Front brakes hanging up

d_ford · #1 (**permalink**) 07-05-2006, 06:41 PM

Bob,
I want to pick your brain. The front brakes on my ERA are hanging up. When it first happened a week or so ago I replaced both front calipers assuming that as much as the car has sat around without being driven over the years that they drew moisture and the pistons were sticking. That apparently wasn't the problem as I jacked it up today and the wheels would barely turn by hand. After prying the calipers apart they roll freely. I would normally suspect that the hoses had collapsed inside but they have the stainless braided hoses which I didn't think would collapse? I was wondering about the possibility that it could be the master cylinder? Any ideas appreciated. Thanks.

ERA Chas · #2 (**permalink**) 07-05-2006, 07:17 PM

If you bought your car used, the previous owner may have installed a 2lb. residual valve, which would hold pressure. A sticking front master (the larger one) would do the same. I had to rebuild a Tilton which had 2 yr. old fluid in the system and corroded. Change fluid annually.
Hope this helps.

cobred · #3 (**permalink**) 07-05-2006, 07:31 PM

Jack up the front and with the rotor stuck loosen the hard line into the caliper hose. If it frees up its from the line to the master, if not the problem is the hose or caliper. This may sound silly but check that the carpet or floor mat is not stuck in the slot of the floor the pedal travels in keeping the brakes on.

d_ford · #4 (**permalink**) 07-05-2006, 08:36 PM

I'll check those suggestions tomorrow. Thanks for the ideas. I'll post here and let you know if I figure out anything.

d_ford · #5 (**permalink**) 07-05-2006, 08:39 PM

I should add that it's BOTH front brakes, making me think it's probably farther back in the line or the master. Anyone know how to check the master cyl. to see if it's sticking?

strictlypersonl · #6 (**permalink**) 07-06-2006, 04:30 AM

Check for a problem in the master cylinder by opening a bleeder when the brakes are dragging. If that fixes the symptom, the master is the problem.

On the early cars, it was possible to adjust the pedal travel with a stop at the front of the brake box. Sometimes, the master cylinder would stick, and people would adjust the play out of the pedal. If the adjustment was too tight, it prevented the piston to open the master cylinder return port, thus keeping pressure in the system all the time.

The other thing to examine is the balance bar angle and whether it's free. See here.

If you still have the cast iron (VW) master cylinders, I strongly recommend updating to the later system. It's fairly involved, but worth the effort.

d_ford · #7 (**permalink**) 07-06-2006, 04:53 PM

Bob, here's what I've found so far....
Cracking a bleeder on one caliper DOES free up both front brakes so as I understand it the master is the problem? There is no interference from the carpet or anything else keeping the brake pedal from returning. I adjusted the balance bar so the front (outside) master rod is approx. 1/4" longer than the inside. With the brake box removed (no pedal stop) the brakes still stick after pressure is applied and then released. The manual says that the back of the pedal should be about 7" from the front of the footbox, mine is about 6" but when I tried to adjust the rod lengths to move the pedal back I ran out of rod on the front master. ( it came out so I had to thread it back in enough to hold so I end up about 6" from the foot box again) I do still have the cast iron masters, can you tell me what all is involved in upgrading to the better system and the cost? Would I be better off to just replace the one bad master with a rebuilt same unit? Thanks again.

strictlypersonl · #8 (**permalink**) 07-06-2006, 05:36 PM

The Tilton upgrade requires welding and is described here. The upgrade kit is several hundred dollars and includes the master cylinders, new hard lines, chassis bracket and hardware.

Otherwise, you can replace your current master cylinder for a lot less.

The details are on the bottom of the page I referenced above.

d_ford · #9 (**permalink**) 07-06-2006, 07:55 PM

I Guess for now I'll just replace the existing master cyl. Thanks again for all the help, you guys are the best.

strictlypersonl · #10 (**permalink**) 07-07-2006, 04:08 AM

D_Ford,

One possibility that I hadn't thought of (until I got into bed) is that the previous owner had replaced the master(s) and failed to disable the residual pressure valve as described on this page.

trularin · #11 (**permalink**) 07-07-2006, 05:44 AM

I do not have the same pedal setup, but I had a simular problem and ended up putting a return spring on the brake pedal. It seems to work fine.

It's just a suggestion.

d_ford · #12 (**permalink**) 07-07-2006, 02:29 PM

Thanks for the suggestion tru, seems I spent a bunch of money on repairs I didn't need after all on the hocking hills cruise. I'll get this figured out.
Bob,
After your last post I thought about it and that almost seems probable. I'm stuck at work for the next two days and have plans I can't get out of sunday but the minute I can get back in the garage I'm going to pull the master, disassemble it and see if the original builder didn't make the required modification after all. If he didn't, I'll bet the master for the rear brakes is the same. I'll check it too. I'll keep you posted. Thanks.

ERA Chas · #13 (**permalink**) 07-07-2006, 03:01 PM

Do You Have A Residual Valve?

edwhite7 · #14 (**permalink**) 07-07-2006, 04:35 PM

Don,t replace the master cylinder before checking the pedal free play. If the pedal is adjusted incorrectly the piston will block the port that connects the reservoir with the master cylinder. If this happens, and it happened to me, the fluid will expand and bring on the brakes. Their should be some play between your pedal and the piston in the master cylinder.

d_ford · #15 (**permalink**) 07-07-2006, 05:24 PM

ERAChas,
I'm not sure, where should I look for it and what would it look like?

edwhite7,
The pedal box is completely off the car right now so there is no pedal stop in place. The brake pedal puts no pressure against the master cyl. and will freely flop back and forth without the pedal stop. I even pulled back on the pedal by hand to see if the pressure released, no luck. The only way to relieve pressure is to pry the piston back in the caliper or crack a bleeder. I won't replace the master until I have a chance to see if the modifications that are required were done to it.

edwhite7 · #16 (**permalink**) 07-07-2006, 05:58 PM

If I understand it correctly the residual pressure valve is designed to hold about 2 bs in the line on cars that have the master cylinder below the wheel cylinders. If this is not the case then they can be removed but even so they should not be a problem unless thery have failed. I had residual pressure valves in my car and I removed them. I did not notice any change but my master cylinder is above the wheel cylinders. It sounds like the pedal free play is not the issue, I suspect the master cylinder but only cause it can't be much else.

ERA Chas · #17 (**permalink**) 07-07-2006, 06:39 PM

http://www.strangeengineering.net/catalog/pdf/107.pdf
Wilwoods are black, some are brass but they are plumbed in the line from the master to the front junction block. They are for cars with the master lower than the caliper, but they are not needed for ERA's.
If you have one, remove the entire line, re-flair a new one from the master to the junction without the valve in place. Bleed as normal.

ERA Chas · #18 (**permalink**) 07-07-2006, 06:45 PM

d_
You have a beautiful ERA but you need to lower it about 1 1/2 inches. Download the ERA manual for Bob's great instructions.

strictlypersonl · #19 (**permalink**) 07-07-2006, 06:51 PM

Quote:

Originally Posted by edwhite7

If I understand it correctly the residual pressure valve is designed to hold about 2 bs in the line on cars that have the master cylinder below the wheel cylinders. If this is not the case then they can be removed but even so they should not be a problem unless thery have failed. I had residual pressure valves in my car and I removed them. I did not notice any change but my master cylinder is above the wheel cylinders. It sounds like the pedal free play is not the issue, I suspect the master cylinder but only cause it can't be much else.

The RPV's built into the early ERA master cylinders maintained about 10 psi because the master was originally intended for a drum brake system.

Which is why it must be disabled.

d_ford · #20 (**permalink**) 07-07-2006, 10:01 PM

Chas,
Thank you for the compliment on the car. If I drop the front end any lower, the oil cooler scoop will pick gravel up off the road!

My old ERA #002 wasn't nearly as low as this car is, I have a hard time getting a jack under it.

Bob,
The RPV you are referring to is the modification you talked about earlier inside the master correct?