Thermostat Replacement

[rkr]

Does anyone have video or pictures of the location and how to replace the thermostat on my 1999 Rx 300? One thread said it was on the right under the air filter box and another said to follow the upper radiator hose which ends up on the left side of the motor. I purchased a new thermostat with rubber O rings but no traditional gasket for the housing. I'm not a big no it all about the Rx 300 but was just trying to save a few bucks doing it myself. Any input would be appreciated

[TomC]

Are you having a problem with the thermostat? If not and the radiator fluid has been kept clean the thermostat should be good.

[lenore]

The thermostat faces toward the left fender from the valley between the two cylinder heads. You need to take off the Shroud on top of the engine to get a better view. It will be on your right when facing the engine from the radiator. follow the hose. This picture is looking from the left side of the engine. Unforturnately I had a intake manifold leak of Coolent.

[rkr]

Are you having a problem with the thermostat? If not and the radiator fluid has been kept clean the thermostat should be good.

I took my car to AutoZone and had the computer read which came up with PO125 code , saying faulty thermostat or CTS circuit faulty, not knowing what a CTS circuit is I thought I would replace the thermostat.

[lenore]

The quality of the original is quite good, why are you changing it.?

[rkr]

The thermostat faces toward the left fender from the valley between the two cylinder heads. You need to take off the Shroud on top of the engine to get a better view. It will be on your right when facing the engine from the radiator. follow the hose. This picture is looking from the left side of the engine. Unforturnately I had a intake manifold leak of Coolent.

Thanks for the picture and info, it will help me to find the location. I hope it's not much of a job, going to attempt it over the weekend.

[TomC]

The code description does not tell you what parts to change. Run the diagnostic tests for that code to find out what's really wrong. Changing parts may make you feel good put likely won't clear the code and fix the problem.

[rkr]

The code description does not tell you what parts to change. Run the diagnostic tests for that code to find out what's really wrong. Changing parts may make you feel good put likely won't clear the code and fix the problem.

How do I get or do a diagnostic test for the code?

[lenore]

I would go to an autozone, and read the codes. Also reset them...Buying a code reader is very affordable now, great tool for making some diagnostics to trouble shoot. They sell them online cheap or even at Harbor Freight tools with a 20% discount coupon...Good luck, the Thermostat is probably not the issue, probably a Air / Fuel sensor on the exhaust manifolds, but you need the secondary codes if they are there.

[rkr]

I had the code read at Autozone and it is PO125. Says insufficient coolant temperature for closed loop.

Fuel control

Probable cause Faulty thermostat

CTS circuit faulty

I have no idea what a CTS circuit is but figured I would replace the thermostat and see what happens.

[TomC]

www.alldata.com - 1 year subscription for one vehicle is $29.95.

[lenore]

Question is did they look for secondary codes at autozone? Through my search the code has not generally been the only code...

[rkr]

Question is did they look for secondary codes at autozone? Through my search the code has not generally been the only code...

Okay, thanks, I'll go back to Autozone and have another scan done and see what code I get. If it is the exhaust manifold is that a do it yourself deal or leave it to a mechanic?

[Domenico Nelli]

Question is did they look for secondary codes at autozone? Through my search the code has not generally been the only code...

Okay, thanks, I'll go back to Autozone and have another scan done and see what code I get. If it is the exhaust manifold is that a do it yourself deal or leave it to a mechanic?

I too had a P1150 and a P1155, and the code reader said it was Air/Fuel Metering and it isn't the mass air flow sensor either. Lexus calls the O2 sensors Air/Fuel Meters. I did the one between the fire wall and back side of the engine. Never doing it before, working with room for only one hand, blind it took me 50 minutes to figure out how to unplug it then it was easy to unscrew it from the exhaust manifold. The front one recently went on me hence the aforementioned codes. I thought, "oh this is gonna be a 15 minute job". I ordered a new air fuel meter from oxygensensors.com for $125, including shipping (Lexus wanted $260) and I was sure to get a Denso which is stock on the car. I read not to use universal sensors as they won't work correctly. The front A/F Meter took two seconds to unplug once I removed the battery and tray. However, unscrewing it with the oxygen sensor socket became a nightmare. I wound up using a 1/2" impact wrench on it to zip it out as it was frozen and no amounts of penetrating liquid or Roost Off worked. I then had to get a tap and chase the threads as they were boogered up. All in all, it became an all afternoon job, but I still saved cash doing it myself, even after dropping $20 for the M18 X 1.50 tap.