greasemonkey48227 Posted March 25, 2013 Share Posted March 25, 2013 Hi everyone,I have a question about spring brakes. My truck is an 89 Econodyne. The brakes are slow to engage and release. I'm kinda new to air brake systems, but I found the bendix air brake manual and read the whole thing. I've traced the parking brake piping and found there is no SR-1 valve in the system the pipe runs from the delivery at the knob to a T on the firewall and then to a double check and to the spring brake side of the chambers. When I push the brake knob there is a large exhaust and then it will weep for several seconds in the dash and the quick release valves don't dump. I took the double check off and tested it and it is working correctly. There are no air leaks in the system and I've replaced the quick release valves(before I realized there wasn't a spring brake relay). I searched quite a bit and the information I found seems to say this truck should have one on the rear cab crosmember. Am I way off base or is there something I'm missing? There are three valves on the dash and all are working correctly and plumbed the right way, and it doesn't matter if I use the park knob or the tractor park knob it does the same thing. Any help is appreciated, thanks in advance,Tom Quote Link to comment https://www.bigmacktrucks.com/topic/30542-slow-parking-brakes/ Share on other sites More sharing options...
thomastractorsvc Posted March 27, 2013 Share Posted March 27, 2013 have you checked to make sure that the slack adjusters and s cam are all loose, free and working with grease thats where I would start then look for sticky valves Quote Robert"I reject your reality and substitute my own." Link to comment https://www.bigmacktrucks.com/topic/30542-slow-parking-brakes/#findComment-174516 Share on other sites More sharing options...
greasemonkey48227 Posted March 30, 2013 Author Share Posted March 30, 2013 I have adjusted all slack adjusters and eqaulized the travel of all four and greased all lube points. The frictions are all wearing equally. The brakes hold well and release completely they just take 45 seconds or so to go from applied to released and back again. I was thinking that if there was supposed to be a relay in the line my problem was without the relay all spring brake air had to go through the button and when pressure was released it didn't come down fast enough in the air line to allow the quick release valves to open, but once again I'm new to air brakes. Thanks for the reply.Tom Quote Link to comment https://www.bigmacktrucks.com/topic/30542-slow-parking-brakes/#findComment-175166 Share on other sites More sharing options...
b61mack Posted September 30, 2013 Share Posted September 30, 2013 I have adjusted all slack adjusters and eqaulized the travel of all four and greased all lube points. The frictions are all wearing equally. The brakes hold well and release completely they just take 45 seconds or so to go from applied to released and back again. I was thinking that if there was supposed to be a relay in the line my problem was without the relay all spring brake air had to go through the button and when pressure was released it didn't come down fast enough in the air line to allow the quick release valves to open, but once again I'm new to air brakes. Thanks for the reply.TomI would replace the quick release valve, I don't have a relay valve on my truck and the park brake works fine. Quote Link to comment https://www.bigmacktrucks.com/topic/30542-slow-parking-brakes/#findComment-209108 Share on other sites More sharing options...
Freightrain Posted October 2, 2013 Share Posted October 2, 2013 I have a relay valve in my truck(only because the new rear frame section came with it), but I'm thinking you need new quick release valve(s). Can you hear an air "whoosh" at the axle when you push and release the brakes?If they are stuck, you have to wait for air pressure to work against itself to apply and then release the brakes. That may be also the air you feel when you release the trailer lines. Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/30542-slow-parking-brakes/#findComment-209604 Share on other sites More sharing options...
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