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Old 11-11-2018, 08:24 AM   #1
mrscullini
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Default running too cool

'79 scout II, 345, t-19 with about 125k

the thing just doesn't get warm. radiator is stock. just replaced the t-stat to a 180, thought this was the issue. i'm judging the temp by the gauge and i'm pretty sure it is not just the gauge with a false reading. i've got pretty low air temp from the heat and defrost. i'm sure the heater control valve is sending coolant to the heater core.

any thoughts? figure i'll get a 195 t-stat from the store here.
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Old 11-12-2018, 08:29 AM   #2
Scoutboy74
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Default Re: running too cool

The stock temp gauge should not be trusted until independently verified with an IR temp gun at various under hood locations following sufficient engine run time. In addition to verifying that heated coolant is indeed circulating through the heater core, you must also have fresh air inductively pass through the core to force the maximum amount of heated air to the blower fan for distribution inside the cabin. That is up to the "Air" slider on your dash control that operates a cable actuated blend door inside the ducting.
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Old 11-12-2018, 02:38 PM   #3
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Default Re: running too cool

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Originally Posted by Scoutboy74 View Post
The stock temp gauge should not be trusted until independently verified with an IR temp gun at various under hood locations following sufficient engine run time. In addition to verifying that heated coolant is indeed circulating through the heater core, you must also have fresh air inductively pass through the core to force the maximum amount of heated air to the blower fan for distribution inside the cabin. That is up to the "Air" slider on your dash control that operates a cable actuated blend door inside the ducting.
thanks. definitely don't trust the stock temp gauge. although i do get a reading. per the gauge, the temp does seem to tick up when sitting at an idle. i can also feel the change in temp at the defrost vents. once i start driving, the temp drops per the gauge and per the feel of the air at the vents.

the air slider does seem to work properly, i get much more flow when it is actuated.
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Old 11-12-2018, 05:17 PM   #4
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Default Re: running too cool

Let's get back to the coolant flow control valve. What condition is it in? Does the cable motion actuate it freely? Do you suppose the valve could be stuck closed with the actuator arm still able to move, in other words, broken? That would give you the impression that it was working externally, but internally not so much. I could see that as a real possibility.
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Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVWR/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/RC 4" SUA/34x11.5 TSLs/33g Fuel/8K# winch
Lemuel - '72 1210 LWB 4x4 CS - 304/TF727/NP205/RA D60 4.10 - "Pull Lemuel, pull!"
Mongo - '71 1210 LWB 2WD - 345/TF727/RA17 D60 4.10 Krac-lok - "Mongo love candy! Duh, huh, huh!"
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Old 11-14-2018, 04:16 PM   #5
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Default Re: running too cool

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Originally Posted by Scoutboy74 View Post
Let's get back to the coolant flow control valve. What condition is it in? Does the cable motion actuate it freely? Do you suppose the valve could be stuck closed with the actuator arm still able to move, in other words, broken? That would give you the impression that it was working externally, but internally not so much. I could see that as a real possibility.
thanks. i'll give the heater control valve a closer look. it does actuate externally, but may not be working internally.
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Old 11-14-2018, 08:13 PM   #6
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Default Re: running too cool

I know you just replaced the t-stat. Although unlikely, it could be stuck open, preventing the engine from warming up properly. This is just another spitball I thought I'd toss out. That's about all anyone can do until you take and post some temp readings.
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Favorite hobby...Driving Salma Hayek in my Scout

Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVWR/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/RC 4" SUA/34x11.5 TSLs/33g Fuel/8K# winch
Lemuel - '72 1210 LWB 4x4 CS - 304/TF727/NP205/RA D60 4.10 - "Pull Lemuel, pull!"
Mongo - '71 1210 LWB 2WD - 345/TF727/RA17 D60 4.10 Krac-lok - "Mongo love candy! Duh, huh, huh!"
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Old 11-15-2018, 01:14 PM   #7
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Default Re: running too cool

Has this been a problem for awhile, or did it begin when it started to get cold up there in Truckee? I used to run three row core radiators in my 510's, and had to cover part of the radiator opening with cardboard when I took them where it was cold.
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Old 11-16-2018, 07:24 AM   #8
mrscullini
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Default Re: running too cool

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Originally Posted by Hondo View Post
Has this been a problem for awhile, or did it begin when it started to get cold up there in Truckee? I used to run three row core radiators in my 510's, and had to cover part of the radiator opening with cardboard when I took them where it was cold.
thanks hondo. no, it has been a problem even through the summer, which is really odd. i was going to cover part of the radiator this weekend and see what happens.

i'll pull some temps with an infrared thermometer. @scoutboy74, where should i pull temps and what should i expect to read?
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Old 11-16-2018, 08:56 AM   #9
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Default Re: running too cool

Thermostat housing, upper/lower radiator hose fittings at the tanks, intake manifold runners at various points on both sides of the engine, and any freeze plug you have line of sight with. Following sufficient run time, you should expect to see approximately your t-stat set point, but it could fluctuate as much as ten degrees either direction at any given point.
Multi/thick-core radiators are more commonly associated with excess coolant temps from what I've seen over the years within these vehicle platforms. It should have no trouble reaching operating temperature following 30 minutes of idling in your driveway, even on a colder day.
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Favorite hobby...Driving Salma Hayek in my Scout

Coal Trickle - '99 Dodge Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVWR/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Krac-lok RA/RC 4" SUA/34x11.5 TSLs/33g Fuel/8K# winch
Lemuel - '72 1210 LWB 4x4 CS - 304/TF727/NP205/RA D60 4.10 - "Pull Lemuel, pull!"
Mongo - '71 1210 LWB 2WD - 345/TF727/RA17 D60 4.10 Krac-lok - "Mongo love candy! Duh, huh, huh!"
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