Moss Motors, Ltd

Motorbill,

Drove the old girl to work this morning, and she definitely is grabbing on the right front brake.  I pulled the caliper to check the pads and the rotor and nothing is out of place.  It's possible I got some dirt in the line when I replaced the brake hose.  I'm going to bleed them again and if that doesn't take care of it, I may invest in rebuild kits for both the front calipers and the rear brake cylinders.

zach

Motorbill,

Drove the old girl to work today.  The pedal was bearable, but the right front brake is grabbing under firm pressure.  I pulled the caliper and checked out the pads and rotor surface and all seemed okay.  Will try to bleed again.  Maybe I got some dirt in the line when I replaced the brake hose.  If it continues, I'm considering rebuilding the front calipers and the rear cylinders.

Zach

All,

On Friday, the right front brake kept grabbing to the point that it was leaving rubber on the road.  I managed to get it home and today I pulled the caliper.  Never having done this before, I didn't realize that I should have used the brake pressure to push the pistons out of the caliper.  Now I have the caliper off and one piston is about 3/16th inch exposed and the other is flush.  The exposed portion of the one piston is shiny and clean, the other is dirty and looks like it is stuck.  Anyone have any ideas?

Zach

zach,

We don't usually eject the pistons with hydraulic pressure while the caliper is still on the car. We put a chunk of wood between the pistons and blow into the hose port with shop air. BE CAREFUL IF YOU DO THIS!! If you have a finger in there you will lose it!! Usually, only one piston will come out. We put it back in and lay the caliper that side down on the bench. Then we hold that piston in place by placing our weight on the piece of wood(which protrudes from both sides of the caliper) and introduce air again. You may need three hands to do this, unless you can find a way to clamp things down. Be ready in all this for some flying brake fluid. This usually releases the stuck piston, after which they can be levered out by the dust seal retainer lips machined into the pistons. I hope this will work for you. Sometimes you have to get creative and find another method. It's possible that the one piston you describe is so rusted in place that it just ain't gonna happen. If so, purchase a pair of rebuilt calipers,not just one. Whatever you do to a brake or suspension system, always do it to both sides or be set to be disappointed.

If you do decide to rebuild the calipers, be very critical of the condition of the pistons. They must be rust and pit free. There are often stainless steel pistons available. If you can afford them, they are much better. Chrome plating, which is used on the plain steel pistons, is porous and pits easily. I'm sorry you've been through so much with this brake system. It goes to show that the most important thing to do when starting to work on any system is to asses the condition of ALL the components in that system.

It's possible that the bad pedal was indeed caused,at least in part, by the stuck caliper piston. It could be that the rotor was actually being sprung toward the stuck piston side when the pedal was depressed, giving the spongy feel. The more thoroughly you can rebuild a brake system, the better the overall result will be, assuming good parts, correctly installed and adjusted. Good luck, and let me know how it's going.

---

Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Zach-

Instead of rebuilding you can try to see if Advance Auto will honor an online price for calipers.

http://www.partsamerica.com/ProductList.aspx?PartType=5003&PTSet=A&SearchFor=Caliper

Use zip code 94564 and print the page for Cardone rebuilt caliper 19445 and 19444 or the loaded ones 17445 and 17444.  For some reason the price varies by zip code.

I purchased some Cardone rebuilt calipers (loaded) from Car Quest; big mistake!  It was supposed to take three days and it has already been 6 days. They say the calipers had to come from Canada and should be here tomorrow.  We'll see.

Zach

Sounds like they're being hand carried. How special!

---

Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Okay!  The calipers came in today and I installed them and bled the system.  Still have a soft pedal, but at least the car stops straight and doesn't pull!  At this point, I'm very frustrated; although I did get to test drive her with the top down.  Oh, yeah!  I'm going to take her in to have the transmission rear seal replaced, and I may just have a professional try bleeding her.  Any ideas?

Zach

Zach,

I have confidence that you know that something isn't quite right. I'm asking the following question to help my thought process, since I can't be there to experience the problem for myself. Although it is a given that the pedal feels soft, how's the effort? do you have to push pretty darn hard against that soft pedal to achieve a good stop? or does the car stop with a relatively light touch. Still thinking.....

---

Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill,

You have to press pretty hard.

But, let me throw another monkey wrench in.  Drove to work this morning with no problems; but then it was interstate most of the way and I didn't use the brakes much.  Drove home on the back roads and everything was going okay until about half-way home.  Stepped on the brake and I started feeling that pulsing - like before I replaced the calipers - in the right front brake.  The closer I got to home, the worse the pulsing got and then it started grabbing so that the tire squealed.  What is happening?  I've thought of two things and maybe with your experience you can tell me if I'm full of it: 1) although the master cylinder is new, it could be bad, and 2) the rotors are worn too thin.  Possibilities?

zach

Zach,

Is this a wire wheeled car? Have you checked for bad wheel bearings? how thick are the rotors? (it sounds like they should be replaced anyway) And the biggie. Have you checked for a bent spindle? I've seen this one before, and it will confound you if you haven't experienced it.

To check for this, turn the wheels in the opposite direction of the spindle you want to examine after jacking up the front end and removing the wheel(s). Now you can look in the end of the caliper from the direction that you insert the pads. Is the disc parallel to the sides of the caliper?, or are the pads being forced against it on a bias? If it doesn't look right remove the caliper and the hub/disc assembly and take a good hard look at the actual spindle. (the part the hub spins upon) Look at it end on and see if you can detect a problem. Don't do all this unless the first examination makes you suspicious. Let me know...

---

Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill,

No, wire wheels; Rostyle. And I did not check the wheel bearings, but there doesn't seem to be much play.  As for the thickness of the rotors, didn't mic them, but with a steel rule, they measure about 11/32; of course, that's the outer edge.  I can pull the caliper off and check it.  What is the minimum acceptable thickness.

I did as you suggested and checked for a bent spindle.  All seems to be in order.  I'm befuddled.  This problem originally surfaced after I replaced the master cylinder, and it only manifests itself after I've been driving for some time and have used the brakes a lot, such as driving through town or on back roads.  The master cylinder and hoses are new (Moss) and the calipers are rebuilt (Cardone).

The worst part of this whole thing is that we are supposed to have mid-70s weather and sun the rest of the week!!

Frustrated in Kentucky,

zach 

zach,

No matter what the thickness of the rotors, it sounds like they're warped. I've pretty much given up on having rotors ground. The time it takes to bring them to, and pick them up from, the machinist, plus the cost of the service and the likelihood that they won't "spec out" has caused this to be a losing proposition for a shop such as ours. Rotors aren't all that expensive anymore. If the pedal really pulsates replace both the rotors. Oh how I wish this car was here for me to look at! I'm certain we'd have it figured out in a moment or two. There's some piece of information we are missing here. I suppose it's possible that you have a brand new, bad master cylinder, especially because the problem only manifests after things heat up. But it goes against my nature to blame a new part which hasn't cured an existing problem. Zach, take a long hard look at the ENTIRE system, including the hard lines, the springs used throughout the system, and all the connections. In short, all the parts of both the mechanical and the hydraulic portions of the system. Something is either not moving into position or not returning from position. Look for kinks. Look for looseness. Get back to me with ANYTHING you question. This is a tough one, but keep the faith. If it's any consolation, it's supposed to rain here this weekend after a beautiful week when I was working on everyone else's roadsters...

---

Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon

Motorbill,

Just finished ordering new rotors from Moss. Took a look at the tubing for the right front brake and all seemed to be in order.  Will check out the rest of the system this weekend.  It's 75 degrees today.  This is really eating me up!  Ah, well.  I'll keep you informed on developments.

zach

Received the brake rotors from Moss and went to install them.  In order to replace the rotors, you need to remove the hubs.  If I have to remove the hubs, I might as well go ahead and replace the suspension bushings.  To replace the suspension bushings, I need to disconnect the tie rod ends.  If I have to disconnect the tie rod ends, I might as well go ahead and remove the steering rack so I can replace the engine mount, etc., etc., etc..

zach