'64 F100 Wont Stop

Not quite sure what else to do! The truck has the stock drums all the way around, fairly new brake lines, a dual chamber master cylinder kit with brake booster. The brakes have been adjusted and the truck still does not stop, if not worse than it did before the dual chamber setup. Any suggestions?

 

How much vacuum do you have at the booster ?

 

So.. what did we start with? Before the booster and such did the brakes work? are the cylinders any good? if they are siezed no amount of bleeding will do much to make them work.

 

The brakes on the truck sucked from when we bought it. The original single chamber master was so clogged and rusted my father wanted to install a dual chamber. Last time I remember the wheel cylinders were in good shape and the rest of the brakes are all new. (shoes, springs etc.) I'm not sure about how much vacuum though. You really gotta stomp on the brakes and the truck just glides to a stop.

 

If the MC was pooched and full of nasty, I'd be checking all the cyls and lines. Is the bore of your new MC the same as the old one? if it's smaller there could be an issue. also if the front and rear lines are reversed.

 

It doesn't stop? Or it doesn't stop like the four wheel disk brake daily driver you have?

Do you have a firm pedal or a mushy pedal?

Are the wheel cylinders in good condition? Either new or freshly rebuilt.

Are the brake shoes in good condition and not glazed over or worn down?

Are the brake drums within specifications and not turned over the limits?

When you replaced the brake lines did you use the same size as the original lines?

Are all of the shoes installed correctly? With the shoe with the least lining on the front and the one with the most lining on the rear. Usually the secondary shoe will have longer lining than the primary shoe or some primary shoes have a groove cut though the middle of the shoe length wise. Some cheap ones also have a different compound in the primary and secondary shoes.

Most of the problems with brakes when someone brought me a car to straighten out after they had "done the brakes themselves" come from installing components wrong, leaving parts out or getting grease or other foreign material on the brake lining when they installed the brakes.

 

Meaning you looked at the wheel cylinders and they didn't appear to be leaking but did not take one or more apart to actually check the insides of the cylinders I assume. I would pull the wheel cylinders apart and take a look at the insides of them. My bet is that the pistons are stuck in the bores of some of them if you haven't had them apart and cleaned them up.

 

Is your MC mounted on the frame? if so you need residual pressure valves.

 

By '64 the MC was on the firewall. To the original poster, did you bench bleed the MC before you installed it?

 

Here is onw that none else asked. Is the new master the same stroke as the old master cylinder? If the stroke is longer, which is common it won't matter what you do to the rest of the system it will never stop well.

 

It seems that he has pedal... just hard to push and have it stop. I would check the booster first. Pump all the air out of it, step hard on the pedal, start the truck. The pedal should drop a little, I'd say around a 1/2" at least. A non-op booster and the pedal will not drop at all.

I like the other tip on glazed linings since the brakes were always bad. Have the drums cut, give the shoes a good 60-grit sanding or replace them. Of course this assumes you have completed Brake 101 and have gone through the hardware, hydraulics, etc first.

Bob

 

Good point... can't have a 6" stroke with a 4" tool....

It may be bottoming out before it gets enough stopping done.

Bob

 

New master cylinder, power booster and the old drum brakes...

Gonna suppose the MC and booster are of the Street Rod variety and the bore size is 1.125" diameter?

Far too many variables to determine what is wrong, some systematic troubleshooting is in order.

 

AFU flex lines?

 

Stroke is a good point, however as brakes sucked before, I'd look at what has not been changed.

 

How new are the brake hoses? I've seen old ones that looked great but were plugged up and had no flow that would give these kind of problems. But like Elpolacko said too many variables without a systematic troubleshooting checkup.

 

You can bleed brakes all day long. Just because you have fluid at the bleeder doesn't mean the cylinders are working. Check the wheel cylinders 1st but sounds like beaner hit it again. Your stroke on the brake rod is to short to fully activate the master cylinder.

 

First, did you buy a disc brake MC by mistake?? Are both reservoirs the same size?? Or is one larger?? If its a disc MC, there are no residual valves built into the front. Let's take this step by step. Tell us what you bought.

 

Flexible brake lines swolen shut ? Vac hose for booster soft and collapsing?
Wasps built a nest in vac fittings ,hoses?
If everything else o k try above.
kenny.

 

Had the same problem with my 61 when I changed to a dual MC. Check the length of the pushrod. It might not be contacting the piston til 1/2 stroke.

 

Yeah there definitely seems to be some factors to look into. Granted, all of this stuff was installed awhile ago and now we're working on it again. We're going to start from the ground up. Clear all the lines, inspect all the wheel cylinders again, check push rod length and check the vacuum on the engine. From what my dad can remember he bought the dual MC and booster kit from Speedway.

So my next question is does anyone know what the bore is on the stock single MC? I'll check it with the bore on dual MC we have now.

Thanks for the help fellas.

 

check for collapsed flex lines, have to remove them as they dont show visably.Had that problem with mine drove me nut's for a week and 3 masters

 

I always buy a stock off the shelf MC close to the size of the vehicle it's going into. In your case, I'd be buying a '67-ish dual master from the same series Ford truck. This eliminates any bore size issues and sometimes the fit is ridiculously easy.

Bob

 

Make sure the portion of Master cyl meant for the front brakes is actually hooked to front brakes[largest side of reservoir]......lots of folks confuse this.
As to wheel cylinders and shoes and =LINES=, get off yer ass and put new ones[properly adjusted] on with metallic shoes and it will then have a decent braking action.....

 

Yep, they can break down internally and become like a check valve. I had one that would allow fluid forced to the caliper, but would not let the caliper release. It wasn't until I removed the line and tried to blow into it that I realized the problem. Could be yours are plugged up.

 

With a collapsed flex hose, you usually get a pull condition, it pulls to the operating side. I would still replace all of them just to rule them out and especially of they are suspected to be original.

I still think the basic poor-stopping condition is probably due to glazed linings/drums or a pedal stroke issue. Possibly a master bore incompatibility.

Bob