Cooling System Bleeding Procedure

[So Cal Mark]

there should be two sending units; one red and one black. The red one controls the lower portion of the gauge, the black one controls the overheat part of the gauge. Make sure the wires are connected properly. Remove wires from both senders and ground them one at a time with the key on. When you ground the wire for the red sender, the needle should go just past the middle of the gauge, the wire for the black sender will make the needle peg

[Torxx]

The front wire when grounded, made the gage go to 1/2 point on gauge 190 deg, the back wire (closest to firewall) made the gauge budge only slightly. What does that say, does that say anything about the sensors units? My sending units don't seemed to be colored. It was the front one that was replaced, not that long ago. The rear is probably orig.

P.S. please verify that my t-stat is installed correctly, it seems to be working fine??

[rlux4]

Torxx, your T stat is installed correctly on your very nice looking engine.
Ron

[Torxx]

Thanks Ron

[So Cal Mark]

you need a red sending unit in place of the rear black unit

[Torxx]

Does the bad unit suggest that the car is probably running at proper heat range, but giving a false reading?

Thanks for the help

[So Cal Mark]

no way to tell the temp without an infrared gun or thermometer, but if the fan cycles on and off it's probably at the right temp

[Torxx]

Maybe there is light at the end of the tunnel.

This night be a dumb question, but, if the wire that I grounded is not connected to the sending unit, how does that test the sending unit itself?

[So Cal Mark]

grounding the wire tests the gauge. If the gauge and wiring work properly, the sending unit is the only item left

[Torxx]

Mark, I am still confuded about one thing, you said the wire that goes to the black sender unit when disconnected and grounded (closest to firewll) will peg the guage. Mine did not move the guage. What would that have told you if it did peg the guage?

[So Cal Mark]

faulty gauge, if it has 12 volts on the power side

[Torxx]

Well, after Mark lead to the answer I was looking for, I was thrown a welcomed curve.

As I was reconnecting the wires to the sending units (in anticipation of ordering a new one) I had the bright idea to take a little sandpaper to the connection points before reconnecting...To my elated surprise, the car is running perfect. Temp gauge stays at about 180 deg. and will rise to 190 if sitting at idle for a little while, and then the fan kicks in like a champ and brings it right down...priceless.

I was chasing a Ghost.

[rlux4]

Well all right Torxx!!
"the car is running perfect" What could be better.
Ron

[pc124]

Good evening. My car is a 78 spider.

I decided to replace a few hose clamps.

I disconnected the top radiator hose at the radiator and at the union. I disconnected the union-to-thermostat hose at the union only. I replaced the clamps and reconnected everything. I also replaced the clamp at the overflow-to-radiator connection.

Then I removed the choke hose closest to the fender. Held it high and added water until the radiator overflowed. Recapped the radiator. Then I added water until the choke nipple flowed coolant.

Then I started the car.

Now my fan won't cycle. I only let it get the gauge get about 40% of the way between 190 and 260 before I shut it down. Everything was fine (fan on at about 200 per the gauge) prior to this move which I am now regretting.

Any ideas??

Thanks much.

[So Cal Mark]

make sure the fan connections are still good, then rebleed the cooling system