Radiator hose is soft when motor is warm - 1998 Lexus ES 300

Although I have no heard of this happening on your particular car, there is one thing.
When the car is warm, have someone who is extremely careful feel the lower radiator hose whilst the motor is running.
Some cars will have a tired and soft lower radiator hose that will suck together when the engine is revved.
This normally does not happen whilst the car is in the driveway, you actually have to have it running down the street, so it would not normally be noticeable just by revving the engine .
God bless your efforts.

Yes, you could have bought a bad T stat. But you might want to check the radiator also.

you might want to have your water pump checked, and the soft hose replaced

How many miles on system. One item that most people never check and it has burned up too many motors to mention is the bottom radiator hose. The hose gets soft with age and it will look normal when you are looking at it, but once the engine is warm and the motor starts running at a faster speed, the volume of water moving through the system creates a suction that collapses the lower radiator hose and the engine gets hot because there is not enough circulation. If you have higher miles or years and haven't changed the upper and lower radiator hose, do so any way.

c'mon man, girl, relax , this is not even a problem, did you change thermostat ? hope so, is it installed in the right position ? are your radiator hoses bad, replace if worn , soft, etc., with truck warming up watch to see if hoses collapse, if old replace anyway . use 50/50 coolant mix, are heater hoses ok, not leaking ?

need to check to see if radiator is circulation the water . hose good make sure their no soft an sucking shut especaily the bottom hose . you can get a temp gauge take radiator cap off ,let warm up til thermostat opens put gauge in radiator see what temp. is . (wife got meat or candy temp gauge this will work) last it could be heater core bad.

Make sure the reservoir coolant tank is at 'full'. Start the car from cold and observe. After a couple of minutes when the engine has begun to drop in revs ( the coolant temperature sensor should tell the ECU to begin to shorten the injection cycle as the engine warms) the top of the engine and the coolant passage to the thermostat housing should become warm to the touch. When hot the top rubber hose to the radiator should become warm and then hot as coolant begins to circulate. If the top hose fails to get hot at any time then the thermostat is at fault. If you have electrically driven radiator fans these should now come on. If they fail to come an at all you need to check the coolant temperature sensor, the electrical motor fuses and the motor relay. Lastly check the motor itself (just run a 12v supply to it directly). As the ar continues to idle, with the fans running, the bottom return hose from the radiator to engine should also become warm. If the bottom hose fails to become warm this points to circulation problems. Either the radiator had become clogged with rust sludge and needs an extensive flushing out with a high pressure hose or the pump is not functioning as it should. Quickly check that the interior heater works by asking for 'full heat with fan on full'. If the interior heater works this indicates that the main coolant pump is probably OK. To check the thermostat more thoroughly, remove it from the car and drop it in a pan of near boiling water; the 'stat should pop open. As the pan cools, at 88 degree centigrade or so, the 'stat should pop closed. Failure to observe this tells you the 'stat is a dead and needs to be renewed.

If you were to take the upper radiator hose off the engine, and look into the resultant hole, you would see the thermostat.

The thermostat on all cars blocks water leaving the engine and going to the radiator, until the thermostat warms up enough to open.

While the thermostat is closed, water circulates through the heater hose, straight back to the inlet of the water pump. This circulation prevents hot spots, distributing the heat evenly to warm the engine up, and also brings that warmed water to the thermostat.

When the t-stat gets hot enough to open, water leaves the engine instead of circulating through it, and that allows cool(ed) water to flow from the radiator through the bottom hose to replace the water that left through the upper hose and t-stat.

The stub that the upper hose attaches to on the engine should be part of a small housing that is bolted to the engine. Removing that housing is how you remove the t-stat.

When was the last time you had your thermostat changed . Also is the fan belt in good condition and turning properly everything. Also ensure the water pump is working properly while the engine is cold start vehicle, remove the cap to your radiator let the vehicle warm-up and see if the water is circulating if so then you can rule that out... If not then your water pump is probably bad.
I hope this helps and good luck.

The place to start is the thermastat. Sounds like it is probably stuck closed.