Engine fans

[rbsteve]

Me again

I have been having some trouble with my engine temperature lately, and have been digging deep to try and find the root. Highway driving the temperature is at the max of the thermostat, which is fine. But when im in city traffic the temperature shoots up to 2/3 (100 C) at stays there until i get moving at speed.

My thermostat is working fine (checked by boiling it up on my stove). I have a new water pump since the old one started leaking a couple of months ago. There are no leaks in the system, and no coolant is getting into the engine oil.

I saw in a previous post that on my car (98 SE 3800) that the fan control was strictly computerized and that there is no temperature switch on the fans themselves. I am led to believe that my fans are set to come on at 100 C. However i would really like for them to come on at 85 C in order to keep my engine temperature constant. I always thought that the temperature was supposed to be constant anyways.

So my question is, does my car have a fan switch which could need changing, if not can my computer be reprogrammed at the GM garage to have the fans come on at a lower temperature ?

Thanks in advance guys

Steve

[BNaylor]

Are you running the stock 195 degree thermostat? If so try a 180. And when was the last time a cooling system flush was performed and new Dexcool added?

Your car does not have any separate fan switches. Both cooling fans are controlled by the PCM computer via low and high speed relays. The PCM references to the ECT - engine coolant temperature sensor. The same sensor feeds the temperature gauge.

To get them to turn on at for example 180 degrees you'll need to get your PCM re-programmed. I really don't think the dealer will do this for you. You can get a re-programmed PCM from companies like DHP or Intense. You may have to request a custom programming job for an SE with the 3800.

Another option would be to hard wire a switch to turn the fans on. The low and high speed relays are located in the engine compartment fuse box. Its a relatively simple and straightforward circuit.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[rbsteve]

I put in a new 180 F thermostat a couple of days ago, testing it beforehand in boiling water. Last time the system was flushed and refilled was at the beginning of the summer. The coolant still looks very new. The temperature sensor is spot on also, checked it with a seperate thermometer.

I was just wondering whether this is normal behavior for the car and if this is the fan ON temperature for all your cars.

Ill have a look at the circuit on the weekend.

-Steve

[jimmytroanoke]

Generally the fans in late model GM cars are set to turn on at around 225(107 c). Seems kind of high to me but it helps emissions. For best emissions they have to toe the line between engine life and efficient smog controls which the hotter the better for smog.

[BNaylor]

Originally Posted by jimmytroanoke

Generally the fans in late model GM cars are set to turn on at around 225(107 c). Seems kind of high to me but it helps emissions. For best emissions they have to toe the line between engine life and efficient smog controls which the hotter the better for smog.

I agree with JimmyT. But the temperature readings on any of my "W" body cars never exceeds 190 degrees and I'm located in the hot Southwest. I think this gentleman lives in Canada.

At one time or another one or both fans should turn on with the AC turned on so he can at least tell the fans are working at all.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[jimmytroanoke]

[quote=bnaylor3400]I agree with JimmyT. But the temperature readings on any of my "W" body cars never exceeds 190 degrees and I'm located in the hot Southwest. I think this gentleman lives in Canada.

At one time or another one or both fans should turn on with the AC turned on so he can at least tell the fans are working at all.



[quote]
Clarification: Usually with the a/c on one of the fans should run continuously. A/c off, no fans until 225. On my GP the car actually ran cooler on the gage by a few degrees with the a/c on! With a 195 stat it ran right at 200 with the a/c on and around 210 in stop and go with the ac off. You must have a really clean radiator to run that low, Bnaylor. I assume your DHP is kicking them on lower as well.

[BNaylor]

You're absolutely right JimmyT. They seem to run cooler with the ACs on. I do the flushes and coolant changeout religiously. This summer we went 40 days straight at 100 degrees or higher. It finally started cooling down into the 90s.

On the GTP, the DHP PCM turns them on at 180 but I very seldom get over 170 on it. My Regal GS is stock with the 195 degree thermostat.
Also on the GTP I switched over to Prestone Extended Life coolant and got rid of the Dexcool.

Personally, its hard for me to comprehend a car running hot up North like in Canada unless there's a problem.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[jimmytroanoke]

The problem is with Dexcool and the 5 year BS! RBsteve probably needs a good flush followed by having his raiator removed and boiled out or replaced. After boiling out if he passes a leak test, all is well, if it has pinholes, replace. A lot of pinholes won't leak as they are plugged by Dexcool sludge.

[BNaylor]

Originally Posted by jimmytroanoke

The problem is with Dexcool and the 5 year BS! RBsteve probably needs a good flush followed by having his raiator removed and boiled out or replaced. After boiling out if he passes a leak test, all is well, if it has pinholes, replace. A lot of pinholes won't leak as they are plugged by Dexcool sludge.

I agree and good suggestion. It worked for this guy we helped out a while back on the GP forum in Southern California. When the radiator shop removed the radiator, they found 5 lines clogged.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials

[rbsteve]

Hi,

Thanks for the suggestions. After reading the many comments on coolant quality, i decided to take a little from the drain on the radiator instead of looking from the top. There is quite a bit of "sludge" in it. Browny-red pastey chunks, for lack of a better description.

Must a flsuh be performed at a garage, or can you do it at home with a hose pipe or compressor ?

I have also read reports that the Dexcool can be replaced with the good ole' green antifreeze. Has anyone tried this ? Is it recommended ?

Thanks again

Steve

[BNaylor]

Originally Posted by rbsteve

Hi,

Thanks for the suggestions. After reading the many comments on coolant quality, i decided to take a little from the drain on the radiator instead of looking from the top. There is quite a bit of "sludge" in it. Browny-red pastey chunks, for lack of a better description.

Must a flsuh be performed at a garage, or can you do it at home with a hose pipe or compressor ?

I have also read reports that the Dexcool can be replaced with the good ole' green antifreeze. Has anyone tried this ? Is it recommended ?

Thanks again

Steve

Prestone extended life antifreeze is green and can be mixed with any residual Dexcool. I run it in my GTP.

You can do the flush yourself or by a shop/garage.




Thrasher CAI, DHP v1.0 PCM,
3.25 SC pulley, CAIT GMAF, 2.5 DP/Hi-Flow CAT,
u-bend delete, 160 TS, ZZP Stage 1 TB,
TB spacer, MSD 8.5mm wires, Autolite 104s,
Goodyear Gatorback Serp. & SC Belt,
Nitto NT555R Drag Radials