I have a 1986 olds cutlas supreme v8 and the water is over heating by the thermostat. I hv change It and It still does the same thing. I even change the water pump. What 2 do next ?

Dumb question did it do this before the thermostat was replaced? An assuming you mean water temp gauge and was it the thermostat you replaced or the coolant temp sender first?

Sry Chris Im not as Smart as ( U ) but It was doing this b4 I replace the thermostat. And I only change the water pump, because after 17 owning the car I neva replaced It so I did buddy

check the flow of your radiator....a temp spot gun will do this for cheap~

Once that's done Roy then what.. Im not car Intelligence at all, buy willing to save my self sum money

using water instead of 50/50 ethylene glycol mix is a suicide move...the block and heads will Immediately begin rusting...proceeding to choke off the radiator and impairing coolant flow....unsavory as this is (because the operating temperature will not necessarily be reached) you may run without the t-stat altogether....and drain out and flush the rust out, then perhaps some rust inhibitor and 50/50 mix...if we're lucky will not have baked the motor and caused headgaskets to go out~

if you've got the scratch, pony up for a NEW radiator, new t-stat and let's try to put it in proper condition~

or check the old fashioned way and grip the upper and lower hoses to see if there is a temp change at l east its free ...above alswo correct just go get yourself a plastic T and hook it inline with your heater hoses run water through one side and drain all back out, prestone actually makes a readiator cleaner that gets all deposits out but make sure all the water is completely out of the system by removing the lower radiator hose

you must capture the glycol/rust water with five gallon buckets and take it back to the autoparts store for recycling....if you put it on the ground birds drink the sweet water and die~....bad moojoo man~....do the right thing and deal with this rust-water responsibly~

btw...this car is AWESOME...you must do everything in your power to keep it alive and serving your automotive needs~

...after a while you don't own the car anymore....the car owns you~!

Thx Roy and Chris .

Chris there are no dumb questions, that's why people come here to ask