New vette owner, over heating problems!
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
New vette owner, over heating problems!
Hey guys,
I recently got a 79 vette on trade for another car i had built. This is my first vette and i absolutely love the car. I’ve been reading the forums on the common issues on em and after some research i thought i had my heat issue under wraps.
I have a crate 350 that was replaced roughly 20k miles ago by previous owner, only know mods were a holly intake and a few chrome pieces under the hood. When i got the car i noticed it was running hot, 220+ so i immediately went to the internet to see what other owners were saying. I ended up replacing the stock radiator with a 4 row aluminum champion radiator and removed the stock cooling fan and replaced with dual 10” electric pull fans on a relay that kick on at 180 degrees. I changed the thermostat to a 160 AC/Delco and had the entire cooling system flushed. I picked the car up today from the mechanic and for the first part of the 30 Min car ride home it stayed at or under 200 degrees. I made one stop for 10 min and after leaving got caught in some mild traffic and by the time i pulled into my drive way (10-15 Min later) that car was back up to 220. I’m in Florida and it is 95 degreeses today (in the shade) but i didn’t have the AC running.
Prior to going to my mechanic for the radiator i replaced the temperature sending unit and the temperature gauge so i would have the most “accurate” reading and could narrow down the issue. Could it be a water pump issue or the wrong thermostat thats causing it to run hot? I’m scared to use the “h” word but could it also be the head gasket? Oil is clean but i know there’s other ways it can blow.. car runs great and has plenty of power, just won’t stay cool.
any and all help would be greatly appreciated!!
I recently got a 79 vette on trade for another car i had built. This is my first vette and i absolutely love the car. I’ve been reading the forums on the common issues on em and after some research i thought i had my heat issue under wraps.
I have a crate 350 that was replaced roughly 20k miles ago by previous owner, only know mods were a holly intake and a few chrome pieces under the hood. When i got the car i noticed it was running hot, 220+ so i immediately went to the internet to see what other owners were saying. I ended up replacing the stock radiator with a 4 row aluminum champion radiator and removed the stock cooling fan and replaced with dual 10” electric pull fans on a relay that kick on at 180 degrees. I changed the thermostat to a 160 AC/Delco and had the entire cooling system flushed. I picked the car up today from the mechanic and for the first part of the 30 Min car ride home it stayed at or under 200 degrees. I made one stop for 10 min and after leaving got caught in some mild traffic and by the time i pulled into my drive way (10-15 Min later) that car was back up to 220. I’m in Florida and it is 95 degreeses today (in the shade) but i didn’t have the AC running.
Prior to going to my mechanic for the radiator i replaced the temperature sending unit and the temperature gauge so i would have the most “accurate” reading and could narrow down the issue. Could it be a water pump issue or the wrong thermostat thats causing it to run hot? I’m scared to use the “h” word but could it also be the head gasket? Oil is clean but i know there’s other ways it can blow.. car runs great and has plenty of power, just won’t stay cool.
any and all help would be greatly appreciated!!
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
Hey mike thanks for responding, yes it was full when i picked up the car. I just checked it after about an hr or so of it sitting and it was half way between hot and cold levels in the expansion tank.
Race Director
Joined: Mar 2016
Posts: 14,332
Likes: 8,139
From: Napa Valley California
But 220 might be a little high with the new 4 core aluminum radiator.My all stock 73 454 runs 220+ on warm days and traffic.
Is the OEM air dam still installed under the front grille?
There could also be air trapped in the cooling system.
There are several threads on how to get the air out.
One simple method is to drill a small hole in the thermostat.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
If that fan relay is adjustable, I would have it come on a whole lot lower than 180*. It won't change the maximum temp but the fans should be cooling sooner, like 140*. ( A clutch fan starts cooling way before that). That's the thing about electric fans. When they are not running they are doing nothing but blocking air movement.
You stopped for 10 mins, temps went up. Your cooling system is not getting enough air through it. Some people are comfortable with 220*. That's too close to the red zone for my liking.
There is an old saying:
Overheat at idle is an "air" circulation issue.
Overheat at speed is an "water" circulation issue.
You stopped for 10 mins, temps went up. Your cooling system is not getting enough air through it. Some people are comfortable with 220*. That's too close to the red zone for my liking.
There is an old saying:
Overheat at idle is an "air" circulation issue.
Overheat at speed is an "water" circulation issue.
Last edited by HeadsU.P.; Sep 18, 2018 at 05:50 PM.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
Thanks guys,
I do have the stock air dam in the front. The mechanic stopped by on his way home and checked the cooling system for air and it appeared there wasn’t any. We bypassed the fan relay and had them on the entire time the car was running. I think I’m just going to wire them to the ignition and let run entire time car is. We idled it in my driveway for 30 minutes and monitored the temp with a gun. Nowhere on the motor got above 187 degrees (other than the exhaust manifolds). The radiator never got over 120 degrees and the gooseneck never got over 180. I did add some super line coolant enhancer to the radiator before i started it.
I’m guessing faulty gauge, even tho it’s new, faulty temp sensor or the temp sensor is picking up some of the exhaust manifold temps??
i really appreciate all the input, you guys are great. I’m hoping this is my first of many vettes!
I do have the stock air dam in the front. The mechanic stopped by on his way home and checked the cooling system for air and it appeared there wasn’t any. We bypassed the fan relay and had them on the entire time the car was running. I think I’m just going to wire them to the ignition and let run entire time car is. We idled it in my driveway for 30 minutes and monitored the temp with a gun. Nowhere on the motor got above 187 degrees (other than the exhaust manifolds). The radiator never got over 120 degrees and the gooseneck never got over 180. I did add some super line coolant enhancer to the radiator before i started it.
I’m guessing faulty gauge, even tho it’s new, faulty temp sensor or the temp sensor is picking up some of the exhaust manifold temps??
i really appreciate all the input, you guys are great. I’m hoping this is my first of many vettes!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Racer
Joined: Apr 2009
Posts: 330
Likes: 44
From: Cincinnati Ohio
I had similar issues, finally changed to the high flow Edelbrock water pump. It solved the problem on both my 73 and 76. I think there is a fine line between increasing flow and getting it moving too fast so it doesn't have time to get cooled in the radiator. You have a big radiator so it should cool. On my 37 Chevrolet with a big block, I had issues with fan shroud restricting air flow, the openings with flaps weren't big enough. I ended up cutting slot in fan shroud to increase air flow underway.
Tech Contributor
Joined: Jun 2004
Posts: 20,857
Likes: 959
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Hey guys,
I recently got a 79 vette on trade for another car i had built. This is my first vette and i absolutely love the car. I’ve been reading the forums on the common issues on em and after some research i thought i had my heat issue under wraps.
I have a crate 350 that was replaced roughly 20k miles ago by previous owner, only know mods were a holly intake and a few chrome pieces under the hood. When i got the car i noticed it was running hot, 220+ so i immediately went to the internet to see what other owners were saying. I ended up replacing the stock radiator with a 4 row aluminum champion radiator and removed the stock cooling fan and replaced with dual 10” electric pull fans on a relay that kick on at 180 degrees. I changed the thermostat to a 160 AC/Delco and had the entire cooling system flushed. I picked the car up today from the mechanic and for the first part of the 30 Min car ride home it stayed at or under 200 degrees. I made one stop for 10 min and after leaving got caught in some mild traffic and by the time i pulled into my drive way (10-15 Min later) that car was back up to 220. I’m in Florida and it is 95 degreeses today (in the shade) but i didn’t have the AC running.
Prior to going to my mechanic for the radiator i replaced the temperature sending unit and the temperature gauge so i would have the most “accurate” reading and could narrow down the issue. Could it be a water pump issue or the wrong thermostat thats causing it to run hot? I’m scared to use the “h” word but could it also be the head gasket? Oil is clean but i know there’s other ways it can blow.. car runs great and has plenty of power, just won’t stay cool.
any and all help would be greatly appreciated!!
I recently got a 79 vette on trade for another car i had built. This is my first vette and i absolutely love the car. I’ve been reading the forums on the common issues on em and after some research i thought i had my heat issue under wraps.
I have a crate 350 that was replaced roughly 20k miles ago by previous owner, only know mods were a holly intake and a few chrome pieces under the hood. When i got the car i noticed it was running hot, 220+ so i immediately went to the internet to see what other owners were saying. I ended up replacing the stock radiator with a 4 row aluminum champion radiator and removed the stock cooling fan and replaced with dual 10” electric pull fans on a relay that kick on at 180 degrees. I changed the thermostat to a 160 AC/Delco and had the entire cooling system flushed. I picked the car up today from the mechanic and for the first part of the 30 Min car ride home it stayed at or under 200 degrees. I made one stop for 10 min and after leaving got caught in some mild traffic and by the time i pulled into my drive way (10-15 Min later) that car was back up to 220. I’m in Florida and it is 95 degreeses today (in the shade) but i didn’t have the AC running.
Prior to going to my mechanic for the radiator i replaced the temperature sending unit and the temperature gauge so i would have the most “accurate” reading and could narrow down the issue. Could it be a water pump issue or the wrong thermostat thats causing it to run hot? I’m scared to use the “h” word but could it also be the head gasket? Oil is clean but i know there’s other ways it can blow.. car runs great and has plenty of power, just won’t stay cool.
any and all help would be greatly appreciated!!
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
There is no fine line. You can't make water move too fast. The faster it is moving, the higher the temp diff between block and coolant and between coolant and radiator. Higher temp diff equals more heat transfer.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
do you think the stage 3 pump is over kill? Ecklers has a Stewart stage 1 hi-flo cast iron water pump that seems reasonable and doesn’t mention requiringe a hi flow thermostat. I plan on using the car a lot so i want it reliable and would love to get some longevity out of it.
Race Director
Joined: Mar 2017
Posts: 11,930
Likes: 4,497
From: Virginia
I'd make sure you have a cooling problem before you throw more money at a problem you might not have. Do an at-load test, and either instrument your engine compartment with a known digital thermometer, or pull over and get IR readings periodically. On a 90 degree evening, my 79 will reach steady state on the highway at about 180 degrees (as measured by a thermocouple taped to the upper radiator hose). Parked with the engine off, that will climb quickly to 200 or 210 degrees. This is a stock L48, with stock components, auto trans. I'm pretty sure of the timing, though. If you have a digital timing light, it is worth checking.
Does your car ping under load, or run-on (diesel) after turning off the ignition?
Does your car ping under load, or run-on (diesel) after turning off the ignition?
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
I would have to ask why are you running a 160* stat? Stock for a stock motor is 195*. Your motor will not run any cooler with the 160* stat installed. When it opens it's flowing wide open, it opens sooner before the motor is warmed up that's all. Your motor will only run as cool as it's going to run once the stat is fully open. So, if your system is working correctly, it should stay around 185*-190*, but 195* is fine. 220* to me as well is too hot for a Gen I motor IMO and I would keep my eye on the gauge since you are rather close to overheating the motor and maybe warping the heads if that happens.
Also, is it getting hotter at idle or while cruising? If at idle, you are not drawing enough air flow through the radiator. If while cruising it does not get cooler, you have other cooling system issues or indications. Like mentioned, use an IR gun at the stat housing to see if it matches the gauge or is even close. If you replaced the water pump, I would make sure you installed the correct pump shaft length which may put the fun deeper into the shroud if too long and cause the motor to run hotter since it will not draw the air through the radiator effectively and just cavitate the air. The correct fan depth will be 1/2 the fan blade width sticking out from the edge of the shroud. GL with your cooling and hope this helps a little.
Also, is it getting hotter at idle or while cruising? If at idle, you are not drawing enough air flow through the radiator. If while cruising it does not get cooler, you have other cooling system issues or indications. Like mentioned, use an IR gun at the stat housing to see if it matches the gauge or is even close. If you replaced the water pump, I would make sure you installed the correct pump shaft length which may put the fun deeper into the shroud if too long and cause the motor to run hotter since it will not draw the air through the radiator effectively and just cavitate the air. The correct fan depth will be 1/2 the fan blade width sticking out from the edge of the shroud. GL with your cooling and hope this helps a little.
Last edited by Buccaneer; Sep 19, 2018 at 02:06 AM.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
I'd make sure you have a cooling problem before you throw more money at a problem you might not have. Do an at-load test, and either instrument your engine compartment with a known digital thermometer, or pull over and get IR readings periodically. On a 90 degree evening, my 79 will reach steady state on the highway at about 180 degrees (as measured by a thermocouple taped to the upper radiator hose). Parked with the engine off, that will climb quickly to 200 or 210 degrees. This is a stock L48, with stock components, auto trans. I'm pretty sure of the timing, though. If you have a digital timing light, it is worth checking.
Does your car ping under load, or run-on (diesel) after turning off the ignition?
Does your car ping under load, or run-on (diesel) after turning off the ignition?
i have same set up, auto with L48, other than the Holley intake and now radiator/fans car is bone stock, I’m going to run it today and stop periodically and hit it with IR gun to see what temp it is actually running. After iidling for almost a half hr in the driveway yesterday evening it didn’t overheat. The IR gun never showed a temp over 185. My gauge tho was showing 200 then up to 220. But IR gun was showing nothing over 185 no matter where i pointed it on the engine. That also wasn’t under any load. My exhaust manifolds tho on the other hand were reading close to 400* +. I just installed a new temp seasor and it’s located just below the exhaust manifold on the block, could it be picking up some of the heat from them and giving me the false reading?
Race Director
Joined: Mar 2017
Posts: 11,930
Likes: 4,497
From: Virginia
The idle test is promising. Your plan for today should give you some more data, and any excuse to drive your car is a good one. The stock location for the temperature sensor is right on the head as you describe. It should be reading head temperature near/in the coolant passageway at the tip of the sender. I'd suspect your gauge first. You can shoot the IR thermometer close to the head in this location to confirm.
If the rest of your engine compartment is stock 1979 L48, you should have up to three vacuum switches near the front of the engine, two in the water neck and one right next to it, that could be replaced with a temperature sender, though with a Holley Intake you may have already removed one or all of these. Can you post some pictures?
If the rest of your engine compartment is stock 1979 L48, you should have up to three vacuum switches near the front of the engine, two in the water neck and one right next to it, that could be replaced with a temperature sender, though with a Holley Intake you may have already removed one or all of these. Can you post some pictures?
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
The idle test is promising. Your plan for today should give you some more data, and any excuse to drive your car is a good one. The stock location for the temperature sensor is right on the head as you describe. It should be reading head temperature near/in the coolant passageway at the tip of the sender. I'd suspect your gauge first. You can shoot the IR thermometer close to the head in this location to confirm.
If the rest of your engine compartment is stock 1979 L48, you should have up to three vacuum switches near the front of the engine, two in the water neck and one right next to it, that could be replaced with a temperature sender, though with a Holley Intake you may have already removed one or all of these. Can you post some pictures?
If the rest of your engine compartment is stock 1979 L48, you should have up to three vacuum switches near the front of the engine, two in the water neck and one right next to it, that could be replaced with a temperature sender, though with a Holley Intake you may have already removed one or all of these. Can you post some pictures?
here’s two pics, i think those vacuum switches have been long removed. The sensor coming out of the gooseneck is for the fan relay.
Le Mans Master
Joined: May 2006
Posts: 9,993
Likes: 1,136
From: League City Tx
What temp does it run when going down the road at 40-50 mph?
Maybe your fans just don't pull enough cfm but....a basic 350 should be plenty easy to keep cool with a big aluminum radiator and a good fan setup.
Zirgo makes a good 180* temp switch if you want to turn your fans on a little sooner. I use this switch, I have it in the radiator tank and it switches on about 186-187* and turns off at 178*.
I never see over 190* during the summer with the AC on, and that's a big block with iron heads.
Maybe your fans just don't pull enough cfm but....a basic 350 should be plenty easy to keep cool with a big aluminum radiator and a good fan setup.
Zirgo makes a good 180* temp switch if you want to turn your fans on a little sooner. I use this switch, I have it in the radiator tank and it switches on about 186-187* and turns off at 178*.
I never see over 190* during the summer with the AC on, and that's a big block with iron heads.
Last edited by ajrothm; Sep 19, 2018 at 08:56 AM.
Thread Starter
Intermediate
Joined: Sep 2018
Posts: 30
Likes: 1
From: Merritt Island FL
The fans are 1530 CFM each, i don’t know what temp it’s actually running as I’m suspecting the brand new gauge isn’t reading correctly. I’m going to run it today and check the engine temp with the IR gun and compare with gauge.