Heres the deal, my bros got a 91 camaro rs, 305 TBI, AT, AC. Now the cooling fan is only kickin on sometimes. It usually will kick on when you turn the key to the on position when the engines hot, but sometimes it doesnt. When idling the coolant temp will get up to 240+ before we shut it off. When on the road it stays around 220-230. I dont beleive the incoming air is enough to keep it cool when driving but i cant hear the fan when driving so im assuming its on. Is there a way to test the fan manually? Is it supposed to come on at different temps when idling and driving? The wiring is sound so i dont beleive its a bad connection. We live in Arizona so the ambient tempature is always between 90-115 degrees outside. If thers an air bubble in the block would that keep the fan from turning on? What do you guys think?

[This message has been edited by Riggster (edited June 19, 2005).]

[This message has been edited by Riggster (edited June 19, 2005).]

First thing I'd do though it change the t-stat. It's ~$4. Get a 195* though. Anything lower and the ECM won't want to go into closed loop mode.

The temp switch that kicks the fan on might be going out. It doesn't happen to often, but it can happen. I wouldn't suspect the relay for the fan switch because it isn't temp sensative.

Keep in mind that 200*-220* is normal operation temp for those cars. So until you're getting into the red I don't know if I'd worry a whole lot.

Oh. If the car has A/C unplug the black plug (closest to the front/pass side) and then turn on the A/C. It'll kick the fan on but won't kick the compressor on.

You can drive around with it like that to check to see if it is actually doing it's job.

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350CID, Vortec 062 heads, Magnum 280, Performer Intake, Holley 650 DP, 3.42 rear w/ Auburn posi, 2600 Stall/TC
"Things are more like they are now than they ever were before."
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[This message has been edited by AJ_72 (edited June 19, 2005).]

Also look under the front nose and make sure the air dam is still there.

They hang pretty low and can get ripped off by speed bumps, etc.

Those third gen cooling setups get complicated. Might want to check out a dedicated third gen site and this one is a good one:

http://www.thirdgen.org/techbb2/forumdisplay.php?s=&forumid=49

Lots of experience with that particualar model- including a 92 RS I own now.

There are only 2 ways the (single) fan can turn on:

1. You turn on the A/C.

2. The temperature switch screwed into the pass. side cylinder head between the #6 & #8 spark plugs reaches it's turn-on temp, grounds the wire attached to it and turns on the fan. The ECM CAN NOT activate the fan on these single-fan cars (but they can on the TPI cars with dual fans).

There is a relay that actually supplies the high-amp power to the fan itself. It's triggered by the A/C switch or temp switch, above. It's one of the 3 relays located on the firewall over by the brake booster. I forget which but I could look at mine tonight if you want. (FYI- this also makes a convenient tap-in point for installing a manual fan turn-on switch).

Stock turn-on temp for the factory fan swtich is 228*F. REALLY HIGH, and I have found the gagues often read even higher than actual on most 3rd gens when you get up over 200* ACTUAL engine temp. Aftermarket units are available from Hypertech and other with lower turn-on temps and are a sensible upgrade if matched with a lower temp thermostat. A 195* stat is stock. 180* and even 160* stats are just fine even with the computer controls and the engine most definitely WILL go into closed loop at anything over 100*F- well below the temperature of even a 160* stat- if the O2 sensor is up to operating temperature (measued by the ECM by the number of 02 sensor "crosscounts"). I usually use a 180* unit in most of my 3rd gens.

You can test your factory temp/fan switch by simply unplugging the single wire connector attached to it and grounding the wire to something while the ignition key is in the "On" position. Fan should immeditately fire up. That will at least prove that everything else in the system IS working, aside from the fan temp switch.

I highly recommend you also replace the OTHER temperature sender that works the temp gague in the dash. It's also a single wire unit and is located in the driver's side cylinder head between plugs #1 & #3. This can sometimes make the stock gague give more "sane" temperature readings. Sometimes (often) the stupid, inaccurate factory gague simply isn't calibrated correctly and nothing you do will make it read right. If you have access to a scan tool you can get TRUE engine temp readings that are supplied to the ECM by a THIRD temp sender mounted on the intake manifold next to the thermostat housing (it's a 2 wire unit called the Coolant Temp Sender and supplies information ONLY to the ECM).

Last things......

1. You MUST MUST MUST have the plastic "chin spoiler" under the radiator support. It must be present, properly attached and in good condition. It is CRITICAL to keeping temps down during highway driving. LOTS of 3rd gen owners have been driven to the gates of insanity by overlooking this simple but critical part.

2. Old radiators are no fun at all. You can get a replacement unit from just about anywhere for under $150 and install it in 2 hours with common hand tools. Isn't it worth your peace of mind? How sure are you that a 2-decade old original radiator is in good shape?

3. Water pump. My RS had overheating problems BAD when I first got it. Found out somebody installed a standard rotation water pump on the car. That's a no-go with a serpentine drive belt setup. Installed a correct reverse-rotation unit I got at Pep Boys for $50 and 80% of my cooling problems vanished, never to return. Again, isn't this worth your peace of mind? You car remove/replace a water pump on these serpentine belt cars without removing ANY other front end accessories- quite handy versus older v-belt cars.



[This message has been edited by Damon (edited June 21, 2005).]