Is 240 Degrees overheating or not?
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Pro
Joined: Oct 2007
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From: Crusing the roads of the great USA
Is 240 Degrees overheating or not?
I need some help in looking at a 68 vette. The car is modified with a bigger cam, (not radical) electric fan and an aluminum radiator. Here's what I need advice with... when I went to look at the car, it was warmed up, parked in the shop and covered. Upon sitting in the car, I see the aftermarket gauges.... water gauge, dolphin brand, is reading about 240 degrees. I said, I see the car runs hot? Here is the exact reply I got, please tell me if it makes sense... "when the car is turned off, the water doesn't circulate, causing the temp to rise" my thoughts are, maybe a few degrees, not 240, and shouldn't the fan stay on till the engine cools? I don't know..
Race Director
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That is a high temperature but what was it when the engine was running? How is the fan set up, what temperature does it come on and shut off and what temperature thermostat? The fans are not necessarily wired to continue to run after the car is turned off. You have to ask the shop some more questions.
Last edited by MelWff; Feb 11, 2014 at 04:58 PM.
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Race Director
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From: Chino CA
Drifting
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From: East London/SW Essex UK
Last edited by roscobbc; Feb 11, 2014 at 04:59 PM.
Team Owner
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From: Crossville TN
240*F is pretty high for dino oil if the engine is running. That's also high enough to get 50/50 mix of water/glycol to reach boiling point.
But, if the running temp is less than 220*F, it's probably not a problem. Still, if I were thinking about buying the car, I would be concerned that the radiator might be on its "last legs".
But, if the running temp is less than 220*F, it's probably not a problem. Still, if I were thinking about buying the car, I would be concerned that the radiator might be on its "last legs".
Racer
Joined: Feb 2012
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From: Harrisburg PA
Also, how was it "covered?" That couple prevent some heat from naturally dissipating as well...
Running the electric fans would cool the radiator down, but not the "soak back" as mentioned above. 240 does seem a bit high, but could be a number of factors...
Take it for a test drive, highway and city (put her through her paces) and see how she reacts...if she runs hot on you, then you know...also, check the idle temp as well...start it up, and see how quickly it "cools down" to 180-190* at idle...
Running the electric fans would cool the radiator down, but not the "soak back" as mentioned above. 240 does seem a bit high, but could be a number of factors...
Take it for a test drive, highway and city (put her through her paces) and see how she reacts...if she runs hot on you, then you know...also, check the idle temp as well...start it up, and see how quickly it "cools down" to 180-190* at idle...
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Race Director
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I'm glad somebody was reading the OPs post and understands that engine was shut off at the time.
Next time you doubters are out in your car, turn the ignition back on about 15 minutes after shutdown. 220-240 is very typical.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
I have an aftermarket capillary tube gauge on the cyl 1-2 spot...and it reads about 10-15f to high.....confirmed by various gauges....
SO to get an accurate head temp reading, and go from there.....
and yes, when engine is off, the temp reading in a cyl head will rise....
SO to get an accurate head temp reading, and go from there.....
and yes, when engine is off, the temp reading in a cyl head will rise....
Safety Car
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From: anchorage ak
The temp deffinately rises after the engine is shut off. What you would want to know is what it does the when the engine is running, I'd say 240 running is to hot, nothing I'd wory about while the engine is not running, but if the gauge had been changed & the sending unit was the oem model it could be the wrong ohms causing a false reading. Some fans are wired to stay on after the engine is shut off, but this only does any good if the water pump is electric and also stays on after the engine is shut off. But the seller was right in what he replied. Good luck.
Last edited by bluedawg; Feb 12, 2014 at 01:03 AM. Reason: pit bull wont quit humping my leg.
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With aftermarket gauges and send units I would always wonder about compatibility/accuracy. I would confirm the accuracy of the gauge by using an IR gun shot in the area of the thermostat housing/hose area.
As was said, the temp will always go up after shutdown for the first few minutes.
As was said, the temp will always go up after shutdown for the first few minutes.
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From: New Or-leens Loo-z-anna
Like they said.....
you need to start the car with a "cold engine"/
drive the car/
pay attention to ALL gauges for normal readings/
& exhaust pipes (for white/black/blue smoke)/etc.
you need to start the car with a "cold engine"/
drive the car/
pay attention to ALL gauges for normal readings/
& exhaust pipes (for white/black/blue smoke)/etc.
Drifting
Joined: Jan 2011
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From: Hamilton Virginia
As the others have said, temp will go up after shutdown. I have my electric fan wired so when the key is off, the fan is off. Test drive the car from cold start to shutoff and evaluate then. Very good point, if the gauge is new but the sending unit is original, might not be getting the right reading.
Le Mans Master
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From: melbourne florida
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The temp deffinately rises after the engine is shut off. What you would want to know is what it does the when the engine is running, I'd say 240 running is to hot, nothing I'd wory about while the engine is not running, but if the gauge had been changed & the sending unit was the oem model it could be the wrong ohms causing a false reading. Some fans are wired to stay on after the engine is shut off, but this only does any good if the water pump is electric and also stays on after the engine is shut off. But the seller was right in what he replied. Good luck.
Le Mans Master
Joined: May 2002
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From: Lebanon Township New Jersey
The engine itself does not get hotter after it is shut off. With no combustion and no friction there is nothing to create additional heat. The coolant in the engine at the time of shut off, does get hotter until it reaches the temperature of the engine. The temp gauge is reading the temp of the coolant in the engine, somewhere. Normally, with the engine running, the coolant is cooler than the engine since it is circulated thru the radiator. If there was no temperature difference between the engine and the coolant, there would be no heat transfer from the engine to the coolant. Delta T (temperature difference) is the driving force of heat transfer.
Drifting
Joined: Jan 2002
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From: Schaumburg IL
On a 454 after running and shut down the "heat soak" during the summer runs the gauge up to 230-240 which is normal. Start the engine and within 30 seconds the temp is down to 200 because you are moving the coolant again and changing with the amt in the radiator.
If a car is running at 240 with the engine running then that is way too hot for a cast iron carb'ed car. The fuel will be almost be vaporized in the intake. New cars with alloy and alum parts will run at that and they do, not the old guys.
If a car is running at 240 with the engine running then that is way too hot for a cast iron carb'ed car. The fuel will be almost be vaporized in the intake. New cars with alloy and alum parts will run at that and they do, not the old guys.
Race Director
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From: Chino CA
On a 454 after running and shut down the "heat soak" during the summer runs the gauge up to 230-240 which is normal. Start the engine and within 30 seconds the temp is down to 200 because you are moving the coolant again and changing with the amt in the radiator.
If a car is running at 240 with the engine running then that is way too hot for a cast iron carb'ed car. The fuel will be almost be vaporized in the intake. New cars with alloy and alum parts will run at that and they do, not the old guys.
If a car is running at 240 with the engine running then that is way too hot for a cast iron carb'ed car. The fuel will be almost be vaporized in the intake. New cars with alloy and alum parts will run at that and they do, not the old guys.
Is that to say putting aluminum heads on an engine will make it run hotter ?!!!!!!
Pro
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From: Catoosa Okla
I'm not surprised to see 230-240 on an accurate temp gauge after the car has been sitting from a run, with the hood closed especially. All cars will do this. What I want to know is what it runs after about 10 minutes of zooming around town. If it's 240 while running, it's overheating. I'd also look at things like a proper shroud around the electric fans. I've seen a LOT of overheating issues on electric add on fans because someone zip ties the fans to the radiator and expects it to actually cool.
Pro
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Is the car a big block or small block. My small block Vette runs at 180 and after shut down will get up to 210-220 depending how hard the car was ran. I also have a 71 and a 72 chevy trucks. One is a small block and other is a big block. They both run in 180-190 range running and the small block truck will, like the small block in the vette get up to 210-220 after shut down but the big block will always go to 240 after shut down. When started back up it will be under 200 in less than a minute.