Low operating temp?

[C.E.Divine]

Hi everyone,

I am trying to get my 94 K2500 350 back in to good running shape. It has always had this issue that I can remember since my grandfather owned it, but the operating temperature is VERY low. After a 1.5 hour drive, according to the gauge, the temperature of the truck hovers around 110-120. It barely registers on the gauge. What is confusing is the heat in the truck will run you out, the motor feels pretty hot when you open the hood, but it is just the stinkin' gauge. I replaced the coolant temp switch and coolant temp gauge when it was loading up with fuel, and it fixed the starting issue, but not the temperature gauge issue. Could this be a problem with the gauge itself? I have not checked to see if my grandfather pulled the t-stat out one day and just left it open to save money, so at your suggestion, I will start there if it is a possible issue. He doesn't seem like the type that would do that though, so I have gone on benefit of the doubt. The truck doesn't smell rich after it has been out to stretch it's legs, only on startup. It has nearly 274,000 miles of that helps. I worry that it is not going in to closed loop even though judging by smell it does.

 

[skylark]

The temp sender for the gauge is on the drivers side head between #1 and #3. Check the resistance with a multi meter. Do the samesing with the one on the thermostat housing. The thermostat housing one is for the computer. You should be able to find resistance charts for both senders. Compare the two and see if they agree with each other. If not, swap the bad one. If they are both low then you have a problem in your cooling system.

 

[C.E.Divine]

I hope that the parts I bought were not bad out of the box. Both were replaced about 2k miles ago, and although the temp switch fixed the startup issue with the engine flooding, the temp sender in the block made no difference whatsoever. I'll look around and see if I can find those resistances, and pull out my ohmmeter tomorrow. If the sender checks out, what sort of issue beyond a missing or stuck open t-stat could it be? i know there was an option for an HD water pump, but no matter the amount of cooling happening, wouldn't the truck eventually get warm enough to open the t-stat if it is there?

 

[magimerlin]

Thermostats are an easy job.. I would put in a new one if you are thinking it might not be there. And the sensor gets its ground from the engine block so make sure that your negative cable coming from your battery and going to the intake somewhere is good, clean and tight..

 

[C.E.Divine]

All sensors and ground are within spec. Something else I found today as I was troubleshooting an EGR code- the truck warmed up to 160-170 after I just started it and let it warm up without moving. The minute I moved, it went back down to what I described above, and then warmed up again after sitting idling to 160-170. I'll change the thermostat when I remove the intake manifold to clean the EGR passages, but do you guys think that with it warming up at idle and then cooling down too much when driving that it could be the fan clutch is too stiff? It isn't totally locked, but it isn't easy to move by any means. It doesn't continue to move when I give it a hard fling. Sorry for lack of better way to describe the fan clutch. It is just very stiff.

 

[Scuby]

Did you test the fan clutch cold or hot? Obviously hot it won't be easy to move....

Mine runs too cool as wel. But I don't trust the gauges as my voltage also reads 10-11v while at the battery I've got 14.3v.

I'd go the route of re-doing grounds and adding an extra one. Electrics are always the first thing to get dodgy on older vehicles.

 

[C.E.Divine]

Scuby, clutch was tested first thing in the morning before it was started. And thanks for the advice on adding an extra ground. I'm thinking about doing the big three electrical upgrade anyway, so this is a good time to do it.

 

[SCOTTYINWV]

I suspect a faulty fan clutch not unlocking. Having the same issue with my zr2. Driving Temps, doesn't get above 150-160. At idle it comes up to around 185.