I'm really bugged about the temperatures these 3rd gen engines run at. On the highway it never gets hot enough to turn the fan on, but it still runs 15 or 20 degrees hotter than the thermostat (195 F thermostat). My 81Z never gets more than 5 F over the thermostat no matter how hard I run it or how long it sits in traffic. I keep looking for ways to make the fan come on at a lower temp. Does someone make a lower temp. switch that turns the fan on? It's a 305 TPI '86 IROC, by the way.

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Z's r Best

 

JET makes a lower temp fan switch or you can ground out the fans and make them run all the time

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Webmaster: www.IROC-Z.org

 

Z's R,

There are several aftermarket fan controls that can solve your problem. Derale and Hayden offer adjustable fan controls that parallel the existing fan wiring, leaving it completely intact in case the aftermarket control fails.

They are generally about $40.00 and are relatively simple to install. The beauty of the adjustable unit is that if you decide to change the thermostat to a different temperature later, you can adjust the control to match it.

As a second note, since you have an '86 TPI, have you ever checked your ECM PROM? The original PROM shipped with EVERY '86 TPI had some programming defects. There is a TSB on this problem, and GM offers a replacement upgraded PROM for about $50.00. In my case, it was well worth it. The problem was acknowledged in October of 1986 - well after the last '86 model was delivered.

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

 

Hey Z's R Best, scroll down the posts, and you will see a lot more posts on cooling. I have the same problem. And got some real helpful info from the guys here. Like I said there are a lot of posts on cooling, you just might have to scroll a few pages. I just bought a 170 degree thermostat (I ordered it from GM) about 6 dollars, and I ordered a Hypertech fan switch from Summit racing (about 45 dollars) Part # 4028. It turns your fan on at 200 degrees, and off at 185. Much better than the stock switch. There are lots of options. I haven't installed my parts yet, so I am not sure how much better they will cool me down, but I am sure it will be a lot better. I am also considering getting a 4 core Desert cooler radiator for about $230 through "Ames Performance Engineering. Try their website at www.amesperf.com
Take care man
Mike

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Smokin 1989 GTA- Bone stock except for exhaust. (no catalytic-stainless pipe into Flowmaster 2 chamber.

 

My Iroc is the same as yours but 3 years newer - I think something is wrong with yours if you run above thermo temp on the highway. Mine runs right at the lower mark on the guage (190-195 verified with autoxray) on the highway which is right at thermo temp. It runs around 210-220 in traffic but yeah that second fan takes way too long to come on. I think you have another problem though. Do you have an air deflector? Mine has stock water pump and rad (133,000 miles) but new hoses, thermo, cap, and coolant. Just some hopefully helpful advice.

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"Life is pain! Anyone who says differently is selling something."

 

By GM's design our cars do run hot. It is a cheapo attempt by GM to reduce emissions by running a hotter engine.

Your car is running "within" normal op temps by GM standards and with as many post that are on this board about overheating, you're one of the lucky ones........LOL

If you are 15 to 20 degrees above 195 then you are running about 210 to 215 and your fans come on at 234. That's why your fans aren't engaging.

Vader is right. First install a 170/180 thermostat and an adjustable fan switch to lower your overall op temps to a respectable range.

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<FONT SIZE="2" COLOR="red">Red 86 T/A</FONT><FONT SIZE="2"> 5.0 TPI</FONT><FONT SIZE="1"> </FONT><FONT SIZE="2">(LB9/WS6)
~HyperTech Cap/Coil/Rotor/AFPR
~Derale Adjustable Fan Switch ~ 170° Stat
~Flow Matched Injectors ~ K & N Air Filter
~Ported Plenum ~ Pirelli 245/50/16
~SLP TB Airfoil
~All Else Stock</FONT>

<A HREF="http://www.gmtips.com/3rd-degree/"><FONT SIZE="1" FACE="MS Sans Serif"><IMG SRC="http://www.gmtips.com/3rd-degree/cg/3rd-logo.jpg" WIDTH="100" HEIGHT="80" ALIGN="BOTTOM" BORDER="0"></FONT></A>

 

https://www.thirdgen.org/newdesign/tech/cool.shtml

read this and do a search,, there are a lot of posts on cooling issues

 

Thanks for the help. I just recently put in a Hypertech switch (ordered at the same time as the airflow thing - don't remember what it's called - that bolts on the inlet of the throttlebody) but it didn't work. Boiled that sucker over waiting on the fan to come on. You should have seen that expansion tank swelling up and burping hot antifreeze out the top! Don't know why the Hypertech switch didn't work. Checked it with a meter and it never did close. I hooked the stock one back up. Once the fan comes on, you can watch the temps drop like a rock. For the sake of the transmission fluid and oil I'd just like to see the fan come on at lower temps to keep the antifreeze in the radiator cool enough to actually cool the engine down. Thanks again. The adjustable switch sounds like the way to go.

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Z's r Best