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 DT 466 coolant circulation
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Jay Graham
New Member

7 Posts

Posted - 01/12/2014 :  1:26:54 PM  Show Profile  Reply with Quote
I have been working on a 2002 DT466 that will not circulate coolant through the bus heater system and will not circulate into the expansion tank from the thermostat. Engine cools OK. Radiator is not plugged, water pump has been replaced, have tried 2 different thermostats, have by-passed all heaters and still will not circulate into surge tank from thermostat at head. I am wondering if anyone else has experienced this situation and has any answers. I didn't notice last winter that this bus would not make warm air out of the heaters at idle. Engine had to be speeded up to keep coolant circulating enough to maintain heater output at idle. Any help would be greatly appreciated. I have run out of ideas. International dealer says head gasket problem, but I am lucky if the cooling system builds 11 pound pressure with the radiator cover over with a piece of card board.
Thank you in advance!!
Jay Graham, Substitute school bus driver/mechanic, St.Clairsville-Richland City Schools, St.Clairsville,OH

Edited by - Jay Graham on 01/12/2014 5:08:04 PM

Southsider
New Member

4 Posts

Posted - 01/16/2014 :  05:26:48 AM  Show Profile  Visit Southsider's Homepage  Reply with Quote
Have you checked the heater temp control valve? We had a couple that came apart internally and plugged.
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Thomasbus24
Administrator

USA
3369 Posts

Posted - 01/16/2014 :  3:38:17 PM  Show Profile  Reply with Quote
Two memories come to mind... A CAT 3208 with a new water pump did that to me...drove me nuts...the impeller broke off the new pump.

DT466...all sorts of weird like this...head gasket (I don't know, don't ask me, we put the pressure tester on the tank and started it, pressure went up fast. Gasket cracked between cyls 4&5 if memory serves.)
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Jay Graham
New Member

7 Posts

Posted - 01/16/2014 :  4:08:52 PM  Show Profile  Reply with Quote
quote:
Originally posted by Thomasbus24

Two memories come to mind... A CAT 3208 with a new water pump did that to me...drove me nuts...the impeller broke off the new pump.

DT466...all sorts of weird like this...head gasket (I don't know, don't ask me, we put the pressure tester on the tank and started it, pressure went up fast. Gasket cracked between cyls 4&5 if memory serves.)

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Jay Graham
New Member

7 Posts

Posted - 01/16/2014 :  4:18:56 PM  Show Profile  Reply with Quote
The circulation valve is not the problem. Coolant will not circulate into the surge tank form the thermostat housing and will not circulate with only the stair well heater plumbed into the heater circuit.

The replacement water pump does the same as the original water pump which does not appear to be faulty. I am at the point of pulling the head and checking for cracks and or cracked head gasket. We had a 2006 DT with a cracked head a little over a year ago which built very high pressure in the cooling system immediately upon start up of engine. This engine is lucky to build 10 pounds with the radiator completely covered over with a piece of cardboard. These symptons are no where near the same as the 2006 DT episode. I have basically ruled out all external visual problems. The head will be coming off next week it appears. Thanx for everyone's input!!! I will report whatever I may be lucky enough to find the problem to be.
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RBrian
Active Member

United States
24 Posts

Posted - 01/17/2014 :  03:28:32 AM  Show Profile  Visit RBrian's Homepage  Reply with Quote
We have had several 2001 dt466's this year not building heat when temps were down. Replaced thermostats, still no heat. Temp gauge barley gets off 140 degrees. All of them had after market replacement radiators. Long story short the oem radiator top tank has a separate area in it that circulates coolant. Aerator hose from top of the engine head goes in one end and the other 3/4 inch hose goes to the water pump inlet on the back side of the front cover. After market radiator did not have that separate area so it was by-passing the thermostat and circulating the coolant in the top tank enough on cold days to keep the engine from building heat.
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Jay Graham
New Member

7 Posts

Posted - 01/17/2014 :  10:50:41 AM  Show Profile  Reply with Quote
Thank you for the reply!!! As far as I know this is the original radiator. The temp quage does climb to proper operating temp. I will check into radiator further.

Thanx again!!
Jay

quote:
Originally posted by RBrian

We have had several 2001 dt466's this year not building heat when temps were down. Replaced thermostats, still no heat. Temp gauge barley gets off 140 degrees. All of them had after market replacement radiators. Long story short the oem radiator top tank has a separate area in it that circulates coolant. Aerator hose from top of the engine head goes in one end and the other 3/4 inch hose goes to the water pump inlet on the back side of the front cover. After market radiator did not have that separate area so it was by-passing the thermostat and circulating the coolant in the top tank enough on cold days to keep the engine from building heat.

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christitzer
New Member

United States
2 Posts

Posted - 01/21/2014 :  5:11:03 PM  Show Profile  Visit christitzer's Homepage  Reply with Quote
I have run into a similar problem on a 2000 Amtran FE with DT466.There is a 1" hose that goes from oil cooler water pump front cover area to top radiator tank. I put a vavle in that hose and turned it almost all the way off. It appears to taken care of my heat/ circulation problem. With cold temp next couple of days in single digits It will tell if this cures problem.
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dwight
Active Member

USA
42 Posts

Posted - 01/22/2014 :  09:50:17 AM  Show Profile  Reply with Quote
I found that almost 40% of the school buses I purchased from Bluebird in the 1980s & early 90s were plumbed backwards with the heated coolant from the engine going to the step heater core first, then to the back of the bus & returning thru the left front core & the heater water control valve & back to the engine. If your specs called for the optional in-line heater water booster pump, the pump when turned on would almost stop the flow thru the the heater hoses especially on engine idle. Dwight DSBSI LTD

20 SCHOOL BUS FLEET OWNER/OPERATOR (Retired)

Edited by - dwight on 01/22/2014 09:52:40 AM
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RBrian
Active Member

United States
24 Posts

Posted - 01/23/2014 :  06:02:13 AM  Show Profile  Visit RBrian's Homepage  Reply with Quote
quote:
Originally posted by christitzer

I have run into a similar problem on a 2000 Amtran FE with DT466.There is a 1" hose that goes from oil cooler water pump front cover area to top radiator tank. I put a vavle in that hose and turned it almost all the way off. It appears to taken care of my heat/ circulation problem. With cold temp next couple of days in single digits It will tell if this cures problem.


That is what we did. Put a heater control valve in and shut the flow down. Plan on opening the valve this spring.
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