Thermostat not working, no coolant leaking from water pump, no pressure on upper & lower hoses

[Andrew Koetz]

I put a brand new thermostat in my 84 K20 Chevy Suburban 350 last year & toook note the gauge was not working so I changed the thermostat and the sender on the block; still no indication of temperature. At this time I installed a new temp gauge in the dash cluster; and things started working; until I noticed the temp went up to 260 degrees in apprximately 10 minutes run time and teh truck was not very hot; cold start. Is there possibly a ground I am missing from the dash to the firewall? I am tempted to try and run the truck without a thermostat just to see what happens for a day. Also keeping the old addage in mind; "just because it's new does not indicate it will work properly."

 

[75gmck25]

There is a black dash cluster ground up under the dash, either grounded to a post on the emergency brake mechanism, or in later trucks to a ground bus screwed to the firewall. If the cluster ground is disconnected it usually screws up both gauges and turn signal indicators.

Also remember that the sending unit should be installed without Teflon tape or a bunch of sealer (or barely enough so it does not leak). It needs to make metal to metal contact with the head because that is where it is grounded. Also disconnect and check the sending unit wire to verify it has power when the truck is running.

 

[Blue Ox]

Invest in an inexpensive infrared thermometer and verify the gauge reading. If you were really running 260° there would be other signs.

Temp gauges that have a faulty resistor will read crazy high for no reason.