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Yvan Lacroix
October 23, 2022

Bus Maintenance Musts

Editor’s Note:  Crawling under a bus can be very dangerous.  If you are not familiar with your bus’s suspension system, or your jacks, then you should take your bus to a heavy-duty bus or truck mechanic.  People are killed every year by jacking them up improperly, by airbags that blow out unexpectedly, or when they fall off blocks and other support items that should never be used for jacking up a bus.  Neither I nor Bus Conversion Magazine assumes any liability for what you do or how you do it.

Unfortunately, many bus conversion owners do not maintain their bus as they should, having been erroneously led astray by mechanics, friends, YouTubers, and old wives’ tales (it’s a million-mile motor for example). If you’re looking to purchase a coach, or you just bought one, here are some things to consider.

Your bus will reward you when properly maintained with safety, reliability, comfort, and peace of mind. Our bus moves us roughly 50,000 miles a year, and we never worry when hitting the road.

Maintenance will always cost less than repairs, and won’t leave you stranded. The following list applies to both someone inspecting a bus for purchase, or once it’s yours to make sure it’s safe and reliable. 

If you are considering a coach to purchase, ask the current owner for the service history (with invoices for proof), and what their maintenance schedule is. (Unfortunately, many bus charter companies, destroy the maintenance records before selling their buses for liability reasons. If you buy one of their buses, it is up to you to inspect their buses thoroughly.) 

Many owners maintain their coaches properly, and keep meticulous records, while some live in blissful ignorance and repair their bus when something breaks. The following list is only for the mechanical side of the coach, the conversion side will be dealt with in a future article. 

  • Tires should be in good repair, have no cracks, be less than seven years old, and preferably be equipped with a TPMS (Tire Pressure Monitoring System). Look for cupping, uneven wear, and other signs of abnormal wear and abuse. Check tire pressure and adjust to the tire manufactures suggested pressure for the weight on each axle. If the tires are showing abnormal signs of wear, take it to a bus alignment shop and have it checked out. 
  • Wheels should have no cracks, dents, or rust. 
  • Wheel studs should protrude from the nuts a minimum of three threads (it varies by jurisdiction, but that’s an average number), and be tightened using a torque wrench. If you own a bus, you should have and know how to use a torque multiplier or large impact wrench, and a torque wrench to ensure you do not over-torque your lug nuts.  Also, know what the torque spec is for the lug nut tightening for your bus. 
  • Wheel hubs should be checked, for the level and/or quantity of lubricant, oil, or grease. 
  • Inspect the back of the hubs, wheels, and tires for visible oil or grease leaks, and change any seals that leak.  Regular driving of your bus will keep them lubed and healthy.

Indication of a wheel seal leak.
  • Inspect brake adjustment and lining thickness, and ensure that there is no rust on the shoe deforming the lining. Inspect all brake lines for wear and leaks. Break hoses should never be touching another object, lest they may eventually wear through.
  • Suspension. If your bus has airbags, check them for cracks, leaks, and missing bolts. Replace any that show signs of aging or wear.
  • Verify all shock absorbers are in good condition. Chances are they should be changed; they are a wear item with an average life of 50,000 miles. If they show any signs of leaking, replace them.
  • Verify all suspension bushings, mounting points, and axles for wear, rust holes, and towing damage. 
  • Check tie rod ends and kingpins for play.
  • Check airlines, fittings, and valves for leaks. Tighten or replace as needed. 
  • Check all brake and suspension grease fittings (there are at least 100 lubrication points on a coach). If it moves, chances are there’s a grease fitting.  Lubricate them as recommended in your bus’s maintenance manual. 
  • Do a DOT Air Brake system check. The tank drains should all be tested and the tanks drained after each trip. Consider the air dryer a part that should be serviced or changed regularly (See Below). 
  • Inspect all bulkheads for damage, cracks, rust/corrosion. 
  • From both inside and under the bus, look at the rivets, and replace them if needed. Most coaches are monocoque construction, and every rivet is part of its structure.
  • From a cold start, does the engine smoke, stumble or hesitate? Look at the exhaust under full acceleration, a puff of black smoke is normal, white or blue isn’t. 
  • Any visible oil leaks should be repaired.  A leaking Detroit Diesel 2-Stroke is an unfortunate myth; they will not leak if they have been properly maintained.
  • Inspect all belts, hoses, and engine mounts. 
  • If buying a used bus, you need to budget for a complete fluid and filter change. This will be your baseline for all maintenance after this point. If possible, get an oil analysis for the engine and transmission before purchasing. 
  • Check radiator(s) for corrosion, missing or bent fins, and leaks.
  • Ensure that all gauges are functioning and that both engine bay and dash gauges read the same. 
  • Make sure the thermostat(s) open and close at the designed temperatures by running the engine up to temperature and paying attention to the coolant line’s temperature after the thermostat(s).  They should remain relatively cool until the engine gets up to about 180 degrees, or whatever the thermostat temperature rating is in your engine.
  • Check batteries for terminal corrosion, electrolyte level, age, and secure mounting.
  • Ensure that main battery cables are sound and well connected and that the cut-off switch is operable and functional.
  • Check that all headlights, tail lights, running lights, and switches work properly. 
Failure to maintain your bus properly could result in a hefty tow bill to get your bus to someplace that is qualified to work on a bus conversion.

Doing the above verifications properly will take 4-5 hours, will require some tools, and a safe way to get under the bus. The suspension and brakes are not to be trusted if you’re crawling under the bus. Properly support the bus with the factory jacking points and block the wheels to prevent your bus from rolling when the brakes are released.

After you get the coach home, it could take a few days to replace all the fluids, the air dryer, shocks, etc. Taking the time to put your coach in safe running condition will give you a solid foundation to go from and allow you years of enjoyment. 

Learning what to look for and how to maintain your coach will save you thousands of dollars over the life of your coach, and give you the confidence that you know the condition it’s in. Remember, breakdowns on the road, can cost significantly more than when you are home with a known mechanic.



7-Step CDL Air Brake Check

CDL Air Brakes – 7-Step Check According to HYPERLINK “http://dotmobileinspec-tions.com/” DOTMobileInspections.com
The 7-Step Air Brake check is designed to test the governor cut-in and cut-out pressures, air pressure leakage, warning buzzer, brake valves, and air pressure rebuild rates. Perform these steps in the order listed below.

  1. Engine on / Brakes on – Check gauges to make sure the governor cuts the compressor off at 120 PSI. Pump brakes until the pressure drops below 100 PSI to make sure the governor cuts the compressor on.
  2. Engine off / Brakes off – Do not touch brakes – Watch gauges to make sure pressure does not drop more than 3 PSI in one minute.
  3. Press and hold brake pedal – Watch gauges to make sure pressure does not drop more than 4 PSI in one minute.
  4. Key on / Engine off / Brakes off – Pump brake until the pressure drops to 60 PSI –warning buzzer should sound at or before 60 PSI.
  5. Continue pumping brakes until reaching 20 to 40 PSI – Emergency (red) and Service (yellow) brake valves should pop out turning brakes on.
  6. Rebuild air pressure in the tank – Hold accelerator at 1500 RPM. Watch air gauges and notice that the pressure rate of build between 85 PSI and 100 PSI should not take more than 45 seconds.
  7. Perform tug tests. Tug against Parking Brake only. Tug against Emergency Brake only. Tug against Hand Brake only. Test service brake by accelerating to 5 MPH and pressing the brake pedal. If the ve-hicle pulls to one side, this indicates a brake adjustment problem.

If there is a problem discovered while testing the Air Brakes, do not drive the vehicle. Never operate a vehicle that is unsafe to drive.
It is your responsibility to make sure it is repaired by a qualified mechanic.

Article written by Yvan Lacroix
Yvan and Sylvie are fun loving grandparents and teachers. They travel the world teaching detailers how to improve quality, efficiency and safety.Their first conversion was a 1964 GMC SDM 5302 (Click HERE to read about their first conversion in the February 2018 issue of BCM).The second conversion was a 1973 GMC Buffalo 4905A called the Lacroix Cruiser. Click HERE)to read the April 2021 issue of BCM featuring the 1973 GMC.Now they are traveling and living in their third conversion, a 1995 MCI 102DL3.

You can follow along with their conversions and travels on Facebook, Instagram, and YouTube.

You may contact Yvan at: yvan1lacroix@icloud.com

Click HERE to read other articles by this Author
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