Leave your aircon switched on when doing extensive idling

Ken4 · Nov 24, 2003

Ever since installing a water temp gauge in my 4cyl camry, I discovered some interesting things.

http://web.singnet.com.sg/~kppjw/Oil_Gauges7.jpg

http://web.singnet.com.sg/~kppjw/Water_Temp_Sender.jpg

Water temps in general rise when idling (95C), when cruising (85C), when driving hard & fast (80C).

The stock OEM water gauge is kindof useless, the needle rises to the center of the gauge and just stays constant. For the last 4 years I had thought that water temp was always constant in my vehicle, but boy was I wrong.

The interesting thing is that with the aircon ON, the water temps never get past 95C when doing extensive idling. But when I switch OFF my aircon, the water temp soars to 102.5C when idling. The camry has two electric fans sitting behind the radiator, my guess is that with the aircon on, the fans kick in earlier. Or the aircon condensor coil mounted in front of the water radiator provides some cooling when the aircon is running.

Patman · Nov 24, 2003

My car also runs cooler with the air on. That's because as soon as the air conditioning compressor comes on, so does the second of the two fans, the high speed one.

Bob Woods · Nov 24, 2003

Mounting the sender in the return line you should see water temp changing with engine load. Its a function of the cooling system to carry that heat from the engine to the radiator. A more accurate point to measure is right in front of the thermostat, what you are reading is heat being removed from the engine.

On every car I've been around the radiator cooling fans come on when the A/C is turned on, the condenser coil requires air flow for the A/C to work.

greencrew · Nov 24, 2003

This is good news for those stuck in traffic on a hot day, but only applies to engines with electric fans.

TooManyWheels · Nov 24, 2003

Ken4 - You can rest assured that the A/C condensor does not provide COOLING to the radiator. It transfers to the incoming air stream the heat that was previously in your interior.

Ken4 · Nov 24, 2003

quote:

Originally posted by Bob Woods:
Mounting the sender in the return line you should see water temp changing with engine load. Its a function of the cooling system to carry that heat from the engine to the radiator. A more accurate point to measure is right in front of the thermostat, what you are reading is heat being removed from the engine.

I've mounted mine on the top radiator hose which is the recommended location. It measures the water before it is being cooled by the radiator. The 4 cyl camry thermostat is mounted near the water pump where the return line of the radiator connects. I believe most horizontally mounted jap engines follow this design.

Spector · Nov 24, 2003

Merc Mystique, fan kicks on with the A/C switch and runs constantly as long as the A/C is on. I confirmed if this was kosher with the dealer and they said yes. This is the 4 cyl Zetec. So, runs cooler with the A/C on.

Drew99GT · Nov 25, 2003

quote:

Originally posted by Ken4:

Originally posted by Bob Woods:
[qb] Mounting the sender in the return line you should see water temp changing with engine load. Its a function of the cooling system to carry that heat from the engine to the radiator. A more accurate point to measure is right in front of the thermostat, what you are reading is heat being removed from the engine.

Click to expand...

Click to expand...

Bob, Toyota designed their cooling systems in a reverse flow fashion of sorts. The upper radiator hose, at least on 4 cylinders, is not the hose coming out of the thermostat housing but it still is the outlet hose from the engine where heated coolent enters the radiator. The hose entering the engine after it has cooled (lower hose) is where the thermostat is located, so Ken's location is perfect. The upper and lower hoses are kind of switched from the traditional sense.

Drew99GT · Nov 25, 2003

Ken4, I was thinking. Not only is your setup more accurate because it's a real gauge, but the 4 banger Toyotas have the factory gauge sendor in the location of coolent AFTER it has gone through the radiator. I think that's why the gauge just goes up and constantly stays in the middle and never moves. That's how mine's situated on my Corolla. Kind of defeats the purpose of having the **** gauge.

SteveD2 · Nov 25, 2003

That's why I put in a switch for the aux. electric fan on my Jeep.

On my Jeep the idle also goes up slightly with the AC on, so the main mechanical fan and water pump turn faster.

Ken4 · Nov 25, 2003

The factory water temp senders of the 2.2L 5S-FE are located on the engine near the upper radiator hose.

http://web.singnet.com.sg/~kppjw/Factory_Senders.jpg

There are two. A grey one which is single wire and a green one which has two wires coming out. This is the most ideal location bcos it will also measure the bypass coolant temp (before the thermostat opens).

But the beauty of my new sender location is that I can tell exactly when the thermostat opens. From a cold start, it takes only about 3~4mins for the thermostat to open. My aftermarket gauge will slowly rise to 50C, then suddenly jumps to 85C! Good way of detecting a stuck thermostat.

I dont know why the Toyota factory water temp gauge just stays in the middle. Im guessing it is Toyota 'logic' so as to not alarm the driver. But Im beginning to see a trend that Toyota is no longer seeing a water temp gauge as useful gauge. Besides, hardly anybody keeps on eye on the needle whilst driving, even when it reaches the red zone, by then it would be too late. My new Toyota Ipsum 2.4L 2AZ-FE no longer has a water temp gauge, but instead has a water temp light. When I first start the engine, it's lit blue, then in about a minute it goes off, if the engine overheats it is supposed to light up red. I suppose toyota has determined that that is a more useful alert for the driver and probably is.

http://web.singnet.com.sg/~kppjw/Ipsum_Dash.jpg

The old MBs are a different story, their water temp gauges are so sensitive. Sitting in congested traffic, the needle keeps going up & up nearly hitting the red zone. Gives me the jitters all the time. Have you noticed the MB A-Class and C-Class dont have water temp gauges?

[ November 26, 2003, 03:02 AM: Message edited by: Ken4 ]

Drew99GT · Nov 25, 2003

Ken4, I guess I'm having a hard time understanding how Toyota designed their cooling systems. Is the thermostat on your engine located where the outlet hose goes from the engine to the radiator? In other words, do you have your aftermarket sendor in the hose that carries heated coolent to the radiator or the hose that carries the "cooled" coolent as it has already passed through the radiator?

My Corolla must be different because the thermostat housing is located on the engine where the hose returning from the radiator carying cooled coolent is located. In other words, the upper radiator hose carrying hot coolent to the radiator is not where the tyhermostat housing is like on traditional systems. Which made me wonder, because my temp gauge sendor is located in the return hose right before it enters the water pump, where the coolent would be the coolest because it has already pased through the radiator. But the ECU temp sendor is located where yours is, in the thermostat housing which gets both radiator cooled coolent AND bypass coolent when the thermostat is still closed

I bet that sounds confusing as hell!

manualman · Nov 26, 2003

Yup, the temp gage on most modern cars isn't a gage, it's an idiot light in disguise.

I know because I owned a pre-1995 Saturn and they made the mistake of having the gage ACTUALLY sensitive to temperature changes. So Joe trades in his old Corrola for a Saturn and the first time he sits at a stoplight a long time he freaks because his temp gage has gone from 1/3 to 2/3! That NEVER would have happend with his reliable old Toyota...

You get the picture. They changed the design sometimes after 1995. I laugh when I hear people say that their coolant temperature never fluctuates. Rather violates the laws of physics, no?

Drew99GT · Nov 26, 2003

Actually, even with a real gauge, some cars will not fluctuate that much. GMs on the other hand are all over the place, especially in stop and go, because the fans don't come on till 215 and 225 respecitvally for low and hi settings.

Ken4 · Nov 26, 2003

quote:

Originally posted by Drew99GT:
.....do you have your aftermarket sendor in the hose that carries heated coolent to the radiator......?

Yes.

quote:

My Corolla must be different because the thermostat housing is located on the engine where the hose returning from the radiator carying cooled coolent is located.

Mine is the same.

Dr. T · Nov 26, 2003

Most temp. guages that read normal once the engine has reached operating temp. is just that...a range of acceptability. It's only when there is a change from that range up or down that the needle starts moving. This is completely acceptable. My BMW is like this.

Although the water temp. may be decreasing due to the electric fans coming on...there is an added load on the alternator for this and an even bigger load on the engine from the power-sucking a/c compressor coming on. Can you commment on whether this increases oil temps.??

mdv · Nov 26, 2003

quote:

Originally posted by Dr. T:

Although the water temp. may be decreasing due to the electric fans coming on...there is an added load on the alternator for this and an even bigger load on the engine from the power-sucking a/c compressor coming on. Can you commment on whether this increases oil temps.??

Dr. T, I have a 1990 325is. The stock water temp gauge moves up and down slightly depending on use. It runs noticeably hotter when idling, but cools right down when moving. After running a quick errand and returning to the car, upon initial startup the gauge indicates higher and will quickly settle back down in about 30 seconds.

I also installed an aftermarket oil temp gauge in this car. When idling on a hot summer day, I see a 10-20 degree rise in oil temp. Car typically runs at 180F, will creep to 200F in traffic and runs 235F on the track.

Ken4 · Nov 27, 2003

quote:

Originally posted by Dr. T:
Although the water temp. may be decreasing due to the electric fans coming on...there is an added load on the alternator for this and an even bigger load on the engine from the power-sucking a/c compressor coming on. Can you commment on whether this increases oil temps.??

No, there is no increase in oil temperature.

JohnBrowning · Nov 29, 2003

My 1986 4Runner and 1982 Starlet guages were accurate and would flucate all over the place if you were in Georgia traffic jam , 4Wheeling hard or Towing up a moutain etc... other then those types of extremes the guage would pretty much barley come off of cold mark and stay their. Todays vechiles I agree that they do not budge at all. THey seem to come up to some predetermined point and do not budge until you have a serious coolant or oil failure!!

Ken4 after you have reached operateing temp do me a favor in traffic turn you heater on full power and tell me what happens to your temp! I am wounder how big of a drop you are going to get?? Do not run a/c at all!

Ken4 · Nov 30, 2003

quote:

Originally posted by JohnBrowning:
Ken4 after you have reached operateing temp do me a favor in traffic turn you heater on full power and tell me what happens to your temp! I am wounder how big of a drop you are going to get?? Do not run a/c at all!

Interesting. The water temp drops from 102.5C to 92.5C! That is with MAX heater. With LOW heater it doesnt drop so much, around 97.5C.

Leave your aircon switched on when doing extensive idling

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