Temperature Gauge/Engine temp help

[Duck.E]

I recently just finished a head gasket job on my 72 chevy c10 and before I did that the temperature gauge was fine. I got everything together and went for a drive and shortly after gauge went into red. I let it cool and took it on highway to see if it bony did it at low speeds, still went up into red. Radiator, water pump, and gauge in cluster are all new. I never had a thermostat before so I put one in and started truck and gauge immediately went to red and truck hadn't been ran in 2 hrs. Can someone tell me how to diagnose the problem, is it gauge, sender, etc. Coolant is full, No leaks, and water pump isn't leaking as well.

[70cst]

Here is a bump for you. Hopefully someone will chime in with some ideas.

[picklito]

Have seen this happen. The replacement waterpump was accidentally for a motor with serpentine belt... so reverse rotation.

[Duck.E]

Originally Posted by picklito

Have seen this happen. The replacement waterpump was accidentally for a motor with serpentine belt... so reverse rotation.

Well, before I did head gasket job the new pump had been on for a while and I didn't have any problems, pump seemed to be working fine and never had the gauge do that. Now idk. Thinking of maybe buying an aftermarket mechanical wate temp gauge to see the actual temp and if gauge is faulty.

[67swb72klb]

this might help you diagnose the problem if the sender wire is grounded it will be full hot

[Duck.E]

Originally Posted by 67swb72klb

this might help you diagnose the problem if the sender wire is grounded it will be full hot

Thanks, I will check that as well tomorrow. I don't think it is because it didn't go directly to hot right away. A couple of trips around the block with a thermostat installed it shot all the way up.

[Sklptrljay]

Mine did the same thing. The temperature gauge is probably on it's way out like mine. Check the sender first, but I would bet you need a new gauge. My gauge eventually just stuck on full hot no matter when, even with the power off.

[Ironangel]

Originally Posted by Duck.E

I never had a thermostat before so I put one in and started truck and gauge immediately went to red and truck hadn't been ran in 2 hrs.

Did you place the thermostat in the manifold with the Spring Down? The spring must be down to receive the heat from the coolant that has been heated in the block. Also, the sending unit in one of my 72's had a loose inner element causing a low temp or no read at all situation. I replaced it recently wishing i had done so long ago. If replaced, make sure the new sending unit is exactly like the unit taken out. The green wire leading to the unit should be sheathed and the insulation in good shape to eliminate any chance of grounding or shorts. Do not use teflon tape on the threads of replacement sending units as it will inhibit a proper ground. Hope this helps ;0

[Duck.E]

Originally Posted by Ironangel

Did you place the thermostat in the manifold with the Spring Down? The spring must be down to receive the heat from the coolant that has been heated in the block. Also, the sending unit in one of my 72's had a loose inner element causing a low temp or no read at all situation. I replaced it recently wishing i had done so long ago. If replaced, make sure the new sending unit is exactly like the unit taken out. The green wire leading to the unit should be sheathed and the insulation in good shape to eliminate any chance of grounding or shorts. Do not use teflon tape on the threads of replacement sending units as it will inhibit a proper ground. Hope this helps ;0

Thermostat was placed spring down into manifold. The sender wire is sheathed and doesn't look to be grounding out anywhere. The wiring harness in the truck was replaced a while ago so it's fairly new. Could be sender or gauge. Just weird it all worked before i replaced head gaskets nownits not, but I'm going to try a a few things today and see what happens.

[Duck.E]

Got a hold of a temp gun and shot it while gauge was in red and radiator was 180 and intake was around 190. Nothing was over 200. So my guess is gauge or sensor.