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Infiniti FX 35 overheating

I have a 2003 Infiniti FX 35 with 107000 miles. Over the winter the heater would not work all the time. A few months ago it started to overheat…or at least the thermostat would climb then go down within minutes. The first mechanic could not find an issue. Recently while driving in traffic in 75 degree weather it actually overheated. While trying too cool it down the heater would not work. Took it to a new mechanic whom could not reproduce it but suggested trying to replace thermostat and radiator with hoses. It was done…did not seem to fix it. Randomly occurs…mostly with periods of stop and go or going uphill. Any thoughts?

The problem might be with air trapped in the cooling system. And this is something you can check yourself.

Get the engine up to operating temperature. With the engine idling loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip it between the upper radiator hose and the neck on the radiator. Allow the engine to idle until all the air is purged from the cooling system. Remove the screwdriver and retighten the hose clamp. After the engine cools down, check the coolant level in the coolant reservior.


have the same problem we need to research more

I’d Consider Properly Pressure Testing The Cooling System And Testing The Radiator Cap.

You could just try a new OEM (or better) radiator cap that meets manufacturer specifications.

I’ve posted before about 1999 & later Nissan vehicles’ radiator caps and a TSB (technical service bulletin) written for Nissan technicians. There’s a similar one (3 pages & photos) for Infinity vehicles (February, 6, 2004).

The caps have been know to have the rubber gasket (the one backed by the plunger) to swell up and lose sealing ability. The seal should not be larger in diameter than the metal plunger. You should see some metal when looking straight at it. Also, tecnicians are advised to check for foreign material or waxy deposits on the seal and radiator neck seating area and make sure it’s all clean.

Nissan says that if the vehicle has evidence of leaking coolant or overheating or if the cap is removed for any reason that the cap needs checking.