I have a 1998 Lexus es300 and when I drive the temperature gauge is showing the needle in the middle which is good but when I come to a light I notice the needle rising to high but when I start driving again it goes back down to normal temperature. Also when I am parked and the car is running same thing, temperature starts rising. Any ideas on what it could be?

Thanks

 

Can you observe the fan running when the car is idling and starting to get hot? If should be and if not, that may be your issue, the fan is either dead or the sensor is.

If the fan is running, you then looking at the rest of the system. I assume you have checked the coolant level and quality? Dirty or low coolant is a real issue and needs to be addressed. Might be time for a flush.

After that, you are looking at radiator issues or the thermostat.

Good luck.

 

- faulty thermostat
- clogged plumbing
- faulty radiator

 

Everything that was said so far, but could also be a faulty radiator cap.

Phil

 

Yep check the basics and report back.

 

Also check for severe bug denting to the AC condenser fins in front of the radiator that would block air flow to the rad. Also shine a strong light through the rad and see if you can see the light from the front to check for bird feathers, etc that made it through the condenser and are blocking the radiator.

 

Right after I posted the thread my check engine light came on. Took it to autozone and the error given was for the thermostat. Today I had time on my hands so I flushed the radiator (made a huge mess) did a whole system cleaning and new thermostat. Took it out today and it ran fine, but today was pretty cold outside so I'll run it again on a warm day just to be sure.

Thanks for all the input and help guys!

 

I'm having another problem now guys, when I'm driving my heater works fine but when I get to a stop the heater stops working and it blows hot air. Any ideas?

 

You might have air pockets in the line somewhere...
Try running with the cap off and turn to max heat while idling for a good 20 minutes.