I know it is not a traditional rod, just my daily driver and wheels to get to BTTFs since the coupe is a long way off. In the process of converting my 64 Malibu from manual drum, brakes to power disk and have hit a problem. CANNOT GET A HARD PEDAL, IT DROPS TO THE FLOOR. It does not pump up either. The components: The front disks/spindles are 70 GTO. The Master Cylinder (1 1/8), Booster are 72 Chevelle specd for a power disc set up. The rear cylinders are 15/16. All components are new, Wagner, the only rebuilt unit is the booster. The combination valve is a stock 72 Chevelle. Basically the components that would be used in a 70-72 Chevelle with power disk brakes. Pedal assembly is 64, with the push rod set in the power brake position. The hard lines from the combo valve to the frame are new and feature about the only thing that doesnt look stock. The three vibration loops in each line are vertical not horizontal due to lack of space. The process: Bench bled master cylinder and got a good clear stream from both ports with no air bubbles. Installed in car and bled brakes and got clear streams for at least 10 pumps at each wheel. Thought the master cylinder might be leaking internally so replaced it with another new one, no change. The question: What am I missing? What can I try? HELP guys and gals. If I don't get this thing fixed, BTTFs ain't going to happen. Canuck
Fresh lines (lots of air) can fool you as they pass fluid PAST an air pocket - happens alot actually - bleed entire system SEVERAL more times - before panicking. As for your "NEW" booster - the easiest way to check this is to apply pressure to the brake pedal and hold it there - now START the engine - a functioning booster will now DROP the pedal a couple inches as it "works". No DROP = No good. Gravity bleeding works IF you have the time. Power bleeders are nice IF you have/can borrow one. I have even used a large syringe to "purge" the majority of air from the lines before bleeding them "normally". I agree with double checking the pushrod lenght into the booster - I adjust mine so it's anywhere from LESS than a 1/16" to almost touching the piston - depends if you have a gasket or not. No gasket and I adjust it to the LOW side - with a gasket I adjust to the HIGH side (1/16"). Let it gravity bleed over night and re-bleed everything first thing tomorrow. Of course if you're IMPATIENT (like me) you can also try to "reverse bleed" it by "working out the bubbles" With a M/C mounted HIGH (as in your car) you can work the pedal and actually draw the air bubbles UP to the M/C. Slowly depress PEDAL - remove quickly - REPEAT - REPEAT REPEAT................
there was a neat tool made from a garden sprayer, thread was on garagejournal about a bmw. power bleeder with one person. my lines were crossed and had the same problem you had. if one end shoots up, that could be the problem.
Try gravity bleeding.You open all the bleeders at each wheel, so that fluid can exit freely,and position something to catch the fluid if you dont want a mess. Check the master cylinder fluid level, every now and then, refill if needed.Allow this to happen over a period of a few hours.When you feel confident most of the air is out, close the bleeders, and cap the master.Check your pedal then. If its better, but not 100% use the normal bleeding procedure one more time and you should be alright.This has worked for me very well several times.
Couple of tips, first start bleeding form the calliper furtherest away from the master cylinder and two use a set of brake clamps on the two or three rubber brake lines that you are not bleeding at the time, remove them as you go-it should force the flid to take one path at a time and eliminate air bubbles. Other things-make sure the pistons and sliders on the callipers are not siezed. make sure the rubber brake lines are new-old ones can expand when you put you foot on the pedal and take up the fluid that the master cylinder is supposed to feed the calliper pistons.
i just had the smae problem with my drum brakes..it ended up being the pedal rod was to short..had to add an inch ..thats it just an inch..and it works great now...i know an inch doesnt sound like much but it was my problem...and now its not...unbolt the pedal and lift it up..if theres any distance from the rod to the lifted pedal .thgeres your problem
Just in case, are the calipers mounted with the bleeders at the top? I'm seen them remounted upside down by mistake after folks have had them off for work or whatever. The result is chasing pedal that will never come. It's a simple thing, but it happens.
I have the exact problem, squishy pedal, with a 60's open wheel oval car I'm restoring. All drum brakes, new lines and cyls.. It appears to be clear fluid from all four........ but as the above replies state, I think I might be fooled also. I'll try the posted cures and let everyone know how I make out. Maybe it will help someone else in the future. Phil
There was an article in one of the 'Muscle Car' type magazines a few years back that had them building a power bleeder - yes, they actually built something they could have bought - I was shocked. Looked pretty simple. It was essentially an air-hose bung (sorry for the lack of proper terms) mounted on a piece of steel plate a little larger than the average master cylinder with a sheet of rubber on the other side. You put the rubber side over your open full master cylinder with the non-hose side of the bung in the fluid reservoir, connect the air hose, and turn the compressor up to 15 psi or so. Repeat the procedure on the other side if you have a dual m/c and you're done. Haven't tried to make one yet, but it's in the future as I need to completely redo the brakes on our Olds. I'd prolly use an air drier/cleaner from HF to make sure oil and/or condensation from the compressor didn't end up in my brake lines...
With the master cyl. cover removed (dual reservoir type) when pushing on the brake pedal, is it normal for fluid to squirt up from the front reservoir from the hole in the bottom? It seems to do it only when the pedal first starts it's travel.
Yes... the squirting is normal... Don't worry about that.... Have you been Vaccume bleading, or gravity bleading??? The combination valve has a spring and check ball inside.... It is there to allow the rear drums to start activating slightly before the fronts.. The rear drums have farther to travel before making contact..... If you are trying to gravity bleed the fronts, it will not work..... If you are trying to use vaccume, you will have to have something like 40lbs of vac. before you can override the check valve.... If you look at one end of the combination valve, you will see something screwed into it.... That is the check valve. On most newer setup's there is a way to de-activate it for bleeding.... Your best bet is to have someone pump up the peddal a few times, and crack the bleeders. Then lather, rinse repeat.... You must get the rears done right first, since it is actually the pressure for the rear system in the master,that pushes against the piston to activate the fronts.... You should also make sure that your rears are properly adjusted... You have to do the initial adjustment yourself, then they self adjust from there.... You might also look to see if some crap got stuck in the combination valve....
Thank you for the information. This particular car is a 60's open wheel oval race car. It has drum brakes and the lines come from the master cyl. directly to the wheels, no valves etc.. simple from the master to a 't' then to each wheel. Might this set up make for a soft pedal? I did the traditional pump and hold and bleed, then tried gravity but it didn't make a difference. Phil
i used a vette m/c, and they squirted when i started to pump the pedal. I had the front going to the rear and v.v. (vette ones are backwards i found out) the bigger res. goes to the front. they don't geyser up much now that its done right.
don't underestimate a tiny air bubble. Once had to take a caliper off and hold it horizontal with the bleeder up to get the air out. Found it in a "what the hell why not try it" after replacing everything else.
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