Home » Public Forums » GMCnet » Why won't my motor come to operating temp? (New Thermostat didn't fix the problem.)
| Why won't my motor come to operating temp? [message #199354] |
Fri, 22 February 2013 17:39  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
|
Senior Member |
|
|
OK, I'm officially stumped. My coach runs cold...really cold. I suspected the thermostat and sure enough it was a SuperStant that had failed open. Replaced it with a 180 degree RobertShaw that I ordered from JimK. Figured that would do it. I had let it idle a few times for 15 minutes or so and it got up to 120 or so. I have two gauges and the correct sending unit for the dash gauge.
I have a 4 year old aluminum radiator. The antifreeze looked green and clean when I drained it. No problem there.
Just got back from a 40 minute drive. Its about 60 degrees out. Water temp shows about 120 and my really cheap infrared thermometer agrees. Drained my oil and while it was warm, it wasn't HOT and the thermometer showed it was about 120 also. I did notice during some hard WOT runs the temp would rise a bit but drop right back down. What the heck???? Over.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
|
|
|
|
| Re: Why won't my motor come to operating temp? [message #199360 is a reply to message #199354] |
Fri, 22 February 2013 18:03  |
chasingsummer
Messages: 434
Registered: May 2011
Location: asheboro, nc
Karma: 0
|
Senior Member |
|
|
If our radiator fan ran all the time, would that keep coach from reaching higher temps?
If wheel liners were removed, and in 60 degrees, would that somehow cause?
Otherwise does it run good? back barrells open when you floor it at 35 or so?(i dont think mine does, but my carb may need a little attention)
It does not sound broke to me, just confused.
brian
asheboro, nc
75 eleganza, 74 build
119k miles and counting,
DOG HOUSE
|
|
|
|
|
|
| Re: [GMCnet] Why won't my motor come to operating temp? [message #199364 is a reply to message #199354] |
Fri, 22 February 2013 18:29 |
 |
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
Kerry,
Remove the thermostat and suspend it in a pot of water on an electric cooktop, slowly increase the heat to bring up the temp slowly
when you see it begin to open shoot the thermostat with the IR temp gun.
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
-----Original Message-----
From: Kerry Pinkerton
OK, I'm officially stumped. My coach runs cold...really cold. I suspected the thermostat and sure enough it was a SuperStant that
had failed open. Replaced it with a 180 degree RobertShaw that I ordered from JimK. Figured that would do it. I had let it idle a
few times for 15 minutes or so and it got up to 120 or so. I have two gauges and the correct sending unit for the dash gauge.
I have a 4 year old aluminum radiator. The antifreeze looked green and clean when I drained it. No problem there.
Just got back from a 40 minute drive. Its about 60 degrees out. Water temp shows about 120 and my really cheap infrared
thermometer agrees. Drained my oil and while it was warm, it wasn't HOT and the thermometer showed it was about 120 also. I did
notice during some hard WOT runs the temp would rise a bit but drop right back down. What the heck???? Over.
Kerry
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
|
|
|
|
| Re: Why won't my motor come to operating temp? [message #199365 is a reply to message #199354] |
Fri, 22 February 2013 18:32 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
|
Senior Member |
|
|
Just a thought, if all the air is not out of the system, the senders may not be immersed giving false reading. Is it drawing from the overflow as it cools? When cool, open the cap be sure it's to the top and overflowing remembering the heater core is up high on these babies. You've got a problem lot's would like to have. Thermostats don't have a real good accuracy record, like all my dial tire pressure gauges read differently.
John Lebetski
Woodstock, IL
77 Eleganza II
|
|
|
|
|
|
|
|
|
|
| Re: [GMCnet] Why won't my motor come to operating temp? [message #199379 is a reply to message #199371] |
Fri, 22 February 2013 19:15 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
G'day again,
I thought the low coolant temps that result when running an aluminum radiator was because of the flow through the bypass "snout;"
however, BobD pointed out that the flow through that snout goes back into the water pump and not into the radiator.
Reference MM-7525, Section 6K Engine Cooling, Page 6K-7, Figure 8 - Thermostat Installation
GeneD has advised NOT to use Robertshaw "race" thermostats as they bypass flow.
SteveF has noted not to use Stant thermostats because the break.
Question: Do the "standard" Robertshaw thermostats bypass flow?
There HAS to be flow going through the radiator to keep the engine below the thermostat setting. There is NO WAY air circulating
around the outside of a 455 is going to keep it cold!
Now watch, someone will prove my last sentence wrong! ;-)
Regards,
Rob M.
Sydney, Australia
AUS '75 Avion-The Blue Streak TZE365V100428
USA '75 Avion-Double Trouble TZE365V100426
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
|
|
|
|
|
|
| Re: Why won't my motor come to operating temp? [message #199388 is a reply to message #199354] |
Fri, 22 February 2013 19:50 |
shawnee
Messages: 422
Registered: February 2004
Location: NC
Karma: 0
|
Senior Member |
|
|
| Kerry Pinkerton wrote on Fri, 22 February 2013 18:39 |
OK, I'm officially stumped. My coach runs cold...really cold. I suspected the thermostat and sure enough it was a SuperStant that had failed open. Replaced it with a 180 degree RobertShaw that I ordered from JimK. Figured that would do it. I had let it idle a few times for 15 minutes or so and it got up to 120 or so. I have two gauges and the correct sending unit for the dash gauge.
I have a 4 year old aluminum radiator. The antifreeze looked green and clean when I drained it. No problem there.
Just got back from a 40 minute drive. Its about 60 degrees out. Water temp shows about 120 and my really cheap infrared thermometer agrees. Drained my oil and while it was warm, it wasn't HOT and the thermometer showed it was about 120 also. I did notice during some hard WOT runs the temp would rise a bit but drop right back down. What the heck???? Over.
|
Kerry,
You might want to try blowing through the thermostat. If you can blow through it then it isn't right. I had a Robertshaw that you could blow through and it wouldn't come up more than 140 degrees. Now I check every one I get by trying to blow through them. Most you can't. The Robertshaw I got from Mr. Gasket wouldn't go over 120 degrees and had a large bypass. I suspect you have a thermostat with a large bypass. The bad part is they all physically look the same. If the thermostat is working properly, there is no way it can be completely closed and not overheat.
Gene Dotson
74 Canyonlands
www.bdub.net/Motorhome_Enhancements New Windows and Aluminum Radiators
|
|
|
|
| Re: Why won't my motor come to operating temp? [message #199392 is a reply to message #199354] |
Fri, 22 February 2013 20:09 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
Karma: 15
|
Senior Member |
|
|
So by blowing through it, you mean just putting the whole thing in my mouth and seeing if it passes air right? I can do that. I'm getting good at draining the coolant.
This is not the race Robertshaw. This is the one that Jim K sells. I don't have a problem blocking the radiator but everything I thought I knew about engine cooling has me thinking that the thermostat would not let coolant to the radiator UNTIL it got to it's open temp. In other words, the engine should rise to 180 and stay there (or get hotter if the heat load is more than the radiator can shed.)
I didn't do a hot water test but will when it's out tomorrow.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
|
|
|
|
|
|
|
|
|
|
| Re: Why won't my motor come to operating temp? [message #199425 is a reply to message #199354] |
Sat, 23 February 2013 06:50 |
Larry
Messages: 2875
Registered: January 2004
Location: Menomonie, WI
Karma: 10
|
Senior Member |
|
|
There are two other things in your system that may be cooling you motor. One is the heater core. I found that in cold weather (below 30*) that if I don't restrict flow through the heater core that engine temp has a hard time rising above 150*. The second is the house water heater. Coolant going to that water heater (intended to heat house water while you are driving) can also cool the motor down more that you expect it to. That water must also be restricted. So a combination of both could certainly keep that motor quite cool, particularly in cool to cold weather in combination with low load on the motor. Correct me if I'm wrong, but I believe that there is a physical restriction built into both heater core water and the House water heater. If you have (for what ever reason) removed these restrictions, either put them back or put a valve in the line that you can close to restrict flow.
Just my relatively informed, off the cuff, back yard mechanic, gut level, eyeball it up and guestimate, opinion....that's all...
Larry 
78 Royale w/500 Caddy
Menomonie, WI.
|
|
|
|
| Re: [GMCnet] Why won't my motor come to operating temp? [message #199430 is a reply to message #199425] |
Sat, 23 February 2013 07:30 |
|
USAussie
Messages: 15912
Registered: July 2007
Location: Sydney, Australia
Karma: 6
|
Senior Member |
|
|
Larry,
Good point!
There is a restrictor in the fitting in the right rear of the intake manifold:
http://www.gmcmhphotos.com/photos/intake-manifold-pics/p26351-installing-aluminum-intake.html
that supplies the heater core and the house water heater. IIRC it's between 1/4 and 5/16 inch.
Regards,
Rob M.
-----Original Message-----
From: Larry
There are two other things in your system that may be cooling you motor. One is the heater core. I found that in cold weather (below
30*) that if I don't restrict flow through the heater core that engine temp has a hard time rising above 150*. The second is the
house water heater. Coolant going to that water heater (intended to heat house water while you are driving) can also cool the motor
down more that you expect it to. That water must also be restricted. So a combination of both could certainly keep that motor
quite cool, particularly in cool to cold weather in combination with low load on the motor. Correct me if I'm wrong, but I believe
that there is a physical restriction built into both heater core water and the House water heater. If you have (for what ever
reason) removed these restrictions, either put them back or put a valve in the line that you can close to restrict flow.
Just my relatively informed, off the cuff, back yard mechanic, gut level, eyeball it up and guestimate, opinion....that's all...
--
Larry :)
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426
|
|
|
|
|
|
|
|
| Re: [GMCnet] Why won't my motor come to operating temp? [message #199442 is a reply to message #199430] |
Sat, 23 February 2013 08:41 |
tphipps
Messages: 3005
Registered: August 2004
Location: Spanish Fort, AL
Karma: 9
|
Senior Member |
|
|
Aluminum radiator has about a 35% greater cooling capacity. AL radiator is new, OEM is 35 years old. Al is available, OEM is only available as re-built. you may be able to get OEM cooling coils replaced, but the end caps are unique.
Small market results in limited options. I appreciate our specialized GMC suppliers. They make it possible to own a GMC in a rational manner. Ask our resident Revcon owner, with only one supplier ($400 for a steel replacement wheel).
This is my take on the aluminum radiator, your mileage may vary. When I replaced the OEM on my other coach, I thought that the water temperature gauge was broken, the needle barely moved. Finally, running in the mountains across West Virginia, it finally moved.
Tom, MS II
2012 Phoenix Cruiser model 2552
KA4CSG
|
|
|
|
Goto Forum:
Current Time: Fri Jan 17 00:31:49 CST 2025
Total time taken to generate the page: 0.07583 seconds
|
GMCforum
Search
Help
Register
Login
Home
