Running very cold

[JTodd]

This morning I set out for what was to be a long trip. Overnight temps were in the upper twenties. Truck fired up immediately-as usual and ran fine. About 5 miles from home noticed the temp was climbing way above normal. It got to around 230 before I pulled over and let it cooled down, which began as soon as I stopped and let it idle.

The thing is, it kept cooling all the way down to approx 165* and won't come back up above that. I have not put on the winter front yet, but even without that it would generally climb to normal operating temp (190*) over time. I checked the coolant - fine, but the upper radiator hose was not hot, warm but not hot and semi-warm air from the heater confirm this. Rear heat did not seem to work at all.

Does anyone have any ideas about what might be going on?

[Marlin]

Okay, first things first. Have you checked the coolant level. If the top hose is not hot that could be the problem. Fill and Bleed the air out of the system. The bleeder valve is on the metal hose neck by the thermostat.

Marlin

[JTodd]

Resevoir is full and nothing but coolant came out of bleed screw.

[Hubert]

Barring a low coolant event or big air bubble. I'd say its probably was sticky or failing thermostat(s). Since its cool out the stat(s) was probably cycling open/shut. It then stuck shut (or partially closed) and heated up. May have opened up some then stuck too far open and won't get back to full operating temp.

Sometimes stats can hiccup before complete failure. Had a car do it once overheated in drivethru for no apparent reason (had been driving fine in a mix of traffic). Decide to eat there. After it coolled coolant was full enough and it ran fine after. Changed the stat later and it never happened again.

[Robyn]

T Stats would be my first stop.
As long as the little monster is not puking coolant over the top (Reservior) and the hoses are not hard as rocks.

New stats are probably a good place to start.
One may have failed and then the other stuck closed and then never went shut all the way to maintain the temp.

Good luck

Robyn

[Kenneth]

My stat did a similar thing last winter. I was up in Rexburg idaho where it gets really cold during the night. Most of the early winter the engine never got above 170, even on the freeway, but would run mostly at 160. It would also overheat a lot on short trips. I didn't catch it once and it overheated and blew the upper radiator hose. I installed a new hose and stat and the motor always ran at 190 and never overheated again after that.

[JTodd]

T-stat must be the culprit. I just took it for a quick ride after putting the winter front on. Was gone for about 15 minutes and it went a touch beyond before, but not much. Air from vents is barely warm, but not cold, so the tepid water is circulating

[d]

I have had some overheating in cold weather that might be related. I have a 1994 with the original water pump (low gpm) and single thermostat. The only time I have had it overheat is in -30 F degree weather. I figured out what was going on by watching the water temp gauge. It did a pendulum swing from hot to cold until it overheated. You generally don't have problems with it too cold, but you have more problems with it too hot( even for a short time).

I think a radiator holds an excess of cold coolant at low temp on an engine not being worked very hard. At very cold temps and it has to go through the engine before the t-stat reacts. For me, a winter front slows down the cooling and keeps more even temperatures and a smaller pendulum swing.

I wouldn't think 20 F degrees would have the same problem, but maybe with the increased flow that you have it would cause the same effect.
BTW I replace t-stats on alot of machinery every 2-3 years because of poor heater output in the winter. I think they get tired and let more coolant through. It gets cold here.
David