redvette1991

My 91 temp really rises in stop and go driving. Higher speed cruising it is in the normal range but slow down where more idling is involved temp gauge gets into the danger zone. I think maybe the passenger side cooling fan might not be kicking in but I'm not quite sure. When does second fan kick in? Does temp gauge have to be pegged before that happens?

billschroeder5842

Of course check and see if the fans are working, but have you checked the cavity between the radiator and the condenser? That area picks up a lot of debris and will really effect your cars heat exchange at low speeds.

Bfenty

There's a very good chance that's part of it. I'm not so sure with the '91 but on my '85 if you ground the relay for the cooling fan it should kick on. You might check that it is-you can drive at highway speeds without a working fan and the engine will stay pretty cool. It's the stop-and-go that you will notice the cooling fan not working.

oldspeedr

Agree with Bill. When I purchased my 1990, that area was full of misc stuff. Really impacted my stop and go temp. I cleaned the a/c condensor, the radiator and cleaned the void between. No more high temp issues. Yes, it get hot idling, but not excessive. I also hose out the void whenever I wash the car. Amazing how much it picks up in 250 miles of driving.

whalepirot

Fans add nothing to cooling airflow above about 35mph. The blockage issue is well discussed on all Corvette boards.

The expert advice I got, when chasing a cooling probelm was, if it's a slow speed issue only, the fans are not doing their job.

Bfenty

One thing I found, the PO on my car had rewired the fan on backwards, so it was actually blowing hot engine air into the radiator rather than pulling in cool outside air. Once I fixed that (just swapping positive and negative wires) it cooled MUCH better.

Tom400CFI

Guys...we need some clarification from the OP before WAGing.

First; is this on the analog gauge? The analog gauge is pretty worthless; it operates like a "cold, warm, hot" idiot light...that looks like it's a gauge. You need to verify actual temps and the easiest way to do that is the digital read out on the DIC/speedo portion of the cluster. (Do '90's provide that info there?)

Second, Coolant fans do not kick on until ABOUT 230*F which on your analog "gauge", will look like it's about hitting 260. Second cooling fan doesn't come on until about 238*F.

At low speed, there is no airflow through the radiator, so naturally, temps will climb....until ~230, when the fan (driver's side only) kicks on. At that point, w/a normally functioning cooling system, the temp gauge will appear to be just kissing the "danger zone".

SO....OP, can you confirm the actual temp at which your one fan is coming on?


.

belairbrian

OP has a 91 so yes the LCD will display coolant temp. Pretty sure 90 will as well.


As stated sitting still will cause temp to rise. After I did break in on my brakes Sunday, I did a little experiment. Pulled in at the house and with walls on left right and front, I sat at idle and watched temp rise. Ambient was 85. Once it hit 212 I turned on A/C. In less than a minute of both fans coming on, temp started to drop. Around 204 I got bored and shut it off.


Did it just to prove to myself that turning on A/C really does drop engine temp. In my youth we were always told to turn off A/C if car was getting hot.

Tom400CFI

In the old days, what you heard was true. The fan was belt driven...essentially it was always running. If you are old enough, it was literally always running (fixed fan). Anyway, no matter the belt driven fan type, there was always a copious amount of airflow over the radiator. Turning on the AC only added to the heat load on the radiator...car would run hotter.

Now days, we have zero airflow over the radiator at a stop...until the engine gets hot enough and the fan comes on...OR you turn the AC on. AC condenser has to have airflow over it to work, so AC on, fan comes on...and now you have airflow over the radiator even if you don't need it.

TBSS/85vette

I found that after I switched to full roller rockers in my 1985 my temps never even get close to hot anymore, even with the AC on and on a hot day. After finding some articles on the how and why it seems the reduction in friction from the stock stamped rockers reduces heat in the engine pretty well. I used PRW full stainless 1.6 by the way.

whalepirot

Amazing how that works!

Some folks should not own tools!

DGXR

Stole the words from my mouth/fingers.

Also, OP you should read this thread (it's a sticky):
https://www.corvetteforum.com/forums...peratures.html