the you know what, because you have to run new fluid through the system to evacuate / replace the old completely, but if it were me I'd go that route.

The prop valve could be the culprit (if it were only the rear), but since it is all 4 wheels, I don't think that's what it is.

 

Ba and Buzz - Ok, I'm going to replace the proportioning valve and drain all the fluid going to the front discs. I have an old Power Bleeder that I picked up off of CL, so bleeding actually goes pretty quick. Since the proportioning valve is cast iron or steel and it leaked dry, there may be corrosion in there buggering things up.

Buzz, I went over every inch of the brake lines/mc, etc after running the truck for about 15 mins, and no part other than the rotors were warm. Whoever did the work on the truck did a good job...everything seems to be neatly placed and secured, and none of the lines come anywhere near the headers or exhaust.

I'm going to post a pic of the MC in the morning to see if anyone can ID it. At minimum, I need to get a new rubber gasket for the cover since it's shot.

Chris

 

It's likely the early 60's Vette master cylinder...that's typically the upgrade for these trucks - it happens to be the one I used on my '56.

 

When the M/C piston is fully retracted, the reservoirs are open to the brake lines. At the expense of a lot of ridicule, I'll say it again: When the M/C piston is fully retracted. The reservoirs are open to the brake lines. This allows brake shoe springs to push fluid back into the M/C.

A retracted M/C means pressure cannot build in the lines due to heat or any other cause. Pressure would also build in the reservoirs.

If petroleum products were used to 'clean' or hone wheel cylinders, the introduction of DOT3 will bloat the rubber cups and seals, causing them to stick. The same holds true for rebuilding the M/C.

Some folks think that the more expensive brake fluid is better so they inadvertently MIX DOT3 with DOT5. That turns the fluid in the lines to a brown muck. If that happens, cleaning it out isn't practical. Replacing your lines IS.

DOT3 is glycol-based (like green antifreeze). It is VERY hydroscopic, meaning, it sucks up water faster than scotch. When saturated with water (after three years) it rusts brake lines from the INSIDE and it can freeze or boil, so change your DOT3 every two to three years.

If you change from one type of fluid to another, use LOTS of alcohol to clean the lines out before adding fresh brake fluid. Then, change it after the first season.

How do you tell the difference between DOT3 and DOT5? Put a few drops in water. If it floats, you have DOT5. If it easily mixes, it's DOT3 or DOT4. - Dave

 

Simply -

Point well taken. I've always used nothing but DOT 3 for this truck, and the brake fluid, although a bit foggy in the reservoir for the rear wheels, is NOT brown muck. I'm aware that you can't mix different types of brake fluid, and I have never done so.

The complicating factor in this situation is the proportioning valve, which is clearly made of steel or cast iron, since it's rusty on the outside.

Since DOT 3 is hyGROscopic (NOT hydroscopic, no such word according to Webster), as you mention, it's very likely that the brake fluid absorbed moisture from the atmosphere, especially given that the MC cover seal is shot, and rusted the proportioning valve and, possibly, the MC, internally.

One thing I did not mention is that this truck sat...for at least a year, probably longer, outside, which only serves to back up my theory.

Anyway, I know that the lines aren't kinked, the calipers retracted easily when I installed the shoes, nothing's getting overheated, and the pedal and rod are properly adjusted, so I really don't know what else it could be besides the proportioning valve or MC.

Thankfully, the parts cost on both is about $100, so the pain isn't that great, although they are a pain to install, so I'll just put on my big boy diapers and go out and do it when the parts arrive.

If anyone else has anything to add, have at it...I sure as hell am not an expert...

Chris

 

there is a bleed back hole in the bottom of the m-c that gets full of sludge & stops up,when this happens it holds pressure in the lines----you will need to remove master cyl & take apart for a rebuild when you hone out the cyl look inside where the cups go you should see a very small hole----clean it with a torch nipple cleaner & put it all back together -its fixed

 

Chris, you're right. I should have had my spell checker on. You're probably right about the prop valve, too. I get my brass or aluminum combination prop valves from Old Irish Dave in New Mexico. He sells new MBM disk brake conversion kits and parts on eBay and he is a professional brake guy. If you want, here's his number: 575-544-4729.

I see you're in Conn., but here in Detroit, when our brake lines rust open, we use CUNIFER brake line. The alloy is, CU=copper, NI=nickel, FE=iron. This stuff is amazing and it invert-flares like butter. New cars in Europe come with it from the factory, like Audi and Volvo. Even though the price is double that of steel, it's well worth the money because it never rusts. If you need some, I can get it for you. - Dave

 

Dave -

Thanks for the tips. I've gotten stuff from Old Irish Dave before and have no complaints. I may well go with an adjustable proportioning valve, just 'cause I believe that having the ability to adjust is better than not.

I'll have to look into the lines you mention. If I can't find it locally, I will drop you a line.

I'm curious to see if we can ID the MC. Took me a week and a half to ID the rear end and brakes. I'd like to know what it's out of, since I suspect that I may have to replace that as well.

BTW, where in Royal Oak do you live? I lived there for 4 years in the early-mid 90s when I worked for the Stroh Brewery. Lived on 9th street, right off of Woodward. Had a house with 3 other guys...single, of course, and Royal Oak was a great place to be young and single at the time...probably still is.

Miss those days, except when the cops used to bust our parties, which was every time...

Chris

 

Barsteel, I have the same problem, except that I have 4 wheel disc. Everything is brand new, everthing. I bought a mc, power brake set up off of fleabay. When I drive
for maybe 15 minutes, I can feel the front brakes locking up and it takes more and more power to get it back home. As soon as I get home, I jack up the front end and I can't turn the wheels. The back wheels are fine.
Like you, I checked everything and could not find the problem. I have come to the conclusion that the combination valve has to be at fault. I've had three different mc's on it, all new.
I am now in the process of taking the combo valve off and putting a Wilwood adjustable proportioning valve in its place to see what it does. Good luck with yours
and if you figure out what the problem is, please post it. I'll let you know if it fixes mine.

 

my truck was also doing this but has the original drums . I bled the system really good and adjusted all 4 on the loose side . also rebuilt 1 wheel cyl . replaced shoes and drum on that one too , it seems fine now . this truck was sitting for a very long time . just driving around the block for now staying close to home .

 

Thanks to everyone for their help so far.

Here's part II of the saga...trying to ID my MC.

Pictures speak louder than words, so here it is. Mounting bolts are 3 3/8" center to center. Cover is held on by a single wire bale.

Anyone recognize this MC?

Thanks...

Chris

 

I think late '60s/'70s GM, I know it's old and needs to be rebuilt or replaced. It matches the vintage (+ or - 40 years) and condition of the cast iron combo valve.

 

Bob -

I think you're right. Did some digging on Rockauto.com and Raybestos.com, and found that the most likely match is their part #MC36317, a manual disc/drum MC with a 1 1/8" bore, used on '69 Camaros and 69 - 74 Novas. It matches visually and has the same center to center measurement for the mounting bolts (3 3/8 as I measured it, 3.4" according to NAPA's tech line).

I could also use Raybestos MC36376, what the tri-five guys call the "C3" MC, used from '69 - '76, with a 1" bore.

There's actually a really good thread on Master Cylinders on trifive.com http://www.trifive.com/forums/showthread.php?t=33201

I know that a smaller bore MC is supposed to be better with manual brakes at the expense of pedal travel, but I'm going to wait until I pull the MC to see what was on there before I order a new one. I was going to see if the problem was fixed with a new proportioning valve, but since a new MC is only $30 or so and I don't know how old my existing one is, I might as well replace it while I'm under there and dirty.

Chris

 

Man! Seeing that MC makes me glad I live on the West Coast. At least our rust comes from above with the fog, not from underneath from the salt in the roads.