Lex3486

My car has begun overheating recently and I can't figure out why. I replaced the radiator a few months ago and ran strait water in the system for a couple hundred miles, to flush the system out some. It never overheated in the summer when I had just water in it. When I drained the water out, it looked sorta rusty, but nothing terrible. I put the orange Dex-cool antifreeze in it and it drove fine for quite a while. The temperature when workin right, is right above the second line on the guage; right at halfway. Recently, I can drive it for a while (usually 30 minutes or so) in the city, on backroads, the highway, wherever without any trouble, but eventually the temperature begins to rise. Usually it'll go back down momentarily, indicating the thermostat opening and closing I suppose, but after a while of this, it will go sky high at which point the system can't recover and I have to stop and let it cool down. I've visually checked the thermostat and gasket, as well as tested it and it works just fine. The cooling fan also appears to work alright (it runs continuously at a slow speed and speeds up as temperature goes higher. stays on full blast when it gets really hot). The cooling system has no leaks, and as I said earlier, the radiator is new. One thing I've noticed is that when I very first start the car, I can hear the sound of rushing water behind the dash (possibly air in the cooling system moving through the heater core my dad says). Also, as the car is running, the coolant overflow tank will slowly fill up above the full line till it's almost full, but the temperature is still normal. Performancewise, the car still drives 100%. It does smoke some on initial startup, but it's not white smoke and doesn't smell of antifreeze. It's more bluish and smells of gas, so...but it is an older car, so I don't think this is any major concern. My dad used to have a Toyota Supra which did almost the same exact things, except his antifreeze began to get oil in it (hasn't happened to me); he had a blown head gasket. We're thinkin what's happening with my car is that I've got a slow leak somewhere, either a head gasket or cracked head/block, which is slowly as you drive pressurizing the cooling system causing it not to work correctly and overflow and/or cause the thermostat not to work as it should. I know this isn't unheard of on an ES, and I was just hopin to hear some symptoms from people who have had this problem so I can determine if it's head gaskets, cooling system, etc.

JUSROLLIN

Sure sounds like a headgasket to me. Are you adding coolant often? Getting bubbles in the resevior after you shut it off? Coolant stains aroung the resevior? Losing large amounts of coolant with no sign of leakage is the #1 sign. The reason for the overheating in cars with blown headgaskets is the pressure from the combustion chamber leaking into the cooling system under acceleration. With the air pressure coming in, coolant is forced out of the resevior, until there is not enough coolant to cool the motor effectively. I'd get the compression checked on each cylinder. If you have a deviation of more than 10-12 PSI from one cylinder to another, your definately looking at a headgasket. Running straight water is also known to cause headgasket failure. Good luck.
Brandon

Lex3486

Damnit, I knew I shouldn't run straight water!!! Oh well, damage is done now. Keep the responses comin. I'll try the compression thing soon as I can. Thanks!

1loudlex

I am having the exact smae porb with my 92 and i have also just had my radiator replaced... I have to fill up my coolent some times and my gauge is above the middle.. I also have that bad burning smell we have talked about many times andknow what it is but im not gonna fix it.. Sorry o hear that you have my prob too but im selling my car soon or just trading it in so no fixing for me...

Adam

Lex3486

Well good luck sellin it, or (God forbid) tradin it in as is. I'm sure you know that you're gonna get screwed since it's broken, but that's your choice I suppose. Just hope you're gonna stick with the Lexus name! What's this "burning" smell you refer to? What does it smell like? Mine smells like one of two things constantly; oil and more recently antifreeze, but I know exactly what the cause of those two things are and hope to fix them both soon, especially if I have to do major work on the engine, which I'm not crazy about doin, but I basically have no choice. Call me crazy, but I take more pride in a car which I've done some work on anyhow. That's just me though. Fixin cars just gives me a sense of accomplishment lol.

1loudlex

The smell is burning oil which we have all talked about before in a couple of threads.. My problem is not as bad as yours it is just that i had that happen to me but now its fine.. I just have that burning oil smell coming through my vents when i stop at a light and the vent is on to go through the car not just to stay inside.. Second I have put so much money into this car in the past four months that there is no point anymore if i want a new one.. I have just put in.. a new winshield, new radiator, new struts, new brakes, new tire... Just for example.. My car is old 92 with 130000 miles on it.. I dont expect to get that much and trading it in wont change anything cause i would get a flat trade in value.. But there are many people out there that will take my car and fix the problem..

Lex3486

Oh, the oil smell. Yeah, I've got that too. It's really not that hard to fix, but I understand that there comes a point where ya just have to throw in the towel. Sounds like you're car's not that bad though really, especially after all that work you've done recently. I know if I were in the market for a used ES, yours would be a potential for me, but as I said earlier, I'm a DIY guy, so small problems like yours don't bother me. That's why I'm fixin my cooling system problem, even if it means replacing head gaskets.

steventnm

Lex 3468

I have the same problem with overheating and I tried replacing the thermostat and water pump but the problem remains. Most of the mechanics will tell you that it is the head gasket, radiator, or radiator cap. Don't trust them because some of them have no clue. I replaced the radiator fan switch and it solved my problem.

Symptoms: Overflow of coolant in the radiator reservoir, during idle, engine turns off during hard stop, engine temperature rises after long drive during idle but cools down when you hit the gas pedal.

**Engine fan is malfunctioning even though the fan is still spinning or looks fine. It is spinning too slowly at certain time, which causes your car to loose coolant and overheat over time.
Try replacing the fan switch ($85.00) located next to the radiator reservoir and save $$$.

Lex3486

Will definitely look into that! Thanks a ton. My car seems to want to overheat when I'm going at slower speeds, like at or below 45, but mostly below. Also, steppin on the gas doesn't always help, but it does sometimes. Nevertheless, I'll try out the fan switch and see what happens. I'll keep ya posted on what I find.

JUSROLLIN

Your right about that. The headgasket will usually only leak pressure (enough to force the coolant out) into the cooling system under acceleration, so the car will usually act completely normal sitting in the driveway running no matter how long it sits there. If you get the overheating before you lose the coolant, and in turn causing the loss of coolant, there is a problem with the cooling system itself. With a leaking headgasket, the temperature is in the normal range while the coolant is being forced out, since heat is not the cause of the overflow. The car overheats after there is not enough coolant left to cool the engine properly. If the car will idle all day at a normal temperature, but then loses coolant under acceleration it points more toward the headgasket. If the car overheats sitting at idle, you do the same things listed in the post above, T-stat, water pump, fan check, radiator flush, ect. I hope you find out that's it's just your fan. Good luck.
Brandon

Lex3486

Well, new radiator caps didn't fix the problem. I suppose the "fan switch" is next, but I'm having problems finding exactly what and where this is...One thing I noticed is that when it overheated today, the fan was barely spinning; I in fact reached my hand down and stopped it from spinning. I never once heard it come on while I was driving, so I think this may be our next area of focus. Looking in the Lexus repair manual though, I can't find a "fan switch" but rather just a solenoid and a cooling fan ECU. Any suggestions steventnm?

steventnm

It is the fan switch SENSOR near the radiator reservior at bottom right corner. It looks like a small screw but it has a sensor built in.
Contact the Lexus dealer regarding that ($85.00)..

Lex3486

I will look into that, but the car has started smoking white smoke and spewing liquid (both of which smell like antifreeze) as well as missing at low RPM's (indicating "fluid" fouling a spark possibly) so I have pretty much no doubt that it's the head gasket(s) given those symptoms. Thanks for all the help everyone, and I'll keep y'all updated as I go along in fixing it. Man, I've got alot of work ahead of me!

steventnm

If oil is leaking, you need to fix the front or rear valve cover gasket and o-ring.

Lex3486

Yeah, it's supposed to have new ones, but I'm gonna check that out when I tear it apart. It doesn't leak oil, but it smells like it occasionally when I'm stopped at a red light with the fan blowing outside air (something I've learned is very common with the ES) so I'll make sure to fix that when I tear the engine down.