Coolant temp

[DLP]

This summer I was running a 180* thermastat. Could have stayed with the 195 because the temp here doesn't get much above 80. But I pull a trailer several hundred miles on most weekends. So I figured it wouldn't hurt. The Scan Gauge showed about 185 or so on the motor and around 170 to 190 on the trans depending on coasting smooth or climbing a hill. I do have a tranny cooler. Well, as the weather got colder, I changed back to the 195. The motor never gets much above 180 and the tranny stays below 165. I have taken the thermastat out and checked it. It opens at 193 in a pot on the stove. It has been in the 20s here most of the time, so I understand it running cooler on the road. But it never gets up to the 190s ideling in the barn. Any ideas? I thought about blocking the radiator to keep a little more heat under the hood. The inside temp is great. The truck heats up in a few minutes. I was just wondering if the puter senses the motor running cold and adjust for more gas. I get about 16 to 18 MPG in normal daily driving including warmup time.

[HenryJ]

...changed back to the 195. The motor never gets much above 180 and the tranny stays below 165... it never gets up to the 190s ideling in the barn. Any ideas?

I would replace the thermostat. While they do run within a range +/- that far below is on the low side for a 195° thermostat.

[JaVeRo]

I got a code P0128 on two different vehicles last week. That is for engine coolant temperature below what it should be. The book says this diagnostic check runs once each ignition cycle after the motor should be warm and the temperature threshold is 178 degrees.

It has been cold here but this is East Texas. The first truck to set the code was the '01 crew that my wife uses and I know I drilled a 1/8" hole in the thermostat. That didn't surprise me. The other was the '03 Blazer and it still has the original thermostat. Maybe it is time to change it.

James

[Dabber]

My 05 Blazer still has the original t-stat.

[DLP]

Thanks. That it what I was thinking too. It's a new stat and I even tested it. But it's a cheep enough part to swap out. I will try to swap it this weekend and report back.

[roadrunner]

I changed out my OE T-stat after I started getting the P0128 codes set a year or so ago. Since then I installed a Scan-Gauge II and the temps on there spike to 201-205 degrees before it opens then drops down and settles in at 191-194 degrees. Dash gauge does not indicate that warm during warm-up or normal run. No further codes related to temps since new install.

[DLP]

My son and I took the quads up north this weekend after I replaced the thermastat Friday. I pulled the trailer in 3ard at 70mph. The motor was running about 2800 RPMs. The outside temp was between 24 and 32 degrees. The motor temp stayed steady at 193 degrees and the tranny was at 129degrees. Dropped the trailer off at the cabin and got back on the expressway to my sisters. Running 70 mph in OD at 2000 rpms. The motor temp was reading 180 to 183 and the tranny was at 165. Just like it did with the other 195 stat. I don't understand the tranny running cooler pulling the trailer at higher RPMs. I see the motor running warmer because it was working harder. But why doesn't the motor stay at operating temp going down the road? I am thinking of bypassing the tranny cooler until warmer weather. Or at least insulating the front grill.

[HenryJ]

I'm guess that you installed your aux cooler after the radiator cooler. Is that right?
You are running a stat with the bypass valve, correct?

I don't know what to tell you on the stat having such a broad range. Maybe that brand thermostat just has a very wide range. If your bypass is not sealing, that could explain some of the broadened range.
Once warmed up my 180° stat allows the engine to operate between 182° and 206°. This depends upon whether I am towing or cruising and the loads applied as well as the outside temperature. The air movement also plays a part there too. 10-15 degrees either way is probably acceptable.