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2001 Overheating - Stumped


DaveV

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Hey Guys, I recently completed the 90K mile service on one of my 2001 Lexus ES300. I changed the timing belt, water pump, pulleys, belts, and cabin filter using all of the info from this forum. :lol: Tested everything out and it ran great. After a short test drive, it over heated. :( Back at my garage I tested again letting it idle for a longer time. Everything ran fine: engine heated up, thermostat opened, coolant flowed. After about 15 minutes, hit the red line. I noticed that the fans never came on. Back to the Lexus Forums. After chasing the Power Steering sensor wire disconnected topics for a while I realized that I have the electric cooling fans. I tried to see if I knocked loose some connectors but didn't see anything obvious. I performed a couple of basic tests on the fans - 1) with the ignition on, the fans do not operate, 2) with the ignition on and I disconnect the #1 ECT switch connector, both fans run at full speed. Compared to my other ES300, the fans cycle on and off briefly when idling.

The service manual says that if the fans don't run after the coolant reaches 208F, replace the ECT switch connector. Seems more likey that I just didn't connect something correctly rather than a sensor breaking at the same time. Tomorrow I plan to put my other ES300 side by side to see if anything is obvious. Anyone have any ideas?

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Hey Guys, I recently completed the 90K mile service on one of my 2001 Lexus ES300. I changed the timing belt, water pump, pulleys, belts, and cabin filter using all of the info from this forum. :lol: Tested everything out and it ran great. After a short test drive, it over heated. :( Back at my garage I tested again letting it idle for a longer time. Everything ran fine: engine heated up, thermostat opened, coolant flowed. After about 15 minutes, hit the red line. I noticed that the fans never came on. Back to the Lexus Forums. After chasing the Power Steering sensor wire disconnected topics for a while I realized that I have the electric cooling fans. I tried to see if I knocked loose some connectors but didn't see anything obvious. I performed a couple of basic tests on the fans - 1) with the ignition on, the fans do not operate, 2) with the ignition on and I disconnect the #1 ECT switch connector, both fans run at full speed. Compared to my other ES300, the fans cycle on and off briefly when idling.

The service manual says that if the fans don't run after the coolant reaches 208F, replace the ECT switch connector. Seems more likey that I just didn't connect something correctly rather than a sensor breaking at the same time. Tomorrow I plan to put my other ES300 side by side to see if anything is obvious. Anyone have any ideas?

If when changing the thermostat and the water pump you drained the antifreeze and then refilled it, you probably now have some air pockets trapped in your cooling system. If additionally, the air pockets are trapped near the temperature sensor, than the temperature sensor will not be able to obtain a correct coolant temperature reading, and consequently not activate the fans.

You have to BURP the system in order to release some of the trapped air. Several cycles of highway driving (with the heater set at full high temperature) and cooling down overnight should bring things back to normal. Your coolant level will also decrease as the air escapes. So you will need to add some additional antifreeze until everything stabilizes.

Phil

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:P Thank you Phil. I did as you suggested and it seems to have solved the problem (although I still haven't seen the fans spin yet). I'll do a longer test drive tomorrow. I also found a post on Toyota Nation where a guy changed his timing belt and had the same problem after the initial fill. The sensors are apparently very sensitive to air.

His post also had me thinking whether I had put camshaft pulley's on correctly. After peeking under the cover, I confirmed I had not ... I put both with the lips on the same side instead of alternating. I don't know if it would cause a problem but figured I couldn't sleep knowing it was to spec. I spent the day redoing the timing belt change again. I've got it down now.

Thanks again,

Dave.

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what happens to fan when you turn a/c on? I never heard air pocket and temp sensor relation, I did lots of time flush and fill in my toyota's , never happens to me and yes you will gona have air pocket. that is the reason you needs to keep eye on resorvisor bottle for couple days. I could be wrong.

to me its looks electrical problem.

please update us.

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Camlex and Phil,

No more overheating. I believe that I neglected to put in enough coolant and did not "burp" the system. I turned on the AC at the end of the test drive and both fans fired up. I'll keep monitoring the fluid for the next several days but I feel confident that it's been corrected. Thanks to you both for your help.

Merry Christmas!

Dave. :D

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