Are your cooling fans on???

[tjenkins]

90 coupe - last two years, after warming up in the first 15 minutes or so, the temp gauge would read straight up (in the middle).<P>Yearly antifreeze flush now causes the temp gauge to very slowly move up and takes over an hour to read straight up.<P>Noticed my two cooling fans come on immediately after starting, yet I was almost positive that they didn't before last week.<P>Does anyone have any ideas as to if the fans are supposed to come on (push/pull fan), or, if there is some common component causing this?<P>--Tom<BR>

[Guest Stan Leslie]

Sounds like the thermostat could be part of the problem (missing?). Was it removed during flushing? As for fans, I'm not sure but there have been other discussions about fan on sequences you could check. Both fans on would obviously slow down warm up but probably not as much as you describe.

[Reatta Man]

Tom,<P>Most of us turn on the heater to its maximum setting to flush the heater core as well as the engine block. If you have been turning on the defroster instead of the heater, this will cause the A/C compressor and the fans to come on. This is programmed into the temperature control unit on most newer cars because warm DRY air (with the moisture removed by the A/C evaporator coil) will clear a windshield much faster than warm moist air. <P>If you are running the defroster, and therefore by default the A/C compressor, the fans will also come on immediately, whether it is 10 degrees or 100 degrees outside. <P>As for your temperature gauge operating irradically, you may have an air bubble trapped inside the highest point of the engine block. Air passing over the sensor instead of coolant will not give an accurate reading. Try elevating the front end of the car or check to see if there is a screw with an allen head near the water inlet or near the high spot on the engine. If it does (I can't remember if the 3.8 has one--I forget something new every day) remove it only with the engine off and cool. <P>If you feel confident that you have gotten any air pockets out of the engine, it may be time for a new temperature sending unit. <P>Good luck and merry Christmas!<P>Joe<P>------------------<BR>1965 Wildcat Custom Convertible<BR>1970 GS coupe<BR>1990 Reatta coupe<BR>1999 Regal GSE<BR>2002 Reatta II coupe (I wish!)

[Guest Stan Leslie]

Here are some exerpts from previous posts regarding fan operation and troubleshooting.<P>Now about the fans. The engine has a 195 degree thermostat and should run at 195 degrees unless stopped in traffic. Then the engine coolant temperature will rise over 200 degrees. At 214 degrees, both fans go to low speed. If the coolant temperature still rises, at 226 degrees, both fans run at high speed. The fans are controlled by the ECM and three relays. If the air conditioning is operating, the fans will run at low speed if the AC high side refrigerant temperature reaches 122 degrees. If the refrigerant temperature reaches 149 degrees, the fans will run at high speed. So if the AC is off and the engine coolant temperature is below 214 deegrees, the fans will be off.<P>There are three relays, all located in the front drivers side of the engine compartment (inside the black box). Relay "C" operates both fans, so that should not be at fault, since one works. Relay "D" operates the rear fan and Relay "G" operates the front fan. One way to isolate the problem is to switch the relays around and the bad relay should cause a previously working fan to not work. Both fans get their power from the same fuse so the fuse should not be the problem.<BR>

[tjenkins]

Thanks VERY much for the above comments. Now, background and status as of this morning.<P>Background - 90 coupe bought in 97 with 33K miles, now with 71K. Ever since bought, the temp gauge would rise fairly quickly (10 minutes?) on highway speeds and stay right on at 12 oclock, regardless of the outside temp or AC (which I run all the time).<P>Every fall (November), I change the antifreeze with Prestone. I bring the car up to normal temp, stop it, open up the cock, drain the antifreeze, open up the pressure relief valve and pour in the Prestone flush cleaner (1 quart), run for 10 minutes at operating temp, flush entire system with water, refill with water, run up to warm, reflush again, and finally pour all the gallon antifreeze into the radiator, and fill the other half with water. Last week will have been the third time I've done this. And, yes, all three times I've turned on the heater to 90 degrees to ensure flush of the heater core as well.<P>Since I bought the car, I have not really checked the fans, but I could have sworn that they did NOT come on after startup, yet would turn when the temp was really hot outside (90 and up), so I can't tell if this is a normal condition for my car or not.<P>As far as I know there is a thermostat in place - I have not removed it, but I would *assume* that there is one, since the temp would rise quickly to 'normal' and stay there.<P>Again, the temperature seems to rise very slowly to the 10 and 11 oclock position and stay there, even after 40 minutes of driving.<P>Status as of today:<P>I understand that there are three relays in the Relay Center that control the fans from the ECM. I swapped out all three with the Horn Relay (, but no change. The fans still came on when the engine started. I then pulled relay "G" (actuates the puller fan) and the fan did NOT come on. This would indicate to me that there is not a relay problem. I checked the service manual, and it would appear that both relays operate in either series (slow speed) or parallel (high speed) depending on the ground signal from the ECM (for both fans). Pulling relay G, directly between the 12V power, fan and ECM, stops the fan. Doesn't that seem to point to the ECM?<P>I don't think there is an air bubble in the cooling system, as the antifreeze is full-up on the radiator, and between the full/add marks when hot on the expansion tank.<P>Nearly all of the time I run with the AUTO/AUTO setting on the temp control panel and let the computer do the rest. In the morning, I usually set it to 72 or so, yet in the afternoon, have to raise it up to 78 or 80 to achive a comfortable setting in the car. I do NOT run just the defrost setting.<P>The heater does work - there is hot air when I turn the control to 90.<P>Some questions<P>1) When YOU start your car, do(es) your fan(s) come on immediately?<P>2) If I do decide the swap out the thermostat, I note that its under a series of engine parts with only ONE bolt. Is this a challenge? Can someone email me as to the procedure? I would prefer to further troubleshoot before I tear into this <P>3) Would unplugging the battery, and consequently resetting the ECM help? Armed with the schematic, it would seem that the ECM is sending both fans a ground signal to turn on immedately. Is there a way to troubleshoot the ECM with a resultant code?<P>4) Can someone confirm that 1-Gallon of antifreeze, with the remainder water, is correct for this engine?<P>5) Does the temperature sensor affect the ECM setting, and thereby the fan operation? If it failed, wouldn't the gauge react accordingly and not read correctly? Does the ECM interpret the sensor reading to turn on the fan(s)?<P>(PS - I will try to turn off the AC this afternoon when it cools and check the fan operation).<P>Thanks in advance for all your help!<P>--Tom<BR>

[Guest]

Hey Tom,<BR> I changed my thermostat with 1/4" drive ratchet and a long extension with a swivel on the end. I think it was a 10mm socket.<BR>Once the bolt was removed I was able to wiggle the hose and the housing came right off. I changed my hose at the same time and the whole operation took about 25 minutes. It looks harder than it really is.<P>Good luck and Happy Holidays,<P>------------------<BR>Jim

[tjenkins]

Thanks... even if I change the thermostat though, that won't stop the fans from coming on upon engine startup.<P>Do your fans come on right away? Both of them?<P>--Tom<BR>

[tjenkins]

It appears that I have answered 1/2 of my question. With the AC off, or HEAT/VENT, the fans DO NOT COME ON. This would indicate that indeed, the problem may be in the thermostat area?<P>I'll purchase one from Napa today and install it. (Thanks Jim!)<P>--Tom<BR>

[Guest]

While the system can be flushed with the thermostat in place, it generally works better with it out. You can backflush the system through the upper hose and force the water out the top of the radiator with the cap off. I wonder if the caustic nature of the cleaner has any effect on the t'stat? The car is ten years old and if the thermostat hasn't been changed it's a good bet it's gone bad. On the curious side, why do you service the cooling system so often? Every two to three years should be enough to keep it clean, especially if you use an additive such as RMI-25.<P>------------------<BR>Hal, btk@vbe.com

[tjenkins]

Yep - the thermostat was indeed the problem. Changed it out, and it's rock solid at 12 noon!<P>Thanks to all for the help.<P>Btw, I'll be darned if I can figure out why Buick only used one bolt to hold the thermostat housing!<P>--Tom<BR>

[Guest]

Per the shop manual on my 88: Temp that does not reach normal indicates a thermostat stuck in the open position.<P>Also per the manual: with engine running and all else turned off there should be no fans running until 98 degrees is reached then only the main should run at low speed until 108 degrees then both the main and the pusher fan should run at high speed.<P>Coolant Fans "ON" at all time is only two pages. If you need those please send me your fax number -email:jtaylor@cartbean.com<BR>

[tjenkins]

Thanks ... found the answer in the replacement of the $7 part <P>--Tom<P><BR>