Running Cold

[DA BIG ONE]

On my last trip out to AZ I ran into a problem with the engine running cold below 70mph.

In hot or warm weather the truck temps are fine.

I covered the radiator and still had the problem, yes, I am stumped on this one.

[Andy Chesek]

Last week my SES light came on. Had Advance Auto scan it for free, and the two stored error codes stated "insufficient coolant temperature"

Guy at the counter said he sees it all the time, and pulled a new coolant temperature sensor off the shelf. $8 for the new sensor, and 5 minutes to replace the old one and I was good to go.

[Gapper_ca]

Sounds like your thermostats are stuck open, have seen it happen lots. when they are wide open the coolent just free flows never getting very hot.

[Hubert]

I'll second the open thermostat. My 97 with dual thermostats ran cold I replaced them both with 180F version fixed it. Lots of opinions on what to replace with.

Feel the motor if its cold I would say thermostats if its hot I'd say sensor. Its ironic that with all the worry of overheating the 6.5 it sure runs cold with an open T-stat.

[slagona]

Depends on what you mean by "feel the engine". If you mean feel the radiator hose - that may not give you a good indication of the engine temp if the thermostats are in fact wide open. When wide open, the coolant is not traveling slow enough to absorb the engine's heat. Therefore, the engine itself (oil temp, for example) will be very high as the coolant isn't able to do its job, but coolant temp itself will be low.

Just a caution for those wanting to feel the engine..... The engine itself will always be hot. The coolant hoses may not give a good indication of the actual engine temp.

A good clue for thermostats being stuck open is the code P0126 - especially if it only happens on colder days. If the coolant doesn't get to operating temp in a certain time frame - the code is thrown.

[markrinker]

1) Take your truck out for a few runs, until water temp is as high as you can get it.

2) Stop truck, shut it off, pop the hood and grab the top radiator hose. Squeeze.

3) If no pressure, you need thermostats.

4) If pressurized, you need a new temp sender.

5) If none of my advice works, replace both smile.gif

[diesel65]

Mark,
Having the wrong coolant cap would also cause you not to have pressure.
A standard radiator cap is vented, our trucks use a non vented cap.

[DA BIG ONE]

Thanks everyone, I will do the thermostats, already did the sender.

When this running cold happens there is no heat.