Replaced the master cylinder. Brake lights always on. Help!

[Jim Ed]

I have a '73 non Super Beetle.
I replaced wheel cylinders, shoes, and master cylinder. I bled the brakes with a power bleeder.
I test drove it in my driveway today. The brakes almost locked up and the brake lights stay on all the time.
Does that mean I have adjusted the brakes shoes too tight or does it mean the master cylinder push rod needs to be adjusted or both?
TIA!

[Piledriver]

Probably both.

The pushrod must have SOME clearance so the MC piston is sure to move back past the transfer port.
It's possible you have it sealed off and also tightened the brakes up too much.

[Jim Ed]

This is my first time with semi-metallic shoes.
It seems that they do not grab and/or stop as well as the asbestos shoes did.
It acts like it has ABS brakes. Will this go away after the new shoes have become accustomed to the drums?
TIA!

[Piledriver]

It always takes a few good stops to seat the shoes, even if you have the drums turned.
If you don't it could take quite a few stops and a second adjustment before it's all happy.

[Ol'fogasaurus]

Jim, in the old days before 'arcing the shoes" was invented (a gimmick?) and disc brakes were in vogue we used to adjust everything up then go out and do a few hard stops to "seat the shoes" to the drums then recheck the adjustment. Unless the shoes were "arced" their arc/curved shape was usually larger than the drums and so the contact, until worn away, was only at the ends of the shoes. I don't know if they even arc the shoes anymore and not everybody believed in it but the setting-in of the shoes is still a good idea.

If the brake light is still on I would suspect that the brake rod needs to be adjusted for them proper end play. It sound like pressure it still being applied to the MC. The shoes should have no bearing on the brake light even assuming everything is adjusted and bled correctly including pre-bleeding the MC.

[Marc]

Did you fiddle with the pedal stop position? Theoretically, adjustment of the M/C pushrod length is only done once, at the factory. Of course, after this many years, and considering that replacement parts may not be as closely-matched to the originals as was once the case, it isn't shocking to find that adjustment is sometimes needed - but start by measuring from the underside of the pedal to the firewall. If it's less than 8", adjust the pedal stop before tampering with the pushrod.

viewtopic.php?f=18&t=60118

[Ol'fogasaurus]

Good point Marc; also check to see if the push rod is set properly in the piston as they do get miss-positioned once in-a-while during the installation of the MC. I've had that happen to me once or twice.

Lee

[Dale M.]

I don't disagree with what other have said, but I always try to get here one way or another...



Dale

[Jim Ed]

I set the m.c. pushrod clearance yesterday. Apparently, I had sprayed rust penetrant on the rusty pushrod and did not see if it had loosed up before installing it.
After I removed it to check it, I noticed that the lock nut was loose. I cleaned it up to make it look like new and coated it with some engine oil and wiped it off.
I installed it and set the pedal play so that it would be just a little over 1/4 inch before the pushrod comes into contact with the m.c.
All seems well but, if I pump the brakes the brake lights will sometimes stay on for a second or so after I release the pedal. Then they go off.
Since I am sure I made the correct adjustment I think that is caused by the new Vargas master cylinder. It only happens if I pump the brakes.
I think it will go away. If it does not I will increase the play in the pushrod adjustment.

[Marc]

Could be a "slow" switch too I suppose.

[Jadewombat]

Never had any luck with those power bleeders. If you still have air in the system:

http://forums.vwvortex.com/showthread.p ... ight=bleed

[Marc]

Symptoms reported don't really indicate entrained air.
When I worked as a mechanic for USPS we had "bomb" pressure bleeders (diaphragm-equipped accumulators) which work great on Detroit iron, but on a car with a remote-mounted reservoir like an ACVW my preferred weapon is an eductor bleeder, that pulls fluid through the system using the suction created when an air compressor is plumbed in so as to draw a vacuum.
If that's too spendy, Harbor Freight sells one that works for ~$25. My son had a circle-track car with a manual RF brake pressure-limiting valve in the cockpit - about 12 feet of extra plumbing between M/C and caliper which refused to bleed until I broke down and bought the cheapo H.F. tool.
If you don't have a compressor, Mityvac also makes a hand-operated vacuum pump - but that's too much like work for my tastes...better to put the money towards a compressor, you need one anyway if only to fill a tire.

[Dale M.]

My experience has been good old two person manual method works every time ... Never had any luck with various pressure/vacuum bleeder systems.... BUT that is just my opinion...

Dale

[Piledriver]

I created a hard to bleed high spot in the hose over the top of the trailing arm when I converted to MK4 Jetta-like rear calipers, std 2-person bleed or even the Mity-vac couldn't get it despite repeated attempts and almost 1/2 gallon of brake fluid.

Ended up buying a pair of speed bleeders (internal check valve setup) worked very well, very fast, plus it became a 1 man operation.

[Jim Ed]

I took it for a test drive in a nearby Church parking lot. It acts like it has ABS brakes. The brakes do not lock up. It gradually comes to a stop.
No more problem with the brake lights staying on except for just a second longer than they should and this is just once-in-a-while.
I think the problem might be in the coiled brake pedal return spring.
I wired in a green dummy light on the speedo so I can tell if the brake light switches are sending juice to the brake lights.
Then I took the back streets to an O Reilys Auto parts store and made it back OK. I think it will be like PileD. said earlier.
"It always takes a few good stops to seat the shoes, even if you have the drums turned.
If you don't it could take quite a few stops and a second adjustment before it's all happy."
May also a second bleeding of the brakes.
If all else fails, I might get a German or a Brax master cylinder and install it the next time I remove the gas tank to replace the steering dampner and tie rod ends. But first I need to save up for new front tires.