Running Hot
Thread Starter
7th Gear
Joined: Aug 2013
Posts: 7
Likes: 0
Running Hot
Guys, I'm as green as they come to classic cars, but I just bought a 1977 Corvette. I noticed the faster I drove it, the higher the Temp got. By faster I mean 65mph. It will run around 220 degrees when driving 60-65. Would probably get hotter if I kept that up but I backed off. If I keep it around 50-55 it will stay around 200. I know that's too high. I replaced my thermostat but it stills runs same temp. I was going to order a flex a lite fan, then decided to come here and ask expert opinion first. Help me out please. It is a clutch fan. Thanks.
Pro
Joined: Nov 2008
Posts: 542
Likes: 3
From: Bloomfield Hills MI
First just run it with no thermostat installed. I had an issue with a hi flo water pump and a lo flow thermostat. Installed a high flow stat and works great. Theory is that the high water flow starts to close the stat at higher speeds, or the normal thermostat does not allow enough water to circulate.
As soon as I ran the car with no stat I knew straight away. Temp Never went over 170 even flat out down the fwy. FYI, I have all new Dewitt radiator, seals, clutch fan. Don't install a flex flan unless you like listening to jet engines.....
Also, vac advance not connected correctly can also cause a high temp situation at cruise.
Good luck!
As soon as I ran the car with no stat I knew straight away. Temp Never went over 170 even flat out down the fwy. FYI, I have all new Dewitt radiator, seals, clutch fan. Don't install a flex flan unless you like listening to jet engines.....
Also, vac advance not connected correctly can also cause a high temp situation at cruise.
Good luck!
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,753
From: Charlotte NC
Guys, I'm as green as they come to classic cars, but I just bought a 1977 Corvette. I noticed the faster I drove it, the higher the Temp got. By faster I mean 65mph. It will run around 220 degrees when driving 60-65. Would probably get hotter if I kept that up but I backed off. If I keep it around 50-55 it will stay around 200. I know that's too high. I replaced my thermostat but it stills runs same temp. I was going to order a flex a lite fan, then decided to come here and ask expert opinion first. Help me out please. It is a clutch fan. Thanks.
Because you stated you are "green" to classic cars. I hope that does not mean you are green to automotive service. SO...PLEASE excuse me if I mention "things" that you know already...but I do not know if you know what I am going to mention.
1.) Have you checked the radiator cap and it should be 15 lbs CLOSED SYSTEM.
2.) Have you pressure tested the system. The reason being you can have a small leak high up on the engine and NOT allow the system to build pressure...and thus allow the coolant to steam out. If the leak is lower in the water line area...it would show up on the ground or on the intake manifold.
3.) The heat hose that is attached to the fitting on the intake manifold on the passenger side is where you can check and feel for heat when the engine warms up and if the water pump is actually circulating coolant....which I am sure it is.
4.) Are you sure that you filled the system all the way with the coolant mix??? When the system looses coolant...the coolant passages in the cylinder heads take some time to get filled up and all the air out. This is why I drill A VERY SMALL hole( the size of a hat pin) in the thermostat to allow the air to expel out into the radiator when I am filling it up....and then add coolant to the overflow tank.
5.) Make sure the hose from the radiator to the overflow tank is in good condition. IF you have a hole in it...the system can draw air back into the radiator due to this hose being bad or a hole in it.
6.) 200 degrees is NOT hot. Not by a long shot. And for what it is worth...the ohm to ground value that your temperature sending unit sends to your gauge is so slight when you get to 190 degrees...and goes to 200 degrees...you could be dealing with a bad sending unit. On problematic cars...I install my racing fluid filled gauge which is much more precise to verify what the car is actually doing. The reason I know that 200 degrees is NOT hot. Because the 1985+ Corvettes from the factory with electric cooling fans get to 228 degrees BEFORE the cooling fans come on....and the cooling fans will shut off around 211 (give or take). The AUXILIARY cooling fans come on at or around 256 degrees. SO I REALLY WORRY when the temp rises and keeps rising at or around 260 when the car is driven and the HEATER is on high. Your engine has cast iron heads...unlike the later years with aluminum heads. So these cast iron heads can take the heat. So trying to make your engine run at 180 degrees (for example) all the time is pointless...because trying to get the thermostat and other factors to all work in unison to achieve this is highly unlikely...or if achieved...was time consuming and is not gaining any benefits (in my opinion).
7.) MAKE SURE that you have ALL of the foam seals that go in between the radiator and the radiator support....and any seals between the radiator and shroud. Also any seals that go ON TOP of the radiator support and seals to the underside of the hood. WITHOUT these seals...and due to the angle of the radiator...air will not be as easily directed through the radiator...but instead it will go up, over and around it. Also the lower air dam extension is needed...or air will go under the car...instead of helping direct MORE air into the radiator.
8.) As I was told by a guy who knows/sells coolant systems. A thermostat goes FULLY OPEN 15 degrees ABOVE the rating of the thermostat. SO...a 195 degree thermostat is FULLY OPEN at 210 degrees. WHICH IS STILL NOT HOT enough to be concerned about. When it is full open...the hot water in the engine goes into the radiator...and the cooler water that has been cooling off in the radiator goes into the engine...and when it hits the thermostat...the thermostat shuts off so the hot water in the radiator can begin to cool off again so the cycle can repeat. SO running an engine WITHOUT a thermostat can overheat due to the water never has enough time to cool down and it will keep getting hotter and hotter as time goes by. Not my opinion...but rather a fact due to repairing a car for overheating...and all it needed was to install the removed thermostat.
9.) Also ...by the same guy...he mentioned that the water circulation AT IDLE should not be shooting out of your cooling fins in the radiator at a high rate...if anything...the most it should be is that coolant is coming out of the fins and going HALF the distance of the width of the tank. I am happy if I see a "tranquility fountain" effect when the water is coming out of the fins with the thermostat OPEN.
10.) Last but not least is to service the coolant system completely. Removing the block drains and draining out the coolant from the engine block along with the radiator. When the coolant is out of the radiator...you may be able to look down and see the condition of the coolant fins at the bottom. Sometimes you can not see them due to the transmission cooler being in the way. IF you have doubts in any blockage down low in the radiator which is where it will occur. Remove the radiator and either replace it or have it serviced.
DUB
Thread Starter
7th Gear
Joined: Aug 2013
Posts: 7
Likes: 0
Yes, Im green mechanically. Very green, but thanks for the advice. I will learn all this stuff eventually and figure out what the problems is. Thanks so much for both reply's. I know it will get me to what I need. Thanks guys!
LONG RESPONSE
Because you stated you are "green" to classic cars. I hope that does not mean you are green to automotive service. SO...PLEASE excuse me if I mention "things" that you know already...but I do not know if you know what I am going to mention.
1.) Have you checked the radiator cap and it should be 15 lbs CLOSED SYSTEM.
2.) Have you pressure tested the system. The reason being you can have a small leak high up on the engine and NOT allow the system to build pressure...and thus allow the coolant to steam out. If the leak is lower in the water line area...it would show up on the ground or on the intake manifold.
3.) The heat hose that is attached to the fitting on the intake manifold on the passenger side is where you can check and feel for heat when the engine warms up and if the water pump is actually circulating coolant....which I am sure it is.
4.) Are you sure that you filled the system all the way with the coolant mix??? When the system looses coolant...the coolant passages in the cylinder heads take some time to get filled up and all the air out. This is why I drill A VERY SMALL hole( the size of a hat pin) in the thermostat to allow the air to expel out into the radiator when I am filling it up....and then add coolant to the overflow tank.
5.) Make sure the hose from the radiator to the overflow tank is in good condition. IF you have a hole in it...the system can draw air back into the radiator due to this hose being bad or a hole in it.
6.) 200 degrees is NOT hot. Not by a long shot. And for what it is worth...the ohm to ground value that your temperature sending unit sends to your gauge is so slight when you get to 190 degrees...and goes to 200 degrees...you could be dealing with a bad sending unit. On problematic cars...I install my racing fluid filled gauge which is much more precise to verify what the car is actually doing. The reason I know that 200 degrees is NOT hot. Because the 1985+ Corvettes from the factory with electric cooling fans get to 228 degrees BEFORE the cooling fans come on....and the cooling fans will shut off around 211 (give or take). The AUXILIARY cooling fans come on at or around 256 degrees. SO I REALLY WORRY when the temp rises and keeps rising at or around 260 when the car is driven and the HEATER is on high. Your engine has cast iron heads...unlike the later years with aluminum heads. So these cast iron heads can take the heat. So trying to make your engine run at 180 degrees (for example) all the time is pointless...because trying to get the thermostat and other factors to all work in unison to achieve this is highly unlikely...or if achieved...was time consuming and is not gaining any benefits (in my opinion).
7.) MAKE SURE that you have ALL of the foam seals that go in between the radiator and the radiator support....and any seals between the radiator and shroud. Also any seals that go ON TOP of the radiator support and seals to the underside of the hood. WITHOUT these seals...and due to the angle of the radiator...air will not be as easily directed through the radiator...but instead it will go up, over and around it. Also the lower air dam extension is needed...or air will go under the car...instead of helping direct MORE air into the radiator.
8.) As I was told by a guy who knows/sells coolant systems. A thermostat goes FULLY OPEN 15 degrees ABOVE the rating of the thermostat. SO...a 195 degree thermostat is FULLY OPEN at 210 degrees. WHICH IS STILL NOT HOT enough to be concerned about. When it is full open...the hot water in the engine goes into the radiator...and the cooler water that has been cooling off in the radiator goes into the engine...and when it hits the thermostat...the thermostat shuts off so the hot water in the radiator can begin to cool off again so the cycle can repeat. SO running an engine WITHOUT a thermostat can overheat due to the water never has enough time to cool down and it will keep getting hotter and hotter as time goes by. Not my opinion...but rather a fact due to repairing a car for overheating...and all it needed was to install the removed thermostat.
9.) Also ...by the same guy...he mentioned that the water circulation AT IDLE should not be shooting out of your cooling fins in the radiator at a high rate...if anything...the most it should be is that coolant is coming out of the fins and going HALF the distance of the width of the tank. I am happy if I see a "tranquility fountain" effect when the water is coming out of the fins with the thermostat OPEN.
10.) Last but not least is to service the coolant system completely. Removing the block drains and draining out the coolant from the engine block along with the radiator. When the coolant is out of the radiator...you may be able to look down and see the condition of the coolant fins at the bottom. Sometimes you can not see them due to the transmission cooler being in the way. IF you have doubts in any blockage down low in the radiator which is where it will occur. Remove the radiator and either replace it or have it serviced.
DUB
Because you stated you are "green" to classic cars. I hope that does not mean you are green to automotive service. SO...PLEASE excuse me if I mention "things" that you know already...but I do not know if you know what I am going to mention.
1.) Have you checked the radiator cap and it should be 15 lbs CLOSED SYSTEM.
2.) Have you pressure tested the system. The reason being you can have a small leak high up on the engine and NOT allow the system to build pressure...and thus allow the coolant to steam out. If the leak is lower in the water line area...it would show up on the ground or on the intake manifold.
3.) The heat hose that is attached to the fitting on the intake manifold on the passenger side is where you can check and feel for heat when the engine warms up and if the water pump is actually circulating coolant....which I am sure it is.
4.) Are you sure that you filled the system all the way with the coolant mix??? When the system looses coolant...the coolant passages in the cylinder heads take some time to get filled up and all the air out. This is why I drill A VERY SMALL hole( the size of a hat pin) in the thermostat to allow the air to expel out into the radiator when I am filling it up....and then add coolant to the overflow tank.
5.) Make sure the hose from the radiator to the overflow tank is in good condition. IF you have a hole in it...the system can draw air back into the radiator due to this hose being bad or a hole in it.
6.) 200 degrees is NOT hot. Not by a long shot. And for what it is worth...the ohm to ground value that your temperature sending unit sends to your gauge is so slight when you get to 190 degrees...and goes to 200 degrees...you could be dealing with a bad sending unit. On problematic cars...I install my racing fluid filled gauge which is much more precise to verify what the car is actually doing. The reason I know that 200 degrees is NOT hot. Because the 1985+ Corvettes from the factory with electric cooling fans get to 228 degrees BEFORE the cooling fans come on....and the cooling fans will shut off around 211 (give or take). The AUXILIARY cooling fans come on at or around 256 degrees. SO I REALLY WORRY when the temp rises and keeps rising at or around 260 when the car is driven and the HEATER is on high. Your engine has cast iron heads...unlike the later years with aluminum heads. So these cast iron heads can take the heat. So trying to make your engine run at 180 degrees (for example) all the time is pointless...because trying to get the thermostat and other factors to all work in unison to achieve this is highly unlikely...or if achieved...was time consuming and is not gaining any benefits (in my opinion).
7.) MAKE SURE that you have ALL of the foam seals that go in between the radiator and the radiator support....and any seals between the radiator and shroud. Also any seals that go ON TOP of the radiator support and seals to the underside of the hood. WITHOUT these seals...and due to the angle of the radiator...air will not be as easily directed through the radiator...but instead it will go up, over and around it. Also the lower air dam extension is needed...or air will go under the car...instead of helping direct MORE air into the radiator.
8.) As I was told by a guy who knows/sells coolant systems. A thermostat goes FULLY OPEN 15 degrees ABOVE the rating of the thermostat. SO...a 195 degree thermostat is FULLY OPEN at 210 degrees. WHICH IS STILL NOT HOT enough to be concerned about. When it is full open...the hot water in the engine goes into the radiator...and the cooler water that has been cooling off in the radiator goes into the engine...and when it hits the thermostat...the thermostat shuts off so the hot water in the radiator can begin to cool off again so the cycle can repeat. SO running an engine WITHOUT a thermostat can overheat due to the water never has enough time to cool down and it will keep getting hotter and hotter as time goes by. Not my opinion...but rather a fact due to repairing a car for overheating...and all it needed was to install the removed thermostat.
9.) Also ...by the same guy...he mentioned that the water circulation AT IDLE should not be shooting out of your cooling fins in the radiator at a high rate...if anything...the most it should be is that coolant is coming out of the fins and going HALF the distance of the width of the tank. I am happy if I see a "tranquility fountain" effect when the water is coming out of the fins with the thermostat OPEN.
10.) Last but not least is to service the coolant system completely. Removing the block drains and draining out the coolant from the engine block along with the radiator. When the coolant is out of the radiator...you may be able to look down and see the condition of the coolant fins at the bottom. Sometimes you can not see them due to the transmission cooler being in the way. IF you have doubts in any blockage down low in the radiator which is where it will occur. Remove the radiator and either replace it or have it serviced.
DUB
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
I may see 200F idling in line at a drive-up window (maximum, no matter how long). normally, it keeps 180-190F in spirited driving in the hills in NW Arkansas.
This is a hopped-up L48 with a new radiator, functional 180F thermostat, OEM clutch fan and OEM replacement water pump. I have good pressure seals around the radiator (Doc Rebuild) and the OEM fan shroud.
pressure test your system
15lb psi radiator cap
how are the seals and shroud around your radiator? OEM or aftermarket? Pictures?
If you are going to run a thermostat, I would not go above 180F
This is a hopped-up L48 with a new radiator, functional 180F thermostat, OEM clutch fan and OEM replacement water pump. I have good pressure seals around the radiator (Doc Rebuild) and the OEM fan shroud.
pressure test your system
15lb psi radiator cap
how are the seals and shroud around your radiator? OEM or aftermarket? Pictures?
If you are going to run a thermostat, I would not go above 180F
Last edited by TedH; Sep 1, 2013 at 07:14 PM.
Le Mans Master
Joined: Jan 2006
Posts: 9,192
Likes: 27
From: Boca Raton Florida
There are a whole list of things to check and be sure of that can cause heat, although as stated above 200 is not to high. The thermostat is probably a 180 or 190, this sets the minimum operating temp for the engine.
Things to check;
Radiator cap
Radiator to support seals
Air Dam in place
Radiator to hood seals
Timing, what is it set at? Does the advance mechanism work?
Lower radiator hose should have a spring in it, if not it will collapse at speed.
More things to check if it gets hot at low speed;
Timing
Fan Shroud to radiator seals
Fan Clutch
Fan to shroud clearance
Air in the system can do it, of you can't get the air out you can drill a 1/8" hole in the t-stat, but I have never needed to do that.
Congrats on the new ride, Post some pics
Things to check;
Radiator cap
Radiator to support seals
Air Dam in place
Radiator to hood seals
Timing, what is it set at? Does the advance mechanism work?
Lower radiator hose should have a spring in it, if not it will collapse at speed.
More things to check if it gets hot at low speed;
Timing
Fan Shroud to radiator seals
Fan Clutch
Fan to shroud clearance
Air in the system can do it, of you can't get the air out you can drill a 1/8" hole in the t-stat, but I have never needed to do that.
Congrats on the new ride, Post some pics
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Former Vendor
Joined: Jan 2000
Posts: 5,593
Likes: 631
From: Brighton
Guys, I'm as green as they come to classic cars, but I just bought a 1977 Corvette. I noticed the faster I drove it, the higher the Temp got. By faster I mean 65mph. It will run around 220 degrees when driving 60-65. Would probably get hotter if I kept that up but I backed off. If I keep it around 50-55 it will stay around 200. I know that's too high. I replaced my thermostat but it stills runs same temp. I was going to order a flex a lite fan, then decided to come here and ask expert opinion first. Help me out please. It is a clutch fan. Thanks.
Race Director
Joined: Apr 2009
Posts: 19,294
Likes: 2,753
From: Charlotte NC
I always forget something. When the engine is cold...squeeze your lower radiator hose and feel for a spring that keeps if from collapsing when it runs. IF you have no spring in it...which can occur because many companies do not install them when they sell you a new one...it can suck shut when you rev it up.
Just one more thing to add to the list.
DUB
Just one more thing to add to the list.
DUB