1996 LT4 Runs Hot...I think
10-10-2014, 02:38 PM
#1
Melting Slicks
Thread Starter
1996 LT4 Runs Hot...I think
What temps should the stock fans turn and off at? I noticed that both fans turn on and off at the same time as well. I read in other posts that the fans operate independently from each other (one on temp switch and the other by ECM) My digital gauge doesn't match the analog and reads lower but still seems high. I have an infra red temp meter and when focused at the area near the temp sensor located in the front of the water pump, the fan ON temp is around 210F and Off is around 195F. The digital gauge shows about 10F higher and the analog shows about 20F higher.
Thanks.
Thanks.
10-10-2014, 03:24 PM
#2
Safety Car
Temps seem ok..... 1 fan on at about 228, both on about 236.... off about 218.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
10-10-2014, 03:39 PM
#3
Race Director
Temps seem ok..... 1 fan on at about 228, both on about 236.... off about 218.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
10-10-2014, 03:39 PM
#4
Melting Slicks
Thread Starter
Temps seem ok..... 1 fan on at about 228, both on about 236.... off about 218.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
Digital temp sensor (water pump) is the only one that matters to the
ECM..... analog (pass. side head) just moves the needle in the analog dash gage.
When was the last coolant flush (including removing the knock sensors)? A thorough flush can reduce temps 5 - 10 deg.
There seems to be an issue then with both fans turning on at the same time then. If it is the ECM making the decisions regarding both fans, not sure what the issue could be.
Just checked it again, both fans turn on when the digital T-stat reaches 235ish.
Last edited by KJL; 10-10-2014 at 05:00 PM.
10-10-2014, 08:02 PM
#5
Safety Car
Not sure what you mean: "both fans turn on when the digital T-stat reaches 235ish." May just be an incorrect reference. You may have meant: when the digital gage reaches 235ish. The tstat (not digital, nor analog) just opens as designed (i.e.195 deg)..... it is just a valve that opens and closes according to coolant temp. The tstat has no connection to fan activation. The digital temp sensor 'tells'
the ECM how hot it is, and the ECM activates the fan(s).
10-10-2014, 08:10 PM
#6
Le Mans Master
Your first fan should go on at 228, 235 is too high. Like Seabright said the po may have them wired to go on together. I did the same thing because when racing I want it to cool down quicker.
10-10-2014, 08:17 PM
#7
Race Director
The needle on the analog gauge will be very close too (but not quite into) the shaded area on the gauge, when your digital temp gauge reads in the 227°F range.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
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Jimhry (07-09-2023)
10-10-2014, 11:16 PM
#8
Melting Slicks
Thread Starter
It is possible the the previous owner rewired the fans.
Not sure what you mean: "both fans turn on when the digital T-stat reaches 235ish." May just be an incorrect reference. You may have meant: when the digital gage reaches 235ish. The tstat (not digital, nor analog) just opens as designed (i.e.195 deg)..... it is just a valve that opens and closes according to coolant temp. The tstat has no connection to fan activation. The digital temp sensor 'tells'
the ECM how hot it is, and the ECM activates the fan(s).
Not sure what you mean: "both fans turn on when the digital T-stat reaches 235ish." May just be an incorrect reference. You may have meant: when the digital gage reaches 235ish. The tstat (not digital, nor analog) just opens as designed (i.e.195 deg)..... it is just a valve that opens and closes according to coolant temp. The tstat has no connection to fan activation. The digital temp sensor 'tells'
the ECM how hot it is, and the ECM activates the fan(s).
10-10-2014, 11:30 PM
#9
Melting Slicks
Thread Starter
The needle on the analog gauge will be very close too (but not quite into) the shaded area on the gauge, when your digital temp gauge reads in the 227°F range.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
10-11-2014, 01:14 AM
#10
Burning Brakes
The needle on the analog gauge will be very close too (but not quite into) the shaded area on the gauge, when your digital temp gauge reads in the 227°F range.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
1996 factory fan settings:
The PCM will command low speed fans ON at
104°C (219°F) and OFF at 98°C (207°F) and, high
speed fans ON at 109°C (228°F) and OFF at 103°C (214°F)
Note: On the '96, both fans run together (either low or high).
Also, Running the A/C will cause the fans to run.
10-12-2014, 07:07 PM
#11
10-13-2014, 05:01 PM
#12
Melting Slicks
Yes; Rollo left that piece of info out. When the A/C is turned on the fans run at low speed, until the [High side] refrigerant, pressure exceeds 2** psi I don't remember that exact value, so yes; the engine tends to run a more constant temperature with the A/C turned on.
10-13-2014, 08:31 PM
#13
Instructor
hot engine
What temps should the stock fans turn and off at? I noticed that both fans turn on and off at the same time as well. I read in other posts that the fans operate independently from each other (one on temp switch and the other by ECM) My digital gauge doesn't match the analog and reads lower but still seems high. I have an infra red temp meter and when focused at the area near the temp sensor located in the front of the water pump, the fan ON temp is around 210F and Off is around 195F. The digital gauge shows about 10F higher and the analog shows about 20F higher.
Thanks.
Thanks.
My intention to buy this car was drag racing, so I wanted it to run
cooler. In my case I did two things.
1 - I put in a 160 degree thermostat
2- bought a hypertech programer, on of the PCU adjustments
there is for the fan on and off time.
With this combination of these two things, my temp now runs between
180 and 190 degrees.
Putz
10-15-2014, 11:37 PM
#14
[QUOTE=KJL;1588014664]Just installed a new Dewitts aluminum radiator about a year ago.
Hi, my 90' c4 likes to run hot while driving in town when the outside temp. is 90 or above. Did the aluminum radiator help any....it gets frighting hot...240 or more in stop n go traffic..thx
Hi, my 90' c4 likes to run hot while driving in town when the outside temp. is 90 or above. Did the aluminum radiator help any....it gets frighting hot...240 or more in stop n go traffic..thx
10-16-2014, 07:52 AM
#15
Melting Slicks
Thread Starter
[QUOTE=azmark6corvettes;1588052497]
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
10-16-2014, 10:50 AM
#16
Burning Brakes
[QUOTE=KJL;1588053490]
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
The problem is Airflow or, lack thereof. When sitting in traffic, if your fans aren't on, there is no airflow across the radiator. C1 - C3 Corvettes had a fan belt which turned a mechanical fan at engine speed, even at idle. Additionally, anti-freeze is a poor coolant. Water is 140% more efficient at drawing heat from hot surfaces than is modern anti-freeze.
Anti-freeze is designed to keep from freezing and protecting metal parts from corrodiing while also (and, to a lesser degree) acting as a "coolant." However, if you live in a freezing climate, you need the protection it affords. In Florida, where I live, I run 80% filtered water and only 20% anti-freeze, for those few 30° nights. However, I also run two pints of a product called "Hyper Kuhl" from NoRosion.com, which protects my metal parts. That dropped my temps by 5-7 degrees.
BUT... in traffic, my A/C gets turned on to get those fans turning, even when outside air is in the 60's and 70's. My next step is to have my PCM tuned to get those fans on earlier.
(By the way, you can bypass the fan relays and add a switch to manually turn on the fans. However, it throws a "Check Engine Soon" code and, in my '96, lights up my warning panel.)
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
Anti-freeze is designed to keep from freezing and protecting metal parts from corrodiing while also (and, to a lesser degree) acting as a "coolant." However, if you live in a freezing climate, you need the protection it affords. In Florida, where I live, I run 80% filtered water and only 20% anti-freeze, for those few 30° nights. However, I also run two pints of a product called "Hyper Kuhl" from NoRosion.com, which protects my metal parts. That dropped my temps by 5-7 degrees.
BUT... in traffic, my A/C gets turned on to get those fans turning, even when outside air is in the 60's and 70's. My next step is to have my PCM tuned to get those fans on earlier.
(By the way, you can bypass the fan relays and add a switch to manually turn on the fans. However, it throws a "Check Engine Soon" code and, in my '96, lights up my warning panel.)
Last edited by DrDyno; 10-16-2014 at 10:56 AM.
10-16-2014, 08:17 PM
#17
[QUOTE=KJL;1588053490]
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
Oh No...that was the answer to my Hot ?....my mechanic said what if that doesn't fix it...my c5's don't like hot in town traffic either...so I assumed a aluminum rad. was the answer..thx ..before I bought a few of them.
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
10-16-2014, 08:17 PM
#18
[QUOTE=KJL;1588053490]
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
Oh No...that was the answer to my Hot ?....my mechanic said what if that doesn't fix it...my c5's don't like hot in town traffic either...so I assumed a aluminum rad. was the answer..thx ..before I bought a few of them...
Not enough to warrant the cost. I went alum mostly because I hate plastic tanks. Plastic for rads was a dumb idea. I think to get the temps down, I think Preacher has the right idea.
Mine also runs still very hot in traffic when it is 90+. I plan on messing with the fan temps and stat when I am done fix my truck and getting my 72 back on the road.
10-16-2014, 08:22 PM
#19
Burning Brakes
[QUOTE=azmark6corvettes;1588058642]
If he didn't completely flush the cooling system, including pulling the knock sensors out of the engine, he may still have restricted flow, keeping the temperatures up. If you do a search of "DeWitts" in this forum, you'll find lots of guys with excellent results.
10-16-2014, 08:45 PM
#20
[QUOTE=DrDyno;1588058675]
If he didn't completely flush the cooling system, including pulling the knock sensors out of the engine, he may still have restricted flow, keeping the temperatures up. If you do a search of "DeWitts" in this forum, you'll find lots of guys with excellent results.
Yes I have read the Dewitt reviews...& that's why I was sold on the idea to my problem...two core radiator why not...then you said it wasn't worth it ....darn ...I'm confused...lol the c4 needed a water pump & the cooling system was flushed then...the 99' coupe needed a new radiator because the previous owner made it not square... parking curb or something...flushed & cleaned...along with the other 4 they run hot when its Hot outside...all have stock radiators and everything else...the quote from the mechanic was a prewarning if the Dewitt didn't fix it...thx
If he didn't completely flush the cooling system, including pulling the knock sensors out of the engine, he may still have restricted flow, keeping the temperatures up. If you do a search of "DeWitts" in this forum, you'll find lots of guys with excellent results.