Engine Temp

I have noticed that when I am stuck in miles-long traffic backups(ie: coming back from VA Beach and going over the Hampton BAy Bridge-TunneL) my car temp gauge starts to creep upwards. To prevent the car from going all the way to the red on the temp gauge, I shut off the A/C (even though the temp outside was over 100!) and the temp will go back down slowly. Once I’m moving again, the car temp runs “normal” (less than 1/2 way on my gauge). My brother says I should not worry as this is normal as the only air the radiator can suck in is engine heated air as the car isn’t really moving. Correct or take the car to the dealer for a check-up??

Also, an interesting comment… I have been listening to your show on Saturdays for more years than either you or I would care to admit. I have noticed that your newspaper column is now running in the Richmond Times_Dispatch. Your comments are preferenced by your names. As I am reading I realized that I am “hearing” the words in YOUR voices! See I told you I have been listening too long!

Thanks if you care to reply.

I live is a hot climate, and none of my cars have ever threatened to overheat while idling with the AC on for an extended time. I would guess that is not normal for a Honda either.

Usually the symptoms you have indicate an airflow problem. It could be that your fan or fans are not working, or it could be that the radiator is clogged with dirt where the air is supposed to blow through (this usually happens between the radiator and the AC condenser).

I’d get it fixed before you damage the engine one day.

I would add that a worn water pump can also cause this kind of problem as well as a bad radiator hose (may not leak and may look OK, but it may be damaged internally. In rare cases it may be a bad thermostat.

Low pressure and low coolant are also 2 common problems.

I wonder if the A/C is a red-herring. These days A/C compressors don’t put a huge amount of extra load on an engine and I’d really be suprised if having the A/C on could be the decisive factor between the car overheating and running normally. Especially since there’s an auxillary fan that’s always on when the A/C comes on-- if anything I’ve noticed my car seems to run cooler when idling with the A/C on.

What I suspect is happening is that right around the same point at which you think “uh oh, better turn the A/C off” also happens to be around the same time the main engine cooling fan decides to turn on. This could be a problem with the temperature switch in the radiator, but more likely it’s like Joseph says, where there’s bad flow between the engine and radiator. Since the gauge is measuring the coolant in the engine, but the switch that tells the fan to turn on is in the radiator, if there’s bad flow between the two, even though the coolant in the engine is near-overheating, the coolant in the radiator may be just barely hot enough to turn the fan on.

I don’t think so. It is not the added heat from the engine driving the A/C that is causing the coolant temp to rise, but a marginally functional cooling system dealing with the stress of removing heat from the warmer ambient air from the condenser coils in front of the radiator. With air temps around 100 deg, the condenser coil is most likely running at 160 deg or better. This is warming up the air going into the radiator next, reducing the amount of heat the radiator can transfer to the air compared to the 100 deg air without the condenser heated up from the A/C operation.

Also, the cooling fans are running at max whenever the A/C is on. This is how I test cooling fans for proper function.

Hmm… good point on the condensor. However, I am fairly sure that on my (probably much older) Accord, only the aux. fan comes on with the A/C.

What year is the car and how many miles does it have on it? When was the last time the cooling system was flushed and refilled (or just drained and refilled?

Tardis is right. You need to get this corrected or you risk destroying the engine.

In order for the cooling system to keep the engine cool on a hot day with a full load on the engine (the AC compressor puts a load on the crank) and when stopped in traffic, all of the cooling systems’ component parts have to be operating properly. That includes the thermostat fully opening, the pump pumping the volume intended, the radiator allowing the coolant to flow properly through its core, and the radiator’s tubes being clear inside without undue desposits or corrsion. Additionally, the air has to be able to flow freely through the radiator as mentioned by Tardis.

All of these things, the thermostat (cheaper to replace than to test), the water pump (can be flow tested), the radiator (can be flow checked and thermally mapped), and the cooling fans, can be checked and tested. Additionally, if the vehicle is older, the radiator hoses can be changed. The inner liners can collapse and cause flow restriction.

This condition is not normal. I recommend that you get this to a good independantly owned and operated shop at your earliest opportunity. This comdition will only get worse until you overheat and the engine gets ruined.

Long ago my cousin had the same symptoms in his '86 Accord.
Turned out the connector to one of the two radiator fans was loose.