Vintage Gauges - Temp Gauge Accuracy...?..

[cdurbin328]

Question..
How accurate are the Vintage style Temp Gauges?
I ask because when I hook up my OBDII reader it shows the temp as 10 degrees higher than what the gauge is showing.

[rthomas98]

the guage is only as good as the sensor. Where is your sensor located for the gauge? If it is in the radiator and the engine computer is reading from the manifold or the block, yes there will be a difference.

[phileas_fogg]

Am I correct in recalling the Coyote doesn't measure coolant temperature, but instead measures temperature in the combustion chamber? If so, I can easily see how the temperatures would be different. The gauge is actually making a measurement, while the Coyote ECU is making an inference. [Truth in advertising: I don't have a Coyote so I may be waaaay off base.]

And as rthomsas98 says, measuring in different locations can lead to different temperatures.


John

[edwardb]

Am I correct in recalling the Coyote doesn't measure coolant temperature, but instead measures temperature in the combustion chamber? If so, I can easily see how the temperatures would be different. The gauge is actually making a measurement, while the Coyote ECU is making an inference. [Truth in advertising: I don't have a Coyote so I may be waaaay off base.]

And as rthomsas98 says, measuring in different locations can lead to different temperatures.

John

Mostly right. The Coyote temp reading isn't an actual coolant temp reading. And even those can vary depending on where the sensor is located as already mentioned. The standard practice of the Coyote and a coolant temp sensor is in the port on the LH side behind the alternator. It's used for an optional block heater for DD's. The Coyote has a cylinder head temp sensor, and infers the engine temp based on that reading plus other engine parameters. Unlikely you will get exact readings between the two sources. Best is to drive the car and get a sense of what temp you see on the gauge on your dash in varying conditions. Once you know what is "normal" you'll be able to respond if something is different. Certainly doesn't hurt to monitor the temp from the ODB2 port. But for daily use, the dash temp gauge gets the job done. FWIW, in the two Coyote build's I've had and driven extensively, both with Vintage (Speedhut) gauges in the port already mentioned, they typically range in 190 - 195 F. Every once in a while on a hot day, in stop and go, and with the A/C, it will peak over 200F. But go down with the cooling fan or once moving again. In general, cool and very predicable/stable. Note that's with the stock thermostats (I haven't touched them) and the Mustang style expansion tank and plumbing.

[cdurbin328]

Aprreciate all the input. I installed the sensor on the left side of the block in the location mentioned. I was checking the temp with the OBDII because it seemed like the fan was kicking on really early in the drive cycle. I've only driven the car twice on the road since finishing my build. Both times the temp gauge registered up around the 220 range, which seemed kind of high to me. I'm pretty sure that I've gotten all of the air out of the cooling system. I have a vacuum kit that sucks all the air out of the cooling lines and then back fills with coolant.

[Chainsaw]

My dash gauge for a BPE 306 SBF reads around 220F while the Sniper display shows 175-185F with the fan cycling on/off. The gauge is in a second port in the forward end of the intake manifold on the opposite side of the block, about 10-12" from the sensor the Sniper is using. Speedhut even sent me a new H2O temp sensor (the old indicated 240-260F). Not sure if this is in any way comparable to the Coyote set up.

[Alan_C]

Only way to be sure is to get ahold of a "calibrated", that is one whose accuracy has been verified by a calibration lab and labeled as such. With a calibrated gauge in hand, you can install it where you normally install your vintage style temp gauge and compare.

[cdurbin328]

Understood.
I'm not really concerned with the gauge but more whether or not my motor is running hotter than it should.

[edwardb]

220F is too high. If real, something isn't right in my experience. It should be down in the 190 - 195 range and occasionally just over 200 as I mentioned. If you have the Mustang plumbing with an expansion tank, it's self burping so air in the system isn't an issue. If you have a regular overflow tank and the fittings capped off (like in the Factory Five instructions) you might have air in the system. Although with a vacuum fill system, that seems unlikely. My Coyote builds took about 15 quarts of coolant. Is that about how much you have in yours? What temp is showing in the ODB2 port when the dash gauge is showing 220? The Ford programming for the crate motor is pretty conservative and will run the fan a lot. At the temp you're describing, if real, it should be running continuously. I agree with others. Perhaps the dash gauge isn't registering properly.

[Alex_V]

I added a Codebreaker OBD2 Diagnostic Tools by Ultimate9 mounted under the dash with a velcro strip. Can be easily removed for car shows, etc. Unit reads all the data directly from Coyote ECM in real-time. I don't trust the classic gauges to be super exact, and it gives you another data point on what is going on with the engine. Looks good and is out of the way.

[cdurbin328]

That's what I'm thinking as well... too high.
I'm running an aftermarket, Summit overflow tank. I don't recall how much coolant it took.
Yes the fan, once on, runs continuously.

[cdurbin328]

Well, after doing some research on the interweb... I think I figured out my cooling issue.
It appears that I don't have my degas tank plumbed quite right. doh..
I ordered a couple of fittings from summit to try and correct the issue.
I'll report back with the results.
Thanks again for the input.