94 C4 Overheating
Thread Starter
3rd Gear
Joined: Jul 2022
Posts: 3
Likes: 0
94 C4 Overheating
I am a new corvette owner and previous owner of an NHRA 2002 Trans Am, so this would be my first LT1.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
IB Staff
Joined: Feb 2009
Posts: 10,563
Likes: 4
I am a new corvette owner and previous owner of an NHRA 2002 Trans Am, so this would be my first LT1.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
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1st Gear
Joined: Aug 2022
Posts: 1
Likes: 0
I am a new corvette owner and previous owner of an NHRA 2002 Trans Am, so this would be my first LT1.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
I recently purchased a 94' LT1 and knew it was going to be a bit of work, but after day 1 I'm either missing the "reason for everything" issue, or multiple issues all together. I have the common issues such as my fuel gauge reading incorrectly, though I found it odd that my car smells like it's running extremely rich. It started to smell like everything was burning (No leaks). I know the water pump was replaced as well as optispark. Now onto the issues.
On a cold start, the vehicle will idle as if there is a vacuum leak, revving up to about 1200 and dropping until the vehicle shakes and near-stalls, once I rev the vehicle, there's a bit of a delay, the car "hiccups", revs up, and all is back to normal idling. After driving around for thirty minutes, I noticed my coolant temp was sitting at ~250, at times just barely reaching the line at the 260 mark. This would fluctuate between 240-250. I have no lights on the dash, no codes as of right now.
When getting the vehicle home, it was insanely hot under the hood, I know these vehicles run hot, but this was so hot that after three hours of sitting in my garage, the motor is still too hot to touch. The fans DO kick on while driving, keeping it at a consistent 240-250 while driving it home. The only other thing I noticed is it would appear my power steering pulley is pretty wobbly, feels pretty tight on there but there's a noticeable wobble when the motor is running, maybe the shaft? I've seen someone post in this forum that pulley wobble can be normal?
Coolant levels are fine, though it's definitely boiling in there when the vehicle shuts off for a good thirty minutes or so.
Lastly, my oil pressure will sit comfortably in the mid-section while driving, around that 40-50 mark, and at idle, will sit at ~5-10.
Aside from checking the thermostat and radiator and filters, am I missing one of these "c4 problems" issues? Knowing my fuel gauge is incorrect, is it common for the rest of these gauges to be responding to the drive and just sitting at incorrect numbers, and these lt1's to get this hot and take this long to cool down? Thank you so much for any input.
Team Owner
Joined: May 2004
Posts: 82,175
Likes: 1,319
From: McKinney TX
St. Jude Donor '21-'22-'23-'24
I had the same problems and I changed all kinds of stuff , running out of options I changed the throttle pressure valve on the fuel rail and it fixed all my problems, no gas smell no running roughly no high temp all is great, after spending tons of money the part was 45.00
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Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
Mods - Can you move this to the C4 Tech Forum.
Matoh23 - A normal LT1/LT4 powered C4 will run around 195 degrees on the highway, and will run up to about 230 in traffic. (These numbers are based on the digital temp display - not the gauge). Before going any further - I'd suggest verifying that the numbers are correct with an IR temp "gun" checking the upper rad hose / thermostat housing. Assuming that the temps you are seeing check out - I'll give my standard advice.
Step #1 - Do a full cooling system drain and refill - including pulling the two knock sensors (threaded into the block drain holes). You may be quite surprised with what comes out of those block drains... Refill with a 50/50 mix of distilled water and full strength anti-freeze.
Step #2 - A lot of "crap" can accumulate between the radiator and the condenser. Unfortunately the only way to really deal with this is to remove the radiator and clean out the mess. It's not a fun job and you'll hate the engineer who designed the six little screws that hold the nose of the air duct in place that have to come out to remove the rad. Again - you may be amazed by how much crud can collect in there. I suppose it's possible that you have a thermostat that isn't opening fully - but that is somewhat unlikley (but it's far far far easier to change a thermostat than is is to pull the radiator out).
Matoh23 - A normal LT1/LT4 powered C4 will run around 195 degrees on the highway, and will run up to about 230 in traffic. (These numbers are based on the digital temp display - not the gauge). Before going any further - I'd suggest verifying that the numbers are correct with an IR temp "gun" checking the upper rad hose / thermostat housing. Assuming that the temps you are seeing check out - I'll give my standard advice.
Step #1 - Do a full cooling system drain and refill - including pulling the two knock sensors (threaded into the block drain holes). You may be quite surprised with what comes out of those block drains... Refill with a 50/50 mix of distilled water and full strength anti-freeze.
Step #2 - A lot of "crap" can accumulate between the radiator and the condenser. Unfortunately the only way to really deal with this is to remove the radiator and clean out the mess. It's not a fun job and you'll hate the engineer who designed the six little screws that hold the nose of the air duct in place that have to come out to remove the rad. Again - you may be amazed by how much crud can collect in there. I suppose it's possible that you have a thermostat that isn't opening fully - but that is somewhat unlikley (but it's far far far easier to change a thermostat than is is to pull the radiator out).
IB Staff
Joined: Feb 2009
Posts: 10,563
Likes: 4
Mods - Can you move this to the C4 Tech Forum.
Matoh23 - A normal LT1/LT4 powered C4 will run around 195 degrees on the highway, and will run up to about 230 in traffic. (These numbers are based on the digital temp display - not the gauge). Before going any further - I'd suggest verifying that the numbers are correct with an IR temp "gun" checking the upper rad hose / thermostat housing. Assuming that the temps you are seeing check out - I'll give my standard advice.
Step #1 - Do a full cooling system drain and refill - including pulling the two knock sensors (threaded into the block drain holes). You may be quite surprised with what comes out of those block drains... Refill with a 50/50 mix of distilled water and full strength anti-freeze.
Step #2 - A lot of "crap" can accumulate between the radiator and the condenser. Unfortunately the only way to really deal with this is to remove the radiator and clean out the mess. It's not a fun job and you'll hate the engineer who designed the six little screws that hold the nose of the air duct in place that have to come out to remove the rad. Again - you may be amazed by how much crud can collect in there. I suppose it's possible that you have a thermostat that isn't opening fully - but that is somewhat unlikley (but it's far far far easier to change a thermostat than is is to pull the radiator out).
Matoh23 - A normal LT1/LT4 powered C4 will run around 195 degrees on the highway, and will run up to about 230 in traffic. (These numbers are based on the digital temp display - not the gauge). Before going any further - I'd suggest verifying that the numbers are correct with an IR temp "gun" checking the upper rad hose / thermostat housing. Assuming that the temps you are seeing check out - I'll give my standard advice.
Step #1 - Do a full cooling system drain and refill - including pulling the two knock sensors (threaded into the block drain holes). You may be quite surprised with what comes out of those block drains... Refill with a 50/50 mix of distilled water and full strength anti-freeze.
Step #2 - A lot of "crap" can accumulate between the radiator and the condenser. Unfortunately the only way to really deal with this is to remove the radiator and clean out the mess. It's not a fun job and you'll hate the engineer who designed the six little screws that hold the nose of the air duct in place that have to come out to remove the rad. Again - you may be amazed by how much crud can collect in there. I suppose it's possible that you have a thermostat that isn't opening fully - but that is somewhat unlikley (but it's far far far easier to change a thermostat than is is to pull the radiator out).
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