737av8or

I just returned from an epic 2069 mile journey driving the 2019 Hot Rod Power Tour in my 1975 C3.

It was an incredible trip with only one minor breakdown. 750 miles in to the journey I lost my fan belt while doing 80 MPH down the interstate. By the time I smelled it, I had already overheated the engine significantly. I had a spare belt with me and changed it out and topped off the coolant level but my temp gauge was still showing the car overheating very quickly after being run for only a minute or two.

It was too dangerous to further troubleshoot on the side of the interstate so I called AAA and had it towed to a garage. They located and installed a new temperature sending unit but the new unit showed zero temp on the gauge in the instrument cluster. The temperature was verified to be in normal operating range by the shop with an infrared thermometer. They reinstalled the original sending unit and it did register on the gauge but was reading higher than the infrared equipment said the actual temp was. I couldn’t spend any more time trying to figure it out because we needed to rejoin the tour. We drove about 250 miles with intermittent or no reading at all which was completely unacceptable.

At the next stop on the tour I added a second sending unit and it also didn’t register anything on my gauge. I assume I somehow damaged the gauge itself during the overheat? What do you guys think, if I replace the gauge will it solve my problem?

My solution was adding an old school mechanical gauge so I could continue the tour. It was installed in a hotel parking lot with lots of beers but it got the job done and gave me some piece of mind.

MelWff

considering all the tampering with the wire connector to the sender, I would look for a broken wire in the connector.before anything else.

Rescue Rogers

Go to the willcox site and look up gauge testing. I did it and my gauge was good but the sendor was bad. Ernie explains that the newer sendors arent made correctly so they wont read correctly. You can get one of his adjustable resistors that are a very easy install to get the correct year sendor to read with a same year gauge. I tried to mix and match sendors/ guages and it didnt work.

Check the wire for a direct ground, check the gauge and maybe buy a sendor from Ernie or the resistor.

heres the trouble shooting guides
http://repairs.willcoxcorvette.com/?...&s=temp++gauge

Heres whats up with the new sendors not working correctly
http://repairs.willcoxcorvette.com/1...ender-cleaned/


I had a similar gauge issue but I used the wrong sendor because I didnt want to tap my new aluminum heads out to 1/2inch npt. Ernie helped me solve it with a custom sendor but while I was waiting for it, I did the same as you with mechanical gauges. I since left them installed in the engine compartment so I can see temps while working on the electric fan or anything else and as a backup incase the temp gauge fails

737av8or

Thanks, that is very helpful. I will contact Wilcox to get the proper sending unit. The original sending unit was the only one that read anything on the gauge so that leads me to believe that the mechanic’s assessment that the sending unit was damaged during the overheat is accurate and I just need a proper sending unit to fix my issue. Thanks.

737av8or

Thanks for the advice Rescue Rogers. It turns out that the modern sending unit was in fact the issue. After ordering a properly calibrated sending unit I am back in business. The engine is running at 180 - 190 degrees, exactly as the mechanical gauge was reading. Problem solved!

7T1vette

If your engine overheated when one fan belt failed, that means you don't have the one between water pump and damper. That is the 'fail safe' belt. It's unlikely that both water pump belts will fail at the same time, so overheating due to belt failure is nearly eliminated. Might look into that one... Glad your trip turned out on the plus side!

Rescue Rogers

glad it worked out. I've been trying to find that idler belt and finally found a thread on them. I'm taking 7T1vettes advice and putting one in this week.

737av8or

You are correct, I did not have the second belt. I will be installing one when I get a chance. It appears there is no way to tension that second belt. How exactly is the belt installed? Is the belt just stretched over the pulleys?

OldCarBum

There was a recent thread regarding how to install the belt.
The bolts in the crank pulley need to be loosened or removed, install the belt on the pulleys, then reinstall the pulley.
The belt is snug enough to turn the water pump but there is no adjustment, so purchasing the correct belt is the key.

rberman999

To check the gauge is working properly take the temperature sending unit wire and ground it. That should peg the temperature gauge to full hot. If not there is a problem in either the gauge or the wiring. Very simple and quick to check your gauge. The temperature sending unit in essence is a temperature sensitive variable resistor that goes to ground. Good luck, Russ