Out in my 58 Buick Limited this weekend ( Master cylinder & brakes on all corners gone thru last year ) & a couple of times hard pedal went soft just momentarily, over a 120 mile road. THEN when approaching a roundabout doing 55mph I suddenly had no brakes!!!! SOMEHOW I mounted the very narrow verge and rally crossed the car thru the narrowest of gaps ( 2/3 on verge 1/3 road ) over rough terrain without collecting any road signs or either of the cars in front of me with a manoeuvre that would have made an Indy driver driver jealous I reckon!! So, what's my problem guys? How comes this occasionally happens ( immediately after the incident I had good pedal again ) yet most of the time I have a good pedal & braking? Can these master cylinders fail on occasion but then not? Or is it vacuum I wonder? Any help would be appreciated as I'm not getting behind that wheel again 'til fixed! Thanks.
Has the reservoir dropped? If not you have a bad master. If so you have a bad wheel cylinder. A bad booster will only give you a hard pedal and ineffective brakes. Clarify for us/me that you have the OEM design braking hardware still.
First you need to find out what failed and then figure out why it failed. 1. Is the master cylinder full of fluid or empty? If it is full you most likely have a master cylinder problem like AG F/C suggested or the brakes have taken on air from sitting for a long period of time. If the master cylinder is empty start looking for a leak starting with the back side of the master cylinder and working down through the lines and through the wheel cylinders. hydraulic brakes are pretty much like a log chain in that the weakest link is the one that is going to fail. That could be a brake line that has been rubbing, a brake hose that got overlooked in the rebuild last year or a wheel cylinder that may not have been up to par to begin with. Or a piece of hardware in the brakes in one of the wheels could have fallen out of place. Looking at Jim's post, is the tailpipe real close to or touching the brake line/hose where it goes over the rear axle? Or if you had a custom exhaust put on the car is there a spot where the exhaust pipe gets very close to the brake line? And when you did the brakes did you (or your mechanic) use fresh brake fluid out of a sealed container or use one of those pump things sticking in a gallon can that had been sitting around for a period of time. Large brake fluid containers tend to be a magnet for moisture and the cans with a pump on them are very susceptible to drawing moisture. Plus one more thought on the subject. Is this is the first four wheel drum brake vehicle you have had and driven? The biggest issue with four wheel drum brakes is that after several hard stops in succession or working the brakes hard on a down hill run they have a tendency to fade when you attempt to stop. And as soon as they cool off they are ok again. Did you happen to use the brakes rather hard and often on that trip? And did they act up right after that? Guys like Jim and myself who grew up with drum brakes and were in our 20's or older before we had a disk brake car always have that in mind but younger guys who grew up with disk brakes and are now driving a vehicle with four wheel drum brakes have a bit of a learning experience in that department.
Please describe "no brakes". Pedal to the floor and still no stopee? Hard pedal that's not doing much? Can you pump em up? Pedal to the floor-Master cylinder by passing-Could be trash in M/C or valve going bad. Hard ineffective pedal-Most likely booster problem. Pump up brakes- likely air in system These are general brake problems, Buicks of this vintage are a mite different however. Give us a clue.
A wheel cylinder will just leak or give out completly it won't cause this problem, a booster as stated before would give a hard pedal but would still leave you with brakes, they will be affective you just have to stand harder to make them work, if the booster went bad it would have fluid leak into its vacume chamber on one side and if a cup bypassed it would just be a no brake syndrome within its chamber same with the master if a cup should allow fluid to bypass, I don't see any of these things happen. You didn't say if you had no pedal, clear to the floor or just a longer stroke for moment.
Guys, please forgive me for answering your questions & suggestions in general without names but you have all seperately put forward great views that I will attempt to answer. I have driven many drum brake buicks & lincolns for some time so, yes am familiar with them & usage. No hard braking at any point, just casual cruising. At point of incident the pedal went to floor at first push five mins after last using brakes on a slow stop with good pedal. Pedal went to floor & in panic I just kept stamping on it. When I came to rest I tried again & had pedal! Definitely not pedal fade because it floored on first touch and at not great speed. On viewing afterwards the fluid level seems to have dropped very little if at all, other than some fluid that has blown out of the tiny filler cap vent hole. Brake pedal still up and no leaks at wheels. Since rebuild I have had a good pedal but not as effective braking as before rebuild but adequate ( they were s!*t hot before ). I guess if the fluid passed the cups once, that would be it? So I am thinking not the master itself but the relief valve perhaps? The suggestion regards exhaust being near to the pipe is worth checking tho can't remember anything being rerouted. The occasional flooring of the pedal & good 95% of the time has me beat regards working it out.
sounds like a junk master cylinder if you didnt lose fluid and the pedal was able to be pumped up and there is no air in the system. I would replace with a dual resiviour unit and split the brake circuits like anything else made from 1967 up.
Do you still have the stock single bowl/single line brake system on there? Power assist? Assuming you have stock system: they didn'y have a 'relief' valve, there is an internal flow thru check valve that is included within the 'pressure chamber' of the piston - but it is inclusive and won't let fluid back to the bowl. The only think i can think of - if the brakes were ok afterwards and there is fluid in bowl etc - is there was a piece of trash blocking the 'compensate port' where fluid is gathered up by the piston or the primary cup seal allowed fluid to return to teh bowl. Basically, if the bowl is still full of fluid, the fluid is nice and clear, there isn't trash in the bolw then i'd be pulling the piston out of the master cyl and looking at the seals. IF it were elsewhere in the system there would be a huge leak - blown rubber line etc and be obvious and in no way would pressure return afterwards - it is in the master cyl.
I've had master cylinders (personal & customer cars) that would "bypass" the cup once in a while and the pedal would go to the floor. It usually happens when you're using light pressure on the pedal. Anytime it happened, I could let of the pedal and hit it hard again and it would work. Fix was new cups or mastercylinder. Larry T
This happened twice with my '55. Had a new MC, new lines, dual non power master to front disc and rear drum. Pedal to the floor-no brakes front or rear-. Never was able to pinpoint problem-- I used DOT5 silicone brake fluid. Are you using silicone brake fluid? Is it possible the rod from the pedal effecting the MC? Air bubble from loose fitting? Bad MC (why?) Look forward to hearing the solution as '55 is sitting, Larry
These moisture testers are available for around £15.00, could be worth a try, agree with other posters about water absorbing into the fluid, I had the same problem as a youngster with a mini and re using the old fluid tho save money or because we didn't know any better.
Hello guys, please excuse my late reply but I wanted to inspect the master cylinder before answering you. On stripping it down I found slight rusting in the filler cap & on the check valve. The more I think about it, the more I am convinced that we inadvertently added opened brake fluid that had moisture content when we redid the brakes a year ago. The car has been driven very little in that time and never on a hot day. The day the near wreck happened was HOT, I had done a 60 mile trip, parked the car for ten mins & then the brakes failed 1 mile down the road. I am almost convinced that the heat in the engine bay that hot day evaporated the moisture, giving me an air pocket & then no pedal. I don't know what you al think but it seems feasible to me & I appreciate all the views you have given to help me conclude this. Is there anyone other than Cars & Kanter that supply rebuild kits ofr Delco Moraine 1958 Master Cylinders do you know? Cheers.
If thats a single pot master, I'd upgrade to a dual right away. Also, stay with DOT#3 fluid, 5 is too slippery and bypasses easy.
I may have missed it in some of the suggestions, but some of the master cylinder pistons have check valves on the end. These are like reed valves. They seal against the end of the piston. Trash between the thin reed metal and the piston will allow fluid to by pass and not make pressure. A stab on the pedal sometimes can correct the seal and you will have a good pedal again, but the trash is still in the fluid and it can reoccur. Some rebuild kits have new pistons, if not get a rebuild. good luck,
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