Which temperature gauge to trust? Or, how hot is too hot?

[jangell]

First: 3.0L EFI here.

I replaced the water pump a couple weeks ago. I noticed the engine temp was a little high the other day (near 220, according to the dash gauge), so I bled the system at the radiator, which I forgot to do last time (I have a self-bleeder at the water pump).

Today it was running a bit hot about, about 7/8 of the way to 220 from the unlabeled tick. But this time I had my laptop — TunerStudio showed 201 degrees. This was at highway speed (around 70 MPH in this case). It was 82 out today.

So, which gauge should I trust? MeagSquirt is reading from a sender mounted on the water pump, while the gauge is still using the original sender location on the back of the cylinder head (I think). Or perhaps both gauges are correct, since they’re measuring different locations?

I bled the radiator again when I got home. There was a hiss, some steam, and then coolant after a second or so, so it looks like I still had air in the system, assuming I’m reading that right.

I consider 220 to be too hot. I know it’s not a red line, but I’m paranoid from overheating issues in the past with the old engine. I also have a 2.5 hour trip each way next weekend, so I’d like to rule out any high temperature issues before then.

Any advice is appreciated. Thanks!

— Joe

[jangell]

And here are some pics of the gauges that I took while on the road. Apologies for the quality.

— Joe

[Bitsyncmaster]

The correct sender is very critical to have the gauge read correctly. I did some sender testing and I did get three senders reading the same. The gauge like most old automotive gauges compensate very well for car voltage changes.

I will look for that thread I did for the sender results.

Post #37 has the sensor values for temps. Other posts in that thread also have gauge testing

http://dmctalk.org/showthread.php?15...tterstat/page4

[FABombjoy]

All of the factory gauges should be considered rough estimates. They're indications will change with battery voltage, ground condition, etc. Trust the Megasquirt gauges more!

[Spittybug]

Has either one been calibrated? Procedure to do so is in MS instructions....

[FABombjoy]

If you're feeling enterprising, there are also methods of implementing AC control through megasquirt which can shut down AC in an overheat condition.

BUT look at your gauge RPM vs MS RPM. The original gauges really are rough estimates.