i just replace my termostat and i believe everything else is working properly...but i made a trip to Galveston this 4 o july and when i was driving i notice that the temperature needle was moving up i was doing about 75 miles/hr so i slow down to about 70mph and it drop down...and is been doing that these last three days...i let run a steedy speed and cool off... i dont have a clue... what could be the problem...also yesterday i try to find out why... so i was pushing it about 80 mph in 4th gear and my rpm were about 3800-4000 to me thats pretty normal...but the needle start moving up again so I trow it in 5th gear and drop speed to 70mph and the needle start coming down...

has this happened to anybody before...
Thanks,

 

Check the temperature sensor sending unit that goes to your gauge in your dash. If you follow the upper radiator hose to the egine block (the one that is on the driver's side) you will find two sensor that are right after the connection between the engine and the hose. The smaller one (1st one) is the temperature gauge sending unit, this is the one that sends a signal to the guage in the dash. The second/bigger one is the coolant temperature sensor that sends the signal to the ECU. Check the smaller one with a Multimeter. The procedure is outlined in my Haynes manual in chapter 3 section 7 (3-7).

If this turns out to be ok, then you may want to take a look at the radiator, water pump, fans not working, and radiator cap not working properly.

You can get info on how to check all of these from a Haynes Repair Manual. It is a great manual to have. I think I paid around $13 bucks total on Ebay for it and it has saved me a good chunk of money.

 

Sounds like you might have an air pocket in your cooling system. Take the radiator cap off (WHEN IT'S COOL ENOUGH TOO) & let the engine run for a while. If there is air in the system one it has bleed out the fluid level will drop slightly. Just top it off & see if you still have the same problem.

 

Remember when filling the RAD to do it in a slow and steady way. Don't just tip the bottle and pour it down. Do it slowly, that way you won't get air bubbles and it'll let the air escape.

 

I had a similar problem... I ended up replacing my radiator and I havent had it anymore.