Is300 coolant tank boiling - IS 300 Lexus Cars & Trucks

if the engine is not overheating, and the coolant tank appears to be boiling, chances are you have a blown head gasket which is pumping air into the cooling system the only escape for that air is the coolant tank

If your losing coolant water pump may be leaking, not enough coolant will make it overheat. If not that, thermostat may be bad stuck open or shut. Hope this helps

I just had this , it's was a cracked expansion tank on mine, got it replaced and it's fine now. Jara13

This can be caused by the breakdown of the newer long life coolants, the early formulations broke down and do this exactly as you described, have the tank cleaned and flush the system and refill with the newer coolant that doesn't break down and turn to goo.

you have a blown head gasket.. doesn't have to have coolant in the oil for a blown head gasket... if hoses are rock hard when running then you have exhaust leaking into the coolant via a blown head gasket...

Answer could be a faulty thermostat,or it could be a sign that your head gasket is about to blow ,or last of all your timing could be out of sync.

Answer 2 from Inventus: It means your cooling system is funtioning properly. In a system having a coolant recovery tank, coolant in the radiator is always up to the brim, hot or cold. There is negligible or no air space. When coolant in the radiator expands sufficiently due to warming from the engine, it will squeeze past the pressure cap's bottom seal and flow into the recovery tank. (If no provision for such expansion was present, the expansion would rupture the radiator or your hoses.) Only coolant within the radiator is under pressure, and because of this pressure (together with the elevated boiling point that the "anti-freeze" permits), it normally does not boil. But once past the pressure cap's bottom seal, the overflow is at atmospheric pressure and therefore boils.
This boiling is usually unnoticed after a short, i.e., local, trip because the cooler coolant already in the recovery tank quenches it. But after some highway driving the influx of more hot overflow heats up all the coolant in the recovery tank to the (unpressurized, i.e., "natural") boiling point.
As the engine cools when shut off, the contracting coolant in the radiator sucks back coolant from the recovery tank. Fluid in the recovery tank should never be below the "full hot" or "full cold" marks, lest air be sucked in.
-- BETTER ANSWER ==
Your cooling fans are not turning on. It is not normal for your overflow tank to boil like that. It is true that your radiator is overflowing into the reserve tank, but that means yourr adiaotor is boiling. Check for blown fuses or relays for your cooling fans. IF theya re fine. run your engine for about 15 minutes and drive. When you temp level is at normal operating temp open your hood with the engine runing and see if your fans are on. If they are, then you may have a bad thermostat or a plugged radiator, or a bad water pump. If the fans are not on, get your cooling fan switch replaced if your car has one. Check your temp sending sensor

waterboiling in the coolant tank is not a good sign. water needs air to boil, and if you have air in the system, you are not getting the sufficient cooling you need to keep driving your vehicle. take it in to somewhere and havea coolant flush performed on it. if you would rather do it yourself, you can drain the coolant, fill with new coolant and add some coolant flush to the new coolant to clean out the system. NOTE. DO NOT leave coolant flush fluid in vehicle. You must remove the old coolant and fill with fresh coolant and bleed the system of any air to prevent your boiling. hope this helps.

Where is my 2001 Lexus is300 coolant sensor located at can write at [email protected] o can text 414-856-6955 I'll appreciate

Depending on your system (either sealled radiator without a cap and a pressurized surge tank or standard radiator with cap and an overflow tank) either the radiator/surge tank cap is not holding pressure and the coolant is unable to pressurized and boils at a lower temp, boiling off until you coolant level is so low the engine overheats. More than likely it is either the thermostat or water pump. Commonly it is the thermostat

Try a new radiator cap.