I have a 91 Z28, 305, 5 speed. I installed a 14 inch pusher fan, with a switch, in front of the radiator and the non-AC fan is also controlled with a switch. It is alright when I,m crusing but as soon as I slow down, get in traffic, etc. the temp gauge starts climbing up and over 240 to the 260 range. I plan on installing an oil cooler this winter. Is there any thing else I can do?? This is getting to be a real nuisance.

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• 1991 Z28
• Ultra Metallic Blue
• 305 TPI
• 5 Spd Manual
• 3:08 rear axle

members.fbody.com/rwendt/

 

I have the same car as you do. While not important to your question, both fans are "A/C" fans. The passenger side is controlled by a pressure switch which is "on" when A/C pressure is >232PSI, as well as the coolant temperature switch located btwn cylinders 6 and 8, and the driver's side is controlled by the ECM and also turned "on" by the "A/C" when vehicle speed is <40mph and the A/C control head pressure is > 232psi. The CTS will also tell the ECM what temperature the coolant is and turn it on also.

I have two stock fans and I can easily keep the temperature <200°F (w/o the A/C) using just one fan. But I changed the coolant temperature switch to another one that comes on at 200°F and off at 185°F, along with a 180°F thermostat. I can also control the fans manually with a switch.

I'd suggest you try having a fan "on" all the time. Does the temperature still get >210°F?

If so, remove the thermostat (run without it) and with the fan continuously "on", see what how hot the engine gets.

Also, why did you get another fan (a third?!)?

EDIT:
I re-read your post. I guess that you can have all the fans "on" at the same time since you said that they have a switch. How many fans are there total now?

If you can have the fan(s) on continuously and it still gets that hot, the only thing I can think of is your "pusher" fan is connected backwards, so it's blowing air toward the front. I don't mean to "insult" your intelligence, but I'm just guessing.

Since the temperature is okay at speed, I would think the thermostat is okay - so strike my suggestion to test it without it.

How hot did the car get before you added the "pusher" fan?

[This message has been edited by Stuart Moss (edited August 04, 2001).]

 

RWendt,

I've run into this kind of thing once or twice before. A water pump with a worn impeller can move adequate coolant at higher RPMs but fails miserably at low (idle) speeds. If you are able to open the radiator (when cold) and bring the engine up to temperature, you should be able to see a significant flow in the left radiator tank, even at idle. If not, you may have restrictions in the cooling system or a worn water pump. I had this on a Pontiac once. Several thermostats, hoses, reverse-flushings, flex fans, transmission and engine oil coolers, and a new four-core radiator later, I replaced the water pump and had no more problems.

The impeller can actually erode from cavitation when pumping fluid, and I've seen several remanufactured pumps that have pretty small vanes on the impellers. You can remove the rear cover of any Chevrolet water pump ('cept LT1s) and inspect the impeller for wear/damage.

Just a thought.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

I had a similar problem on my 92 Camaro. I checked everything and found nothing plenty of flow, radiator was clean, thermostat fine. It turned out to be the sender was junk. Find someone with a laser thermometer and have them check it out, I did.