LS - 1st and 2nd Gen (1990-2000) Discussion topics related to the 1990 - 2000 Lexus LS400

Car randomly gets warm

Old 09-25-14, 06:35 AM
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cgawelko
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Default Car randomly gets warm

So my car is being moody. Its 110 degrees here, and if I turn on the A/C on high, it will warm up a little. If I drive it hard on low/medium, it will warm up a little. If I drive at night after driving it during the day, when going 95, it will warm up a little after about 10 miles, but then it goes right back down if I put the heat on low.

Now. If I drive with the A/C on medium, and I drive around town like a sane normal person, nothing happens. If I dont drive it across town twice during the day, and then three cities over at night for work, nothing happens. If im not running the air pump for the stock suspension, none of this happens. But air pump + a/c+ driving hard and it heats up.

HG is fine, water pump is fine, thermostat is a new fail safe one. Im thinking either the fan clutch, or I need a new radiator. The radiator also leaks just SLIGHTLY at the banjo bolt on the passenger side of it.

I just want to make sure if I order a radiator tomorrow that im not just pissing away money.

Last edited by RA40; 09-25-14 at 09:05 AM. Reason: PG to G rated
Old 09-25-14, 06:50 AM
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cgawelko
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Also I will add. It will go WEEKS without anything happening. and then it will come back. Maybe I need to flush the coolant for any obstructions.
Old 09-25-14, 07:15 AM
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billydpowe
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you need to identify what you are driving, different makes and models have their own quirks...

read the stickys at the beginning of the forum .
Old 09-25-14, 09:04 AM
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Ucf10 - '93
Old 09-25-14, 09:20 AM
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RA40
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There is a single wire coolant sensor next to the ECT that goes to the gauge. I'm not having luck finding the diagram at Sewell's site, maybe another member can chime in.
Old 09-25-14, 09:47 AM
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how is this, they are right beside each other, up front
Attached Thumbnails Car randomly gets warm-cts_04.jpg  
Old 09-25-14, 09:49 AM
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I can pull up a pictrure...


Old 09-25-14, 10:36 AM
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did you see it??
Old 09-25-14, 12:26 PM
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Thanks Billy-
Your pic shows it but the single wire sensor location but the parts diagram doesn't show it. One of the ECT threads has a part# for the sensor I'm thinking but I don't know what it is actually called. The sensor is about $25 my memory recalls.

Your car is probably at proper temp but because the gauge sensor is going south it indicates a false reading.
Old 09-25-14, 12:39 PM
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oldskewel
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Originally Posted by cgawelko
... thermostat is a new fail safe one...
Could it be a problem with the fail-safe thermostat? I forget details, but remember reading opinions that it's a nice concept but in practice can actually cause more problems.
Old 09-25-14, 01:42 PM
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other than the sensor, it would be a good idea to bleed the coolant of any air. i find that you really have to run the car for 10-15mins holding the RPMs up to get all the air out.

http://www.lexls.com/tutorials/cooling/coolant.html
Old 09-25-14, 07:58 PM
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cgawelko
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So replace this coolant sensor to the gauge?

I am going to replace the radiator soon and rebleed it all. If I need that sensor too, ill throw it in my cart on rockauto. Anyone have the part number off hand?
Old 09-25-14, 10:07 PM
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Has any work been done on the car,recently, that would require coolant to be added or removed? If so, I would strongly suggest bleeding the system. I had an overheating issue and it was either caused by a faulty thermo or fan clutch. After that, i bled the system and she was back to perfect. Or, it could be as simple as the ECT sensor. Either way, properly bleed the system if you haven't done it. I hope it all works out for you!
Old 09-26-14, 12:29 AM
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Yeah I have replaced the coolant resevoir after the sensor thing was leaking... but since the radiator leaks from that banjo bolt, could I just need some washers for that bolt??? it could be air getting in from there
Old 09-26-14, 06:53 AM
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That would make sense. Personally, I would fix the leak and bleed the system. Using a spill free funnel makes bleeding the system a lot easier and less messy. Good luck.

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