1990 mercury cougar keeps overheating have replaced radiator and thermostat and problem is still happening. waterpump is not making a noise any suggestions Wayne

There is a bolt on the temp sending unit where the system needs to be bled anytime the engine (3.8L) is low on water...if it is not bled, air in the system prevents water from flowing properly

Get your radiator cap checked and if replacing use the one for a overflow tank. If the cap pressure was okay then you want to look at water circulation in the radiator. After the thermostat opens you should see flow inside the radiator. If it does not circulate the block is clogged or the water pump is bad.

Finally, if you have an electric cooling fan there are relays and some have two fan speeds. Autozone may be able to diagnose your problem.