HDX School Bus Heater Control

imported_John Whelan - March 19, 2014

HDX School Bus Heat Control Valve

As time goes on as we all know technology changes and this is still true for controlling the heat flow on a Thomas HDX Pusher School Bus. In the old days the heat control was simply a cable attached to the valve which was a throttle plate plumbed into the hot side of the coolant flow from the engine.

That changed to a motorized control valve controlled by a dial type switch on the dashboard. The one weak part of the control valve is the seals will leak eventually. The piping that connects to the valve uses o-rings to seal coolant. The o-rings are not standard and a universal kit o-ring kit will not help you out.

Access is very easy to this valve with a front compartment door that flips down. If the o-ring does not fix the leak the valve has to be replaced. There is a Technical Service Bulletin for these valves where they have been improved upon to prevent the leakage problem from occurring.

Checking For Outstanding Recalls and Technical Service Bulletins

If you contact your local Freightliner dealer they should be able to look up the technical service bulletin for you. The only place available for Thomas parts is at the dealer for this particular piece so let them know that you need a new heat control valve and heard about a TSB. Once they know your VIN they can look up all the TSB documents and Recalls.

If you are not the original owner of the bus I would advise you to contact the dealer as soon as you can to get an update on this information. A letter is usually sent out to advise owners of effected HDX buses that a recall or TSB is outstanding. This is especially important if you are the second owner of an HDX school bus.

Our group of HDX buses went through several recalls and TSB alerts with the electrical system, throttle pedal push rod, heat control valve as noted above, vehicle interface module etc. It doesn't hurt for you to check in to this just to be sure nothing got missed.

The HDX pusher rides like a Cadillac and is loved by our drivers for the comfort and serenity of a quiet cab. Rear engine buses are known for low engine noise levels and that really helps the driver to concentrate more on the road, the passengers and the instruments.

I hope this helps you out especially if you own an HDX pusher school bus. I've had a lot of experience on these models so feel free to ask me a question in the comment section below. Even better.... join Mechanics Hub and post a question in the forum. There are bus mechanics in the membership area who would love to help you out (myself included).