RX400h

I'm not sure what it looks like but there should be mention of it in your service manual. I believe the advice above is referring to the coolant temperature sensor. Is your idle still a bit low?

Based upon the possibilities below, it can also be a fan relay, if you have one. There should be a way to test the sensor. If it is outputting the signal to trigger the relay, then the relay is probably bad. It's always to good to test before replacing. If the Fan does not Come On at All What is the problem if my radiator fan wont come on? If you notice the fan does not turn on at all, it may be caused by a number of problems but here are the most likely 3 reasons. The temperature sensor is bad. Generally located by the thermostat housing, this should be the first thing to check and replace since it is easy and inexpensive. The fan relay may have failed. If the fan relay is stuck open, the fan will never turn on even if the sensor signals that it should. Replace the fan relay. The fan motor may be bad. This can be tested by unplugging the fan and directly connecting a power source to it.

So the coolant is leaking from the overflow tank? Air in the cooling system could cause a high temp condition, resulting in burping of coolant. The temperature sensor could be bad. Do you have a factory service manual? That would guide you in testing various components and subassemblies..

If you turn off the AC, does the belt stay cool? If so, it could be the AC clutch. See 5 Signs Of A Bad AC Compressor Clutch & Replacement Cost (mechanicbase.com)

I believe the image below shows the antennae routing for the RX400h.

Here's a guide to properly checking ignition coils: How To Test a Lexus IS300 Ignition Coil - My Pro Street (prostreetonline.com)

If there are no codes/warning lights, the only thing I can think of is perhaps a stick-open thermostat. This would prevent the engine from warming up, quickly.

I would take it to an Auto Electric shop for a second opinion. Dealerships often send customers to AE shops because their expertise is diagnosing and fixing battery drain issues.

While measuring current draw, mechanics would pull fuses, one by one to see which one is tied to the source of drain. If the solution is not easily identifiable, an Auto Electric shop, which specializes in locating current drains, may be a good option. I've used them a few times and they always located the source, very quickly.

High idle speed is often indicative of a vacuum leak. If that leak is too big, the engine could stall. I would check for cracked tubing or even an intake snorkel that is cracked. Rubber gets very brittle as it loses its plasticizer. Mechanics sometimes use a smoke generator to locate leaks.

See: 17140-0P150 Genuine Lexus Exhaust Manifold Sub-Assembly, Right (lexuspartsnow.com)

Please let us know how it turns out and what the solution is. 👍

Those condensors appear to be pricey ($1000). Have you thought of adding a stainless-steel screen to block small stones from damaging it? Typically, if some of the fins are bent, that alone should not cause the AC to malfunction.

Have you seen this? How to Adjust a Low Idle on a Lexus LS 400 | It Still Runs

Here's some good and hopefully relevant information: RX400H Audio volume problem - RX 300 / RX 350 / RX 400h / RX 200t / RX 450h Club - Lexus Owners Club

Please let us know if after driving the car for a while, everything is back to normal. Thanks!

Rubber hoses lose their plasticizers over time. As they do, the rubber cannot act as a compression spring of sorts, causing leaks from insufficient conformity to the neck, or from cracking/splitting of the hose.

According to Consumer Reports' data, Lexus and Toyota vehicles are among the vehicles that are least likely to benefit from an extended warrant. Our RX is almost 18 years old and has never required any non-maintenance repairs. Most RXs are similar in that they are very reliable.

Is the temperature in your garage significantly lower than outside the garage? Some manufacturers require a vehicle to be driven at a designated speed for a set period of time, before a new sensor will be recognized. I'm curious how you changed the sensors, yourself. Do you have tire-changing equipment in your garage?

I would've done just what you did to give them a chance to possibly research the connector in your LS. I'm sure they've done so for many applications, so by all means give them a chance to respond. In the meantime, you may get a response here from someone who's gone through the same scenario.

You're welcome. I would never have guessed that a clock spring failure would cause multiple buttons to malfunction.

You might want to take your vehicle to an Auto-Electric shop. The ones I've been to over the years are electrical experts at finding the cause of issues such as yours.

Often brake pads will emit a high-pitched sound when the brake pedal is applied. If so, and you're not savy with DIY brake jobs, then you can always take it to an independent shop to diagnose and fix.

....or a machine shop. Machinists tend to run into all kinds of issues and are good at fixing them.

Okay, then you may want to read this: Should You Get an Extended Warranty for Your Car? - Consumer Reports