Engine runs hot - Fans don't care
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In the Staging Lanes
Joined: Mar 2009
Posts: 85
From: Colorado
Engine runs hot - Fans don't care
I know there are several posts about overheating, but I haven't found one that yet that fits this description along with I’ve already tried to do to fix it (with possible exception to BadBowTie93’s thread). So, I apologize if this issue has already been addressed and I missed it.
I have a 94' Camaro Z28 automatic and it runs hot because the fans don't turn on. By hot, I mean the temp gauge needle will go deep into the red. When I make the fans come on, the engine does not overheat. I am able to get the fans to run at high speed by removing the air pump fuse, so I know that the fans are operational. When the fans are running in this mode, the needle on the temperature gauge stays below the half-way mark. Because the temp gauge reads cool when the fans are running, I have concluded that the water pump, thermostat, hoses, head gasket, radiator, radiator cap, coolant, and fans are all in good working order (correct me if I'm wrong here). I believe the problem is that the PCM is simply failing to turn the fans on at the right time. I have already replaced the engine coolant temperature sensor, all three fan relays, checked all of the fuses, and even replaced the temperature gauge sender, in case I was getting a faulty reading. I also attempted to get a temperature reading from the computer by borrowing a scanner from an auto parts store, but the scanners they have around here only display error codes. In addition, I could not get the scanners I’ve used to pull error codes even back when I did have an SES light. I do not own a voltmeter, so I have not been able to test the sockets on the fuse/relay panel. Of note, there is one yellow and one black wire that connect into the engine coolant temperature sensor and the yellow one looks a little beat up. However, I cannot tell whether the yellow wire has been severed or not on the inside. Is there any way to determine if the wires to the temperature coolant sensor are intact without splicing the wires? I haven’t noticed any obvious damage to any other wires. Is there something else I'm missing? Thanks for the help.
Other notes:
- The only modification I have is a K&N cold air intake.
- There are no SES or other warning lights coming on
- I have already drained and replaced the coolant with 50/50 pre-mixed
- The thermostat is a 180 degree and I tested it in a pot of hot water
- I've replaced the radiator cap
- The drive belt is in good condition
- The engine oil and oil filter was replaced about 2,000 miles ago
I have a 94' Camaro Z28 automatic and it runs hot because the fans don't turn on. By hot, I mean the temp gauge needle will go deep into the red. When I make the fans come on, the engine does not overheat. I am able to get the fans to run at high speed by removing the air pump fuse, so I know that the fans are operational. When the fans are running in this mode, the needle on the temperature gauge stays below the half-way mark. Because the temp gauge reads cool when the fans are running, I have concluded that the water pump, thermostat, hoses, head gasket, radiator, radiator cap, coolant, and fans are all in good working order (correct me if I'm wrong here). I believe the problem is that the PCM is simply failing to turn the fans on at the right time. I have already replaced the engine coolant temperature sensor, all three fan relays, checked all of the fuses, and even replaced the temperature gauge sender, in case I was getting a faulty reading. I also attempted to get a temperature reading from the computer by borrowing a scanner from an auto parts store, but the scanners they have around here only display error codes. In addition, I could not get the scanners I’ve used to pull error codes even back when I did have an SES light. I do not own a voltmeter, so I have not been able to test the sockets on the fuse/relay panel. Of note, there is one yellow and one black wire that connect into the engine coolant temperature sensor and the yellow one looks a little beat up. However, I cannot tell whether the yellow wire has been severed or not on the inside. Is there any way to determine if the wires to the temperature coolant sensor are intact without splicing the wires? I haven’t noticed any obvious damage to any other wires. Is there something else I'm missing? Thanks for the help.
Other notes:
- The only modification I have is a K&N cold air intake.
- There are no SES or other warning lights coming on
- I have already drained and replaced the coolant with 50/50 pre-mixed
- The thermostat is a 180 degree and I tested it in a pot of hot water
- I've replaced the radiator cap
- The drive belt is in good condition
- The engine oil and oil filter was replaced about 2,000 miles ago
April 2011 ROTM
Joined: Mar 2009
Posts: 22,015
From: Tokeland, Washington
ROTM Winner's Club
well did using that artical u posted help any? there is some good suff in there. u may want to pick up a dealer shop/service manusl for your yr and make. they help alot and are 100 times better than a aftermarket books.
Thread Starter
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In the Staging Lanes
Joined: Mar 2009
Posts: 85
From: Colorado
Lengthy Multimeter Test Results
I bought a multimeter and tested voltage and continuity for the connector/wiring on the engine coolant temperature (ECT) sensor, the fuse box relays, and the sockets for the three fan relays in the fuse/relay panel. I based the voltage and continuity tests off of the troubleshooting tips from the shbox website and my Haynes repair manual. After performing these tests, I think the connector/wiring for the ECT is okay, but I’m not sure about the readings I got for the relays or the fuse/relay panel. My results are below and I tried to explain what I did in case I did it wrong.
Engine coolant temperature sensor connector results:
According to shbox’s website, the engine coolant temperature sensor connector should read 5v with the ignition on. I got 4.98v when putting the red meter test lead on the connector for the yellow wire and the black meter test lead on the connector for the black wire. I got 5.02v when putting the red meter test lead on the connector for the yellow wire and the black meter test lead on the engine. When putting the red meter test lead on the connector for the black wire and the black meter test lead on the engine, I got 0.04v. I got the exact same readings when testing the IAT sensor, which the shbox website said would be the same. I was unable to get readings from the ECT sensor itself, but it is new and I doubt both the old one and the new one are bad.
Fan relay test results:
I pulled out all three fan relays in addition to the other three relays of the same type. I think the ABS relay was the only one that was different so I didn’t test it. All six relays produced the exact same results. Per the Haynes Repair Manual, the following continuity tests should be performed on the fan relays.
See attachment at bottom for the numbering scheme for the terminals.
Continuity Test 1: Remove cooling fan relay number 1. There should be no continuity between terminal 1 and terminal 4.
Test Result: No continuity
Continuity Test 2: Apply power to terminal 5 and ground terminal 2 then, test continuity again for terminal 1 and terminal 4. There should now be continuity.
Test Result: I don’t know how to apply power to terminal 5 while testing two other terminals at the same time. Are the relays supposed to be removed from the fuse/relay panel during this test?
Continuity Test 3: An additional test for relay number 3 involves testing for continuity between terminals 3 and 4 when no power is applied to the relay. There should be no continuity.
Test Result: With the relay removed from the fuse/relay panel there was continuity between terminals 3 and 4 and this was the case for all six relays I tested. I wonder if the manual meant to say terminals 1 and 3 because none of them had continuity between those terminals. Is the relay supposed to be removed for this test?
Fuse/Relay Panel Test Results:
See attachment at bottom for the numbering scheme for the sockets.
Voltage test: Test the number 1 socket on the fuse/relay panel for each relay. There should be power at all times, probing with a grounded test light. The number 5 socket should have power only with the key on.
Test Results: I tested voltage on the sockets for all of the three cooling fan relays by putting the red meter test lead in each of the sockets and putting the black meter test lead on the engine. One of the problems I ran into was that the sockets were numbered on the fuse/relay panel and these numbers were different than the numbers on the fuse relay diagram in the Haynes manual. The readings I got are listed below and I used the number scheme from the fuse/relay panel (same as blue diagram above).
Fan Relay 1:
Socket 1 = 12.06v (with ignition on); 12.32v (with ignition off)
Socket 5 = 11.38v only with ignition on
No other sockets had power
Fan Relay 2:
Socket 2 = 11.35v only with ignition on
Socket 4 = 12.06v (with ignition on); 12.34v (with ignition off)
No other sockets had power
Fan Relay 3:
Socket 2: 11.44v only with ignition on and fan relay 2 plugged in
Socket 5: 11.47v only with ignition on
No other sockets had power with ignition on and none had power with ignition off
Sources:
http://shbox.com/1/4th_gen_tech2.html#cooling
Haynes Repair Manual for Camaro and Firebirds 1993-2002 all models, pages 3-3, 3-4
Engine coolant temperature sensor connector results:
According to shbox’s website, the engine coolant temperature sensor connector should read 5v with the ignition on. I got 4.98v when putting the red meter test lead on the connector for the yellow wire and the black meter test lead on the connector for the black wire. I got 5.02v when putting the red meter test lead on the connector for the yellow wire and the black meter test lead on the engine. When putting the red meter test lead on the connector for the black wire and the black meter test lead on the engine, I got 0.04v. I got the exact same readings when testing the IAT sensor, which the shbox website said would be the same. I was unable to get readings from the ECT sensor itself, but it is new and I doubt both the old one and the new one are bad.
Fan relay test results:
I pulled out all three fan relays in addition to the other three relays of the same type. I think the ABS relay was the only one that was different so I didn’t test it. All six relays produced the exact same results. Per the Haynes Repair Manual, the following continuity tests should be performed on the fan relays.
See attachment at bottom for the numbering scheme for the terminals.
Continuity Test 1: Remove cooling fan relay number 1. There should be no continuity between terminal 1 and terminal 4.
Test Result: No continuity
Continuity Test 2: Apply power to terminal 5 and ground terminal 2 then, test continuity again for terminal 1 and terminal 4. There should now be continuity.
Test Result: I don’t know how to apply power to terminal 5 while testing two other terminals at the same time. Are the relays supposed to be removed from the fuse/relay panel during this test?
Continuity Test 3: An additional test for relay number 3 involves testing for continuity between terminals 3 and 4 when no power is applied to the relay. There should be no continuity.
Test Result: With the relay removed from the fuse/relay panel there was continuity between terminals 3 and 4 and this was the case for all six relays I tested. I wonder if the manual meant to say terminals 1 and 3 because none of them had continuity between those terminals. Is the relay supposed to be removed for this test?
Fuse/Relay Panel Test Results:
See attachment at bottom for the numbering scheme for the sockets.
Voltage test: Test the number 1 socket on the fuse/relay panel for each relay. There should be power at all times, probing with a grounded test light. The number 5 socket should have power only with the key on.
Test Results: I tested voltage on the sockets for all of the three cooling fan relays by putting the red meter test lead in each of the sockets and putting the black meter test lead on the engine. One of the problems I ran into was that the sockets were numbered on the fuse/relay panel and these numbers were different than the numbers on the fuse relay diagram in the Haynes manual. The readings I got are listed below and I used the number scheme from the fuse/relay panel (same as blue diagram above).
Fan Relay 1:
Socket 1 = 12.06v (with ignition on); 12.32v (with ignition off)
Socket 5 = 11.38v only with ignition on
No other sockets had power
Fan Relay 2:
Socket 2 = 11.35v only with ignition on
Socket 4 = 12.06v (with ignition on); 12.34v (with ignition off)
No other sockets had power
Fan Relay 3:
Socket 2: 11.44v only with ignition on and fan relay 2 plugged in
Socket 5: 11.47v only with ignition on
No other sockets had power with ignition on and none had power with ignition off
Sources:
http://shbox.com/1/4th_gen_tech2.html#cooling
Haynes Repair Manual for Camaro and Firebirds 1993-2002 all models, pages 3-3, 3-4
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