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Topic: interesting (strange) cooling situation (Read 612 times) previous topic - next topic

interesting (strange) cooling situation

Interesting to me that my engine cooling temperature runs hotter in cold weather than in hot weather.  Sound strange??  When I'm running in hot weather the engine thermostats control engine temp very steadily about 190 deg. F.  When I'm running in cold weather the thermostats do not control the heat and engine temp. raises to about 200 degrees when the cooling fan cuts in.  I have pondered about this and have concluded that the reason for this is that in cold weather I have the heater on  which by passes flow around the engine block and with less flow the temp. increases.  I haven't scoped out the actual piping arrangement, but I plan to do that to see why this is the case. I was wondering if any one else has experienced this situation.  Thanks and have a great day  ----  Fritz
Fritz & Kathy Johnson
1991 36'

Re: interesting (strange) cooling situation

Reply #1 –
When our engine goes over 200 degrees on grades, I turn on the heater and it immediately lowers the temperature. This is a trick I learned early on as a kid. It works with a Foretravel also. Other GV owners have, with success, installed a front radiator and used the existing heater hoses to circulate coolant through the aux radiator.

I think you have to look elsewhere to solve the mystery.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: interesting (strange) cooling situation

Reply #2 –
Fritz, I wonder if the cooling system thermostat plays a role in cold ambient temps by staying closed.

Our large radiator may be sized for hot temps or retarder and may not allow thermostat to open in cold temps.

Flowing hot coolant though heater core also acts to keep coolant temp lower, maybe keeping thermostat closed.

We have not experienced the temp problem, partly because we have not driven in cold temps for a while.

Re: interesting (strange) cooling situation

Reply #3 –
Quote from: Barry & Cindy –
Fritz, I wonder if the cooling system thermostat plays a role in cold ambient temps by staying closed.

Our large radiator may be sized for hot temps or retarder and may not allow thermostat to open in cold temps.

Flowing hot coolant though heater core also acts to keep coolant temp lower, maybe keeping thermostat closed.

We have not experienced the temp problem, partly because we have not driven in cold temps for a while.

Perhaps this is being looked at backwards.

It is the thermostat(s) that decide when and in what volume to send coolant to the radiator.  Irrespective of fan speed, no or little coolant flow is common at start up and while driving under light load in cold conditions. No coolant flow, even with high fan temps has little/no impact on engine operating temperature.

The circuit from engine through water heater and then to the dash heater core IS NOT controlled by the thermostat.  So, if very cold and light load, it CAN take coolant operating temperature below normal.  Same goes for LONG descents where no fuel is injected. Under these conditions, even with thermostat(s) closed and no flow to radiator, coolant temperature can fall below normal controlled temp.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: interesting (strange) cooling situation

Reply #4 –
My situation is that I can be running under steady state conditions with coolant temp normal and turn on the heater and watch the engine temp rise until the fan cuts in and then watch the temp lower until the fan cuts out. The temp will cycle this way until I turn off the heater at which time the thermostats control eng temp.  I don't know how the return heater piping is plumbed into the cooling system, but it could be such as to affect thermostat operation.  I need to determine how this system is plumbed so that I can determine what is happening.  Thanks and have a great day  ---- Fritz
Fritz & Kathy Johnson
1991 36'

Re: interesting (strange) cooling situation

Reply #5 –
MAJOR "puzzlement".  How adding additional cooling (not "supervised" by the thermostat(s)) will RAISE the engine coolant temperature is a "keep me awake at night" kind of question....
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: interesting (strange) cooling situation

Reply #6 –
Hey Bret. ----  When I get it all figured out I'll  let you know so that you can sleep at nights!  Thank you and have a great day  ----  Fritz.
Fritz & Kathy Johnson
1991 36'

Re: interesting (strange) cooling situation

Reply #7 –
I would probably put a new water temp sender in before anything else...
Len Barron
1988 GV36 U280 3208T(250hp)/MT643
1972 Jeep Commando LS2/4L65e
2000 Chevy Express Hightop Campervan
LBZ Duramax /6sp Allison

Re: interesting (strange) cooling situation

Reply #8 –
Based on my recent experience verify dash gauge by pulling over and shooting temperatures at thermostat housing with ir gun. Do this at different temps on gauge.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.