Brake problems.

1935 Ford, 302 engine, mustang II front end. I believe I have 79 to 82 ford rotors (I think they are 11"). This car has only 2000 miles on it since it was built about 9 years ago. It was setting for a while before I bought it. My first problem which seems to be ongoing was poor brakes. I replaced the front calibers, rotors turned, new pads. Turned rear drums, new wheel cylinders. Bled brakes and still very poor stopping power. It has a 7 inch power booster with a 1" bore, 2 port master cylinder (located under the driver side floor board). I just replaced the power booster and master cylinder. Brakes are still terrible. I have tried setting the proportion valve from all the way open to all the way closed. The only positive result was that when nearly setting for full pressure to the rear I have some stopping power but mostly from the rear drums. It seems I am not getting the proper response from the front disk. Today I removed the master cylinder and adjusted the booster rod to the master cylinder so it had just a slight play in it before it pushed the cylinder piston. Slight improvement but not much. I have bled the brakes over and over and have firm pedal. When I stomp on the pedal with all I have the brakes just don't seem to be doing much. I can stop the car but would hate to be in an emergency stopping situation the way the brakes are. I don't know what to do next, short of riping out the brakes and starting over with a new system. Oh, by the way, I have about 16 inches of vacumn at the booster. Any ideas would be appreciated.

Thanks,

Teddy

Might want to try a residual valve, one in the rear line and one in the front.... Most all the companies have them. (Speedway, Summit, Jegs, etc)

I've found that when the master cylinder is at a level lower then the calipers/wheel cylinders the residual valves are necessary, and about the only way to get them bled totally is with a power bleeder.....

Thanks. I forgot to mention that there are two residule valves. A 2 pound for the front and a 10 pound for ther rear. I did bleed with a vacumn pump and also with someone pushing the brake pedal for me. I did not run the engine when I was doing the manual bleeding via the brake pedal. A friend of mine advise that I needed a power bleeder also. Maybe I'll have to try to locate one and give that a try. Thanks for the input.

Teddy

You said that you THOUGHT they were 11 inches---lots of the ford brakes of those types are 9 inch---most of the better ones are 11 inches and also use GM calipers
I have been using speed bleeders on my unusuak stubb as It really simplfies bleeding duties

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Originally Posted by jerry clayton

You said that you THOUGHT they were 11 inches---lots of the ford brakes of those types are 9 inch---most of the better ones are 11 inches and also use GM calipers
I have been using speed bleeders on my unusuak stubb as It really simplfies bleeding duties

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I have never heard of speed bleeders. Can you explain and where do you get them? The rotors are larger than 9". I didn't actually measure them. But a friend told me they were 11". He has 9" and my rotors are definately larger then 9". The calipers are ford. It says ford on them.

Thanks,

Teddyh

I've had occasional problems with the small boosters not developing enough pressure out of the master cylinder. You might want to check this with a brake pressure gauge.... Also, curious what your pedal ratio is????

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Originally Posted by Dave Severson

I've had occasional problems with the small boosters not developing enough pressure out of the master cylinder. You might want to check this with a brake pressure gauge.... Also, curious what your pedal ratio is????

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As far as the small booster, I was wondering a while back if a larger booster would work better. The problem I have is that it is mounted under the floor and there doesn't seem to be enough room to go larger than the 7 inch booster. I purchased it from Chassis Engineering along with the 1" Corvette master cylinder. According to them, this setup should word fine.

I didn't know there was such a device as a brake pressure gauge. I'll check locally and see if one is available. As far as the pedal ratio, I'm not sure what that means. If you mean the distance of throw before the pedal activates the booster, it is approximately 3/4 to 1". I am temped to adjust the booster rod into the master cylinder a little more but I have been cautioned that if this engages the cylinder piston to soon I'll have additional problems. I'm having trouble understanding the need for a power bleeder but it seems that there is an opinion that these type of systems can't be bled properly without one. I have always bled brakes the old fashion way or with a vacumn pump with sucess in the past. Of course this was done to conventional stock cars and not with a hot rod. Since I haven't been successful with my approach I will try what has been suggested by the members of this site. My fear is that possibly the existing setup is not appropriate and I am just spinning my wheels. Again, it seems there is not enough pressure on the front calipers. Your suggestion of a brake pressure gauge should provide that info. What kind of pressure should I read?

Thank you for the suggestions.

Teddy

Speed bleeders are a bleed screw with a check valve so you can do the messy job yourself and without having someone to yell at " pump it - hold" while you're crawling around under the car. They work great. Have 'em in my project (AVATAR) car and just put them in my truck's calipers.

Russell/Edelbrock($$$) and Dorman Products ($$) at your neighborhood real (not Auto Zone types)auto parts store have them

here is info on pedal ratio:
http://www.mpbrakes.com/uploads/docu...alratiopdf.pdf

Pedal ratio is built into the system...it does not change by itself....it is a fixed ratio that the linkage defines.

Thanks to everyone that provided input. I now have some fresh ideas to tackle my problem. I'll let you know how I make out.

Thanks Again,

Teddy

Two things to maybe better simplfy what everyone has said---Most Hot rod Mustang ll type brakes use an GM caliper which has more area than the Ford caliper---also, the 1 inch Corvette master combined with the small ford calipers won't give you a good hydraulic advantage---you might want to use a master with 7/8 diameter

With the speed bleeders I filled the system and did all the bleeding of all 4 corners in less than 10 minutes

Good luck

Teddy, I have an excellent article written by Dean Oshira on braking system theory, components, and operation .... If you'd like a copy of it, PM me your email and I would be glad to send it to you.


Good luck with your problem and let us know what you find out.

Quote:

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Originally Posted by teddy

I didn't know there was such a device as a brake pressure gauge.

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There are several different gauge sets out there. If you're only going to use it once or twice a simple setup like THIS should work just fine.

Quote:

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Originally Posted by jerry clayton

Two things to maybe better simplfy what everyone has said---Most Hot rod Mustang ll type brakes use an GM caliper which has more area than the Ford caliper---also, the 1 inch Corvette master combined with the small ford calipers won't give you a good hydraulic advantage---you might want to use a master with 7/8 diameter

With the speed bleeders I filled the system and did all the bleeding of all 4 corners in less than 10 minutes

Good luck

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Thanks Jerry but I have 11" rotors which I believe are Thunderbird rotors. Also, my neighbor has a 39 chevy with a mustangII front end with 9" rotors. His brakes will throw you through the windshield. His master cylinder and booster is on the firewall where my system is under the floorboard.

Teddy

Quote:

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Originally Posted by Dave Severson

Teddy, I have an excellent article written by Dean Oshira on braking system theory, components, and operation .... If you'd like a copy of it, PM me your email and I would be glad to send it to you.


Good luck with your problem and let us know what you find out.

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Thanks Dave, I'll PM you.

Teddy

Its all a matter of mech advantages via pedal leverage and simple hydraulics/master cyl. area---wheel caliper area

And most brake problems are a miss match of selected components and/or the way they are orientated( prop vavves reversed,etc)

A couple recommended starting points are Manifold vaccume and line pressure front/rear---without acceptable ranges here the other points are moot!!!!!

Quote:

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Originally Posted by jerry clayton

Its all a matter of mech advantages via pedal leverage and simple hydraulics/master cyl. area---wheel caliper area

And most brake problems are a miss match of selected components and/or the way they are orientated( prop vavves reversed,etc)

A couple recommended starting points are Manifold vaccume and line pressure front/rear---without acceptable ranges here the other points are moot!!!!!

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I understand what you are saying. All of the components are installed correctly and have been checked and doubled checked. However, this doesn't mean that they are properly matched. Mustang II front end, 11" ford rotors with matching calipers, rear ford drums (9" ford rear end), 7" booster, 1" bore master cylinder, proportion valve, residual valves (10 pound rear, 2 pound front). All components are new or rebuilt except for the proportion valve and residual valves. The only thing left to try that I know of is ordering a pressure gauge and obtain some pressure readings. I just need to know what pressures to expect for a proper operationg system.

Thanks,

Teddy

Quote:

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Originally Posted by teddy

I understand what you are saying. All of the components are installed correctly and have been checked and doubled checked. However, this doesn't mean that they are properly matched. Mustang II front end, 11" ford rotors with matching calipers, rear ford drums (9" ford rear end), 7" booster, 1" bore master cylinder, proportion valve, residual valves (10 pound rear, 2 pound front). All components are new or rebuilt except for the proportion valve and residual valves. The only thing left to try that I know of is ordering a pressure gauge and obtain some pressure readings. I just need to know what pressures to expect for a proper operationg system.

Thanks,

Teddy

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Everything there should be just fine - but one question - do you have a check valve in the MC?? If so it has to come out if you have the resid and proportioning valves.

Also, a 7/8 or 15/16 MC might work better. At one point with a car, I had small single piston Wilwood's on the front and 15/16 wheel cylinders on the back along with a late Mustang 1"+ master cylinder. I ended up with a 7/8 mc and 7/8 rear cylinders and almost power brakes from virtually none.

And another, if you are using silicone brake fluid - don't. This is one fluid that has a very small amount of compressibility plus will react with any regular ethylene based fluid, causing the seals to expand - and a lousy pedal will be the result. Great stuff for racing, but not for a road car.

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Originally Posted by IC2

Everything there should be just fine - but one question - do you have a check valve in the MC?? If so it has to come out if you have the resid and proportioning valves.

Also, a 7/8 or 15/16 MC might work better. At one point with a car, I had small single piston Wilwood's on the front and 15/16 wheel cylinders on the back along with a late Mustang 1"+ master cylinder. I ended up with a 7/8 mc and 7/8 rear cylinders and almost power brakes from virtually none.

And another, if you are using silicone brake fluid - don't. This is one fluid that has a very small amount of compressibility plus will react with any regular ethylene based fluid, causing the seals to expand - and a lousy pedal will be the result. Great stuff for racing, but not for a road car.

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I don't know if the master cylinder has a check valve or not. I assume not since I purchased it from "Chassis Engineering". It is supposed to be a corvette master cylinder and is supposed to work with residual valves and a proportional valve. Before I made the purchase, I asked them about going to a 7/8" bore master cylinder because I heard if would provide more pressure (less volume, more pressure). They told me I need the 1" bore to provide enough volume for the front disc brakes. I made the purchase to replace my existing booster and master cylinder. Unfortunately it did not make any difference. I did play around with the rod adjustment from the booster to the master cylinder piston. I kept extending it into the master cylinder until it caused a drag on the front brakes. I found with some drag the brakes worked better but with a little more out ward adjustment it would cause the brakes to drag so much that I couldn't turn the front wheels by hand when I raised them off the ground. I have now backed the adjustment off to where the rod just barely pushes on the master cylinder piston and the brakes are probably the best they have been but still not as good as I think they should be.

Thanks,]

Teddy

Quote:

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Originally Posted by teddy

I don't know if the master cylinder has a check valve or not. I assume not since I purchased it from "Chassis Engineering". It is supposed to be a corvette master cylinder and is supposed to work with residual valves and a proportional valve. Before I made the purchase, I asked them about going to a 7/8" bore master cylinder because I heard if would provide more pressure (less volume, more pressure). They told me I need the 1" bore to provide enough volume for the front disc brakes. I made the purchase to replace my existing booster and master cylinder. Unfortunately it did not make any difference. I did play around with the rod adjustment from the booster to the master cylinder piston. I kept extending it into the master cylinder until it caused a drag on the front brakes. I found with some drag the brakes worked better but with a little more out ward adjustment it would cause the brakes to drag so much that I couldn't turn the front wheels by hand when I raised them off the ground. I have now backed the adjustment off to where the rod just barely pushes on the master cylinder piston and the brakes are probably the best they have been but still not as good as I think they should be.

Thanks,]

Teddy

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Teddy,
What you are saying is that you are "preloading" the brake hydraulic system by putting fluid down the lines to partially extend the caliper pistons. That would say to me that you have a mc that's too large as far as piston diameter. I really wonder if indeed you actually have a 1" or something larger. The 1" should be correct but remember, an OEM Corvette with power brakes has a 1 1/8" and you might be the victim of a screw up by Chassis Engineering's supplier. With manual brakes, the Corvette mc is 3/4" !!!! Sounds like something that needs some looking into

I would recommend a master from a late 60s ford that had front disc and rear drums---the corvette is for front/rear discs--these masters can be bought new for 60-70 dollars

Does the pedal feel good ? By that I mean spongy or too hard ?
One thing I have encountered in the past is front brake pads that are to hard, especially some of the metallic pads, and not just the cheapies I have seen problems in some of the top name stuff where the car just would not stop.
The answer after several hair pulling hours of diagnostic time was to simply switch the front pads to organic and the darn car would then throw ya thru the windshield.

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Originally Posted by IC2

Teddy,
What you are saying is that you are "preloading" the brake hydraulic system by putting fluid down the lines to partially extend the caliper pistons. That would say to me that you have a mc that's too large as far as piston diameter. I really wonder if indeed you actually have a 1" or something larger. The 1" should be correct but remember, an OEM Corvette with power brakes has a 1 1/8" and you might be the victim of a screw up by Chassis Engineering's supplier. With manual brakes, the Corvette mc is 3/4" !!!! Sounds like something that needs some looking into

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I will follow up on the master cylinder with Chassis Engineering tomorrow. I should have insisted on a smaller piston size.

Thanks

Teddy

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Originally Posted by HWORRELL

Does the pedal feel good ? By that I mean spongy or too hard ?
One thing I have encountered in the past is front brake pads that are to hard, especially some of the metallic pads, and not just the cheapies I have seen problems in some of the top name stuff where the car just would not stop.
The answer after several hair pulling hours of diagnostic time was to simply switch the front pads to organic and the darn car would then throw ya thru the windshield.

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I was asking a friend today if maybe another pad would work better. The pads I have look to be a metallic type. I may try to go to another pad after I talk to Chassis Engineering about possibly getting the wrong master cylinder as others have posted. Thank you for your input and I thank everyone else fore great responses. I am going out of town next Monday for maybe 6 to 8 weeks and if I don't get the problem resolved in the next few days it will have to go on the back burner for a while. When I get this problem resolved I will surely post again to let everyone know if and how it all works out.

Thanks to all,

Teddy