Dragging brakes

Brake system is pretty straightforward system right? Here's the isuue I have been having. 65 beetle, front brakes are ghia calipers and rotors on dropped CB spindles. New, dual circuit master cylinder is correct and adjustments at the pedal cluster are also correct. All parts are not worn or old. The front right brake caliper drags on the rotor. No matter what I have tried, a mechanic has tried, the caliper drags. I have an indicator light inside the cabin which is wired as a brake light, going out when brakes are applied. For some reason the caliper is holding pressure when the pedal is pumped. Also when the brake fluid heats in the sun, the pedal gets harder due to the thermal expansion, and the brake drags. The hoses and line are both new. When the actuator rod was adjusted short, pressure would build and break the rear circuit seal, as it was not returning to the brake fluid resevoir. When adjusted long it would only catch the front circuit. The diaphragm in the resevoir is clean and not binding. My question is twofold:

  1. Is there a specific way the brake lines to the master cylinder need to be routed? I believe modern cars are plumbed in an 'X' pattern alternating sides front to rear. I believe I am plumbed rear brakes into rear circuit, front into front.

  1. In passing I have heard mentioned a pressure valve designed to compensate for the variance in distance of extension between the rear slave cylinders and front caliper cylinders.

Has anyone here heard of this type of problem? I even brought this to a mechanic (OMG!) with a whole buncha certificates on the wall, whom I believe is quite competent. This has become a real headscratcher and really quite annoying as well. Anyone? Thanks.

Reply to
jtbartlett
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ONLY the right front caliper drags??

Both fronts are plumbed together at the M/C. Both rears are fed from a single line to rear of M/C. I assume this is the way you have it.

Try this: Allow pressure to build in the right front so it drags. Then, loosen the brake line fitting for that wheel right at the M/C. Does pressure disappear and wheel spin free? That should help narrow it down.

Reply to
Speedy Jim

Sounds like dodgy brake hose acting as a non return valve to me

Neil

Reply to
Neil

Odd allright. Being in the sun should not make any difference to pedal pressure. The fluid gets a darn sight hotter when in use than in would get in the sun. I just had to replace the front calipers ( only RHS side packed up but did both) on my Type 3. Symptom was the pad dragged, same as yours. Turned out to be the caliper piston rusted/corroded into the caliper. Jamming the brakes on managed to push piston forward onto disc but there wasnt sufficient force for piston to retract back into caliper. If the problem hasnt been resolved by other blokes suggestions make sure the piston isnt frozen into caliper. Cheers John

Reply to
John

New brake hoses are money well spent.

Old ones can semi-fail on the inside, leaving a flap to act as a valve.

Reply to
Mark Dunning

Reply to
Dennis

Reply to
jtbartlett

The one side of the caliper might be closer to the disk surface, and the new brake pad might be dragging on the disk because it is too thick to fit. Do you have a worn set of pads to try and see if they drag? Your calipers might be installed a bit off center so that there is more room for the one pad and less room for the opposite pad of the pair.

Bill Spiliotopoulos, '67 Bug.

Reply to
Bill Spiliotopoulos

Ok, I drove the car to work nd home today- 14 miles round trip. Morning, brakes were A-OK no dragging at all. Temp this morning was about 40 F. I parked the car in direct sunlight (75-80 F)and as before, really hard brake pedal and front right was dragging. I drove home and cracked the line at the MC and pressure released, brakes released. SO...that rules out the MC. I know the MC, line and hose are brand new too so they are out. The caliper has maybe 200 miles on it - new. Same symptoms prompted me to replace it earlier as well.

The heat thing has me thinking maybe I have a worn spindle (!?!?) If the bearing is sitting closer to centerline then the rotor too is misaligned. I was reasoning that since the caliper is bolted directly to the spindle it shouldn't matter but this seems to be the only plausible explanation. The heat thing is what has led me to this conclusion. Am I nuts or is this a possibility? Thanks for the earlier replies.

Reply to
jtbartlett

Whoa! You cracked the line at the M/C and there was pressure?

That means that the fitting in the M/C or the M/C itself is allowing pressure buildup. Normally, residual pressure from the caliper should be allowed to go back thru the M/C to the reservoir so no pressure build occurs.

There is something fishy going on in the M/C port.

Jim

Reply to
Speedy Jim

MC piston not returning all the way? Pedal rod doesn't have enough free play? Free play was set when the piston was not fully retreated to it's resting position?

Jan

Reply to
Jan

rule out pedal freeplay.... if someone has adjusted the mastercylinder pushrod instead of the pedal stop you can have the same symptoms... if you have plenty of freeplay, i'm thinking the same thing Jim is, the mastercylinder, no matter how new, could be bad...

Reply to
Joey Tribiani

damn it.....should have read ahead....bite me Jan!!!!

Reply to
Joey Tribiani

Certainly. where would you like it, Sir?

:)

Jan

Reply to
Jan

wait....i didn't mean it....really.....take your hands off me!!

Reply to
Joey Tribiani

OK....EUREKA!!! (maybe) I pulled the MC actuating rod out this morning and replaced it with a different style rod. My 1965 rod has a bulbous end which 'might' have been stopping the MC from returning all the way. The later rod fites nicely inth the MC tapered bore so mebbe this is gonna fix it. Disc brake conversion is pretty simple....looks good on paper, reality is sometimes more complicated. Thx for all the help.

Reply to
jtbartlett

Please, as a courtesy to anyone that may find this thread in an archive search in the future, report back, especially if this does fix your problem....lots of threads die "unfinished" once problems are fixed....thanks.

Reply to
Joey Tribiani

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