I just moved from New York to Texas few weeks ago with my 2000 rx300

one day I stopped my car in a parking lot and my car was running in idle for 20 mins. I stopped car and started again AC started blowing hot air. I checked the thermometer in dashboard my engine is heating so I stopped and checked radiator coolant it was bubbling and reservoir is getting filled. Later I saw that one my fans in the assembly is broken of off the hub. The right hand fan is the radiator.

during this time my left hand side fan was good later that day I changed Freon gas and changed new radiator fan assembly. When we attached the fans to electrical outlets both of them are working after running engine for 15 mins I am just trying to make sure that fans come up. But the left one is not coming on. Mechanic checked and told me to get a new relay. So I ordered new one from Lexus and put it on it’s been acting up same.

so after careful checking and thinking I switched of the AC in the car and I let car run for 10 mins. Now with the AC OFF both fans are working. But when ac is switching on left fan is shutting down.

some times when it’s hot outside and if I stop long time at a light temperature goes up and engine is making weird noise


thank you in advance

 

Welcome to ClubLexus and to Texas.

Please find a circuit diagram and check voltages.

There is a temperature switch in the radiator body that completes the circuit to ground to turn on the basic [first] fan. The second fan is turned on with the AC as the AC heat needs to be radiated for the cooling to work [AC is transferring heat from one place to another .. law of thermodynamics.].

Lexus engines run hotter than normal and the basic fan typically does not turn on when you are driving even in summer heat of central Texas. When you get to stop and go you will see the temp gauge rise, if the basic fan is not operating.

Please verify the relay you bought is indeed right. Relays come in two flavors, Normally Open and Normally Closed.

Just make sure you have proper amount of coolant and don't let the engine overheat. Shut the engine off and never add cold coolant to a hot engine [there are techniques but then again opening a hot radiator is dangerous]. Having an antifreeze is the coolant is necessary when the temperatures are about to hit freezing point, but in the middle of the summer you can log without antifreeze till the cooling problem is resolved. Also you can not count on the temp gauge when there is no coolant.

Also check for air in the coolant. Check the DIY thread for instructions.

Strange noise needs to be pursued. I would expect that the water pump should be replaced every 160K miles.

Saliim

PS: With enough coolant keep in eye on the temp gauge. Near halfway is right and if starts creeping above, Switch out AC and turn up heat, open windows and shutoff if the gauge goes up to 3/4.

 

i think is a Normally open relay I will check it ones again. Coolant in radiator is full but some times I loose coolant in the reservoir. I always fill it to full. What I observed is the black hose that goes from radiator to engine where the temperature sensor is present. I can see some white stuff deposited upon checking it’s been coming from that hose.

the fan is coming on but only if the ac is off. With the ac off and engine hot both fans works good. My only issue is that the fan is not kicking in when ac is on and I am idle. Which is not making engine cool hence I have this hike in temperature.

i have been checking the temp of the coolant lately when idele with 108•f outside my engine coolant temps are 103•c while idle and 92-98 while driving in highway

i just changed the radiator fan do you think bad ground is the reason for the to not switching ?

 

Please do not follow hunches to solve your problem. Use diagnosing techniques to find the issue and fix should be based on what is wrong. Trying one thing or another will most likely be a misdiagnosis.

The temp sensor at the top is the "temp sensor" that is connected to the display temp gauge and the ecu uses this information for other engine control. The radiator fans are switched with the "temp switch" which looks like the temp sensor but it is strictly on/off switch and is threaded on the radiator. From your description I am inferring that it is OK, but then you really need to re-observe and rethink.

The coolant system in Lexus typically develops a leak at 120K+ miles. Blame it on the plastic parts but not every Lexus develops this issue. Rent a tool from auto part store and that will allow you to pressurize the coolant circuit without heating up the coolant [Do not exceed or better still come close to the safety relief number printed on the radiator cap]. Emulsification on joints or white spray pattern in the engine indicate a leak, but the test is by pressurizing and observing the pressure is kept. If the clamps are not placed in identical position, you can develop a leak.

Coolant loop integrity is different from cooling [they are related, but verify that there are no leaks an air pockets in the coolant]. Then move on to cooling aids like the base fan. Once those are out of the way, move on the AC and additional heat transfer [I am not using cooling here] requirements.

I would spend time to make sure my original relay is indeed bad and all it takes in a test light. If any mechanic tells me it is bad, I would verify to make sure. The test is simple and most likely there is another identical relay which can be used to swap and test [do not blindly swap].

As you have already identified things are not working right. As I read your post, things do not make sense. All you need to do is logically work the problem. If needed revert to original relay.

Salim