I am having fits with intermittent overheating of my 2003 Infinity FX 35, 217K miles

Asked by GuruB15DN Jan 04, 2019 at 10:37 AM about the 2003 INFINITI FX35 AWD

Question type: Maintenance & Repair

I have replaced radiator (which developed spraying leaks), thermostat, and
Water pump.    First hint is always heater stops heating,, blowing cold air
instead.  I do not see any extra smoke or odd look of oil.  I don't see bubbling
in overflow tank unless pulling off the radiator cap while still too hot.

Somewhere I heard of a second thermostat...might have been FX 45s only.

All help truly appreciated.

3 Answers


It *could* be a head gasket causing the overheating, you do have a lot of miles on the engine. Try testing the coolant with "Block Tester", you can rent the apparatus from any auto parts store (or buy it, it's not that expensive). It will detect presence of hydrocarbons from the combustion process if the head gasket is in fact blown. You could also try a compression test, and most parts stores may even loan out the compression gauge, it just screws into spark plug hole. If any cylinder is more than 10% less than others it's a sign of a failed gasket. A pressure test of the cooling system may also reveal problems with a head gasket and other components of the cooling system. Check that you have coolant flow and fans are coming on as well.

1 people found this helpful.

Is there any water valve, to make engine heat more quickly on start up for this engine? Thanks for your reply!


There are mechanical heater control valves that are on the heater hose running to the heater core, not sure if your make/model has one. Trace along the heater hose or check a manual to see if you have one. A bad valve would impede coolant flow to the heater core, but I don't think that would cause the engine overheating. BTW, regarding the overheating, you may need to bleed air from the cooling system, although your system should purge itself via the de gas bottle (aka coolant reservoir). Make sure the radiator pressure cap is good as well as the hoses connecting the reservoir and radiator. from your description it seems something is preventing coolant flow.

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