Need opinion on brake issues

[prayers1 153]

I redid my entire brake system this year. I installed a rebuilt Brake pwr booster and MC from Mustang Steve's, he also supplied the correct brake pedal.

I have a 1969 Fastback but changed the spindles to a 1970 with the 1970 front disc brakes, The rear has if IIRC, 2 1/2 or 2 1/4 drums. I rebuilt the 1970 port/dist valve, parts were sourced from Muscle Car Research.

I put Stainless Steel Brakes lines all around.  All of the drum brake hardware is new and the rear wheel cylinders are new as well.

Per my other post I installed a vacuum reserve canister due to lack of vacuum from too large of a cam. I haven't resolved that issue yet, but the car is stopping but not as best as I wish.

Here's my concern: I've bleed the brakes several times and made adjustments to the drums to the point that I second guess myself if they are too tight. When I have some one apply the brakes with the car not running I can still with great effort turn both rear tires. When I go for a test drive and slam the brakes the brakes do not lock up. I had the disc and drums on the previous manual system and the rear would lock up but not the front. I was thinking that I have a heavy metallic brakes shoe in front that might keep it from locking up.

I thinking that most of my stopping pwr is coming from the front with very little assistance from the rear.

What can I do to get more from the rear. My adjustment is more on the heavy side so I thought maybe to adjust the parking brake, but I don't know if that would help.

What do you all think?

 

 

 

 

[Brian Conway 264]

Can't really be of any sure cure help but can say that no amount of effort should turn those rear wheels with someone standing on the brake pedal.  Stopping power is roughly 60% front and 40% rear.  On my stock power disc brake car when stomping the brake pedal the rears lock up but not fronts.  When adjusting the rear drum brakes I adjust until I can Just hear the drum/shoe make contact and back off just a touch.  Adjusting the E-brake is best tested on a slanted driveway.  Maybe take a look at those rear drums and check to see that the long (secondary) 10-1/2" shoe is at the rear position ?  Brian

[69Stanger408 82]

Did you bench bleed the MC prior to installation? Without a properly bled MC, regardless of the bleeding at each wheel you will never have sufficient pressure in the system to stop the vehicle as intended.

[jmlay 80]

Not ruling air in the lines or master but the drums had self adjusters. Baskup quickly and apply the breaks with steady pressure until you stop, repeat a couple of times.

[prayers1 153]

Hardware is installed properly, I did do the back up to do the self adjuster and MC was bench bleed.

I'm thinking of getting one of those brake handheld vacuum pumps.

[unilec 57]

Just a couple off questions, do you have a proportioning valve in circuit? Some of the distribution blocks have a built in Piston that can block off feed to either the back or front system, if it sees a difference in pressure, you can check if its moved with a multi meter.

[Brian Conway 264]

10 hours ago, prayers1 said:

Hardware is installed properly, I did do the back up to do the self adjuster and MC was bench bleed.

Well something is not right if you can turn those back wheels by hand.  Brian

 

[LoneWolf2U 136]

From your post, I would look at your prop valve for plunger centered. The pressure is low to the rear wheels.

Do you get a steady pressure flow when you bleed the rear? If so how much fluid comes out?

Minimal flow or amount indicates the plunger is not centered partly blocking fluid to rear.

[jmlay 80]

Does the master have a residual pressure valve for the drum brakes, if not it should or have a valve plumbed in-line.

 

[prayers1 153]

There is a metal pin that you can buy that screws where the  plastic Brake Light Pressure Switch Pin screws in. This allows you to bleed the brakes w/o the Port valve being triggered.

After bleeding the brakes I replaced the metal pin with the correct Brake Light Pressure Switch Dual Pin.  I can say that the brake warning light does not com eon.

I do have weaker pressure in the rear when bleeding the brakes. So now I can say, maybe I messed up rebuilding the Port valve. Maybe the slide bar in the valve is stuck, I don't know?

What Mach 1 Rider mentioned it looks like I may have a Port Valve issue, Still I'm not sure???

[stangs-R-me 120]

Could you maybe have a bad rear brake hose that is partially collapsed ??   I've had this on a couple of cars in the past and the guy at my parts store says it is pretty common.   Although not common, he'd even seen it on a brand new hose too.

The first car I witnessed it on ('95 Taurus SHO) one of the two back hoses was completely collapsed and we could not get ANY fluid out of that side no matter how hard we pressed on the brake pedal.

Doug

[prayers1 153]

There is but the one hose to the rear that divides the two lines, that is new.

[stangs-R-me 120]

41 minutes ago, prayers1 said:

Maybe the slide bar in the valve is stuck, I don't know?

 

Mine was not stuck, but I had a bad piston seal between the two sides of the rear proportioning valve ('68-69 style dist-block with external prop-valve) so my system was bypassing the proportioning valve and giving full brake pressure to the rears all the time ... opposite of your issue.   If the dash light is not on, then the piston has to be centered ... stuck in the middle (with no bad seals) should not cause any problems.

There is some troubleshooting in the Ford Shop Manual that shows the dist-block piston positions ... maybe if the piston was shifted towards the rear brake side it would limit pressure to the back but then your light should be on too.   I'm out of town so don't have access to my shop manual to verify. 

Doug 

[Brian Conway 264]

Have to agree.  If no warning light; will just assume, everything is OK there.  Because you have mixed some of the parts is it possible that the master cylinder or the brake cylinders are the wrong size ?  Pretty sure the manual brake and power brake MC's are different and the same for PDB MC's 69 to 70.  Pictures are of the 69 stuff on my car.  Mustang Steve may be a resource that you should use ?  Brian

[LoneWolf2U 136]

Without you checking the light function insuring it lights, Its a process of elimination to see where the problem lies.

Lines and hose is good.  Wheel cylinders good. master and booster good.

Front brakes work correctly. Rear will not hold with pad adjustment correct.

Only then left in the system is the prop valve, The pin does not have to move much to restrict flow to the rear.

When you bleed the wheel cyl, Does the fluid flow freely and with volume?

If not your looking for the point the flow starts to be compressed. 

Last point is the master cylinder, Does the fluid flow out from it with volume and pressure?

If not maybe the booster rod is not properly set.   Just a thought because your not getting any front lock up.

[prayers1 153]

I never got front lock up even when I had the same disc set up with manual brakes.

I purchased the Booster / MC from Mustang Steve's, there was no adjustment on the Booster rod but the rod did have the drop down as needed for a 1969.

All lines and hoses are new, no kinks. It maybe the Port/Dist block, but I'd like to try a mini  vac at the rear to see that it is properly bleed. Good knows how many times the wife and I bleed those brakes.

 

[Ridge Runner 1,112]

If the proportioning valve is tripped ,and i think that is the problem ,it will not mater how many times you bleed the brakes you will still not get fluid to the rear brakes 

[LoneWolf2U 136]

18 minutes ago, prayers1 said:

I never got front lock up even when I had the same disc set up with manual brakes.

I purchased the Booster / MC from Mustang Steve's, there was no adjustment on the Booster rod but the rod did have the drop down as needed for a 1969.

All lines and hoses are new, no kinks. It maybe the Port/Dist block, but I'd like to try a mini  vac at the rear to see that it is properly bleed. Good knows how many times the wife and I bleed those brakes.

 

Booster adjustment is on the rod that goes into the master cylinder. So you have the correct booster to petal rod for the proper stroke from petal to booster, But do you have the proper rod set up from the booster to master?  Improper length in this rod will cause poor brake operation.

[prayers1 153]

I don't believe there is anything wrong with the stroke of the pedal. It only bottoms out when I bleed the brakes.

How would I know if it needs adjusting and do all have this adjustment?

[RPM 1,190]

I've been following your brake issues here and at MS Prayers awaiting a fix.  I don't remember,  but have you used a brake line pressure gauge at the caliper & drum bleeder port to see what line pressures you have? I purchased a SSBC I think pressure gauge with adapters to fit the bleeder for about $30. It might help eliminate some areas. 

[LoneWolf2U 136]

11 hours ago, prayers1 said:

I don't believe there is anything wrong with the stroke of the pedal. It only bottoms out when I bleed the brakes.

How would I know if it needs adjusting and do all have this adjustment?

Booster to master adjustment is on the rod tip of the booster. You have to remove the master and measure the depth of the masters plungers hole and compare it to the rods length.

If you got the booster/master as a set contact the supplier and see if they preset it to match.

[1969_Mach1 333]

Wow, a lot of brake issues.  I wonder if its something as simple as the rear brakes do not lock up with hard braking because there is not enough power assist?  Without power assist on a power brake system it's almost impossible to apply enough pedal pressure to lock up the brakes.  If not that, not much left other than some type of restriction, maybe the proportioning valve.

The OP has no complaints of a low brake pedal, therefore the push rod between the booster and master cylinder is probably adjusted correct or very close.

[prayers1 153]

When Mustang Steve sent the complete package out, he sent the wrong MC. I was told they only had one other MC left which is the 2nd one sent to me. The difference was the fittings on the MC, they sent a 69 instead of a 70, since I am using the 1970 brake lines and Port valve. Point is, there was no preset match to MC & Booster and I was never told or aware that I had to set the push rod depth, which would of been a very simple thing to do prior to installation.

Yesterday I was running power steering lines for the Borgesen PS box and saw the bottom of the Brake Booster paint all blistered from heat ( I painted it prior to install).  I have the Sanderson's Shorty headers. They are not close enough or touching the Booster but I'm sure a lot of heat does build up there. Could heat be a factor on the Boosters performance?

Yesterday I picked up the Mityvac MV8000 at a local parts store, now I have to find the time and figure how to use it.

 

 

[det0326 179]

How are you running your power steering hoses?  I ran mine initially from PS box around shock tower to pump but quickly decided I didn't like the look of it. So I went thru the rear fender apron to the wheel well and up to the top of apron lip to the front apron and thru to the pump. I also put a cooler for the PS pump due to the heat build up in the PS box form the headers . 

[prayers1 153]

I ran mine from the box around the shock tower but up near the valve cover, then to the pump. I bought the Borgesen 6 cyl hose's since the pressure line was a little longer than the 8 cyl.

I went to a local shop, measured the high pressure line, cut and put a new fitting. But before placing the fitting on I installed a Heatshield Products blackk1000 degree 3/4" heat sleeve.

I think it looks OK, not to crazy about the hose in view, but I am very happy with the Borgesen PS. It feels great to steer the car with one hand at a stand still.