ES300 Overheating Mystery -Help !

I have a '96 Lexus ES300 (same engine as Camry V6 I think) that has a weird overheating problem. I bought it as is and only got about 10 miles from the dealer when the temp needle suddenly flew up and the engine overheated. The dealer claims no knowledge of the defect and says I must have broken it. So after new thermostat, radiator and water pump there is no improvement. The fan and temp sensor both work properly. The coolant system pressure tested fine and you cannot make the car overheat when idling even at high RPM for an hour or more but take it on the highway and after 5 minutes it will suddenly overheat. A dozen of experienced mechanics have puzzled over this now and I am at a complete loss. A couple of mechanics say the only thing it could be is a small head gasket crack but other mechanics say there is no way it could be that cause the car runs too well and because two different garages both tested negative for exhaust gas in the coolant. I tried two products that claim to repair blown head gaskets (Blue Devil & Bar's Leaks), I followed the instructions to the letter but it made no difference at all. I don't want to spend a lot to change the head gasket when that may not be the source of the problem. Any ideas at all would be greatly appreciated.

There is a separate cooling fan temperature switch located down at the bottom of the radiator, near the middle. Unplug the connector to it and then turn the key on. The fans should start to run immediately. If so, you need a new fan temparature switch. If not, your fan relay is faulty. Hope this helps!

I HAVE SOME BAD NEWS...
My CAR was doing the same thing, over , over, no leaks etc.etc.
the water temp dial was fine , it was fine , THEN BAMM IT SKYROCKETS INTO THE RED AND THEN MY OVERFILL TANK IS STEAMING.

I Live in tulsa OK USA,
At my local dealer their head mechanic, (A Lexus MASTER) he knows absolutely everything.
( he worked on Garth brooks GX and stripped it down to the shell looking for an electrical glitch and finally found out that it was a mold problem from the factory in the ecm that controlled the electrically controlled windows, garth would just drive around and his windows would roll up and down for no reason.)

OK now I have established his credibilty :/ he asked me if I had changed my coolant lately? I said no.
Barry said that my coolant had changed polarity from pos to neg??? and had started pulling material off of a thin spot on the back side of the HEAD GASKET!!!
so instead of sucking water into the cylinder(what normally occurs) It is blowing fire into the water jacket.
That is why in one second my car would overheat.


100% sure it is you HEAD GASKET bro

My oil is was all clear too,
I think it was 6 months or so before it overheated for the 2nd time.

I would definitely change the coolant, I do not believe that the mech will notice any compression differences unless they tested it while it was overheating.
I am telling you guys this is a sporadic thing unlike anything I had ever heard of until mine. you will not get any steam coming out of the exhaust either like a conventional blown head gasket .

It may have to do with the head/ head gasket design. (speculating)

I am not speculating on the BLOWN HEAD GASKET!!!!!!!!!!!!!!
IT LEAKS compression THEN WHEN IT COOLS DOWN IT SEALS BACK UP (WEIRD)

I would not Trust it to drive on long trips.

TAKE IT TO OR TALLK TO A LEXUS SPECIALIST BEFORE YOU TOAST IT.
OR CALL BARRY
LEXUS OF TULSA
(918) 665-3987

I am having vutualy the same problem with my 93 es300 184k. will any head gasket repair help?

I would ask your nearest lexus mechanic,
Also you could check your spark plugs, they may show you where the leak is at (if you only wanted to change one side)

i would suggest that you change both if you are going to change one.
but ask you lexus mechanic and if he doesnt know about the things barry in tulsa, oklahoma said, you can tell him about it, or possible he could give him a call. :)

the more I read up on this, I believe it to be a manuf. defect in the actual head gasket type(rare though you really dont hear that many of them.

kelseyb-