coolant boiling out overflow after replacing water outlet, and thermostat. Have no leaks even did a pressure test and used the spill free funnel to burp the system. Radiator fans will not come on and I know they are working because I test drove the car after finishing the work and the first time I realized it boiling I noticed the radiator fan was on.

Temperature gauge on dash shows just under the middle line as it should and it doesn’t move. Heater works fine. Driving me nuts I can’t figure this out.

  • Are you sure you didn't put the thermostat in backwards? Are you sure the thermostat is good? Why did you change the thermostat to begin with? What is the "water outlet"?
    – jwh20
    Commented Mar 25, 2023 at 10:08
  • There was a code for thermostat and the thermostat is built into the housing had to replace the housing/ thermostat both in one piece and the water outlet is on the opposite side of the engine connected to the block, the plastic was broke where the radiator hose clamps onto it.
    – Aj Alturo
    Commented Mar 27, 2023 at 0:20

1 Answer 1


A few things… check the temp sensor on the side of the radiator (passenger side) since it controls the thermostat electronic heating. (electronic control happens before the wax pellet melts and thermostat fully opens at 243F). This doesnt really sound like your problem though.

Fan has 3 speeds, need to make sure all 3 speeds work. If not, check fan fuses and relays. If you have access to a bidirectional scanner, 3 speeds can be easily checked, otherwise you will have to check each fuse and relay manually.

If all fuses and relays check out but the low and medium speed are not working then it will be a problem will the fan’s internal resistors. High speed fan will still work because it bypasses the internal resistors.

As a side note, the temp gauge dial on the dash in these cars is nearly useless because they are terribly inaccurate. They basically stay in the middle until it starts overheating at which point it will go to to high. Digital or OBD Temp is more accurate way to know temp.

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