Temp gauge climbs under load

[RammaR]

Ever since I had to replace the cylinder heads a few months ago, I've been watching my temperature gauge like a hawk. I replaced the thermostat (195F) and the sending unit to the gauge. The old setup never moved much from the horizontal cold line. Now the needle stays at the middle of the gauge while cruising along the hwy at 70 - no issue.

However after climbing the steep hill to my house stays in the middle for most of the climb and then moves as high as 3/4 as I pull into the garage. The needle cools back down after it idles for a minute or two. It does the same thing while passing sometimes. It doesn't fluctuate during steady running - like some threads I've read - only after load changes.

I've replaced the thermostat a 2nd time with no change. I had an exhaust manifold gasket leak and fixed that - no change. I've verified that the cat is fine and not restricting flow. Checked the plugs (new with the heads) - they all look good.

I ran a radiator "cleaner" fluid for about a week when doing the heads. Since the gauge was always at the low end of the spectrum with old thermostat / sender, I'm curious if anyone else notices the temp needle moving like this after heavy load? Maybe it needs a good power flush?

Thanks

 

[bluestream1]

i would guess the sending unit has a bit different output. maybe get a used one and see what happens on the guage

 

[MudXplorer]

check out the wire/wires to the sending unit, mine did the same thing after i did the heads on mine, the wire to the sender was frieds, though it appeared fine

 

[2000StreetRod]

Test the sensor

Did you fill the block with coolant before installing the thermostat? If not, you may still have air in the block. Otherwise, I suggest that you test the resistance of the temperature sensor according to the chart below from BrooklynBay's list of useful threads.