Rear wheels still spin while in drive with foot brake depressed

[The Granny]

I recently had some work done on my car by Madman Racing, I had new axles, posi unit, wheels studs, and a few other misc. items installed. When I picked up the car from him, I took it to the track the next day. Per his instructions, I broke in the new posi unit. I heard a screeching noise on the way back to my trailer after the first pass, and called it quits and loaded up and took it home. I jacked up the front end, spun the front wheels, and they did half a rotation. The front calipers were grabbing onto the rotor for some reason without me pressing on the brake. I got new calipers, attempted to bleed the system (power master) myself but couldn't get fluid out of the rear bleeder valves. Took it to another shop, Century Automotive (owned by Mike Kurtz) a few days later to have them attempt to bleed the brakes.

What he told me is the proportioning valve was stuck shut, so they removed it, cleaned it, and put it back in and the system bled just fine. Charged me $120 for it

Got the car home, as soon as I put it in park, I got a huge transmission fluid leak. I found the source to be a loose cable in the back of the transmission (maybe speedo cable? 200r4 trans.). Tightened it up, and since I had the car on Jack stands I figured I'd start the car and cycle through the gears to check for any leaks. Ran through them just fine, no leaks, but my father who was outside the car watching for leaks saw the rear wheels spinning and told me to put my foot on the brakes. I did and they still spun. I mashed the pedal down and still no change in how fast the wheels spun.

Could it be the proportioning valve stuck shut again, and it's not allowing any fluid to the rear drums? Not too sure of what it could be... Im not blaming anyone and don't want to sound like one of those "ever since you worked on my car it's done this" type of guys, I just want my brakes to work [emoji23] Huge thanks in advance to anyone who can help me out with this.

Giancarlo


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[bryesh]

It could be the proportioning valve, air in the lines (l maybe from a bad line or house), or your rear brake adjusters are out of adjustment. I'd start by checking for leaks, then adjusting your rear brakes. If that doesn't work try bleeding. If bleeding and adjusting didn't remedy, then look at proportioning valve.

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[Chuck Leeper]

Old style prop valve? {Cast iron} If so, change it to the new design, brass valve.

 

[The Granny]

I'll do just that, check for leaks in the lines then try a new valve. I've tried adjusting the rear brakes but it still had the same problem.

Yes Chuck, it's the stock valve actually. The more I thought about it, logically itd make the most sense to be the valve gone bad so I went ahead and ordered one last night. Hopefully this solves it.. once I put the new valve in will I have to rebleed the brakes?


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[Chuck Leeper]

I'll do just that, check for leaks in the lines then try a new valve. I've tried adjusting the rear brakes but it still had the same problem.

Yes Chuck, it's the stock valve actually. The more I thought about it, logically itd make the most sense to be the valve gone bad so I went ahead and ordered one last night. Hopefully this solves it.. once I put the new valve in will I have to rebleed the brakes?


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Yep. Some clamp the valve, so the pin in the ft is depressed, when bleeding the rears.
Also, on the fts dragging, start the engine, and press the pedal several times. Shut off, check to see if the fts are dragging, crack the ft line at the m/c, and see if there's pressure there. Could be the m/c is defective, or the pedal is not allowing the piston to retract fully, holding psi.
Also, if the caliper pins are dragging, the caliper may not be floating, causing drag.
If the disc turns 1/2 and drags, the rotor is warped.

 

[The Granny]

Yep. Some clamp the valve, so the pin in the ft is depressed, when bleeding the rears.
Also, on the fts dragging, start the engine, and press the pedal several times. Shut off, check to see if the fts are dragging, crack the ft line at the m/c, and see if there's pressure there. Could be the m/c is defective, or the pedal is not allowing the piston to retract fully, holding psi.
Also, if the caliper pins are dragging, the caliper may not be floating, causing drag.
If the disc turns 1/2 and drags, the rotor is warped.

I can get a small clamp that is used to bleed them, so I'll try that out. With the new calipers on the front I already did a check spin with the wheels on and they spun like normal. Once I rebleed the brakes when I get the new prop valve in, I'll test it out though. Hopefully the rotor isn't warped, but thanks mentioning that I didn't think about it being warped as a possibility


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[hotairgnx548]

I recently had some work done on my car by Madman Racing, I had new axles, posi unit, wheels studs, and a few other misc. items installed. When I picked up the car from him, I took it to the track the next day. Per his instructions, I broke in the new posi unit. I heard a screeching noise on the way back to my trailer after the first pass, and called it quits and loaded up and took it home. I jacked up the front end, spun the front wheels, and they did half a rotation. The front calipers were grabbing onto the rotor for some reason without me pressing on the brake. I got new calipers, attempted to bleed the system (power master) myself but couldn't get fluid out of the rear bleeder valves. Took it to another shop, Century Automotive (owned by Mike Kurtz) a few days later to have them attempt to bleed the brakes.

What he told me is the proportioning valve was stuck shut, so they removed it, cleaned it, and put it back in and the system bled just fine. Charged me $120 for it

Got the car home, as soon as I put it in park, I got a huge transmission fluid leak. I found the source to be a loose cable in the back of the transmission (maybe speedo cable? 200r4 trans.). Tightened it up, and since I had the car on Jack stands I figured I'd start the car and cycle through the gears to check for any leaks. Ran through them just fine, no leaks, but my father who was outside the car watching for leaks saw the rear wheels spinning and told me to put my foot on the brakes. I did and they still spun. I mashed the pedal down and still no change in how fast the wheels spun.

Could it be the proportioning valve stuck shut again, and it's not allowing any fluid to the rear drums? Not too sure of what it could be... Im not blaming anyone and don't want to sound like one of those "ever since you worked on my car it's done this" type of guys, I just want my brakes to work [emoji23] Huge thanks in advance to anyone who can help me out with thisUOTE]
Why not take it back to the guy you paid to fix it? john

 

[hotairgnx548]

why not take it back to the guy you already paid to fix it? john

 

[The Granny]

why not take it back to the guy you already paid to fix it? john

I thought I could trust them to do the job right the first time, evidently they couldn't so I'd rather do it myself that way I know it's done right. at the time I made this post, I had no clue what the issue could be and that's why I took it to him so he could diagnose it, and if he could fix it easily/at no cost then I'd go that route. I don't mind doing it myself now that I have a clue as to what it could be. I got the new valve in last night and I'll be bleeding the brakes today to see if that's the issue


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[Wahoo]

It's because you have the car in the air. With no weight on the back the tires will spin even with your foot on the brake.

At least it did that with my car.

 

[The Granny]

It's because you have the car in the air. With no weight on the back the tires will spin even with your foot on the brake.

At least it did that with my car.

I couldn't hold any boost on the footbrake. Won't even hold 0psi.

Im going to be bleeding them here within an hour


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[Wahoo]

I couldn't hold any boost on the footbrake. Won't even hold 0psi.

Im going to be bleeding them here within an hour


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Yeah I couldn't brake torque it and make boost either with my car in the air.

I'm sure when you put the car back on the ground it will be fine.

 

[The Granny]

bled the brakes finally tonight, maybe my method is flawed but I'm still not getting good results. after I bled them I took the car around the block, the pedal felt super soft halfway down then firmed up after that and stopping power was normal once again. It was like this for the 10 minutes I drove it. I did replace the stock prop valve for the brass unit. Any other ideas of what could be an explanation? I followed the instruction on here with the exception of performing the actual bleeding 10-15 times as it states. I did it only 3-4 times since the fluid flow became steady and air free at those times. But the pedal was still soft halfway down, then afterwards the pedal became firmer and stopping power was normal. After trying the gnttype method with no success, I tried to follow the same steps again however this time with the ignition off. Same results, soft pedal with no stopping power 1/2 way down and normal pedal with good stopping power after that.

also after I tried these two methods, I couldn't hold boost on the footbrake, just like before.

on my latest attempt to bleed them with the ignition off, while i was bleeding the left front I noticed no fluid came out. then realized the brake like was loose. tightened it up, then I resumed with the bleeding. could this be a possible explanation?

would switching to manual brakes simplify some of these issues? it's something I've been thinking about but haven't done too much research on. sorry for all of these questions, I just want to get this squared away

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[Chuck Leeper]

Been mentioned before.....Get a brake pressure gauge. Not expensive.

 

[Coach]

Have you started with the Powermaster first? There is a process on here that tells you...1st, how long the pump motor should run, 2nd, how to depress the fluid in your accumulator ball, and let it pump back up and then start the bleeding process.
I will actually be doing this entire deal later today as I just got my Powermaster back from Richard Clark. He completely restored it to original and rebuilt the entire thing right done to the pump motor.
I still have the cast iron valve on my car but it has worked flawlessly.
I'll let you know if I expeirence any issues today. Good luck with your adventure. These cars are always causing head scratching.

 

[No disintegrations]

It's because you have the car in the air. With no weight on the back the tires will spin even with your foot on the brake.

At least it did that with my car.

Im sorry but this makes no sense. If it cant hold a 30 pound wheel still how can it slow down a car?

 

[No disintegrations]

bled the brakes finally tonight, maybe my method is flawed but I'm still not getting good results. after I bled them I took the car around the block, the pedal felt super soft halfway down then firmed up after that and stopping power was normal once again. It was like this for the 10 minutes I drove it. I did replace the stock prop valve for the brass unit. Any other ideas of what could be an explanation? I followed the instruction on here with the exception of performing the actual bleeding 10-15 times as it states. I did it only 3-4 times since the fluid flow became steady and air free at those times. But the pedal was still soft halfway down, then afterwards the pedal became firmer and stopping power was normal. After trying the gnttype method with no success, I tried to follow the same steps again however this time with the ignition off. Same results, soft pedal with no stopping power 1/2 way down and normal pedal with good stopping power after that.

also after I tried these two methods, I couldn't hold boost on the footbrake, just like before.

on my latest attempt to bleed them with the ignition off, while i was bleeding the left front I noticed no fluid came out. then realized the brake like was loose. tightened it up, then I resumed with the bleeding. could this be a possible explanation?

would switching to manual brakes simplify some of these issues? it's something I've been thinking about but haven't done too much research on. sorry for all of these questions, I just want to get this squared away

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You likely have some trapped air in the system. It can take a while to bleed a system that's been so far apart like yours.
Maybe you tried this but I like to open the bleeder, then push the pedal. It will move more fluid than the "pump then open "way.
When the pedal stops moving the shut bleeder. Repeat until no air and clean fluid is coming out.

 

[The Granny]

what kind of numbers should be shown on the pressure gauge?

Coach, no I haven't started with the powermaster. I went straight into the bleeding process. Could you post the link to the steps you're mentioning? Thank you for the good luck wishes... I've had this car for about 3 years now and luckily up until this brake issue its been relatively smooth sailing.

I'll try that while bleeding next time, No disinigrations.

Thank you all for your help!


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[Wahoo]

Im sorry but this makes no sense. If it cant hold a 30 pound wheel still how can it slow down a car?

I remember mind doing this as well but I also had to adjust my rear brake shoes to tighten them up.

The front brakes do most of the stopping. When you're launching your car at the drag strip your front brakes are also preventing the car from going forward.

 

[The Granny]

One step forward, two steps back.

I bled the accumulator, then the master cylinder per the instructions here: http://www.turbobuick.com/threads/the-powermaster-bleeding-procedure.218912/ then I bled the cylinders/calipers using a vacuum pump. I only went to 12" on the pump, I got large air pockets to begin with then small ones, then virtually none. Started the car, no brake light on, pedal felt nice and firm while in park, still on jack stands with the wheels off. I then put it in drive and let the wheels spin for a bit then pushed the brake pedal and the right rear drum came flying off soon after. The shoe on the front side of the right rear was offset out of its spot. The master cylinder was spongy on the front side when I pushed it in with my hand, it would compress then return back to its original spot once I released it. I'm thinking this shouldn't be happening since the rear side of the cylinder does the opposite, if I compress it it'll stay compressed?

or maybe the drum flew off and shoes became out of their spots because there wasn't a wheel on?

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