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Thread: Lowly the Lorry. . .

  1. #161
    Join Date
    Mar 2017

    Default Pleasure Cruise Breakdown. . .

    Decided to take the Mrs, kiddos and pooch for a Saturday drive in Lowly truck between the snow flurries. This was Mrs' first real drive in the truck and it was a splendid outing until we broke down a couple miles from home on the return leg. Slowed down coming to a stop sign on a residential street (thankfully this happened on backroads!) and the compressed air reservoir's low pressure alarm started its mind-numbing note. Dash lights began coming on: air pressure tank low, parking brake on. Then the two needles on the dashboard's air pressure gauge slowly dropped below acceptable operating pressure.

    For those not familiar with air brakes (and I'll admit that I am a newbie), when air pressure is lost the parking brakes are activated mechanically. Lowly was not going anywhere and I couldn't shut him off; I'm guessing the electronic kill switch fires off some pneumatic valve/cylinder that kills the engine. So, with the truck idling, unmovable and blocking a lane of traffic I unloaded the family and began a very long trouble shooting of what the heck was going on. Thankfully my parents were called in to shuttle the family home and my long-suffering dad stuck around to help me.


    With my systematic process of elimination and a call to a diesel mechanic friend, the culprit was located - some sort of stuck valve in the compressed air cleaner/relief apparatus upstream of the pressure tanks. When you hear an idling truck or bus emit a loud pop/hiss, that is the air relief valve doing its job. Lowly's was stuck in the open position, letting all the air headed to the tanks vent to atmosphere. We decided to unscrew the incoming and outgoing air lines and mate them up, effectively bypassing the pressure relief apparatus to temporarily restore pressure to the tanks and let me limp the 2 miles back home.

    Meanwhile a friendly man living nearby directed traffic around our Mercedes roadblock as night descended and I frantically Mcguyvered a fix using a plumbing union in an attempt to get home before the next rain/snow squall descended. Here is a pic of the fix with the culprit in the background.


    Limped back home, stopping every time the pressure gauge needles crept above the "happy zone" to activate the parking brake and relieve the tank pressure as my pressure relief was no longer in the loop. Got home to a dinner of spaghetti. The kids thought it was a great adventure. When asked, Mrs said she enjoyed her first ride it Lowly. Whew! I just hope it isn't a sign of things to come!

    - Sheik

  2. #162
    Join Date
    May 2017
    This is a common problem in the RV world, mostly due to lack of maintenance. The air filter might be plugged, but, usually the internal valve, which is replaceable as your mechanic friend would know, gets full of moisture, dirt, etc.

  3. #163
    Join Date
    Oct 2011
    So this goes on the list of spares to carry then I suppose

  4. #164
    Join Date
    Nov 2012
    Ontario Canada
    Valve just needs a good clean. You could not shut down because the kill is air operated.
    You really have to watch your air. The low air warning alarm is an all out emergency, you should catch it before that occurs, I would suggest an air brake operators course even if it is not legally required in your state.
    1993 Mercedes-Benz 917 AF
    instagram joemorrisphoto

  5. #165
    Join Date
    Feb 2010
    Essex UK
    I had this issue many time and no amount of cleaning or repair kits provided a permenant cure. In the end I bit the bullet and bought a new dryer. All good now.

  6. #166
    Join Date
    Aug 2008
    Arlington, Virginia
    New dryer cartridge here, too - if only as a precaution.

    N.B. Google around, you can find any number of air brake primers aimed at school bus drivers. Well worth a bit of your time, if only to understand how things work.


    Certified Expo Poseur - Lives on Paved Road

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