Coolant temperature sensor for guage (not ecm)

[TexasZR1]

Has anyone ever swapped in a three wire coolant temperature sensor for their gauge to get rid of the poor ground / less than favorable location choice for gauge sensor?

I have a 1991 third gen camaro that I installed this sensor (delco; three wire; 10096181) in a thermostat housing with two ports. So now on that car, my gauge reads the temp from the same location as the ECM, and right above the thermostat. It always has ground, so the issue with the stock unit where heat over time can cause a change and resistivity and high readings is gone, AND you can instantly see temperature changes due to thermostat actuation.

Any thoughts on performing a similar modification to a 1990 ZR1?

My current gauge sending unit seems to be reading high. I want to confirm I don't actually have an overheating issue (sticking thermostat, etc). Motor runs normal. It seems to get as high as around 240 on the gauge before coming back down, which is scary high to me. But maybe that's correct and this is normal for these cars?

I've not yet compared to the ECM sending signal.

[TexasZR1]

Adding to this discussion:

I just checked the part number for the coolant sending unit for the 1991 z/28 and the 1990 ZR1 / LT5 and it seems to be the same delco part #2134793.

So if it worked on the third gen, it may work on the LT5, also. Just need to find a place to mount the sensor. Could stay in the same spot with an adapter... IIRC they are different size pipe thread.

[TexasZR1]

Posting an image of where the guage reads vs. What the ac unit says (110c = 230F).

I guess this is about normal?

[TexasZR1]

Going to be contacting Marc H. for a chip soon it seems.

[Reichert]

Also consider replacing your radiator cap .. had to do that to get my cooling under control (in addition to a new t-stat and chip).

[DRM500RUBYZR-1]

Also consider replacing your radiator cap .. had to do that to get my cooling under control (in addition to a new t-stat and chip).

Heed his advice!
Simplest thing to do is confirm that your system is pressurizing to 14-16 pounds.
When it does not, idle temperature tends to run higher, and the car runs hot during driving then heats up much more than normal.
Weak cap. Pressure test the cap and the system.
Check for a very minor leak, loose clamp also check heater core!
Either of those could be your culprit.
I would not be overly concerned with the non-accuracy of the gauge, as that is normal, they are not linear.
Also check to see how much debris is in front of the radiator.
Do those things first and let's assess where you are then.
Good luck!
:cheers:
Marty

[TexasZR1]

System held a pressure test well. Can't test cap with what i have, so i will pick up another.

[Paul Workman]

System held a pressure test well. Can't test cap with what i have, so i will pick up another.

Agreed. Having had several coolant overflow issues with our two Zs over the years has made me a student (at least) of coolant system faults and repairs.

A pinhole leak or bad radiator cap allows air to be drawn in instead of drawing coolant from the overflow bottle from being drawn back in as the motor cools. Then, next time the motor heats up, there is air in the jacket, the motor runs hot, and remaining coolant within the jacket expands (especially immediately after shutting down) and is forced out, over-filling the overflow bottle (in the headlight well).

You can borrow a cooling system pressurizing test kit (from AutoZone), but a new radiator cap is cheap enough. (Besides...the cap should be replaced periodically - perhaps every couple years or so, especially if planning a long trip!)

As for the temp sender for the gauge goes, it resides next to the temp sender for the ECM; both together at the driver-side front of the IH and under the plenum. One (or two) examples does not a trend make, but I've not had any grounding issues with the gauge sender, or do I recall anyone else either having an issue with the sender (the OP) described.

This split in this hose was only visible when under pressure. When the motor was cold, the hose looked normal. However, it had a pinhole leak in it, causing the overflow bottle to...well...OVERFLOW! A new radiator cap didn't fix the problem, leading me to consider other more ominous causes (and a sleepless night or two!).

[TexasZR1]

I used the cooling system with the test kit from Autozone. The system held 15 psi for aboit thrity minutes. Just before this I went around 'pumping' the soft line to burp the sytem as much as possible. There was a little bit of air, so hopefully things improve a bit having burped it.