'93 Ls 400 Coolant Sensor Replace

toothguy57 · September 13, 2014

I have just finished replacing all 4 O2 sensors but before I fire it up I also want to change the engine coolant sensor since I reviewed a post by Zoraone from 9-5-08. He posted pictures which will be very helpful but I would like some additional feedback from anyone.

1. What are the minimum articles that need to be removed in order to access the sensor? Zoraone,9-5-08, said that he removed all the plastic parts from the top of the engine. These included distributer covers,both spark plug covers,the coil pack,and the intake pipe.

2. I am a little intimidated by the apparent necessity in removing the "intake apparatus" but it seems to be necessary since it sits on top of the right cylinder bank and on top of a flange that is part of the right distributer plastic cover that has to be removed in order to free the right end of the wire bridge that covers the sensor.

3 A complication is that one of the bolts that is necessary to remove the left distributer plastic cover in order to free the left end of the wire bridge is apparently stripped and will just spin without disengaging. I would welcome any suggestions in how to remove it.

4. I have disconnected the battery and would like to get the sensor replaced before I restart the car. Having done this will the "main computer" recognize the new sensors and is the car likely to function properly?

5. Are there any special tools required to accomplish this job? I have a 19 mm deep socket to remove and install the sensor. I also have a rather extensive socket and ratchet set. Will there be any gaskets etc that will be necessary to replace?

Many thanks to anyone that may be able to offer help. I am grateful for much help already given me in the O2 sensor replacement.

Vegan · September 13, 2014

I just replaced mine and was peice of cake. Some plastic parts have to come off, not sure about intake. If you can see the sensor, which is left of thermostat while looking at the engine, then you can unscrew it with socket and put in new one that comes with new washer. Supposed to increase gas mileage.

toothguy57 · September 14, 2014

It is impossible to see the sensor. It is totally hidden beneath the wire bridge that forms a channel support for the spark plug wires from one bank of the engine to the other. The bridge is indexed into the distributor covers on each end and in order to move the bridge to gain access to the sensor the covers must be removed. Therein lies the problem. One bolt holding the distributor cover on the left side ( of the car) is stripped and I tried to pry the cover upward against the bolt head while trying to unscrew it thinking that this might cause it to unscrew but it did not. The right side distributor cover has a large flange extending backward under the very large and complex looking air intake assembly which I am not eager to remove without more knowledge than I have by just looking at it. Help still needed . Thank you

landar · September 14, 2014

Charles, these Lexus cars are pretty well build but... the plastic crap around everything can be really, really frustrating to get off. I can empathize with you. What I usually do with a screw that appears to be stripped and will not back out is to apply outward pressure with a tool (screwdriver or small pry bar) behind the plastic while I 'unscrew' the bolt. That usually gets it to pop out.

toothguy57 · September 14, 2014

Thanks for the reply but i have already tried that approach. I'll have another go at it tomorrow. I did find a O2 sensor wrench at Pep Boys that I used to make sure that I had adequately tightened all four O2 sensors easily. It was $ 30.00 but it would have saved me a lot of time if I had had it to start with. If any body needs it I would be happy to lend it to them.

Vegan · September 14, 2014

When looking at engine from front of car (steering wheel to the right of you) the sensor is right to the left of the thermostat housing and has a green connector on it. Not sure if air intake has to come of, but it's only a couple bolts and clamps. You can change air filter while you're at it.

toothguy57 · September 29, 2014

Thanks to all who have helped me replace the O2 sensors. The car seems to run well but I was not able to replace the engine coolant sensor and the gas milage is still terrible and when starting up the engine the idle seems a little rough compared to what it always was up until recently. As per my post on Sept 13 regarding the coolant sensor I think that I am inclined to " chicken out" on doing it myself . I have that stripped bolt and what seems to be extensive dismantiling of the air intake system to deal with and I think that perhaps that it is time to bite the bullet and pay the dealer to do it .Thanks again to one and all for your help .

landar · September 29, 2014

Are you sure you want to throw in the towel on this one? Your O2 sensors had to be 10x worse than changing the coolant sensor. If you can take a picture of your stubborn bolt and post it, we might be able to help.

Take a careful look at this thread and see if it might lend some encouragement for the job -> http://www.clublexus.com/forums/ls400/377171-diy-coolant-temperature-sensor-change-pics.html

vissine · September 30, 2014

Thanks to all who have helped me replace the O2 sensors. The car seems to run well but I was not able to replace the engine coolant sensor and the gas milage is still terrible and when starting up the engine the idle seems a little rough compared to what it always was up until recently. As per my post on Sept 13 regarding the coolant sensor I think that I am inclined to " chicken out" on doing it myself . I have that stripped bolt and what seems to be extensive dismantiling of the air intake system to deal with and I think that perhaps that it is time to bite the bullet and pay the dealer to do it .Thanks again to one and all for your help .

Don't be afraid. I replaced it a few months ago. In my case, I had to drain coolant and unplugged the hose to the bottom of the radiator; removed the ignition coil; removed the cable organizer; used 19 mm socket to open it. It took about 2 hours, but easy. You only need to remove the plastic part of the air intake so you can remove the spark plugs & distributor cover panel. I don't think it is easier than the O2 sensor replacement and requires more work. But, at the time, I replaced the catalysts at the time I replaced the O2 sensors, so I had plenty of room to work.