Hi All,
I recently replaced the intake manifold gaskets and a water pipe on my 94 Altima. Unfortunately, it ran very erratically and still overheated even though there are no water leaks. I got a diagnostic test and the 'code' pointed to the knock sensor. I bought the sensor and am proceeding to replace it.

My question(s) is/are:
1. I will buy new gaskets - should I use gasket sealer on the gaskets?
2. What could be causing the car to overheat when there are no water leaks?

Thanks.

Temp sensor, thermostat if its stuck closed.

or it could be a bad radiator, how long does it take before it over heats?