Posted by Bob on Tuesday, February 27, 2001 at 1:35AM :
To all....My 61 wm300 just started having a
problem and I need some advice. Hadn't run her in about 6 weeks. I started her, pulled her out on the driveway to let her run, put her in nuetral, and went to apply th MICO brake on the dash the way I usually do, to act as the emergency brake. This is the way I usually do it... The MICO handle is down, I flip it up, press on the brake pedal, which
gets solid/hard, and the drum brakes are applied. THIS PART WORKED AS IT SHOULD. The
problem arose when I released the MICO brake handle. Usually the drum brakes immediately release, and the brake pedal goes back to normal. I said usually...Now what happens is that when I release the MICO brake, the drum brakes do not release for a minute or two, and the brake pedal stays solid/hard. Then after a couple of minutes the brakes are released and all is normal. If I then press the brake pedal, If I recall correctly, ( I am not 100 % sure on this) the drum brakes grab an release as they should. I also noticed that if the truck is not running and I press the brake pedal, the drum brakes act normally. I probably need to: A) Verify that the drum brakes act normally after the drum brakes are stuck and released by the MICO
brake with the truck running ( the 2 minute deal ) and: B) How do the brakes act when I
apply the MICO brake and release it WITHOUT
the truck running. I don't know how this MICO
brake works. Does it use engine vacuume ?
Is there some kind of pressure relief valve
associated with it that is supposed to bleed
off when you release the MICO brake handle.
Possibly some portion of the MICO brake unit
needs some sort of lubrication, as it was working fine until I did not use the truck for about 6 weeks. ALSO...can anyone give me the princples of how these MICO brakes work, and what preventive stuff needs to be done to them ? One last thing...My 61 wm300 is a fire truck with a midship pump behind the cab. It has some other oddities that I have not seen on regular power wagons. It has 2 of the big round vacuume booster cylinders on the frame. One I am sure is for the MICO brake. What could the other one be for ? Also associated with one of these boosters is some type of orange fram filter mounted under the seat on the drivers side, and it appears to be screwed down onto a fitting, and it is obviously replacable. I am pretty sure it is piped somehow to one of the vacuume booster cylinders. Any idea what this filter is ? Many thanks in advance to all that I hope will be kind enough to respond to all my questions. Once again,
thanks...From Bob Stopka, 25 year pw owner, presently with a WC54, and my 61 wm300 HOWE
Corp. fire truck..
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