Running Hot

[Schindy]

1988 Gillig Phantom with International DT530
35k lbs and roof raise
—Stock radiator: cleaned/flushed in excellent condition
—original wax solenoid and fan motor
—vickers 12gpm priority for power steering and fan
—10+ gallons of coolant
—Intercooler, plumbed Into coolant loop
—Air over oil for trans, hydraulic, and intercooler in front of radiator.
—4.88 gears
—Allison MD3000
—160* thermostat
—180 fan switch
—no heater/ac/defrost

Flat and small/short inclines, the temps remain modest between 170-180, sometimes as low as 160* but everything has to be perfect. Flat, cool, etc.

Once I hit the hills or long gradual climbs, the temps begin to climb as well. Climbing through the smaller hills out of Santa Fe to Alamosa, I drove most of the way in 3rd or 4th gear between 35-45 mph to keep heat down. Had to pull over a few times to idle up and drop temps because they rose to 220 water and 245 oil.

I feel like HP is good and gear ratio is perfect. The bus wants to flatten the hill but it can’t shed heat fast enough.

Is there any part of my setup that needs to be adjusted?

It seems as though the fan may have slowed down from the first time we fired it up. Wax solenoid? Fan motor rebuild/replace?

What should the fan rpm be?

Any help is greatly appreciated.

[Iceni John]

When I completely rebuilt my entire cooling system a few years ago to address an ever-worsening overheating problem, I learnt a lot about hydraulic gear motors and pumps (what sort does your bus have?) and solenoid directional control valves and radiator shrouds and fans! If you want to know how fast your fan turns, you'll need to buy a small handheld optical tachometer (Harbor Fright has them for cheap). Different buses have different fan speeds, but my bus's fan runs at about engine speed when above 195 degrees, and half speed or less below 195 degrees. If the fan is too slow, it's best to just replace the motor instead of faffing about with rebuild kits: they address wear at the sides of the motor's gears, but wear also occurs between the gears' tips and casing for which those kits are useless. Unless you have a motor custom-built, new motors are not too expensive. Also, is the hydraulic/PS pump producing maximum flow, or is it also worn? Is the priority control valve allowing too much flow to the PS box? Being a Gillig, you may have a small rectangular aluminum block that contains a Danfoss 7WA110-2 solenoid directional-control valve that diverts some of the flow back to the reservoir when below the full-speed temperature: if that valve goes bad you may not be getting full flow to the motor above the full-speed temperature? Whatever you do with it, do NOT touch the Danfoss's threaded adjustment that is factory-set as an over-pressure relief valve. Those valves are almost impossible to find these days, but try a bus breaker yard that has Gilligs, or maybe that company in Riverside CA that rebuilds and repowers old Gilligs.

Is the radiator clean externally, or does it have encrusted dirt on the fins? Are there any cold spots on it that would indicate tube blockage inside? Are there any gaps in the radiator's shroud that allow air to be pulled in?

Good luck, John

[Schindy]

Hi John… thanks for the reply. I tried to answer as many questions as I could down below.

Originally Posted by Iceni John

When I completely rebuilt my entire cooling system a few years ago to address an ever-worsening overheating problem, I learnt a lot about hydraulic gear motors and pumps

(what sort does your bus have?)
—Webster/Gillig 55-14533
https://hydraulic.net/product/gillig-55-14533-163k6044-hydraulic-fan-drive-motor/

And solenoid directional control valves and radiator shrouds and fans!

If you want to know how fast your fan turns, you'll need to buy a small handheld optical tachometer (Harbor Fright has them for cheap).
—picked on up today. I’ll let you know what I find out.


Different buses have different fan speeds, but my bus's fan runs at about engine speed when above 195 degrees, and half speed or less below 195 degrees. If the fan is too slow, it's best to just replace the motor instead of faffing about with rebuild kits: they address wear at the sides of the motor's gears, but wear also occurs between the gears' tips and casing for which those kits are useless. Unless you have a motor custom-built, new motors are not too expensive.
—My fan only turns when above 180* as controlled by fan temp switch and I’ll get rpm number to you.


Also, is the hydraulic/PS pump producing maximum flow, or is it also worn? Is the priority control valve allowing too much flow to the PS box?
—I have a new Vickers 12gpm but I haven’t been able to confirm psi or flow between the 2 valves. No way to adjust proportions between port 1 and 2.


Being a Gillig, you may have a small rectangular aluminum block that contains a Danfoss 7WA110-2 solenoid directional-control valve that diverts some of the flow back to the reservoir when below the full-speed temperature: if that valve goes bad you may not be getting full flow to the motor above the full-speed temperature? Whatever you do with it, do NOT touch the Danfoss's threaded adjustment that is factory-set as an over-pressure relief valve. Those valves are almost impossible to find these days, but try a bus breaker yard that has Gilligs, or maybe that company in Riverside CA that rebuilds and repowers old Gilligs.
—I do have this style solenoid and appears to be working normal but I can’t confirm how much or little it’s allowing once opened.


Is the radiator clean externally, or does it have encrusted dirt on the fins?
—very clean, no debris

Are there any cold spots on it that would indicate tube blockage inside?
—will check to see once I get back up to temp.

Are there any gaps in the radiator's shroud that allow air to be pulled in?
—There were some gaps around the radiator. I filled them today with mud flap to prevent any heat from engine compartment coming around to front of radiator.

Good luck, John

[Iceni John]

Originally Posted by Schindy

Hi John… thanks for the reply. I tried to answer as many questions as I could down below.

That photo looks familiar. Mine's the same: actually Crown used Gillig's (their competitor's!) design of hydraulic fan control because I guess they couldn't engineer anything better themselves, especially as it was only used on their Super II buses which were a low-volume production compared to their twinkies.

One more thing to check: make sure the engine's water pump impeller is not loose on its shaft and is not worn due to cavitation. In the meanwhile you can always run your heaters to dissipate some of the excess heat.

[Schindy]

Good morning John… I was looking over some other forums you have replied to. You mentioned your fan runs at half speed below temp. Mine isn’t turning at all unless I de-energize the solenoid. Any ideas what could be failing or not adjusted to make this happen?

[Schindy]

Originally Posted by Schindy

Good morning John… I was looking over some other forums you have replied to. You mentioned your fan runs at half speed below temp. Mine isn’t turning at all unless I de-energize the solenoid. Any ideas what could be failing or not adjusted to make this happen?

Just checked engine vs fan rpm: could be misleading, just found out I checked rpm in Wrong spot. I went at blade end not the hub.

Energized solenoid:
Fan 0-250rpm
Engine idle-2000rpm

De-energized:
Fan 0-1450
Engine idle-2000rpm

[Schindy]

I placed contrast tape on the hub of fan and got 1150 fan @ 1750 engine.

Originally Posted by Iceni John

That photo looks familiar. Mine's the same: actually Crown used Gillig's (their competitor's!) design of hydraulic fan control because I guess they couldn't engineer anything better themselves, especially as it was only used on their Super II buses which were a low-volume production compared to their twinkies.

One more thing to check: make sure the engine's water pump impeller is not loose on its shaft and is not worn due to cavitation. In the meanwhile you can always run your heaters to dissipate some of the excess heat.