SEBASS

Temp gauge shows what i believe to be low temp on temp gauge.
It's at first line and won't go higher then that.
Car never overheats in summer and in winter pretty much stayed normal which was little below middle line (second line). Both in summer and winter perhaps little lower but never at first line. I'm in chicago and it's 20F right now but again that was never an issue in prior years. Also heating works just fine. Blows hot air inside the car.

Little history here. I have 1991 Lex LS400 with 225k on it. Water pump was not changed since i remember and only once was timing belt changed at 92k miles. I decided not to change timing belt second time until it breaks on its own.

So i went to get my radiator flushed and change antifreeze with a thought that it is either low or very old antifreeze. Which in fact it would be since i have no idea last time it was changed. Long story short. It was changed and nothing has improved. Perhaps it's thermostat. It's open but won't close. For right now i covered the radiator with cardboard box but that's a patch not a solution. I'm sure someone ran into this issue here so any help would be appreciated.

and HAPPY NEW YEAR TO EVERYONE !!!

Mikenbon

Yep, I had the same problem with my 96. If you do a search on this topic you'll be able to verify what fixed my car, which was to replace the thermostat and the sending unit. Simple fix. Happy New Year.

-Mike

SEBASS

Thank you Mike but i did search first with low temp gauge and i did not find the threads.
Would you be so kind and post those links to those threads.

Is it also true that car having low temp don't matter much. Meaning engine won't be effected or damaged? I talked to my mechanic and that is what he has told me.

trukn1

Having low engine temp is a good thing, not too low tho, means that the cooling system for the car is doing it's job properly. My 92 normally sits just a little below the halfway point, and is most likely where yours should sit as well. Suggest changing out the thermostat, as suggested above, to get a more accurate reading. As far as the timing belt, breaking a timing belt WILL cost you more money in the end than just going ahead and changing it. Your only saving grace is that you have a first generation LS, with a NON-INTERFERENCE engine, so snaping the belt will not cause catastrophic engine damage like the later generations (95 and up). In the later models, snapping a belt can also cause damage to the rods and a few other components since those engines are INTERFERRENCE engines. Your timing belt also drives your water pump, so if you snap one,,you WILL break the other. It is always a good idea to change both at the same time anyway since the car has already been opened up and both parts are in the same area(no sense paying to have the same operation twice when you could have just knocked it out in one shot).

deanshark

As trukn1 said, it is good to have it low. My other car (Grand Prix) never went over 140* with a 180* thermostat. You mention your t-stat is open and wont close, that's your problem. It wont close to get the engine hotter. Change the t-stat and the temp will go to were it is supposed to be. It will also help warm the car up quicker in the morning so you get heat quicker.

SEBASS

Yeah sound like it. It possibly got stuck due to extremely cold temps here in chitown 20F-32 but with wind chills probably lower. Hoping it will get unstuck once it gets warmer.

Still question remains if i can damage the engine or anything else with temp being at first marker ?

randal

I do not believe it will damage the engine in the short term but it is NOT good to run a modern engine at low temps for long periods. The engine is designed to run at around 180F (82C) for good fuel economy, fewer emissions and general residue burn off. Running at lower temps can give less MPG's, more pollution, and fuel dilution in the crankcase(oil). These conditions are exacerbated on short trips because your engine never comes close to the designed operating temps.

It is possible that your sending unit is bad and that is all that needs replacing. But many times, thermostats will fail "open" and produce the results you are experiencing. Short term, no problem. However, I would get it fixed as soon as you get a chance.

My1998LS40

iTrader: (1)

I had the same problem. Change new thermostat and coolant temp sensor. Now it's working like normal and I also get hot air coming when I turn on my heater. Yay. It's pretty simple. The thermostat and a required gasket is about $40 at Toyota. There are three 8mm nuts that can be taken off with a 12mm socket. Pull the water pipe out and you'll see the thermostat there. Mine wasn't even there for some reason, lol. Pull your old one out and put the new one in with the little notch at the top pointing directly up. Put the water pipe back in and tighten up the nuts with factory torque. Refill coolant, start up the car and let it run to normal operating temperature. Check on the coolant level frequently on the next few days to make sure. That would fix your low temp problem.

deanshark

The factory torque is 13 ft lbs. Good description, BUT, there are only two nuts to take off and also ya might want to drain the coolant a little (if it's actually full) so it doesn't spill when you take off the t-stat housing. You can check if it's full by removing the water filler plug. (located on top of the water inlet housing) Ya need to take it off to fill coolant afterwards anyway, and to bleed the air out. The torque for this bolt is 33 ft lbs.

My1998LS40

iTrader: (1)

Hmm, I know there were 3 of them on mine. Maybe the 98 is different? And I didn't have to take the water filler plug or bleed the air out of the system. Didn't see why it was necessary. Manual didn't tell you to do that in there. I didn't torque mine to spec because I don't have a small torque wrench. Just tightened it with hand and try not to over tighten it by feel. Should be pretty close because I don't see any leak or breakage, yet.

deanshark

The 98 is different IIRC, from what I've been reading here. 2 or 3, ya ad one, ya miss one, what's the difference as long as it comes off. (lol) The manual doesn't say to bleed it but once you take out the t-stat you're letting air in. Plus if you go by the manual, it says to drain coolant so you would have to take out the filler plug to, umm, fill it. And it is good to bleed it when you're done anyway b/c air in the system could give you no heat. I don't mean to criticise but factory torque is there for a reason, so you don't over, or under, tighten the bolts or nuts.

Thermactor

iTrader: (1)

You can use a thermostat and gasket from a '96 Camry V6 model (don't get the 4 cyl model t-stat, it's too small) and that is a perfect, exact OE replacement for the 95-97, possibly 90-94 LS400 thermostat. If you have a cheaper Toyota dealer than Lexus dealer, that's the way to go. The local Lexus dealer charges MSRP +10 percent just to be dicks. They want eight bucks for a quart of T-IV where the local Toyota dealer wants like four...

randal

My local Lex dealer wants to overcharge too. But, I go in armed with cheaper prices(internet or Toyota dealer) which I present to them and they always cave. They no longer quote me the list price, just net price, which is 20% off in most cases. Have you tried asking for a discount? All they can say is "no". And you can walk right back out the door. I doubt that you will get that far.

Thermactor

iTrader: (1)

I have asked for a discount. They said that they don't do it to anyone who doesn't have a tax ID number. Friggin morons.

deanshark

I just got an aftermarket t-stat from Autozone for $17 and the gasket for $3. The thing works fine and even if I need to change it in a couple years I still save money. Plus I think it has a 1 year warranty.
Not sure if everyone does this but, I boil it in a pot of water to make sure it opens b/f I install it so I know it is good.