stevenelle Posted February 9, 2013 Report Posted February 9, 2013 Have had too much brake pedal for a while; thought it was just needing an adjustment to compensate for shoe wear. But after "trying" to adjust those brakes with some newer thicker shoes, I still have low pedal. Now I think it must be air. I tried the improvised pressure bleeder method (made with pump up sprayer and rubber cork). Pushed a lot of fluid thru all 6 bleeders but no air. Still have low pedal but can pump it up a few times to get more brake. Now I wonder if I have air in Master cylinder, and if so, how can it be purged. I really don't want to remove it if at all possible. Thank you for any assistance on this. Quote
52b3b Joe Posted February 9, 2013 Report Posted February 9, 2013 Check the back of your master cylinder to see if its leaking any. If you can pump it a few times and get the pedal to become harder then its not any adjustments, its a hydraulic problem. Check all your fittings and wheel cylinders too to see for any leaks. If you don't see any leaks then I'd say try to bleed it more to get air out. Quote
JBNeal Posted February 10, 2013 Report Posted February 10, 2013 A spongy brake pedal that firms up after being pumped a few times indicates a leak in the hydraulic system. Inspect the system for any fluid leaks as this would cause a spongy pedal. A poorly formed or split tubing flare or a worn wheel cylinder cup will cause a fluid leak. The master cylinder can be bled inside the truck, but the main fluid line coming off of the master cylinder will have to be removed and a temporary line installed that feeds back into the fill plug opening. This temporary line is to be watched during the master cylinder bleeding process to see when the air bubbles disappear from the fluid stream. If the bubbles do not disappear after multiple bleeding attempts, it may be possible that the master cylinder bore may be scored from abrasion or pitted from corrosion, and the master cylinder piston is not sealing against the bore wall. This would result in fluid leaking into the master cylinder plunger boot. Honing the bore may help to improve piston sealing, but too much honing will result in a worse fluid leak condition. Sleeving the bore or replacing the master cylinder may be the next step in resolving this issue. Quote
55 Fargo Posted February 10, 2013 Report Posted February 10, 2013 Have had too much brake pedal for a while; thought it was just needing an adjustment to compensate for shoe wear. But after "trying" to adjust those brakes with some newer thicker shoes, I still have low pedal. Now I think it must be air. I tried the improvised pressure bleeder method (made with pump up sprayer and rubber cork). Pushed a lot of fluid thru all 6 bleeders but no air. Still have low pedal but can pump it up a few times to get more brake. Now I wonder if I have air in Master cylinder, and if so, how can it be purged. I really don't want to remove it if at all possible. Thank you for any assistance on this. The Lockheed brakes, can and will have a low pedal, if shoes "are out of adjustment", pumping up pedal gives you better brakes, and temporary higher pedal in those cases.Air in the system will give you a spongy pedal, and sometimes require pumping of the brake pedal for firmer brakes. These shoes can be real fussy to adjust, especially with brand new brake shoes. In the old days, they would arc grind the shoes to coincide with the brake drums. I have found with some miles on brand new brake shoes, and adjustments, the pedal gets much higher, and does not need to be pumped for good braking repsonse....good luck Quote
Young Ed Posted February 10, 2013 Report Posted February 10, 2013 Fred is right with these non self adjusting brakes this can be a symptom of out of adjustment. I had this issue with my truck. Quote
Dodgeb4ya Posted February 10, 2013 Report Posted February 10, 2013 If the shoes don't fit you should arc them to fit the drums. Then adjust them properly. Quote
P15-D24 Posted February 10, 2013 Report Posted February 10, 2013 (edited) The test is simple and binary: Low pedal that comes up with a couple pumps is air in the system. And on the next application is goes back down, then can be pumped back up. Low pedal that stays at the same height no matter how much you pump is shoe adjustment. If it's is air in the system and you have done three times around with a pressure bleeder, you have a leak. Start by cleaning off every fitting and joint with denatured alcohol so they are totally clean and most important DRY. Then pressurize the system 5-6 times by pumping the brakes, getting a firm pedal and releasing. Then get a bright light and inspect every fitting for leaks. I use a kleenex to dab around the fitting. If their is a leak you will see dark spot on the kleenex. (This is why cleaning and drying with denatured alcohol is the starting point.) Leaks can be hard to locate, check for cracks in junctions block and unions. You have a leak. Edited February 10, 2013 by P15-D24 1 Quote
Fernando Mendes Posted February 13, 2013 Report Posted February 13, 2013 I solved my front shoes low pedal with new 1219-X linings. Quote
55 Fargo Posted February 13, 2013 Report Posted February 13, 2013 I solved my front shoes low pedal with new 1219-X linings. You must have drums machined way out. If brake shoe clearance it the issue, then proper and correct adjustment, and arcing or some time for shoes to "wear in" would be the remedy. Your shoes would not even clear in my drums with the adjusters turned way in. But my front drums are only 10.030 Quote
Fernando Mendes Posted February 13, 2013 Report Posted February 13, 2013 Don't know,but certainly. Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.