3warnes

Hello all, I am new here and from what I have read so far, it is great! Anyhow, I want to do a coolant flush to my 99 RX300 AWD. Would it be the same as any other vehicle, climb underneath, drop the plug and run water through the radiator for a few minutes? Is there any thing special I need to do?

Also, I now have 135,000 miles on mine and need to replace the fuel/air ratio sensor, any tips or instructions/diagrams?

Is the filter that goes inside the glove box for the A/C really needed? I was rading and noticed this, then I looked and noticed that I do not have a filter nor have I had one in?

thanks for your imput

wing0

http://rx300how2.home.comcast.net/anti_freeze.htm

The drain plug in the back. It's easier if you look towards ur engine from the right front wheel well. It took me some time to find that plug.

salimshah

When you have filled the radiator, I would suggest NOT to put the radiator cap on.
Start the RX and turn the heater (in the cab) to say 85 and fan at low [this will help coolant get hot quicker]. Let the temp gauge move up to normal [I would expect the thermostat to be open and full circulation will be on. The electric fan may also come on at this time.

Important: DO NOT SHUT THE ENGINE OFF and with the coolant in circulation add enough through the radiator top to fill up. Then cap the the radiator and you are done.

Add more coolant if needed, by observing the marks on the auxillary/overflow bottle and only through the aux fill.

Check the coolant level for couple of days.

Salim

Tammy

I upgraded the coolant type when I did mine ...

https://www.clublexus.com/forums/sho...d.php?t=147551

Which air/fuel sensor are you referring to?

Lexmex

As Salim mentioned, do watch your coolant level for a few days afterwards and fill up where necessary. Virtually every time I change mine, I always have the empty coolant reservoir mystery the next morning.

Fuel/Air ratio (I am going to assume the O2 sensors along the exhaust tracts) do not need to be changed out unless you have have an actual problem. I am 110,000 miles as of the other day and mine continue to function despite all the ridiculous items and gas that go in to my RX300. The other sensor we somes times refer to as the MAF sensor after your airbox can simply be cleaned, but let us know which one exactly you are referring to.

As far as the A/C filter, my A/C filter is about the dirtiest you will see in this hemisphere (pure Mexico City air) and it got stuffed really quick. However, it just depends on your environment as to how often you change it out.

You should have one as I also have a 99 AWD. I did a thread about the location of the ECM in the glove compartment and it should also help you locate the air filter, https://www.clublexus.com/forums/sho...d.php?t=217896

3warnes

Thanks to everyone who has replied so far.

I am not totally sure of the actual air/fuel sensor. I have a check engine light and the codes came back to that? I do not know the codes as it has been a while and lost them. Truck seems to run fine but is sometimes sluggish. I will go and get it re-test to get the codes and post them here.

Lexmex

If you post the code, I will be happy to help you out. Sometimes a dirty MAF sensor just needs to be cleaned.

3warnes

Here are the codes:
P0125
P1135

please tell me what they are and possibilities to fix them?

thanks

Lexmex

https://www.clublexus.com/forums/sho...d.php?t=199748 and has photos.

When you say sluggish, I can probably disregard anything else and point straight to the O2 sensor. Usually, the scanner will tell you which bank and which sensor. This is important as otherwise you can spend a lot of labor doing the wrong one. Did the scanner show this?

3warnes

yes, it does show that.

P1130-
Air fuel ratio sensor
Circuit range/perf
Bank 1/ Sensor 1

P1135 -
Air fuel ratio sensor heater
circuit malfunction
Bank 1, Sensor 1

So I am asking where these are located, and any other imput.

thanks

3warnes

Also, I keep reading and see that people are talking about air/fuel ratio sensors and O2 sensors? Arent these two different things. I look at parts online and it lists both sensors. Which is my codes? A/F or O2?

thanks

TunedRX300

People uses both terms to mean the same sensor, but there are major difference between O2 sensor and A/F sensor.
Read this Toyota paper you will know what I mean
http://www.autoshop101.com/forms/h37.pdf

Lexmex

TunedRX300 is exactly right on this.

People have different ways of refering to it.

People like to call all of them O2 sensors so I do not confuse with the MAF sensor by the airbox, we had confusion on that one several times. That is why I show pictures, too.

If you go oxygensenors.com and enter in the information for a 1999 Lexus RX300, it will be Denso part 234-9009, sensor located in front manifold/exhaust pipe before catalyst.

This sensor is located behind the engine block.

3warnes

Is this correct for the Bank 1, Sensor 1 A/F ratio sensor?

Part #C5015-137304
Denso
$200.79

thanks

Lexmex

Yes, that is the one.