Loudgoldwing

So... here's my dilemma. I have the itch to do some fiddling before prime Cabbie Season starts back up again. Aside from the typical plugs, fluids, pads and filters, there's (fortunately) only one mechanical job I'd like to perform. I'll throw my issue out there, and let's see if any of you geniuses can hook me up.

I have these three electrical bits that monitor engine temperature. They are:

[F62] ECT (Electronic Coolant Temperature) Sensor -
Location: Driver's side, screwed in to black metal coolant pipe on the rearward side of the engine.
From what I understand, this sensor communicates with my ECU. The ECU uses this sensor's temp reading to (partially) determine fuel-air mixture, maybe timing, stuff like that. That's not what I'm interested in.

[F76] ECT (Electronic Coolant Temperature) Switch -
Location: Passenger's side, screwed in to black metal coolant pipe on the rearward side of the engine.
Yeah. OK. Same damned thing, basically. But destined for a different purpose. This little guy tells your temp gauge what's up (only sometimes, in my case ), and it lights your warning indicator if the coolant gets too hot. Completely redundant, in my opinion... but hey, it's a German car. Whatever. I'm probably going to swap this one out too, but that's not the real reason for my post...

[F54] Coolant Fan Control Thermal Switch -
Location: Radiator, bottom right (huh?).
THIS is the bad boy I'm looking for. This is the switch that tells the radiator fan to turn on and turn off. That's its only purpose in life. You'd think it would be pretty good at it, wouldn't ya? Not so much.

When driving in warmer weather, but with the AC off, my Ultragauge will read coolant temps as high as 216F before Mr. [F54] tells the radiator fan to turn on. The fan brings the temp back down to about 210F and the [F54] shuts it off. Then, after about 60 seconds, when it climbs back up to 216 the fan comes on again.

I know that I'm a little more finicky than the average weekend wrench, but only a 6-degree swing? That's it? I don't accept it. Especially since, if I have the AC on, my car can sit in a hot parking lot all day long at 196F at the VERY highest while the radiator fan is in "Constant On" mode.

So to make a short question long, does anybody make either an adjustable [F54] Coolant Fan Switch, or is there another model of [F54] that is the same size, but will tell the fan to turn on at like 206F and shut off at 198F? Obviously, as long as the temperature at which the fan shuts off is higher than the full-open temp of my thermostat (190F IIRC), the car will run fine... I think.

Last year at the hight of summer, I took a weekend trip. Wide open on the freeway, no AC running and 96F outside, and my temp reading was constant at 196 until I came to an exit. That seems to be the running temp that the car is happiest, don't you think?It just doesn't seem right that the car is allowed to spike 20 degrees higher than that point before the fan even starts to do anything about it.

I just want to keep the car a little more constant in its temp range, now that she's getting older. Rapid and wide heat cycling hastens death for car engines. And don't EVEN get me started on the crystaline fragility of the 01N automatic transmission when exposed to extreme heat. IMO, ten degrees cooler = ten years happier with this car. Anybody got any suggestions?

Cheers,
LG

kakarot1232001

you can get the switch cooler range, if that is what you want. Mine kick in at 92C first stage, 95C second stage. off at like 87C. This is the radiator exit temperature, not the actual engine temperature, which is much higher. If your thermostat is not matched, like a step colder. Then fan will be cycling on/off very rapidly. Once you under 95C and above 80C its all good. Not sure about V6, but other audi engines like 1.8L and 2.3L run at 87-92C range. Colder you go more power you can gain and lose mpgs.

First things first if you want to make car run cooler. Check that the pressure builds up in the cooling system. If there is no pressure the engine will run at least 5C higher then normal. In my case, the nipple at the expansion tank was bad and no pressure was building up. Normal engine temp was 95C. Once I fixed that now around 91C.

Second thing is depends where you are. A good antifreeze at like 30/70 ratio with Redline water wetter will keep engine cooler. Also can do radiator cleaning from Prestone, not flush, flush too weak.

Another mod I did, which is not good for winter is to put a restrictor into your short loop/heater pipe. This will force more coolant to go to the radiator. during winter, like 20F, the inside of the car, if idling will be warmish, rev up to 2200RPM and burn your face off.

There are other small things that can add cooling capacity. But if the first thing is proper, and radiator relatively clean. when idling, the temperature when the fans turn on would reflect the temperature of the engine. which is what its suppose to be.

too bad this http://getcoolparts.com/ gone out of business, they always had this kind of stuff in stock like cooler thermostats, and cooler switches.

-Yuri

hubturn

I noticed a significant difference in the cycling of the fans after I replaced the radiator. Flushing it multiple times did not have the impact that a replacement had. I tested the new F54 I purchased from the dealership to prove functionality prior to install. With an ohm meter to detect continuity, the test water had to be very close to boiling to switch on. I now regret not having a thermometer in there to be more accurate. So your real world temps that you have discussed seems pretty close to what I discovered.