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1995 Camaro z28 fans and cooling issue?

Old 06-13-2019, 05:45 PM
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1995 Camaro z28 fans and cooling issue?

I have a 1995 Camaro z28 with 150k on it and Iíve flushed the coolant a year ago and changed the coolant sensor. Now that Iím living in Arizona Iíve noticed the car runs a lot hotter. The temp gauge at idle goes well past 210 and goes just about up to the third temp gauge line before the ďred zoneĒ. Iím wondering if this is normal. Had my thermostat replaced a few years back because the head gasket blew due to overheating. Normally driving around with no a/c on and plenty of airflow through the radiator the car just barely gets over 180. But at idle it climbs with the ac off. I jacked the car up and let it idle without the ac on and I watched both fans come on but only on low speed. I waited until the temp gauge got up to the third line and thatís when the low speed fans came on. Then it went back down to the middle and stayed there but the high speed fans never came on. When I run my ac I can see that the fans seem to be running at high speed the whole time which makes my car run cooler so I usually run it with the ac on all the time especially since itís summer and 110 out. I bought a JET fan switch PN 60602 which is supposed to turn the fans on sooner but I havenít installed it yet and thought I would post here to see what you guys think.
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Old 06-13-2019, 08:17 PM
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Re: 1995 Camaro z28 fans and cooling issue?

Here's a thread with basically the same issue from about 2 weeks ago:

https://www.camaroz28.com/forums/lt1...solved-887509/
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Old 06-13-2019, 08:37 PM
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Re: 1995 Camaro z28 fans and cooling issue?


This is the temp that it gets up to maybe just a hair higher almost to the 3rd mark before the LOW SPEED fans kick on. Then it brings it back to the middle just about....
Originally Posted by Injuneer View Post
Here's a thread with basically the same issue from about 2 weeks ago:

https://www.camaroz28.com/forums/lt1...solved-887509/
I appreciate it. I read the article and I guess I have to get Download that scan thing and try and read the correct temps. My problem is very similar to his and I donít know really what the issue could be still.

Last edited by 1995camz28; 06-13-2019 at 09:23 PM. Reason: Adding picture
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Old 06-13-2019, 10:52 PM
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Re: 1995 Camaro z28 fans and cooling issue?

As I posted in the other thread, both fans come on low at 226įF. That's just about where the needle is on your dash gauge. If you assume the gauge calibration is linear, the center hash (just below the needle) is 210į. The gauge in the Firebird is marked with that temp. The next one, just above the needle, is 235įF. That's the temp both fans switch to high speed. Given the extreme ambient temp, your reading at idle is not irrational, and is not hurting anything.

And remember, the sensor in the water pump housing communicates with the PCM. The dash gauge reads the sensor in the driver side head. No assurance they both read the same. Shoebox's link to testing the sensors explains how to check the sensors and the electrical circuits.

If you want it to run cooler, get a 160įF thermostat, and have the PCM reprogrammed for lower fan on/off temps.
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Old 06-13-2019, 10:58 PM
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Re: 1995 Camaro z28 fans and cooling issue?

Originally Posted by Injuneer View Post
As I posted in the other thread, both fans come on low at 226įF. That's just about where the needle is on your dash gauge. If you assume the gauge calibration is linear, the center hash (just below the needle) is 210į. The gauge in the Firebird is marked with that temp. The next one, just above the needle, is 235įF. That's the temp both fans switch to high speed. Given the extreme ambient temp, your reading at idle is not irrational, and is not hurting anything.

And remember, the sensor in the water pump housing communicates with the PCM. The dash gauge reads the sensor in the driver side head. No assurance they both read the same. Shoebox's link to testing the sensors explains how to check the sensors and the electrical circuits.

If you want it to run cooler, get a 160įF thermostat, and have the PCM reprogrammed for lower fan on/off temps.

Thank you for the response. I appreciate it. I bought a jet fan switch kit which basically tells the fans to kick on about 15 or so degrees cooler than normal to prevent temps from getting that high. Iíve read mixed things about the fan sensor kit I was wondering your opinion about it? Or would switching out the thermostat and getting the pcm reprogrammed be a better way.
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Old 06-14-2019, 09:40 AM
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Re: 1995 Camaro z28 fans and cooling issue?

If I recall correctly, the fan switch may cause a trouble code/SES light for the fan relay circuit(s) if it isn’t wired up correctly.

Shoebox has the wiring modification diagram for a manual switch. Maybe somehow integrate the thermal switch with that circuitry in place of the manual switch.

http://shbox.com/1/fan_sw_diagram1.jpg

http://shbox.com/1/fan_schematic_1995.jpg

In the above diagram, your 95 has the “late production” 3-relay system. Although that diagram is from the 95 factory service manual, it was incorrectly carried over from the 94 factory manual, which is the model year (94) when the changeover in fan operation was made.

http://shbox.com/1/fan_switch_wires.jpg

If you opt for a 160įF t'stat, and have a tuner change the fan on/off temps in the PCM, he can also play with timing and pick up a bit of HP, and while tuning, can pick up 10-15 additional HP by leaning out the factory programming's overly rich target A/F ratio in Power Enrichment (PE - think of it as heavy/wide open throttle) mode.

Last edited by Injuneer; 06-14-2019 at 09:42 AM.
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Old 06-14-2019, 10:22 AM
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Re: 1995 Camaro z28 fans and cooling issue?

Originally Posted by Injuneer View Post
If I recall correctly, the fan switch may cause a trouble code/SES light for the fan relay circuit(s) if it isnít wired up correctly.

Shoebox has the wiring modification diagram for a manual switch. Maybe somehow integrate the thermal switch with that circuitry in place of the manual switch.

http://shbox.com/1/fan_sw_diagram1.jpg

http://shbox.com/1/fan_schematic_1995.jpg

In the above diagram, your 95 has the ďlate productionĒ 3-relay system. Although that diagram is from the 95 factory service manual, it was incorrectly carried over from the 94 factory manual, which is the model year (94) when the changeover in fan operation was made.

http://shbox.com/1/fan_switch_wires.jpg

If you opt for a 160įF t'stat, and have a tuner change the fan on/off temps in the PCM, he can also play with timing and pick up a bit of HP, and while tuning, can pick up 10-15 additional HP by leaning out the factory programming's overly rich target A/F ratio in Power Enrichment (PE - think of it as heavy/wide open throttle) mode.

I think ill opt opt for the thermostat and get a tune. Whatís the most common way to tune? Iíve heard mail order is the best but since itís an obd1 car Iím wondering whatís the easiest way to tune the fans. The car is my daily driver so I canít exactly take out the pcm and mail it in.
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Old 06-14-2019, 02:28 PM
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Re: 1995 Camaro z28 fans and cooling issue?

There is software available that allows you to make the required changes, and online tips available to tell you how to do it. Here is a site that has a good writeup on what software is available, and how to make changes to your PCM:

LT1 PCM Tuning - About the Tuner


He also offers tuning services, two different ways - 1) you ship your PCM to him, he tunes it and returns it; 2) he writes a tuning file, you rent a self-tuning kit from him, and he emails you the tune. You download it to your PCM via the ALDL connector under the dash.

There are other tuners that will tune a PCM they have in stock, add a core charge and ship you the PCM. You send your old PCM back for refund of the core charge. I don’t know who currently does this, because LT1 tuners are getting harder to find. The guy in the link above (Solomon) is OK for simple changes to stock setups like the fan temps and target A/F ratio in PE mode. I can’t say one way or the other on more demanding stuff like big cams, strokers, forced induction, etc. - I have no first-hand experience.

One caution I would offer..... it is very rare for a PCM to fail in normal service. But it seems like it isn’t that hard to “brick” a PCM while downloading changes, rendering it useless. Again, my early (late 1990’s) efforts at minor changes to the stock LT1 PCM, using lt1_edit software were uneventful. But when we built the stroker, with the huge shot of nitrous, we opted to use a high end aftermarket engine management system, with a much friendlier, open architecture interface.

One other possibility - find a used Hypertech Power Programmer. That will allow you to make simple changes, like fan temps, rear axle ratio, auto trans shift points, rev limiter, speed limiter, etc. using a hand-held device. Must be the model specifically for your 95, and the original owner MUST have returned his PCM to stock using the device. The programmer is locked to a specific VIN, until the “performance” tune is removed and the stock tune reinstalled.

The Hypertech also has a “power program” that can be installed, but it only seems to produce any real, measurable power gains if you opt for the 160į t’stat and lower fan temps. Note that if you buy a 160į t’stat, it must be specifically for the LT1 engine. Most parts shops will try and sell you one for the earlier small block Chevy engine, and it won’t work.

http://shbox.com/1/tstat.jpg
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