More Brake Questions

burgy711 · May 29, 2007

I rebuilt my calipers a month ago or so and continue to have issues with them. First I thought the problem of not releasing was with my booster but when I by-pass the booster I am ending in the same spot. Bleeding and all is fine, I go for a road test and get about 5 miles out and the brake peddle starts to become very hard and the fronts begin to lock up. I can get out and open the bleeder line on one side of the fronts and things are ok again until I get another 5 miles and have braked another 4 times and back to the same thing. Locked up with a hard peddle. So, what is it that isn't allowing the fluid to ease back. I put new stainless steel pistons and all new rubber seals in. IF this was a piston and seal thing I would assume that the bleeding after a hard peddle wouldn't fix the problem. What do you all think?

Thanks

sunbeam74 · May 29, 2007

Many years ago I had a similar problem. I would check the mastercylinder. Was it rebuilt, too? If it was, then disassemble it and check to make sure that all the pieces are in the correct order.

Steve

mikephillips · May 29, 2007

As Steve said, check the master. Also, if the flex hoses are original consider replacing them. And, ensure that the spring in the master and the one on the pushrod to retract the pedal are working and not broken or weak. If either ine is you could have a problem where the master piston assembly doesn't retract far enough to allow fluid to flow back out of the lines as the brakes release. Thus each time you hit the pedal it pumps more in causing the brakes to eventually stay on.

burgy711 · May 29, 2007

Master wasn't rebuilt. If it was a brake spring - seems pulling up on the peddle would rectify a push rod issue with the spring - no? If it's inside the master cylinder I suppose a rebuild is in order. Is there a simple way to test either one of these theories? What I like about these cars is that they just aren't that complicated. BUT, sometimes they certainly can be perplexing to the weekend wannabe mechanic.

pdq67 · May 29, 2007

Definitely check the flex hoses. I had this problem on a big ugly American car and replaced a whole bunch of parts before I figured out that the flex lines were collapsing when the brake pedal was released.

Fastback · May 29, 2007

Steve:
The concessus is the master might be be the culprit, although I would check the flex lines and also the hard lines. A collapsed flex hose would not allow fluid to return properly (pedal pressure and return pressure are NOT the same), and a crimped hard line would do the same (was the car ever towed or trailered? do a careful inspection of the lines under the car). I'll agree: weekends are made for minor Sunbeam repairs and inverting Guinnesses, and if The Weather Channel is smiling, some topless driving.

Let us know what you find.

Wayne

65beam · May 29, 2007

brakes

we had this problem with one of our series 5 cars. i found one of the front flex hoses was crimped and would not allow the brakes to release.

burgy711 · May 29, 2007

I replaced the flex lines during the 3 year restoration. I do not believe them to be the problem. As well, this is on both front wheels. The rears do not seem to be impacted by this strangness. As well, once I open one front side bleed opening and remove the pressure both front wheels become free. Not sure if that helps or not? If its the master, wouldnt the rears be impacted like the fronts? If it was a flex line wouldn't only that side be impacted while both of my fronts are being impacted?? Could it be the four way spliter valve? Have I told you yet how much I hate brake fluid??

Jeff Scoville · May 29, 2007

Seems your doing the correct detective work.
Here's another suggestion.
Next time try and release the pressure form the line going into the splitter.
If the pressure doesn't release from there, you are probably looking at a flex hose.
Process of elimination.
Is there any chance when you rebuilt the calipers that the dust shields are pinched between the piston and caliper keeping the piston from retracting?
Unfortunatly this is one of those hands on searches.
You'll get it.

burgy711 · May 29, 2007

If it was at the caliper like the dust shield wouldn't they remain locked in place? Wouldn't that impact only one wheel or I guess both if I got both sides pinched. The strangeness is that the four way valve has one input and three exits..... one to the left side and one to the right side and one to the back wheels that is split around the rear axle. When I'm locked and jack the car both fronts are impacted while the rears turn freely. I let one side bleed off the pressure and the fronts both turn freely...... Guess the next step is to pull the front lines and the four way and blow them out. I ordered a master cylinder rebuild kit today as well so we can try that too...... I hate to think my caliper rebuild was flawed and the fact that once I let the pressure bleed off they return to free Wheeling!!! If there was something wrong with the calipers wouldn't they remain tight on the rooters??

britbeam · May 29, 2007

Steve the fourway splitter with brake light switch is just open passage way I doubt your problem is there. But yes blow out your lines to be sure they are clear.I just had the four way out of my car last weekend so I can tell you I saw nothing mechanical inside to fail. Now I have a series 2 Alpine. Wish you the best. i know in a short time you will clear this up. When you do I look forward to hearing what you find. Remember also even new parts can be unserviceable.
Dwain V6 Krazy

sunbeam74 · May 29, 2007

Steve,

Would the rear brakes be affected the same as the front? To some extent they probably are. Remember the majority of your braking forces are coming from your front brakes.

To answer your question if it was the internal spring to the master cylinder failing would it help to pull on the pedal? I don't believe so. All you are doing is pulling the pushrod back - not the piston in the cylinder bore.

I think Mike is correct and the spring is failing to return the seals into postion. The lip of one of the seals is blocking the passage in the bore.

Steve

Bill Blue · May 29, 2007

Steve, the Alpine braking system is a simple, "straight through" system with no regulators. As such, the front brakes will always engage before the rears because of the shoe retracting springs. So you ask, "How much braking effort do the front brakes exert before the rear brakes become active?" I have not a clue.

Bill

burgy711 · May 30, 2007

I have not rebuilt a brake master cylinder before. I have done slave cylinders and a clutch master but not a brake. Any special advise from the group? Any special tools? Does a new spring come with a rebuild kit? Could this be the result of a master sitting around for 3 years?

Jeff Scoville · May 30, 2007

If you've done a clutch master, you've done a brake master.
Same animal, different size.
Hope this solves your problem, like I say, kinda hard to diagnose hands-off.
Interested to hear the final remedy.

mikephillips · May 30, 2007

Pulling on the pedal doesn't do anything for the piston assembly since theres no mechanical connection between the two. So the pedal can move back and the piston doesn't have to. First off when it's apart you'll want to examine the bore for pitting and the piston assembly for missing/broken parts. If the piston is hard to remove, then dirt or corrosion at the end of the bore might be the problem, it could stop the piston from full travel. Problems that I've seen with pistons generally are either broken/corroded main springs, failure of the rod that seals the fluid input hole to remain locked to the piston, and missing parts from prior rebuilds. Unfortunately, there isn't a source of individual internal parts that I'm aware of so if you find that the piston assembly is broken you're going to need to either find a good secondhand one or buy a new replacement, like the Wilwood Girling replica for example.

burgy711 · May 30, 2007

Would be interesting to pump up the lines to lock the fronts and then unscrew the line coming out of the master cylinder and see what kind of pressure I have there??? That might be the proof that the master isn't allowing the pressure to bleed off.

mikephillips · May 30, 2007

Worth a shot, make sure you have plenty of rags packed around it to soak up any fluid.

burgy711 · Jun 11, 2007

Here are my findings. Inability for the brake fluid to ease back into the master cylinder is the root-cause for my front brakes locking up. It would appear that the plunger arm that connects at the peddle is the reason for the internal cylinder not backing out far enough. I've had a similar situation before on the clutch master from a VB purchased master where the plunger opening isn't wide enough for the Sunbeam peddle. It looks like the brake master has the same problem. The plunger U isn't wide enough for the peddle and so it doesn't snug up and leaves the plunger just slightly engaged and the back flow can't happen. I tested this out with air and sure enough with the peddle on the plunger no air flow. Removed the peddle and the plunger will then allow air back flow. I have a feeling this is another VB part that isn't correct for the car. Will order up a new Brake Master from SS on Monday.

RootesRooter · Jun 11, 2007

So the spring and/or spring retainer are binding up around the plunger? Or are you saying the "U" part of the plunger is too narrow to fit around the pedal lever? I can't quite picture this.

burgy711 said:
Here are my findings. Inability for the brake fluid to ease back into the master cylinder is the root-cause for my front brakes locking up. It would appear that the plunger arm that connects at the peddle is the reason for the internal cylinder not backing out far enough. I've had a similar situation before on the clutch master from a VB purchased master where the plunger opening isn't wide enough for the Sunbeam peddle. It looks like the brake master has the same problem. The plunger U isn't wide enough for the peddle and so it doesn't snug up and leaves the plunger just slightly engaged and the back flow can't happen. I tested this out with air and sure enough with the peddle on the plunger no air flow. Removed the peddle and the plunger will then allow air back flow. I have a feeling this is another VB part that isn't correct for the car. Will order up a new Brake Master from SS on Monday.