I'm guessing the stock water temp gauge isn't reliable?

[Nutro]

I'm guessing the stock temperature sending unit is not very accurate? I just put dual electric fans on my 88 and they weren't coming on until the factory dash gauge read almost 260.

Using an infrared gun the thermostat housing wasn't getting hot enough to turn the fans on at 195 degrees until the factory gauge was showing just before 260 and then they would turn off at around 185 degrees which is where it is supposed to, and the gauge was showing just under 210.

Is it worth getting and using a new sender or should I just buy an autometer water temp gauge and run it to the same spot in the head?

 

[tRustyK5]

Try plugging in a "new to you" stock gauge. I've had a few get wonky over the years.

 

[mrk5]

Same thing happens all the time with my C10. It even has a new sending unit. I think it's because they're in the head. That coolant heats up quicker than at the thermostat. My fans come on at about the same temperature as yours and the factory gauge reads at the edge of red when the fans come on.

I have aftermarket EFI that reads the coolant temp near the thermostat and can confirm the temperature there is around 190° when the fans come on and the factory gauge is reading near 250°.

It only happens on the initial warm up. Once the thermostat has opened the first time, the temperature difference doesn't get that far apart.

 

[sweetk30]

Same thing happens all the time with my C10. It even has a new sending unit. I think it's because they're in the head. That coolant heats up quicker than at the thermostat. My fans come on at about the same temperature as yours and the factory gauge reads at the edge of red when the fans come on.

I have aftermarket EFI that reads the coolant temp near the thermostat and can confirm the temperature there is around 190° when the fans come on and the factory gauge is reading near 250°.

It only happens on the initial warm up. Once the thermostat has opened the first time, the temperature difference doesn't get that far apart.

X2

 

[Nutro]

Well that is odd. I let it idle on the driveway for a good 20 minutes and it would go like clockwork. The fans come on at 255 on the dash gauge then off at 180-ish over and over. When the fans come on, it cools it pretty quickly. I kept checking temps at the thermostat housing and exhaust manifold to make sure temps were correct. Now I have to figure out what the smell coming from the exhaust is. I'm praying it isn't coolant.

 

[sweetk30]

Why are your fans coming on at 255* ?

Should be around 15* above t-stat temp and off at or just below .

 

[Nutro]

The factory gauge is reading 255 but the temp at the t-stat housing is showing 188 roughly. The fans are set to come on at 195 and off at 185. I put a 195 thermostat in.

 

[ZooMad75]

Those things were never known for accuracy. Comparing mine vs the readout on my engine data it's 10-15° different.

Part of that is the small sweep and the lack of numbers at more points on the gauge. Having watched mine enough I know by looking at the stock gauge the engine is ok on temp or not.

 

[dyeager535]

There is generally nothing wrong with the factory gauges. Not by design. You are talking ~30 years, things happen. Bad connections, failed resistor, corroded wiring, bad sender, etc. Even at this age, a failed gauge is uncommon.

Below is a pic of a well used gauge that's the same vintage, displaying the oil temp in the engine sump, this winter. Seems reasonable to me given the conditons. My factory coolant temp gauge is within 10* of the temp shown by the ECM at the same location in the intake.

I'd figure out why the swing. Nowhere in the engine should you see that much swing with properly functioning components no matter where measured.

 

[bp71k5]

The factory gauge is reading 255 but the temp at the t-stat housing is showing 188 roughly. The fans are set to come on at 195 and off at 185. I put a 195 thermostat in.

You’ll have more efficient operation shutting the fans off at 195 if you are using a 195 thermostat. That way your thermostat isn’t fighting the fans. Would be better to turn fans on at ~200.