Binding Calipers ??

Hello All:

I’m having some problems. Last fall I replaced my master cyl. (rebuilt) due to leakage. All seemed good but it was very late in the fall and my memory could be incorrect. The first / only drive this year – my front caliper was slightly catching. I didn’t recognize this and drove for 30+ miles and when I got home – the driver’s wheel was severely smoking (literally)!

Replaced brake lines (both sides to be safe), LH caliper and LH bearing (to be safe; with taper setup) & bled system (just fronts as car is elevated and I didn’t think air would flow downwards). I have great / tight pedal response. No sponge whatsoever.

After a brief drive – had more issues. I put up the car up in the air, removed wheels --- BOTH calipers were binding (driver’s more than passenger). I was unable to spin either wheel w/o ‘unseizing the caliper’ – squeezing the pad & caliper to release from each other with the use of my Channel locks).

OK; my thoughts on what could be the issue & I appreciate ALL of yours:


A) * Could master cylinder (despite ‘new’) be bad as valve inside seems to be temperamental?

B) * Bleed ALL 4 wheels (more to eliminate that as an option).


When I am thinking that new parts are bad really states how desperate I am for answers. With this many new parts – I’m running out of things to replace. Any thoughts or ideas on what I should test or replace would be appreciated. Thanks.

Vitals: 1964 AH Sprite. Single line setup. 1275 engine

Tx-

George

George, if you have the car up on stands and press the brake pedal, do the brakes stay "locked" when you release the pedal... or does the locking only happen on a drive when things get hot?

If you can make the wheels lock when the brakes are cool, try opening a caliper bleed nipple to see if fluid comes out. If fluid burps out, you have trapped pressure between the MC and calipers. Since you say you replaced the lines (including flex lines?) stuck brakes would indicate an issue with the master cylinder's internal valve and/or a blocked relief port.

Another somewhat difficult test would be to press the pedal and get the brakes to lock. Then disconnect/pull the master cylinder clevis pin from the pushrod/pedal. If the pushrod moves "out" further when you do this, it could be the return port to the reservoir is blocked.

George,

Can you please specify exactly which master cylinder you bought as a replacement? Your car should have a 3/4" bore master cylinder, but because the 7/8 looks the same, some people end up installing the incorrect one. Each one uses different length pushrods and different valves in the brake bore, and they are not interchangeable. If you replaced your flex lines already, this lock up condition sounds like you either have the wrong MC/pushrod combination or you have the pushrods adjusted wrong, and you have the return port blocked. I can sort out more if I know what you installed. Because the 3/4" bore MC's were not available for decades, it's also possible your original 3/4" might have been replaced with a 7/8" in the past.

When you say you replaced brake lones, does this mean lines or hoses? Hoses if they perish inside could block the fluid returning. Also, is it binding on both sides? If not could the disks be out of allignment?

Hello Doug, Gerard & JP:

I had to check on a few things. First, I kept the old M/C - it is a 3/4" (appears to be p/n TRW / Lockheed 3BT83C). So I have the wrong one. I'm pretty disappointed at the specialty shop I bought it from as I knew there was a difference.

I've also replaced the brake HOSES, not the entire line system. Those all look fine and are not leaking or in poor condition.

Doug; to specifically answer your Q - I just went out (car is cold) and check both calipers - both spun freely. I depressed the brakes and both hang or bind.

Sounds as if I need two things; a new / correct M/C (method to use what I have) and a good & complete flushing. BTW - since going to start new; OK to use DOT 5?

Gerard; I found your article on brake cylinder dot com and through your 'signature' back checked the items I knew about in the fall. Any advice on just get a new M/C or parts swap? I see eng parts nw has one for ~ $160 + shipping. Apple (whose this is is ~ $200). Consider I have to order anything I get - this would be the quickest (I'm not going local anymore). M/C first repl in 2002 (ish) and then again 2016, and it looks like deja vu for 2017 .....

Any and all comments are appreciated. THANK YOU.

George

George, DOT-5 is as much a personal choice as a technical one. Rather than go through the arguments in this thread, take a look at the recent thread from the Healey section of this board.
https://www.britishcarforum.com/bcf...licone-brake-fluid-conversion-existing-system

Gerard's comments were more direct than mine but it looks like we were both wondering if the return port was blocked by a pushrod being the wrong length. Your test mentioned above that has the calipers dragging when cold suggests the return port is blocked. I defer to Gerard on what your best fix is.

George,

If you want to do it right (and only once), you should send me your original master cylinder to have it built right, and to last. A new aftermarket one will not last you as long, especially when it comes to corrosion issues. I have a very large number of people who are still using their master cylinders I rebuilt for them more than 10 years ago, and they regularly tell me they still perform like new today. It doesn't matter if you drive the car frequently or put it away for months, the fact is that what you'll get from me will outlast any reproduction master cylinder tenfold. I think you'd be surprised at how many aftermarket ones I have serviced in the last decade, and that includes those that were purchased new in the last year or two. It'll cost you more now, but it will save you a bundle in the long run.

If you think silicone is the answer to corrosion problems, it is not. Silicone is hydrophobic, meaning it does not mix with water. That means that moisture in your brake system settles out and pools in low spots, and corrosion occurs even more rapidly. I have replaced master cylinders, especially those with the "tin can" reservoirs due to pinhole leaks when silicone fluid was used. If the bore is cast iron, it's going to pit whenever moisture is present. In addition, silicone is not as good a lubricant as glycol. I don't wish to start a debate over this, that's been done ad infinitum over the last couple decades, but the previously mentioned drawbacks are factual. There may be reasons you consider beneficial for using it, and you may feel they outweigh the downside, but that's up to you. You can use whatever you wish in your own car.

George Zeck said:

Hello Doug, Gerard & JP:

I had to check on a few things. First, I kept the old M/C - it is a 3/4" (appears to be p/n TRW / Lockheed 3BT83C). So I have the wrong one. I'm pretty disappointed at the specialty shop I bought it from as I knew there was a difference.

I've also replaced the brake HOSES, not the entire line system. Those all look fine and are not leaking or in poor condition.

Doug; to specifically answer your Q - I just went out (car is cold) and check both calipers - both spun freely. I depressed the brakes and both hang or bind.

Sounds as if I need two things; a new / correct M/C (method to use what I have) and a good & complete flushing. BTW - since going to start new; OK to use DOT 5?

Gerard; I found your article on brake cylinder dot com and through your 'signature' back checked the items I knew about in the fall. Any advice on just get a new M/C or parts swap? I see eng parts nw has one for ~ $160 + shipping. Apple (whose this is is ~ $200). Consider I have to order anything I get - this would be the quickest (I'm not going local anymore). M/C first repl in 2002 (ish) and then again 2016, and it looks like deja vu for 2017 .....

Any and all comments are appreciated. THANK YOU.

George

Click to expand...

dklawson said:

George, DOT-5 is as much a personal choice as a technical one. Rather than go through the arguments in this thread, take a look at the recent thread from the Healey section of this board.
https://www.britishcarforum.com/bcf...licone-brake-fluid-conversion-existing-system

Gerard's comments were more direct than mine but it looks like we were both wondering if the return port was blocked by a pushrod being the wrong length. Your test mentioned above that has the calipers dragging when cold suggests the return port is blocked. I defer to Gerard on what your best fix is.

Click to expand...

I would check the pushrod and make sure you have the correct one. I'm in the blocked return port camp and after doing a lot of research on LBCs as well as other cars the consensus is that dot 5 has no issues regarding rust or pooling of water, but your hydraulic system must be in good shape to begin with. I used all new cupronickel lines, SS Goodridge hoses, calipers built by Peter C at WWAP of Madison, sleeved MC by Sierra, and new rear wheel cylinders and will be adding Dot 5 later this month. Lots of people on this forum as well as others have been using dot 5 without issues for years, good enough for me.
Rut

The real quick test to determine where the issue is....jack up the offending end of the vehicle, do whatever you need to the pedal to get the brakes to lock (if it only does it after a long drive, pull over, shut it off, leave it in gear, pop the bonnet then do the following and you should feel the vehicle take up the slack against the drivetrain when they release) hold a rag under the fitting on the output of the MCyl, crack the line with a flare nut wrench. If it goes "poof!" and the wheels turn, the blockage or whatever is NOT from the nut to the wheels...it's from the nut to the pedal.

If you were a line mechanic, and had this issue come in, and jacked it up multiple times, replaced the hoses, futzed with comparing masters and such, replaced on caliper and wheel bearings (?!?) without determining whether it was MCyl back or MCyl forward, you'd be packing your tools up within the hour.