temperature indicates that the engine is too hot. what are steps can I do to pin point the problem?


Asked by Nov 25, 2007 at 10:57 AM about the 1998 Lexus LS 400 RWD

Question type: Maintenance & Repair

I just bought a used 98 LS400.  The car has only 31K miles and a clean record. The temperature gauge needle points to about 2/5 of the whole range which I thought it is normal because it is usually about half way on many other cars that I have driven.  By chance, I read the owner manual for this car and it indicates that the temperature gauge should point to less than 1/5 of the whole range.  With caution, I open the radiator cap on the radiator reservoir and I felt the was a little of pressure escape from it.  I thought to myself if the engine is hot as the temp gauge has indicated, I would have seen a lot of pressure.  I want to check the temperature sensor unit but I do not know the specification for it.

8 Answers


It could be the coolant temperature sensor, you'll need to find it, should be located either in the intake manifold or the block. You may need a manual to find this. Other possibilities include a faulty gauge (the gauges in the cluster can wear out over time), or a sticking thermostat. Have the cooling system pressure tested to check for internal leaks. You may want to have the coolant flushed as well, it's likely it may not have been done due to low mileage. Good luck, it will take some diagnosis time, but you should find the problem without a lot of trouble.

1 people found this helpful.

Thank you Litlehorn for your advice.


2/5 of the way up the gauge is NORMAL. Myself and other LS400 owners across various forums have found the same thing. I wouldn't worry about it unless it keeps you from sleeping at night, because it certainly isn't hurting your LS.


http://www.clublexus.com/forums/ls400/377171-diy-coolant-temperature-sensor-change-pics.html similar for you '98, some minor changes. same sensor. most likely either missing/low on coolant, due to cracked hoses, or a dead thermostat. or both.

1 people found this helpful.

2/5 of the hole range is totally normal temperature, actually many years ago whith mi first ls 400, i got a big crack on the plastic arround the fan behid the radiator, i don't remember it's name in english; & i took it out, them the temperature only took 1/2 of the way. Them the mecanic told me thas was not any problem for the engine, but the presure on the a/c sistem became too hig & that wass a reason for the car computer to decide open a valve & let the a/c gas come out avoiding other problems. If you wnt to confirm how much your temp gauge have to be indicaiting just go to a lexus shop, but try to find a small one, there is more oportunities to be raelly attended personali


You're fine. My 96 ES300 runs at 2/5th, and my 99 Pathfinder runs at 1/2.


NO NO NO, it is your water pump!! TRUST ME this is common

4 people found this helpful.

This sounds like a water pump problem that will need replacing, not immediately though but the next couple of months if you're to avoid something catastrophic. When my engine warms up the temperate gauge only as far as 1/2 and then comes down. As you explained, that's what the car manual says and anything otherwise would mean a potential problem. I have driven my LS400 a distance of 2,000 km and it never has it gone as high as 2/5. I'd recommend buying the water pump kit which includes the timing belt which should cost you no more than $150. Hope this helps.

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