Pairodocks

Hello Everyone,

I am new here. I have a 1999 Acura TL 3.2L sedan.

CAR OVERHEATING!!

MECHANIC IS STUMPED!!

HISTORY:

1. Car is currently @ 145k miles driven and has been properly maintained. I am the original owner.
2. It has been overheating for 3+ years - when the ambient temp is greater than 95/96 degrees and/or is driven on a grade or when idling in traffic. FYI - I live in the desert where the temps are now over 110 degrees (July 2016). It does NOT overheat all the time - NO PROBLEM when the ambient temp is lower (i.e in Fall, Winter).
3. When it starts to overheat, and I can't pull over, I immediately put on the heater full blast, which usually brings it down, but anyone in the car is dying in the process.
4. I can ONLY driver the car early in the morning or later in the evening when temps are lower!
5. TESTS - Car has been tested for BHG (Blown Head Gaskets) with Chemical Leak Down and Pressure test - Result: PASSED
6. Asked mechanic about Water Pump, he said he had never seen an overheating issue in 1999 Acura TL caused by faulty Water Pump.
7. No Leaking of Coolant. No oil mixed with Coolant.
8. I have REPLACED the following (by the same, honest Certified Honda/Acura Mechanic with 30 years experience):

• Thermostat (3 years ago)
• Driver's Side Radiator Fan -- which mechanic discovered was working intermittently (June 2016). I have heard the fan turn on. FYI - A/C fan has NOT been replaced. A/C is working fine.
• Radiator (July 2016) **After Radiator changed, in 109 degrees, mechanic drove for several miles with A/C full blast, idled in traffic, and parked for a while - NO OVERHEATING. 5 minutes after I left the shop and started driving up a slight grade, the temp gauge started going up fast!

QUESTIONS:

1. Does anyone have ANY IDEAS what could be causing this continuous problem in the hot weather?
2. Could the car pass the BHG tests if it was a BHG?
3. If it was a BHG, wouldn't the car be overheating all the time?

Any help would very much be appreciated. I would like to keep the car.

Thank you in advance.

Skirmich

Have you replaced the Temp Sensor? Not the fan switches but the actual temp sensor that moves the needle in the dashboard....
Its a common failure and can give false high-temp readings.

johnny14

iTrader: (1)

If I had to guess I would say your Condenser Fan might be failing or intermittently working as well. Like you weathers are up in the high 90's if not 100's and Im sure you have the AC on just like me. I just recently went through this myself where I was stuck in traffic and I can see the gauge creeping. Eventually got home and checked things out and it appears that my condenser fan was intermittently working. Does your fan stay on after you turn off the car?

Pairodocks

Thank you for taking the time to reply.
No. I haven't replaced the Temp Sensor.

• Where is that located?
• Is it attached to something?
• Is that a common failure for the 1999 Acura TL 3.2L?
• Is it an expensive part? I have to have a mechanic do it, so labor is involved, too.

Pairodocks

Hey Johnny.

Thanks for replying.

I have not replaced the Condenser Fan only the Radiator fan. The fan does stay on after the car is off. I was told that is normal. Is it the Radiator fan that stays on after the car is off, because I have usually turned the A/C due to overheating?

I haven't been able to look at the fans when the overheating occurs as it is over 105-110 degrees - brutally hot. Also, I immediately turn on the heater, and I am in the middle of traffic - just trying to get home.

Pairodocks

Johnny --

One more thing - as I mentioned in the first post, it also heats up when driving on a grade. After putting the heater on and when I get to a level road, it will return to normal.

MarcDavidoff

Some good suggestions. Has the radiator been replaced? It could be clogged externally with some dirt or internally

ErickUa5

Look around for leaks,
Whats the level of the coolant in the reservoir ?

Are both radiator fans turning on ? to check turn the AC on and look under the hood

Did your mechanic bleed the air out of the cooling system with the climate control set to 90 ? If not then its simply air in the system that needs to be bled out

Has the radiator cap ever been changed ? Sometimes replacement radiators dont come with new caps and the old one is reused

Pressure test the cooling system.

Pairodocks

Thanks for your reply.

Please see my original post for the answer to your question.

Pairodocks

Hey Erick,
Thank you for taking the time to reply with your good questions.

The answer is currently, "I don't know" to all of them. I thought the mechanic mentioned that he saw both fans working, but I will follow up with him with your questions and report back.

Skirmich

It is located/attached on the Intake/Out portion of the Radiator Tubes going into the engine.
Its not a common failure specific to any car its just a sensor that often goes bad on many Hondas.. They don´t last long sometimes (Already replaced mine in my TL-S because of false readings)..
It isn´t expensive and you can DIY very easily so no need for labor use the following diagram to locate it and replace it, Part #15
LINK = (1999 Acura TL TL SENSOR ASSY., WATER TEMPERATURE (HADSYS) - (37870-PK2-015) - Acura Parts Online)

johnny14

iTrader: (1)

Sorry for the late response. Been busy so haven't been able to post. A few things you can try. Drive the car with the AC off and see if it overheats going up hills stop and go, etc. If everything seems fine try it with the AC on and repeat. If you notice that its overheating or creeping up in temp than its most likely the AC Condenser Fan which probably isn't as efficient anymore. Check coolant and check the reserve tank make sure theres coolant in there.

For me I noticed the fan would stay on after the car was turned off which Ive never encountered once since owning the car back in 2003 so I knew something was off but couldn't figure it out. Both fans kicked on when the AC was on and when the AC off. A few days later I was driving and I noticed the temp was creeping up in traffic so I immediately turned around and went straight home. Got home to find out that I had no coolant in the radiator and reserver tank and a lot of steam. Radiator cap was broken and the spring was in the upper radiator. It was bad! I eventually tested the fans and noticed that the AC Fan was intermittent and was probably what caused the overheating. Replaced it, while i was at it flushed the system, replaced the radiator since it was under warranty and other things non related and been driving it since with no problems.

Severin

Pairodocks:

I have the same issue; last three or so years it overheats on really hot days or driving with a loaded car up grades or in stop and go traffic.
I've also had the waterpump and thermostat replaced during that time. I've replaced the radiator cap and coolant fan as well and cleaned between the condenser and radiator to remove debris. Still overheats.
Funny thing is that the temperature will slowly climb and then drop like a rock over 3 seconds when it does drop; all the fans are running.
Maybe I'll try the temperature sensors.
After 323K, my condenser fins are pretty smashed by all the stones and such kicked up into my grill - I don't doubt that the airflow would suck, even with a new radiator behind it.

Pairodocks

Hi Severin,

Thanks for replying. Do you have a 1999 Acura TL too?

In my situation, the only time the car will stop overheating is when I blast the heater with the windows open. In the desert that I live in, that is a very unhealthy thing to do (for the occupants of the car). Then we have to pray we are close to home or get to a gas station ASAP. We are almost to the point of heatstroke when we can finally turn off the car.

As I mentioned in my original post, the car overheats when the ambient temp is greater than 95/96 degrees and/or is driven on a grade or when idling in traffic. Currently, the temps are over 107 degrees (August 2016). They can still climb higher than that. However, it does NOT overheat all the time - NO PROBLEM when the ambient temp is lower (i.e in Fall, Winter or early in the morning when the temp has not reached the high for the day).

I have not yet replaced the A/C Condenser Fan. I was hoping the Radiator would have been the culprit after having replaced the other things. That was an expensive replacement relative to everything else I have done. It started to overheat literally 5 minutes after leaving the shop as I started to drive up a very slight grade . Prior to my leaving the shop, the mechanic had driven it with the A/C on for 10 minutes in idling traffic, and it was fine.

When I next see the mechanic (because I am not one), I am going to take him the info offered here and see what he says. He is stumped and works exclusively on Hondas/Acuras.

The car passed all of the tests for a BHG. I was wondering if a car can have a slightly BHG? Also, is it possible to pass the leak-down test and still have a BHG?

This is a very frustrating issue, to say the least.

Skirmich suggested replacing the Temp Sensor, but what I don't understand is why would it produce False readings only under certain conditions and the same conditions consistently? If that were the issue, I would think it would produce False readings all the time. But what do I know?

Skirmich

Because the heat sensor is a resistor.. When the resistor fails it can exaggerate temps over certain volts, for example at below 96° the voltage can be stable because the heat range allows the Needle to interpret those temps at a given voltage. BUT if the sensor is malfunctioning past certain temperature the voltage will suddenly drop too much giving a false reading. Bear in Mind that sensor and needle is for your information only! it doesn't tell anything to the ECU, The ECU works with the FAN SWITCHES (2x for TL-p and 3x for TL-S) to cool down the car and it gets the temperature out of those Switches..

Sadly the only way to Know for sure if the engine is overheating is when damage has occurred, Otherwise you are following the Temp Needle and the Sensor that makes that needle work isn't 100% Failure Free. Like I said I replaced that temp sensor before because of false readings, mine would actually shoot sky high (FULL RED HEAT) and stay there over long periods of time to then stabilize at normal driving temps.. This scared me a lot and I more than once stop driving because I thought my engine was dying or something..
Pop the hood Check the engine bay and noticed my fans were not even running the car was perfectly fine but my Temp Needle was all over the place. One new Sensor and everything is OK.

Bear in Mind I live in So Cali and do a lot of work to Yuma, AZ where temps get to 120°F all summer.. My TL-S does work overtime with the fans running at 100% load all the time and with the A/C on is a heat nightmare. In your case is not insane to think the fans are working because the car is hot due to ambient temps this is natural.. BUT In all my time working and driving to Arizona I have yet to see my TL-S climb above half the needle range even when the Fans are Blasting.

Do yourself a favor and replace the Needle Temp Sensor and remove a variant out of the equation. Before spending the big bucks on something larger.

Pairodocks

Hey Skirmich,

Thanks again for your thoughts on the situation. You obviously have a lot more knowledge about the inner workings of the car's electrical system than I do. I appreciate your explanations.

Do you think I should replace the A/C Condenser Fan as well. That has never been replaced. The Radiator Fan was replaced a couple of months ago because that was working intermittently. Thermostat replaced 3 years ago when the problem started.

What do you think about the questions I asked about a BHG?

You said, "The ECU works with the FAN SWITCHES (2x for TL-p and 3x for TL-S) to cool down the car and it gets the temperature out of those Switches."

• Does the ECU tell the switches to turn on the fans? How does the ECU get the temp from the Switches? Are there sensors in the switches also?
• What does 2x for TL-p mean?
• Is TL-p referring to the model? I have a TL.

Thanks again for your patience.

Skirmich

The switches work on its own, they flip ON at a certain temp and the Fans turn on. The ECU has no control over this it can only tell when the Fan Switch has triggered at a certain Antifreeze Temp. This is usually FAN A (50% Speed) FAN B (100% Speed) and FAN C (Overhead)
The TL-p (Base Model) Has 2 FAN Switches and the TL-S has 3 FAN Switches.

I dunno about the fans man.. I never replaced mine and they are still working with 215K on them.