Water temp indication full low or full high

[FLFrank35]

Question about water temp indication on a Ford 302/306:

My water temp gauge used to work fine but now it is either pegged at the left or at the right.

I have the Autometer gauges that came with the kit and a Holly Sniper 4150 EFI with the handheld touchscreen controller. When I start the engine the water temp is pegged at the low end (100°) and doesn't rise as the engine warms up but the Sniper's controller display shows the water temp steadily increasing. At about 190° on the controller, the Autometer gauge pegs out at the high end (250°). As the temp decreases below 185-190 the gauge goes back to the low end.

When initially filling the coolant I didn't know to raise the front end so there may have been air in the line. So today I removed the radiator cap, raised the front about a foot and ran the engine. I did see some air bubbles and the thermostat seemed to open/close as it's supposed to. The Sniper temp indication seems to indicate everything is working properly except for the gauge...it's either pegged to the left or to the right.

The Sniper's temp sensor is in a port on the top of the manifold, and the gauge's sensor is right next to the thermostat. I do have the gauge sensor grounded on the thermostat housing...could that be the problem, or something else? Should I move the sensor to another port?

Thanks

[mkassab]

Question about water temp indication on a Ford 302/306:

My water temp gauge used to work fine but now it is either pegged at the left or at the right.

I have the Autometer gauges that came with the kit and a Holly Sniper 4150 EFI with the handheld touchscreen controller. When I start the engine the water temp is pegged at the low end (100°) and doesn't rise as the engine warms up but the Sniper's controller display shows the water temp steadily increasing. At about 190° on the controller, the Autometer gauge pegs out at the high end (250°). As the temp decreases below 185-190 the gauge goes back to the low end.

When initially filling the coolant I didn't know to raise the front end so there may have been air in the line. So today I removed the radiator cap, raised the front about a foot and ran the engine. I did see some air bubbles and the thermostat seemed to open/close as it's supposed to. The Sniper temp indication seems to indicate everything is working properly except for the gauge...it's either pegged to the left or to the right.

The Sniper's temp sensor is in a port on the top of the manifold, and the gauge's sensor is right next to the thermostat. I do have the gauge sensor grounded on the thermostat housing...could that be the problem, or something else? Should I move the sensor to another port?

Thanks

The grounding, most likely is fine, however, hold/attach an new additional ground wire from the temp sensor to a known good ground on the chassis for a quick test. If nothing changes, my guess would be it's a bad sensor and to replace it.

[FLFrank35]

The grounding, most likely is fine, however, hold/attach an new additional ground wire from the temp sensor to a known good ground on the chassis for a quick test. If nothing changes, my guess would be it's a bad sensor and to replace it.

Ok, I'll try that.
Thanks!

[FLFrank35]

I didn't mention it in my initial post, but I am using Evans waterless coolant. Apparently it boils at a higher temp so it produces a lower pressure...maybe too low for the sensor to properly sense. Hmmm...


Speaking of Evans waterless coolant...any opinions on it? Anyone else using it?
One problem is that if it needs a top-off, you can't just add water or off-the-shelf coolant.

[mkassab]

Evans waterless coolant doesn't work that way. It takes a higher temp to boil, but does take on the temp of the engine..... So, No, it isn't too cool. You are also correct that you can't add water to it.... you'll need more Evans waterless coolant.

Therefore, your issues has to be the sensor, the gauge it itself, or the wire.

I have used Evans before with no issues.

Mark

[FLFrank35]

Evans waterless coolant doesn't work that way. It takes a higher temp to boil, but does take on the temp of the engine..... So, No, it isn't too cool. You are also correct that you can't add water to it.... you'll need more Evans waterless coolant.

Therefore, your issues has to be the sensor, the gauge it itself, or the wire.

I have used Evans before with no issues.

Mark

Ok, thanks for the explanation. I wasn't sure of the Evans properties compared to the water/coolant I'm used to. Have read mixed reviews recently, so wasn't confident I made the right choice.

I checked the ground, gauge and sensor. I think the sensor may be the culprit (if I tested it correctly). I'm replacing that today...hopefully will solve the issue.

Thanks again!

[DonImbimbo]

The temperature sensor is a variable resistance device. It is not sensitive to pressure. So you could unplug the wire attached to it and use an ohmmeter to read its resistance. The resistance should change smoothly as the engine warms up.

[FLFrank35]

Looks like the sensor was bad. Initially I purchased a sensor at a local auto parts but it immediately showed a temp of 150° with the key ON and shot to the max within 30-60 sec of starting the engine. Then I learned that the AutoMeter short-sweep gauges require a specific sensor, so I purchased an AutoMeter temp sensor (#2258) and it seems to work fine. The temp from the AutoMeter sensor in the thermostat housing reads a little lower than the EFI temp sensor, which is in the top of the intake manifold, but this is probably normal.

Thanks for all of the responses and explanations!

[FF33rod]

Sounds to me like you used the FFR fan switch sensor for the autometer gauge instead of the variable resistance autometer sensor. The fan switch sensor is an on-off device that switches at 180 (I think) degrees, it usually goes in the radiator and is used to turn the electric fan on and off...

Steve

[FLFrank35]

Sounds to me like you used the FFR fan switch sensor for the autometer gauge instead of the variable resistance autometer sensor. The fan switch sensor is an on-off device that switches at 180 (I think) degrees, it usually goes in the radiator and is used to turn the electric fan on and off...

Steve

Oh! Didn't even think about that, but very well could be.
Thanks!