MCI5-A, 106^ outside, 7% grade, no more overheating

[Boise Belle]

Brief description of alteration:  Simply made changes to the stock bus heater core, using existing equipment, turned it into a 3rd radiator.  Only use it when needed.

Long Description:  This bus was bought direct from Greyhound in 1978, the previous year it went thru the Chicago Rebuild shop, and thus was in perfect condition when purchased.  In this perfect condition, it still heated up, going up hills in hot weather.  All that was needed to keep it cool, was to shift down into 2nd (stock 4sp manual), and climb the hill with RPM's high, and take your time.  This was normal operation for these buses in heat.  Driving in this manner, the bus never overheated.

Then, in about 1995, an Allison MTB 644 automatic was installed.  Which is a heavy duty 4 speed auto, rated for 55,000 lbs.  Great tranny, but it added a heat load to the already marginal bus cooling system.  The old girl, could still climb any hill, max weight, any temp, without overheating by simply keeping it in 2nd, high rpms, throttle just shy of black smoke.  So whats the problem....... I always wondered how difficult, and how well it would work, to convert the abandoned bus heater core into an additional radiator.  It was easy, cost about $30.00 in a new hoses and copper fittings.  Works great.  Now I can climb the 7% grade and never back off on the power, and climb in 3rd, until power is the culprit, instead of cooling.

Basic Changes: Removed heater water control valve (back by engine) and piped direct for maximum flow, removed heater core blower assembly, air conditioning evap (discarded), heater core.  Sealed off the original return air duct.  Enlarged existing fresh air intake on floor of compartment just in front of hearer core, this hole originally was to add fresh air into the a/c heat system, add a second intake hole 12 inchs to the left, to allow for more air intake.  Installed the heater core using new hoses, and filled all holes that would cause leakage with foam and sheet metal.  Sealed off the original supply air ducts that the blower use to blow into.  Cut two holes into the bottom of the compartment floor, that matched the blower discharges, repositioned the blower to blow the air down and thru the new discharge holes.  To operate, I manually turn on the on/off hand valve back back by the engine, and turn on the existing stock "Heat Switch" on the dash.  Works great.  Wish I'd done it 10 years sooner.  Only mistake I think, was I wish I had left the original air operated control valve, which starts and stops the water flow to the heater core.  I removed it for maximum flow.  I wish I had left it in.

[bevans6]

congratulations, that sounds like a very successful project!  Later versions of the heater control valve were electrically controlled, rather than air controlled, if that makes a difference to your future plans for upgrades. 

Brian

[luvrbus]

Johansen, if you can make the climb from Horseshoe Bend to Eagle in Jul and Aug without overheating a MCI you have done a good job on your cooling every time I go over that hill seems like a MCI has shut down some place along highway 55 or creeping at 5 mph, that is a good climb and long too, PS it will warm a Eagle up also lol it would get mine up to around 200 if I left it 3rd gear.


good luck