Back to Basics: The Back of the Bus, Everything Engines, Batteries & HVAC

The American Bus Association’s Bus Industry Safety Council (BISC) and Bus Maintenance Repair Council’s (BusMARC) 2021 Virtual Safety & Maintenance Series offered a sequence of educational webinars early this year, covering a variety of industry-related topics.

Presented as part of ABA’s BISC & BusMARC 2021 Virtual Safety & Maintenance Series

This panel was moderated by Mike McDonal, BusMARC chair and director of reg ulatory compliance and industry relations at Saucon Technologies. Panel members included Robert Hitt (Prevost), David Mailhot (MCI), Dany Landry (ABC Companies), and Derek Brown (TEMSA).


The panel covered topics including performance thresholds, improper battery maintenance, idle pully systems, radiator maintenance, how to avoid battery drain, improving battery health, and maintaining in-use equipment to improve efficiency and performance. It is presented here in an abridged format:

What is the standard maintenance interval for pulley systems?

David Mailhot: The pulley system is incredibly important. As the buses sit, the pulleys can become corroded and the bearings can seize up. Make sure that the pulleys are in good condition. You will loosen the belt and spin the pulleys by hand and feel them, make sure they are moving smoothly and with little effort and no vibration or no pulsing. 

The same would go for anything which that belt is hitting. Your alternator, pulley, and bearings, need to be in really good shape. Check the connections on the back by the engine side. The key is to make sure that everything on that system is moving smoothly and corrosion free, otherwise you are going to have belt problems down the road. I would suggest that when you do check everything and you start your coach for the first time, start the coach from the back. Set up the coach so that you are starting from the rear start switch. That will enable you to see or isolate a problem quickly as opposed to being upfront or leaning into your driver.

What is the standard maintenance interval for alternators?

Derek Brown: You need to look, not just at the alternator, but at the electrical connections to that alternator. Sometimes those can be very challenging to see if they have a shroud with the fresh air intake on the back. But if you are able, look at the connections and make sure they are not corroded. They use the alternator charging system on many coaches as a starter lockout, so if the alternator is charging, the vehicle will not crank the starter. Some coaches use a signal-on J1939 data link, but the connections on the alternator are very important to look at as well for multiple reasons. Not only just charging, but the functionality of, “Will the air conditioning system come on if the alternator’s not charging?”

What are common issues to watch for with radiators and charge air coolers? 

Robert Hitt: Radiators charge air rollers. All manufacturers have different specifications on the radiators and the charge air coolers as far as how to pressure check them, etc. The coolant packages are very important. It would be great if our industry could come together – as far as engine manufacturers –  and have one coolant, but that is not the reality. There is not a one size fits all. The key is electrical connections. Make sure all those weatherproof connectors are in good shape. Take the time to look at your wiring, make sure everything is in place. On our electrical fan drive, we have a test mode that allows us to test those fans which is an excellent tool for technicians to utilize. Any downtime should be used to learn all the different test modes and tools that are built into the coach, and make sure that your technicians know how to utilize those tools.

There are many different coolants available. What happens if a driver mixes coolant?

Danny Landry: Before we get too far into coolant contamination, there are a lot of misconceptions to cover. When we are filling coolant, many people tend to gravitate toward color. Color means absolutely nothing when it comes to coolant. What matters is the actual coolant. You can get into an OAT or an NOAT coolant and three colors from each of them are exactly the same. If you have a coolant that is purple and it is an OAT coolant, and the OAT coolant that you are buying is red, that is fine. As long as they are compatible, there should not be a problem.

When it comes to cooling, there are a lot of misconceptions with rubber and silicate hoses. You lose moisture out of that coolant. You are not losing coolant per se, but you are losing more water content of that coolant. 

When we get coolant and we add more coolant to it, our mixture is already off. We need to maintain a 50/50 split, rather than a 30/70 split or vice versa. It is always a good thing to check your coolant, especially during your maintenance. If you are on the road, I would ask that you put in distilled water if you have it. That would be great, because it is a lot less we have to fix when it comes into the shop. 

What spare parts should a driver have on hand if they need to execute an emergency and safe repair of the vehicle?

Mailhot: If you have a driver that is competent with a set of tools, then you should cherish that because that is a great opportunity. We try to keep the modern coaches as field maintenance or road maintenance friendly as possible. However, the bare minimum would be alternator belts, AC belts, fan belts or coolant belts, and a comprehensive bolt set. Some of the coaches are easy to change bolts, some of them are not. The main thing would be to get the coach off the road, and to keep a coach failure from happening.

Do batteries have a shelf life? What is the best way to maintain batteries in a storage state?

Landry: The big thing is to make sure you are storing them in a cool dry place. Optimal temperature for storing batteries is between 40 and 60 degrees. Realistically, the best way to store batteries is to put them inside of a plastic container. First, so they are not on a grounding source that is going to deplete the batteries. Secondly, so if there is a leakage of a battery, it is contained.

A big thing with batteries is that when we store them, they deplete. So, we still physically need to go out and charge the batteries that we have in storage. If you bring a battery down to 12.4, 12.3 volts in the storage you are at about 60 percent of what that battery can actually hold, so we want to make sure we are bringing up that voltage and we are keeping those batteries maintained. 

When it comes to flooded or lead acid batteries, they do discharge faster than an AGM battery. Electrolyte filled batteries, we want to make sure that they are staying charged, especially for our customers up north. If you are not in a well heated area, if those batteries are not charged. your electrolytes will freeze and your battery is pretty much ruined because it will probably crack the casing. 

The normal shelf life for a battery is five to six years, as long as we are truly maintaining that battery and it is stored within that zone of 40 to 60 degrees in a well-ventilated area. 

 With COVID-19, many operations have added additional filtration to their HVAC systems. What are some recommendations?

Mailhot: If you are putting anything on the coach, you need to make sure that if it has any maintenance interval at all, you add that to your maintenance schedule. With filters, make sure that you check with your OEM on the filter rating. An HVAC system has three rules: airflow, airflow, airflow. If you add a denser filter element, it is going to reduce your air flow and tax your system. So, before you put your filters in, make sure that your system is running as it should. Make sure that your heat exchangers are clean, make sure that your oil levels and your refrigerant levels are up. Make sure your system is running at peak efficiency, then you are going to get the best benefit from the new air filters.

A UV system is a dangerous system to humans, so you want to make sure that you are not staring into the light, or the system has appropriate safety protocols. UV lights have a shelf life, so you want to make sure that you change those on the required intervals. 

UV lights are fantastic, they are killing the virus – but do not just ad hoc throw it into your bus. That UV light is damaging to seals and plastics, so make sure that you follow the installation instructions, and make sure that you use the system that is approved for your OEM as well.