SaleenS7

I was having similar issues. I recently replaced my thermostat. The rubber seal on the inside was a bit torn apart and I'd wager that it was the original thermostat.

I replaced it with a cheap one (stant brand) from advanced auto. I was thinking that it would 'get the job done' but I still randomly get hot air from the vents. 90% of the time I'm getting cool air. This new thermostat looks and feels flimsier than my original one. Plus it doesn't have a bleeder hole.

The engine operating temperature seems to go up and down like it has a mind of it's own. usually it's fluctuates between the third bar from C and even all the way up to H. But the engine does not seem to be overheating. The auxiliary fan does not seem to kick on when the engine shows that it's all the way at the H mark, not sure if related.

I bled the system by parking on a hill, let the car run at operating temperature and remove the expansion tank cover while adding coolant to insure air doesn't get back in the system but still having the same symptoms.

I'm going to buy the original thermostat from the dealer tomorrow and hope that it fixes the problem as it did with omarg.

(pic on the left is the Stant brand thermostat)

RA40

iTrader: (6)

In past days, one could remove the radiator cap and see how the coolant passages were relative to deposits. Now the only way is to remove an upper or lower hose and see if you can look in. Bore scopes are very handy these days.

Temp indicator going up-down is often air bubbles but after extended burping these tend to go away. I doubt a different thermostat is going to make a difference here unless the Stant is defective.

I'd change the coolant temp sensor that is a bit back and left of the thermostat housing.
https://www.clublexus.com/forums/ls4...ange-pics.html

SaleenS7

Thank you RA40,

If the OEM thermostat does not remedy this problem then I will look into replacing the coolant temp sensor.

Either way, With these cool days/nights approaching it will be nice having full heater function back.

EDIT: I just realized the car has green coolant -.- That might be the problem right there.

SaleenS7

Thanks, I may just have to do that if nothing else works..

I've noticed that changing the radiator seems to remedy the problem for a lot of folks. When I find a fix to the problem I will create a new thread and document how it went for future reference.

LScowboyLS

LS400 radiators are typically good for at least 200K miles, if the previous and current owners have kept up the Toyota red coolant + distilled water and not put any crap coolant in there.

SaleenS7

To follow up from another thread, I've fixed my 'overheating' problem and no heater problem. Long story short: Flushed the radiator and bled the system and surprisingly used the original thermostat and everything is back to normal.

Long version:

The Original problem was that the car would appear to slowly overheat if left idling for a good 10 minutes or so. It would return to normal operating temps once you start driving. The engine was not actually overheating though, it was just the temp gauge showing me it was. Sometimes the heater worked but most of the time it blew cold air. Very frustrating for cold nights, if it wasn't for the heated seats it would have been very uncomfortable.

So to remedy this I bought a stant thermostat from Advanced auto. It looked horribly cheaper than the original thermostat but I didn't care as long as it worked. After installing it I realized that this made the problem much worse. Even after burping the air out of the system it would still appear to overheat even while driving. I'd get warm air sometimes and cold air most of the time as usual. I'll be able to return it though as a defective product. NEVER buy an aftermarket thermostat. when the original one is not that much more expensive it doesn't make sense to cheap out...

SO, I went to toyota and bought a thermostat for the LS400. It looked a little bit smaller but otherwise identical looking. I forgot to bring my original thermostat to check and see if it was exactly the same size. So I go home and realize it was indeed the wrong thermostat. The funny thing is every auto part store I went to made the same mistake initially when looking for a 98' LS400 thermostat. They all seemed to give a smaller diameter thermostat.. So since this took place on Christmas Eve and the dealerships were all closed, I was faced with a problem and a disabled car.

I said screw it and just went ahead and flushed the old coolant out of the system and put in some prestone universal and bottled water. I burped the entire system of air. I am still shocked at how much air was burped out. To my complete and utter surprise the engine operating temp was near spot on perfect. After I burped all the air out it went to the third bar after C and stayed there even when left idling for 15 minutes or so. The best news is that the heater was gradually blowing hotter air. Eventually I burped all the air out and the heater now works like new.

Eventually I'll probably replace the thermostat and flush the coolant with red toyota coolant but for now I'm happy the problem is fixed.

On another note I fixed the roaring sound I was having by replacing the old tires which were cupped/chopped. The car now rides like it's on a cloud, no road noise at all.

The only problem I seem to have noticed after letting the car idle for so long was that oil seemed to be slowly seeping from around the valve gasket area from the engine. It's leaking onto the exhaust manifold cover on the passenger side causing a bit of smoke. I may need a new valve cover gasket. Otherwise everything seems to be working now. So far I must say that this is my third favorite car (of all the cars I've ever owned) and that's saying something.

hotdawwg

Damn. Same exact thing on my 1995, except I didn't need to replace the thermostat. Just needed to burb my cooling system. I also changed my coolant temp sensor. Now the car is driving good.

RA40

iTrader: (6)

Glad the solution was simple. In past times Stant had reasonable quality thermostats. I have one for the Cressida that is fairly equal in build to the OEM part I also got from the dealer. With the Lex, replacements parts are bought from the dealer. Wife actually gives me the look if I stop at any auto parts store. Her basic saying is "you're not going to put some cheap part into the car are you?"

I ordered a gas cap for the Celica that was made in Turkey. The thing is a cheap stamping compared to the OEM Toyota cap. Well, at $3.50, one cannot expect much but the seal is good while the car sits in storage.

SaleenS7

Thanks for merging my other post with this thread RA40. (and for all the helpful info)

My dad actually recommended that I get a Stant thermostat if I wanted to choose aftermarket... From now on i'll be more careful with aftermarket parts. The way I see it now; if the aftermarket part isn't an upgrade or more robust than OEM then I will pass... The few bucks you save sometimes isn't worth the possible headache. This problem would have been much worse if the thermostat was in a hard place to reach... Thankfully most everything with this car seems easy.

Merry Christmas everyone. (or Happy Holidays)

LScowboyLS

any critical components that either report to the ECU (O2 sensor, MAF, ECTS, TPS, IACV, crank position sensor, cam position sensor, etc.) as well as thermostat, radiator cap, gas cap, distributor caps, rotors etc. should really be Toyota or original Toyota OEM (i.e. NipponDenso, Aisin, etc.)