curiosul

Before describing the problem, I have to say that the water pump was checked a few months ago and it was fine; I replaced the thermostat and the coolant was replaced by a professional.
So, this only happens if I drive it for at least half an hour at highway speeds (as far as I noticed, if I don't go over 80 in that half an hour, it doesn't happen BUT that doesn't mean I'm usually speeding - I rarely go over 90). After that half an hour, every time the speed drops under 50, the temperature starts going up and after a few seconds it goes down again but not as low as normal. Then it starts climbing again. If this happens enough number of times, the temperature will vary constantly somwhere between 2/3 and red (it never goes on red). If I accelerate over 60, the temperature drops to normal. If I stop the engine for 10 minutes, the problem is still there; if I wait for 15 minutes or more, the problem disappears!
After 2000 miles the oil is fine and the coolant is clean (no bad head gasket, I think!)
This happens with or without the AC and the radiator fans are working even with the AC off.
The only thing I can think of (and even I think it's something veeeeeeery unrelated) is that this might have a connection with the self-blocking toque converter.

Thank you very much for reading this!

01tl4tl

I would put a different thermostat in it first, and buy a thermometer you can place in the radiator as engine is idleing- make sure the guage is working right

The guage on the TL should read just 1 or 2 marks below half all the time- anything else is signal of problem

The driver side fan is the cooling fan- it should be running a lot with the temp you describe

How is the coolant resivoir bottle level and the radiator level- keep bottle at max
Any bad stuff in them now since changed?
Did you use 50/50 mix of coolant/pure water or the premixed 50/50 honda fluid?

curiosul

I forgot to say that it did like this before (not as often as now); that's why I changed the thermostat and the coolant.
Normally the gauge reads as you said - a little bit under half. That's how it reads on my Integra.
The fan is running all the time; in fact it's running even when the engine is stopped.
The coolant level is fine in both places.
After this started happening more often I haven't noticed anything unusual. The car is working fine and I think that no matter what I would do, the temperature won't get to red. It's just that anyone (I think) will start worrying about this kind of stuff.
All the dashboard lights are working and none of then is lit when this happens. It passed the emissions inspection a few months ago without any problems.

Thank you very much for your answer!

01tl4tl

You probably have a bad coolant temp sensor located in the lower part of radiator passenger side
The fan should not run all the time, or more than a few minutes after shutdown

RED is the destruct zone- you dont want to go there ever!
And the engine gets hotter after you shut down becasue no coolant circulation
Have you watched the coolant flow with cap off at normal temp?
How was the w/p inspected?

Go90go

Could be air in the system. Have you burped it recently? The fanswitch IS known to go bad over time as 01tl4tl mentioned. Replace it as it's a very cheap part, and see if that takes care of it. Post back on how you got on.

~Cheers~

01tl4tl

agree with Go on the burping,
my 01 book procedure involved running engine at idle, heater at max temp and cabin blower fan on, with rad cap on to first click but not tight, for 2 cycles of the fan, the remove cap - top off fluid- with cap off run at 1500 until fan cycles, shut off, top off , cap and drive

Not the normal car method by any means!!-

took about 20 minutes and temp is perfect-
I was changing the coolant based on age of 6 years- stuff breaks down- PH goes acidic and eats radiator- no fun at all!

meazz1

Is it an Acura / Honda thermostat or an after market?
I know you are going to have problem with an after market product.

curiosul

Sorry for the delay, I'll try to answer all the questions:
As far as could notice the old thermostat was OEM and the new one is (certainly) aftermarket. I changed the thermostat BECAUSE I noticed something similar and I don't know anything about the old one but the new one should get stuck (if it does) in the open position.
The water pump was diagnosed as "fine" by a service who wouldn't have any interest for me not to change it. My mistake is that I let them to buy the parts so it would have been in their interest to tell me that I have to change the pump also.
The fluid was changed 2 months ago at jiffy lube or something like that (I would have replaced it myself but I was concerned about the eventual spillage). I suppose it was "burped" then.
The strange thing is the timing of the problems. As long as I don't go over 80 mph on the highway for at least half an hour I have no problem even if outside there are 100 degrees. If those problems show up, it only happens if I go under 50 mph. As soon as I go over that speed I can see the temperature going down and staying there no matter what I do. Because of that I started having fear of rush hour.
At first I thought the fans don't start when it's needed and the variation is due to the fans starting because of the AC but then I noticed the fans running normally (well, the temperature was higher than the middle of the scale so the fans were running continuously).
The AC doesn't seem to have any influence on the temperature and driving also. It doesn't matter if I stay still or accelerate or cruising at 40 mph, the gauge still fluctuates.
Thank you very much for all the answers!
All I can say is that I find it very strange ...

X_L

Heh, mine is doing something similar. Changed the radiator, thermostat, and water pump, and flushed the system over the last 3 months and it's still overheating after 30-45 minutes of running. If i go over 60ish it'll go back down to normal and if i turn on the AC it'll go back down for about 10 minutes but then begin to rise again. If i stop at a red light or something it just about reaches the red. It's frustrating and i'm scared of bringing it to Acura because they'll more than likely charge me an arm and a leg but i might just have to.


Good luck though, let me know if you find the solution.. sorry i couldn't help.


edit: Forgot to mention.. yes both of my fans are working normally also.

eibowow

my 96 3.2tl is doing the exact same thing. I thought it was a bubble at first so i got a radiator flush and changed the radiator cap, the car ran fine for a week but now the radiator cracked!.

My tl has 214k miles with a new head, I'm afraid of replacing the radiator and having the same problem over again.

01tl4tl

The radiator being plugged or water pump failing will cause many symptoms listed above
If its going to blow its going to blow and that means it warned you for months ahead of time with fluctuating readings

Coolant- acura says 105k miles or 6-7 years I think
But read carefully and see its a great idea to do at 60k miles or 5 years max- the PH balance goes acidic and well---- steel, aluminum, -acids- you do the math

curiosul

There are a few things not matching a "hardware" malfunction (at least in my case):
1: IMMEDIATELY after going over 65 (when the torque converter locks) the problem disappears
2: IMMEDIATELY after dropping under 50 (when the torque converter unlocks) the problem shows up
3: No matter how warm is outside or how much time the engine has been running, as long as I don't go over 80 this never happens

I have no idea why the torque converter might have any connection with the cooling system but this is the only thing that matches the problem. If this is the only connection I can make, you can imagine I'm really clueless about this.

Thank you anyway for all the answers!

01tl4tl

go have a conversation with the service manager at dealer- he will want to know the answer and ask a tech- then let us know what fixes it because you are not alone!