Engine not reaching operating temperature

[DaisyDart]

Hey everyone,
So i just bought a 1970 dart swinger with a 225 in it, while driving home i realised she never went past the C mark on the dash. I could just go ahead and change the thermostat but i wanted to see if maybe there is known issues with the cooling system or not. I imagine its either a thermostat stuck open, a bad gauge or a bad sending unit?

 

[dragondan64]

I would try one thing at a time starting with the thermostat.

 

[grumpuscreature]

I've never had one that ran much more than 1 or 2 needle widths past the cold end of the operating range. Once or twice the needle got to the middle of the gauge range, but by then they were blowing steam out of the overflow. Don't worry about it, it's normal, in Moparworld...

 

[jdsduster]

I've never had one that ran much more than 1 or 2 needle widths past the cold end of the operating range. Once or twice the needle got to the middle of the gauge range, but by then they were blowing steam out of the overflow. Don't worry about it, it's normal, in Moparworld...

what good is the gauge then?that isnt very accurate.ive never had a /6 swinger,my dusters ive owned have had pretty good gauges.i would check stat and sender.and see just how close the gauge really is

 

[grumpuscreature]

what good is the gauge then?that isnt very accurate.ive never had a /6 swinger,my dusters ive owned have had pretty good gauges.i would check stat and sender.and see just how close the gauge really is

Never said the gauge was "accurate" just reported what I have noticed over 40 some odd years of driving Mopars from A to C with engines from RG to Hemi. Had a '71 Sport Suburban with a 360 that ran roughly 1/8" past the end of the cold range and considered that running hot. As far as "what good is the gauge" goes? Just what exactly do you expect it to reveal? I always knew when the engine had reached normal operating temperature and on the rare occasions when a problem developed I had plenty of time to shut it down and prevent serious damage. What more do you want from a gauge???

 

[72bluNblu]

The gauge should run in the middle of the range, or somewhat close to there anyway. The temp gauge on my Challenger always has, and so does the rallye temp gauge in my Duster.

If you just bought the car, have you ever seen the temp gauge needle move? If not, I'd check all the electrical connections first to make sure its even hooked up. Then try the sending unit. If the engine is running fine and seems to be getting warm, it's more likely to be a wiring/sender/gauge issue. Does the heater blow hot air after the car warms up? If it does, its probably not the themostat.

 

[65cuda360]

Check the gauge and sender by unplugging the wire from the sending unit and grounding it with a jumper wire. With the key on the gauge should swing all the way to the right (hot).

 

[DaisyDart]

thanks! ill check that tomorrow morning and let you know if the gauge goes to the hot or not.
The heater does blow warm air, i wouldnt say HOT but warm. i believe ive seen the gauge move SLIGHTLY since i bought it on friday.

 

[toolmanmike]

Ill bet when you take the thermostat out it will be open. If not, put it in a pan of water on the stove with a thermometer in it and watch when it opens as the water temp rises. When you get a replacement, ask your parts guy for a good one and not a cheapie off the pegboard with a universal gasket. Tmm

 

[nm9stheham]

If you want to test your thermostat, push the valve open a bit and put a string through the opening; release the valve so the string holds in place. Suspend the t'stat in water on a stove and bring the water temp up slowly while monitoring temp on a candy thermometer. When the t-stat starts to open, it will drop off the string. The t'stat running temp rating will be about 5-10 degrees F above the temp at which it drops off the string.

With an old T'stat, you should be replacing it anyway. Get a Stant brand (from NAPA if you have them up there); too many junk t'stat out there nowadays (As TMM notes above).

After the t'stat, the next most likely is that the temp sender is bad, assuming the guage checks OK. At 180F, it ought to read around 30 to 40 ohms from terminal to case.