Im having this little problem and Im wondering if anyone can help shed some light on this situation.

first of all I have a 99 TL

Recently I've noticed that my car is running hotter than normal under certain conditions.

The temperature would increase pass normal If the car idles for a while or during slow moving traffic with out the A/C running. If the A/C is on then the temp stays normal. The temp would increase if I was to be driving up a long hill (only on certain inclines though) driving at a semi constant rate of speed (45-55 mph)
The temp got a little bit below the 3/4 mark for a couple seconds once but if I was to turn on the heater, The temp would instantly go back to normal.

I took a look under the hood to check everything, the coolant level is fine in the reservoir (replaced coolant a year ago) I saw no leaks or any smell of coolant. the coolant level on the radiator is on the top. All of the hoses look fine.
I also looked at the fans to see if they were working and both of them are working. However, I did notice that the cooling fan kick in later than it normally would. (the temp is already a little above the halfway mark). Thinking that it was the fan switch I replaced it but the problem still occurs.

Could it be the coolant temp switch giving me a false reading or causing the fans to turn on late? or could it be something else? Thermostat?

Thanks

 

driver side is temp sensor controlled fan- you say you replaced the sensor on radiator lower corner for that?
passenger side is ac ON controlled

Maybe you need a thermostat- if its not opening at idle in traffic the temp will rise
Have the cap and system pressure tested for leaks

Does the driver side fan come on and off when sitting in the driveway at idle?
Whats the miles- done the water pump and timing belt job yet??- thats due at 7 years or 105k miles...a weak water pump would do some of what you are having

Opening the heater core release a cold amount of stored coolant into the system which will drop the temp- good for emergency use

 

on long hills if 5 speed- drop it in 4th to get back on the powerband and out of D5 overdrive
that will stop it from hunting for the gear it wants

 

99 models are 4 speed tho right? Is 4th OD?

 

I replaced the cooling fan sensor on the thermostat housing. Is there more than one??

Both fans do turn on during Idle if the A/C isnt running. It seems that they kick in later than they should though (at the half or a little above rather than below the half mark). If the A/C is on, both fans turn on normally and the temp doesnt change unless im driving up a long hill. If I turn on the heater. the needle will instantly shoot down to normal driving temp.

I have almost 90,000 miles. I only had the car for a little bit over a year and I dont have any of the previous service history. I'm pretty sure its still on the original pump and belts. I know I'm overdue for that service time wise and I'm planning on doing it soon.

 

The 99s come with a 4 speed tranny.

 

Do you have enough coolant? Is your water pump working properly? If you're at 9 years you should have done waterpump/timing belt which would have invovled new coolant.

If you havent done that yet something might be about to go, or you could be low on coolant.

 

I have enough coolant. I checked and Im not losing any coolant and the coolant level is on the top line. I also replaced my coolant with Honda type 2 blue coolant last year. The thing that gets me is if it is something internally (water pump or thermostat) in the cooling system is about to go, wouldnt the coolant heat up to the point where the fans or heater have no effect on cooling the motor down?

 

no, because the radiator and fans job is to extract heat
If you have a weak water pump that not pushing full pressure- that could be a problem
Or if the radiator is dirty inside or the thermostat is weak
OR try burping it per the book method-never know about the hidden air bubbles
When drain and refilling coolant the heater must be ON to open its mini radiator and get all the old out- and allow new into that heater core- otherwise air gets trapped and first time you use the heat...

You have an odd problem so we have to troubleshoot everything
Have a look at the radiator cap (engine cold only) is the rubber seal ok or cracked-torn-damaged? Parts store will test it for free
Thats a source of problems, as the system needs an exact pressure to operate

 

I've seen thermostats cause cooling system problems that you wouldn't normally associate with a stat. It seems there were quite a few on here a month or two ago. I would only use a honda/acura oe stat. I've had problems with name brand aftermarket stats.

 

i have a heat problem too i think. i can hear my fan go on alot and seems like my neddle is a lil bit above the middle.

 

Well, the car has been running fine for a while and now its acting up again.
Im pretty sure I found the culprit though. A sticky Thermostat. After a 30 mile or so of driving, I opened the hood and felt the hoses. The upper radiator hose was hot but the lower hose was not hot at all. I could wrap my hand around it and leave it there. Im planning on changing it within the next couple of days. (I dont know why I didnt check that earlier )

 

that would be thermostat failure- get it changed NOW

Hot water is staying IN the engine- never being allowed to get to the radiator for cooling. When that happens the guage may still read ok- but inside the actual engine- things are not ok!!
Check your oil- it has been doing extra duty as coolant for the pistons

Wasnt that somewhere in the suggestion list- feel the hoses when running?

 

Didn't see that specific suggestion, but I'll remember it, quick & easy check. Mine always runs 1 tick below 1/2 on gauge.

 

thats the first thing i check on a car running odd temps- is there flow TO and THRU the radiator- observe flow with cap off and engine running- check actual temp of cooant.
And the condition of the hoses, as a soft spot CAN collapse under suction and block flow

sorry if I didnt mention it in this thread- written too many times on too many subjects

 

If a TL runs anywhere but 1-2 ticks below 1/2 on the guage-
even if its 110 degrees outside
with the ac on full blast- going uPhill- at 7000 feet -and ahem mph-

there is a problem that needs attention right now!!

 

u just check the hose and both hose is hot it is pretty hot i can only touch it for about 2 sec. and wen i drive my car the fan be going on alot and the neddle seems like it sits right at half line or something. is there something wrong with my car?

 

i mean i just checked the hose

 

one hose should be hot with coolant coming out of the engine
the other- if the radiator is doing its job- will be substantially cooler but still warm to the touch

the guage can be fooled
If your fan runs a LOT of the time-- its likely a fan sensor- temp sensor, in the lower corner of the radiator
Thats a common failure often found when fan runs and runs after car is shut off

 

i have a funny story: in this thread a month ago i checked my coolant level in the reservoir it was fine.

funny thing is, though, that i checked my reservior level before recently taking my trans out. it was empty, and i thought that was kinda odd. then i took the trans out(i ended up losing near a gallon of coolant doing so) and i refilled my reservoir knowing that i'd probably have to refill it once the engine warmed up. well, it's been driven a good 30+ miles and the reservoir is still at the same level before i got the engine running....but the temp guage is reading normal.

i think i might have the same problem. i've asked this before, but i wasnt able to find the coolant temp sensor because i looked at the lower corner passenger side of the radiator and i couldnt find it. and i think i need to take a look at the thermostat. where is that?

 

both hose is hot. and my fan does run still wen i turn off the car sometimes. so do you think i should get a new fan sensor or temp sensor?

 

so does any one have any ideas what i should do? when im driving i can hear my fan go on alot. is that normal?

 

You've stated both "seems like my neddle is a lil bit above the middle" & "the neddle seems like it sits right at half line or something"-

Which is it? Mine always runs just below 1/2, & 01tl4tl says anything above that is abnormal-
Maybe you have some air in the system that needs to be bled- check manual for the correct procedure.

 

Have you checked the fluid level? Where exactly does the needle sit? just below or at half. Does it ever go higher? Maybe time for a flush and replace teh thermostat.

 

Could it be you're driving in stop and go traffic? This will cause the fans to kick more then on freeway.