Hello,

I have a 2008 ranger 5spd with the 2.3. I recently got a scangauge II. My coolant temperature never gets above 175, even when driving for an hour or more. Today on the way home I got stuck in traffic and it got up to 181, which is the highest I've seen it in the 3 weeks since I've had the scan gauge. Is this normal or too cold? Everything I've read seems to indicate these engines run around 210 or so. I also how have an intermittent hot start issue (although it will start up by giving it a little bit of throttle), which may or may not be related.

By the way it's summer here and temps are routinely in the 80's or low 90's.

 

Oh just thought I'd add, it reaches the 170 degree operating temp it seems to run at quickly, maybe 5 minutes. Years ago I had an F-150 that the thermostat stuck open and the temp would slowly creep up over 15-20 minutes. I dunno if its a thermostat, coolant temp sensor or what at this point. The truck is getting pretty good mpg, right around 28-29 mpg.

 

2008 Ranger is using a 2.3l Duratec(Mazda L) engine
It uses a CHT(cylinder head temp) sensor, instead of an ECT(engine coolant temp) sensor
And no Temp Sender for dash board gauge in 2008 either

Operating temp for the coolant should be 185-195degF after warm up
But you can't see that because there is no coolant temp device

You see cylinder head metal temp from the CHT and the computer sends that out to the gauge and your scanner
Yes, on these engines people often see 200-230degF from the CHT but again its not coolant temp, its head metal temp, so it will be 10+ degrees warmer than the coolant

The thermostat on these is on Lower Radiator hose, so its rated as 180degF
Upper rad hose should be about 15-20degF higher if you want to check it with a IR Thermometer after warm up

It does read like the engine is running a little cooler than it should, MPG will be lower(slightly) but doesn't hurt anything else, if its getting above 180degF on a longer drive

Easy test to see if thermostat is leaking or stuck open
Cold engine
Start it up, turn heat to HOT and fan on low, then open the hood
Feel upper radiator hose and one of the heater hoses at the firewall
Both will be cold of course
Wait two or tree minutes and feel them again
Heater hose should be warming up
Upper rad hose should still be COLD, if its warming up like the heater hose then yes thermostat is open when it should be closed

Radiator is there to get rid of Extra heat, in the winter in northern climates it may never be used at all in winter
So upper radiator hose should stay cold UNTIL there is extra heat, i.e. above 180degF at lower rad hose thermostat, lol

Upper hose thermostats are rated at 190-195degF, just FYI

 

Thank you for the info Ron.

I changed the thermostat today to a new motocraft unit. Running down country roads at 55-60 mph I'm now getting coolant (head) temps of 182-186 degrees. I guess this is on the lower end of normal? Maybe these engines just don't generate much heat unloaded driving on flat country roads.