Have to pump brakes [Archive] - Chevelle Tech

: Have to pump brakes


66fastcarss
May 11th, 09, 12:13 PM
Was wondering if anyone could make a suggestion or has had this problem before and knows the answer.

IN my 66 chevelle drum brakes single reservoir MC, I am having to pump the brakes once (rarely twice) to build up enought pedal firmness to get it to stop. Once the brakes are pumped once, I can hold that pressure there with a little weight on the pedal until I release the pedal. After that first pump they feel just fine and seem to work as needed. Then when I take my foot off the brake until the next stop sign, then need to pump then once again to get the pressure back. Initial pump has slight pressure at the end of the pedal stroke but after that pedal feels pressure right away like I think it should. I have also noted that the pedal will hang down enough after I let off the brakes that the brake lights will stay on about half of the time.

I have changed fluid, cleaned out the master cylinder (had some sludge in it) and bled the brake lines and the MC and feel like the air is out of the lines. I don't see any fluid leakage around the wheels. Could this be a bad master cylinder?

I am trying to nurse the old drum brakes along for one more summer and have plans on 4 wheel discs next summer, so don't want to throw a lot of money into the current braking system. I just need to get them safe and to pass safety tests for registration in my state. Any help would be appreciated. Thanks,

Jeff

chrisbbee
May 11th, 09, 1:43 PM
I would take a loot at the rubber cup inside the master cyl, and maybe even pass hone down the bore of the master cyl to make sure it is all uniform. after a long time the master cyl can "egg" from wear and you wont get good pressure.

66fastcarss
May 11th, 09, 3:07 PM
Thanks! I assume you mean the seal where the plunger enters the MC and not the cap seal is that correct? If there is distortion of the tunnel, can this be fixed with the hone or is it just better to pop for a new MC?

Jeff

novaderrik
May 11th, 09, 4:20 PM
adjust the brakes- a few hard stops in reverse should do it.
back when i had the 4 wheel drum brakes on my Nova, i had to do that about once a week, which was about every other tank of gas. sometimes, the brakes would get so loose that i had to pump them just like you do.
to keep them adjusted, always use the brakes to come to a complete stop every time you back up.

Schurkey
May 11th, 09, 6:25 PM
If the brakes are so far out of adjustment that the pedal has to be pumped--and that's a fair assessment of what's happening, but not a guarantee--then you'll spend the rest of your life trying to adjust them by backing up and stopping.

Pull those drums off and MANUALLY inspect and turn the star wheels.
1. Are the teeth worn off the star wheel at any point?
2. Is the self-adjusting mechanism still on the brakes, or did some moron decide it was excess baggage somewhere in the last 40 years?
3. Are the threads of the self-adjuster seized?
4. Are the shoes excessively worn?
5. Are any of the drums excessively worn?
6. When completely released, do BOTH shoes seat on the anchor pin at the top of each backing plate, or is one or more shoes coming to rest before touching the pin? (Common as dirt when some idiot decides to adjust the park brake cable BEFORE adjusting the service brake.)
7. Any missing/damaged/stretched/distorted brake springs?
8. Any traces of brake fluid under the rubber boots of the wheel cylinders?

The first seven of these items can prevent prevent proper brake adjustment. Number eight is just good practice to inspect--if you have leakage, you might as well buy new wheel cylinders.

66fastcarss
May 11th, 09, 6:38 PM
Derrick,

Thanks for the advice. I will try to "adjust" the brakes first as this is a quick and EASY thing to try. I will hope this does the trick and avoid any further expense and effort until I do the swap. If it doesn't work, then will try to tackle the master cylinder unless anyone else has other thoughts.

Jeff

66fastcarss
May 11th, 09, 6:50 PM
Schurkey,

Thanks for the great list of things to check. If the "adjusting" doesn't do the trick, then will start down that list to see where I end up. I love TC as there is just so much knowledge here and people willing to help. Have been working on my car the last 3 years to get it back to street legal and safe to drive around. Think I might just make it this summer as this is close to the last thing I need to take care of to be road worthy. I really appreciate everyone's help!

Jeff

novaderrik
May 12th, 09, 12:22 AM
If the brakes are so far out of adjustment that the pedal has to be pumped--and that's a fair assessment of what's happening, but not a guarantee--then you'll spend the rest of your life trying to adjust them by backing up and stopping.

Pull those drums off and MANUALLY inspect and turn the star wheels.
1. Are the teeth worn off the star wheel at any point?
2. Is the self-adjusting mechanism still on the brakes, or did some moron decide it was excess baggage somewhere in the last 40 years?
3. Are the threads of the self-adjuster seized?
4. Are the shoes excessively worn?
5. Are any of the drums excessively worn?
6. When completely released, do BOTH shoes seat on the anchor pin at the top of each backing plate, or is one or more shoes coming to rest before touching the pin? (Common as dirt when some idiot decides to adjust the park brake cable BEFORE adjusting the service brake.)
7. Any missing/damaged/stretched/distorted brake springs?
8. Any traces of brake fluid under the rubber boots of the wheel cylinders?

The first seven of these items can prevent prevent proper brake adjustment. Number eight is just good practice to inspect--if you have leakage, you might as well buy new wheel cylinders.

it always worked on my Nova and on the 68 Chevelle Nomad wagon i had back in the mid 90's.

Schurkey
May 12th, 09, 1:14 AM
adjust the brakes- a few hard stops in reverse should do it.
back when i had the 4 wheel drum brakes on my Nova, i had to do that about once a week, which was about every other tank of gas. sometimes, the brakes would get so loose that i had to pump them just like you do.
to keep them adjusted, always use the brakes to come to a complete stop every time you back up.

it always worked on my Nova and on the 68 Chevelle Nomad wagon i had back in the mid 90's.
If your brakes got out of adjustment that far, that fast...I'd say it wasn't working correctly.

True enough, the brakes on our Chevelles are intended to self-adjust when stopping in reverse. But having problems with the adjustment to the point where the brakes have to be pumped before the car will stop--means there is something else wrong.

It also means that the adjustment is so far off that it'll take forever to properly adjust them by backing up and stopping. Much faster to poke an adjuster spoon into the brake mechanism and rotate the star wheels manually--as long as there's a knockout in the backing plate. I haven't had much fun with knockouts in the brake drum. I've had to beat the piss out of a couple of drums to get the knockout to pop free...and then I wonder about the balance of the drum afterwards.

Of course, I prefer pulling the drums so that a visual check can be made of the brake parts.

novaderrik
May 12th, 09, 1:22 AM
of course, it's always a good idea to pop the drums off once in a while to look things over, but they don't have to get very far out of adjustment to cause a dead pedal or cause the car to pull one way or the other. i drove my Nova almost everyday for 8 months out of the year, so it saw some miles. every few days, i'd notice the pedal getting soft so i'd do a couple of good hard stops in reverse to tighten the pedal back up. this was after the first summer of me driving it and wondering why the brakes kept going so screwy. once i remembered that the front drums needed regular adjustments and started driving accordingly, it made a big difference and it never got oo far out of hand.
i do the same with my other cars, too, but being that they are all front disc/rear drum cars (97 cavalier, 84 Regal T Type, 74 Monte), they tend to stay tighter longer. i also always come to a complete stop when backing up before putting the cars in gear.

Two Lane
May 12th, 09, 2:29 AM
If your current single MC fails, you're toast.



A Cardone dual master w/a lifetime warranty is cheap-cheap-cheap.


Buy one now, then sell it to someone else also still risking

a single MC later when you do the planned brake upgrade.



Single MCs are dangerous Fred Flintstone relics.

66fastcarss
May 12th, 09, 12:42 PM
Thanks again for all the advice. I will be sure to manually inspect all my brakes probably this weekend now that I know what to look for. Was also wondering if the brakes being out of adjustment would cause the pedal to sag enought to engage the brake lights (I imagine this is the cause of that issue as well).

I will also look into the dual MC idea as well. Is there a certain model # I would need and is there any change in brake lines that needs to be done to swap to a dual MC?

Thanks and sorry for such simple questions, still working on my rocket science degree needed for this stuff!

Jeff

oktunes
May 12th, 09, 6:14 PM
I would never run a single master cylinder on anything. Why take that kind of chance with your Chevelle. I think every old car I've had the last 20 years, I replaced master cylinder, rubber brake lines and wheel cylinders or caliper O rings soon after buying. Went to dual cylinders on everything.

66fastcarss
May 22nd, 09, 4:05 PM
Just an update and thanks to everyone who gave opinions. I took all 4 drums off (even the ****** rusted on one:mad:) and cleaned up and took the adjuster out and lubed and reinstalled. I adjusted them best I could by hand and then did a couple of hard backup stops. Things are 98% better now. Have good pedal pressure. The only remaining issue is the pedal will sag just a little when you let off and half the time will still trigger the brake lights. Will also look into the dual MC soon to make it even safer. Thanks to everyone for you advice!

Jeff

novaderrik
May 22nd, 09, 6:09 PM
push the brake light switch in a click or two. that should solve the brake light issue.

iowacar
May 22nd, 09, 7:28 PM
Also, there is a return spring on your break pedal. Make sure it is there and in good working order.

gripperrat71
May 26th, 09, 1:27 AM
I also have the same problem but i have dual master cyl., new lines in front, new proportioning/combo valve from year one, added a line lock and added disc brakes on frontabout 4 years ago. My pedal is all the way down at first but still partial brakes and if you pump it you get real good pedal. Sorry to jump in on your thread but I'm having the same exact problem w/ more up to date brakes so it isn't just a drum/drum single master problem.

Schurkey
May 26th, 09, 12:32 PM
I also have the same problem but i have dual master cyl., new lines in front, new proportioning/combo valve from year one, added a line lock and added disc brakes on frontabout 4 years ago. My pedal is all the way down at first but still partial brakes and if you pump it you get real good pedal. Sorry to jump in on your thread but I'm having the same exact problem w/ more up to date brakes so it isn't just a drum/drum single master problem.
First Guess: Opening the hydraulic system allowed air in the system. Bleed, baby, Bleed.

Chris R
May 26th, 09, 9:19 PM
When it comes to problems like this. I always take the proper brake hose clamps and clamp all the hoses and then get in and try the master to see if it still needs several pumps. You narrow down the master this way.

Then. I go and take off one clamp and try the pedal again, re-install the clamp and go to the next hose and try that clamp. I keep removing and reinstalling clamps until I find the circiut that needs the pedal to be pumped up. If its the rear clamp, you have something going on in the rear brakes.