WRoberts

I have a 2004 RX330 with almost 250k miles on it. I've had it for 2 years. When I bought it of course the dealer reset everything and the check engine light came on the next day. O2 sensor was the reading. That's not the problem. It suddenly started overheating. I could put water/coolant in it and it would be ok for a few days. There is no water in my oil or anything milky looking. I do not have large pools of coolant/water in the driveway. No white smoke from the exhaust. I've been told that it's probably the head gasket but reading here that doesn't make sense. Help!

uksparky

I would start with the thermostat replace it.. run the engine and get all the air out of the system.... watch for air at the radiator cap (bubbles)

spinellib

How much water did you add the first time?
Are you sure the fans are running when they're supposed to?

matts6887

sounds to me like a themostat as well; but another possibility is the water pump. Have you checked underneath on any of the driveline components for leaks near where the water pump and or thermostat are? if not id get under and check. If u dont see anything its probably due for both im guessing a water pump and t stat replacement. Ive been told by my indy shop which i can safely say is VERY reputable the original factory water pump and tstat should be good to at least 200,000 miles or a little over but since u are at 250, i would highly consider getting both replaced.

WRoberts

Each time I've had to put water in it there has been lots of bubbles. My friend, who is a diesel mechanic, no experience with Lexus is the one telling me it's the head gasket. The 1st time this happened it took gallons of water.. it was fine for 4 or 5 days then started heating up again. I'd add water to the reservoir and it would be fine again. The intervals became more closely spaced until it would overheat no matter what I did. The water is going somewhere.

iMSQ

Pull out oil stick. Is there anything white/yellow on it? If yes then you have coolant in your oil.

Vincenze

"Gallons"? That's a lot of moisture to disappear. It has got to be a leak.

Savnout

I too would think it's the thermostat. I had to replace mine at 120k. Easy way to tell if it is the head gasket is to go to AutoZone and get a test kit. Like $25. Comes with the fluid. Easy to use and will test for vapors in your coolant. Very good test to see if head gasket is going. The test fluid will change color.

I would also check the radiator, especially bottom of the coolant overflow reservoir. Mine has a small leak, and seems to settle at the low mark, but doesn't overheat, just runs low on coolant, Every few months I add a little coolant. Too lazy to replace, cause I would have to replace the whole radiator. I guess the overflow is built into the radiator.

Sav

matts6887

yes; like sav above said; definitely check the radiator. Last october(oct 20) i was having to add a bit of coolant every day to the radiator after checking it; then one evening on my way home from dinner before i got in the car i saw a spot on the ground under my rx. I thought this better not be what i think it is. So next day i went to have it checked and turns out one entire side of my original 13 year old radiator was cracked; leaking coolant. So yea the radiator can be a possibility.