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Author Topic: Parking brake does not release all the time  (Read 14719 times)
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1980 MCI MC-5C

« Reply #30 on: December 22, 2013, 02:52:18 AM »

Sorry...  I was setting in my arm chair and not my driving chair when I wrote that, and actually working the PP valve is so automatic, I got it backwards...    Shocked


1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Tatamagouche, Nova Scotia
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« Reply #31 on: December 22, 2013, 05:11:33 PM »

Thanks to everyone for the tips and advise. I drove the bus about 25 miles yesterday. The brakes released and locked with no problem. I have never had to make a foot application to release the brake. About the pressure, I have 3,TR3 valves that are the inversion valves. One is for release, One is for parking, And the lower one is the trigger valve for engaging the parking brakes. I released and locked the brakes about 15 times total yesterday. I did note that when they don't release, In cold weather, I can hear a small hiss coming from the bottom r-8 relay valve. With the motor off and wheels blocked. Other times when they don't release, I don't hear any air leaking, But will notice a small drop in air pressure on the gauge over time. I rarely have to hold any foot pressure when I lock the parking brake. Florida is mainly flat. The first valve I replaced was that lower r-8 valve because it was leaking. I looked at my records and it was done in the warm months. Had no trouble until that fall. Then I had the chambers rebuilt and all the valves and hoses replaced. Again this only happens when it is below 50 degrees or so. Some times it will stick up to 60 degrees. So I think if the plumbing was wrong it would not work at all. I know the r-8 valves uses little pressure to operate, But maybe it isn't working all the way. I don't see where the cold weather would effect it. Thanks again and keep the advise coming. And I wish every one a MERRY CHRISTMAS.  God bless  David.
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