My 2001 Lexus IS300 is overheating and it wont blow any hot air with the heater on. Its also making this funny knocking noise behind the dash. Its done the knocking in the past but got louder since this problem started yesterday. It only makes the noise when I left off the gas. I took the radiator cap off and a piece of it had fallen down into the radiator. I was able to get it out and am hoping that a new radiator cap will fix the problem. I just had the car serviced Friday and stated to the dealer I was heading to the mountains and to check everything. They stated they did. Im not sure if its cause I took the car from warm Orange county up to freezing Mammoth, CA that this problem occurred. Any info would be greatly appreciated.

 

Are you using water or antifreeze. SOunds like you might have an air bubble in your lines. Just flush out the fluid and fill in with new fluid. Just remember to burb the motor

 

possible its the thermostat

its not opening at the right degree and might as well replace your waterpump

 

I was thinking it could be either of those problems. Could that also be causing the knocking sound? Any other ideas of possible problems. I am suppose to drive 400 miles home tomorrow but doesnt look like thats gonna happen.

 

reset the ECU by unplugging the battery for 15-30 min. then see if the knocking is still there.

 

that sound could be the air bubble. ide do a flush and go from there. if you think about it, if there is no fluid circulation due to an air bubble there would be no hot water running in the heater coil ....thus no hot air.

good luck

 

what an ironic screen name

 

No hot water = no hot air

LOL

 

Turns out it was the thermostat. The car overheated because the radiator cap was broken which cause the thermostat to go.