Thermostat?
 

Hello all!

I have recently started driving my 1995 Ranger to work in an effort to save on gas. It has been pretty much sitting idle for about 8 mos and was only driven to Home Depot and back a handful of times during that period. Well, my commute is about 45miles each way (all interstate) and I am getting horrible gas mileage. I do have some clues, however, that point me toward the thermostat as the culprit.

1) When I crank the car after sitting all night I immediately hear water running through the heater.
2) The heater gets warm very quickly (as in less than 3 minutes) but never HOT
3) The temp gauge needle stays just about on the top right corner of the C printed on the guage face.

Does my diagnosis sound reasonable?

I have a 1995 Ranger 4cyl manual with 130k

Before i started driving it again I cleaned the MAF, changed all 8 sparkplugs with Bosch Platinums, replaced the front O2 sensor and waxed it real pretty-like.

i dont think a thermostat will cause you a loss in gas milage. i could be wrong but ill need that explained

Matt

If the thermostat is stuck open and the engine never reaches operating temperature, then it will run rich (like when you first crank it) and never switch to running off of the sensors. This can KILL gas mileage. People that take alot of short trips never get good gas mileage because they never reach operating temp.

u said your heater was hot.. theirfore the engine is too

Matt

Actually, in my original post I stated in point #2 the following : 2) The heater gets warm very quickly (as in less than 3 minutes) but never HOT.

Of course the heater would get warm if the thermostat is open but it may never reach the 180-190 degree operating range.

ah, but still.... is the top hose warm? if its warm to hot the thermostat is fine...

Matt

With all due respect, I would agree if the problem were related to the thermostat sticking closed. If it were stuck closed, the coolant would never flow and the engine would overheat. The upper hose would never get warm because there would be no flow. In my case, its stuck open so coolant is always flowing and the thermostat never closes. The coolant will be warm because the engine is running but the thermostat is never closing to regulate the engine temperature and keep it in the 180-190 range. My guess is that the engine is running on the closed loop because it is too cold. ;)

I think that the fact that I immediately hear the coolant flowing through the heater at a cold crank, coupled with the fact that the engine temp always stays low proves that my engine is running too cold and therefore too rich.

You say that the gauge never moves past the C. Did it used to? My '97 4-cyl runs with the temp gauge right in the middle, but that seems to be somewhat unusual for a 4-cyl from what I've seen on FTE. A lot of guys trucks run cooler than that.

Thermostats are cheap, and often do not last forever. If it was my truck, I'd change it out.

*Side note, a lot of people here have not had good luck with Bosch plugs in Rangers. I think there is some info on it in the Tech sticky. I doubt that's your problem, though.

i agree with the bosch comment, mine fouled and the truck ran like crap with only a couple hundo miles on them.. but i do have the 6cyl

Matt

I agree somewhat that n ot reaching operating temperature will hurt your gas milage. An engine when cold runs in open loop which means the computer is running on presets and not paying attention th the senors because the sensors need to be up to a certain temperature before output from them can be trusted. Consider open loop like open circuit. The connection to the sensors is opened by the computer. When temp is reached the conputer closes the connection (closed loop) and starts reading the sensors. I don't believe the required temperature for closed loop is full operating temp but somewhat less so it could be other problems as well but changing the thermostat is easy and inexpensive and a good place to start.

Ok well I'll jump in (late). It's the thermostat. I'll bet ya ten bucks on it.

And yes, no Bosch's. Not a good reputation around here on them, from anybody really. I stick with Ford Racing plugs/wires. But that's just me.

RP
Zach

Why not just take it apart and see? Its not hard nor is it expensive. If its not the thermostat all ya lost is a little bit of coolant if it is, you lost a little bit of coolant and 5 bucks for another thermostat.

Why don't you start it cold with the hood up and hold the top hose, it should remain
cold until the stat opens and then should be that hot you can't hold onto it for very long. If on start up it trickles warm through the hose a new stat is in order.

UPDATE!

Yup. It was a bad thermostat. Engine now operating in the mid point between C and H and gas mileage has returned to the normal 27mpg range. What a PITA to change though. Scheeeeeech.

27 mpg ???