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Member
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Location: England. | Hello all. I haven't been able to log on for a long while due to family illness, I hope you can answer my urgent question. About 8 years ago, I took my 58 Plymouth out for a spin with no problems. Upon reaching home, doing only about 5mph, I suddenly had no brakes, my foot went straight to the floor but the brake returned again soon after. My son was only about 5 years old so I took no chances and my good buddy Dean changed the GM style master cylinder for me and bled my AAJ disc brake conversion kit on all for wheels. My engine was rebuilt by Dean a few years later (an excellent job) and I've driven her many times since with total confidence that I didn't have when I first shipped her out from Tennessee. However, I took her for a trouble free drive a few hours ago and once again, upon reaching home and doing only about 10mph, I had no pedal, my brake pedal went traight to the floor. I was heading towards a neighbour's car and panicked, luckily she slowed in neutral and the brake pedal retuned again soon after. Although a risk, I took her for a very careful 1/2 hour drive, testing the brakes all the way, I had no problems. There is plenty of brake fluid in the master cyclinder. The only thing I did notice was the rubber seal in the master cylinder lid, please check out this link: https://www.performanceonline.com/master-cylinder-rebuild-kit/ The circles on the reat half of the large rubber seal pictured on the right of the link are a little distorted and not quite circular. Any idea why I'd lose a pedal, extremely infrequently only for it to return soon after (my booster tank is original)? The master cyclinder was new several years ago and I haven't probably even done 1000 miles since, the disk brakes were bled back then too. Today is an extreely hot day (for Engiand). I'm worried because my son has his leaver's high school prom at the end of the week, I was lucky not to have my brake fail on the open road today, and am worried about driving him there on Friday. Thanks guys. Lee UK.
Edited by Doobster 2023-06-25 11:30 AM
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Expert 5K+
Posts: 9674
   
Location: So. Cal | Since your setup is not original, a couple of pictures would help - especially of your booster. But there are three possibilities that I can think of:
1. There is an issue with your rear brakes, like they are way out of adjustment, but get jammed to make it work most of the time. When it un-jambs, then you have the problem.
2. You have an intermittent vacuum leak or the one way valve isn't working to hold pressure. This is especially possible if you actually still have brakes, but you have to push really hard to get them to work.
3. An intermittent problem inside your power booster.
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Expert
Posts: 3399
Location: Chestertown, NY ( near Lake George) | No pedal indicates a loss of hydraulic pressure, if you can get this to happen and in some way, pedal down, crack one of lines on the master see if it squirts fluid. If none and no leaks, then it would seem the master is the culprit. Is the system seperated by a proprtioning valve? This may take 2 people of course. To add If the rear calipers are the Cadillac type with e brake built in, the bleeding procedure is very specific for the rear calipers, check into this.
Edited by Shep 2023-06-25 2:57 PM
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Expert
Posts: 3778
Location: NorCal | Doobster - 2023-06-25 8:20 AM
The only thing I did notice was the rubber seal in the master cylinder lid, please check out this link: https://www.performanceonline.com/master-cylinder-rebuild-kit/ The circles on the rear half of the large rubber seal pictured on the right of the link are a little distorted and not quite circular.
The circled areas are there to prevent a vacuum above the fluid as the fluid level lowers with normal use. The rear system of the master cylinder is the front brakes and disc brakes will lower the level in the master cylinder reservoir. Not to worry.
Any idea why I'd lose a pedal, extremely infrequently only for it to return soon after (my booster tank is original )? The master cylinder was new several years ago and I haven't probably even done 1000 miles since,
The only way the pedal can drop like that, if there is no external leakage, is due to internal bypassing i.e. the master cylinder piston seals are weak. Failures like this can be intermittent because the seals are merely weak, not totally failed. Replace/rebuild the master cylinder. |
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Member
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Location: England. | Thanks for the information guys. My disk brake set up was from AAJ (Roger) "For front 1976 Monte Carlo, for rear 1984 Monte Carlo". I beleive the Master Cylinder is GM.
Edited by Doobster 2023-06-28 5:05 PM
 (Master C.jpg)
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 Master C.jpg (78KB - 59 downloads)
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Member
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Location: England. | I took the lid off of the master cylinder, it looked a little rusty, I'm surprised as I would have thought the brake fluid would help stop any corrosion. She's a garaged car too, the MC was new about 8 years ago, I'm surprised it looked like this:
Edited by Doobster 2023-06-28 5:06 PM
 (Corroded lid.jpg)
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Member
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Location: England. | The lid rubber seal had some gunk on it, I'm not sure whether it was rust or some kind of dried brake fluid.
As found:
 (Dirty seal 1.jpg)
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Member
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Location: England. | The lid cleaned up pretty well with emery cloth and the seal cleaned up well with WD40 which I ensured I cleaned off too:
 (Brake cleaned.jpg)
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Brake cleaned.jpg (74KB - 54 downloads)
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Member
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Location: England. | The brake fluid was about 5mm below the top face of the master cylinder so I topped it up, I don't think I've got a leak as I'd have lost a lot more over 8 years. I tested the brake pedal after and all seemed good. My car enjoyed a full engine rebuild after I shipped her from Donnie Taylor in Tennessee (before he went to prison). I didn't pay him to rebuild the engine and shipped it out of Tennessee ASAP when I found out he was a crook. Clive was a big help sorting her out when she came over. I've driven less than 1000 miles since I shipped her over thanks to Covid, the engine rebuild etc. The engine rebuild took priority and time so became a focus as she kept on breaking down, I lost confidence in her. I guess I assumed the brakes would still be good after the rebuild but time flies and I guess I took them forgranted, I checked the fluid level but didn't really inspect the lid as it was hidden by the rubber seal. I'll drive the 15 minutes to the Prom very tentatively on Friday (I've got Lap belts as I have kids). Sunday I've a local "Vintage Weekend" show, I'll head to that and another little show later on in the year. Then I'll plan a big overhaul/ service when I get some money together and get the brakes looked at by a professional (IE my mate Dean, a mechanic with a Silver Special and a 58 Plymouth project on the go). Thanks for the tips guys, I've learned a good lesson, despite not doing many miles, it's not just a matter of checking oil, water etc. Can anyone recommend a good place to buy a new Master Cylinder kit (or cylinder), I have to be careful of shipping costs to the UK. I'll be in the US in August so could get it shipped to my hotel. All the best. Lee. London.
Edited by Doobster 2023-06-28 5:11 PM
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Veteran
Posts: 101
Location: Palm Beach County Florida | Standard glycol-based brake fluid absorbs moisture at the rate of 2% volume per year. When you get the brakes overhauled, flush the system and convert it to Silicone fluid for longer life. Plus, it will not wash the paint off your backing plates when you bleed the system. |
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Expert
Posts: 1348
Location: Valley Forge, Pa. | IF you go to silicone, make sure the system is completely free of old fluid. The 2 fluids are NOT compatible.
I went to copro-nickel brake lines. More expensive but MUCH easier to bend, stronger than steel lines and it won't rust. |
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Expert
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Location: NorCal | udoittwo - 2023-07-15 6:55 AM
IF you go to silicone, make sure the system is completely free of old fluid. The 2 fluids are NOT compatible.
In order to receive DOT certification, all brake fluids must be able to co-exist in the same system without ill affects. The main issue is the two fluids won't mix...they will separate with the heavier fluid settling to the bottom. |
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No pedal.
