Do you need gasket sealer for the o ring on oil cooler a 350 Chevy engine?

No, you should not use gasket sealer with an O-ring on an oil cooler or any other application designed for an O-ring seal. O-rings rely on their precise shape and the compression between mating surfaces to create a seal. Adding sealer can interfere with this process, potentially preventing proper compression and leading to leaks. The sealer may also contaminate the oil system.

If you're having trouble with an oil cooler leak, check these things first:

* O-ring condition: Is the O-ring damaged, deformed, or deteriorated? Replace it with a new, correctly sized O-ring.

* Surface condition: Are the mating surfaces clean, smooth, and free of scratches or burrs? Clean them thoroughly.

* Correct O-ring: Make sure you're using the correct size and type of O-ring specified for your oil cooler.

* Proper installation: Ensure the O-ring is properly seated in its groove before installing the oil cooler. Avoid twisting or distorting it.

* Tightening torque: Over-tightening can crush the O-ring, while under-tightening won't provide sufficient compression. Consult your engine's specifications for the correct tightening torque.

If you've checked all of these and still have a leak, then you might have a more serious problem with the oil cooler itself or other components.