When I turn engine off after driving around for a while, I noticed that it gets much warmer while its off! right after I turn it off I read 200F right on the thermostat housing using infrared gun thermometer, when I check it 10 min later it gets 220F or so. I remember one time it was 240F!! is that normal??

Also, what is the maximum "safe" temp. for a big block? I know thats a common question, but I've searched the forum for a bright answer with no luck.

Cheers,

Hamad

 

Thats normal. When you shut off your coolant flow stops and what is in the block sits in the block soaking up all the heat transfer from the block. Very normal. As far as max safe temp- ? I only know what my own "target" is as far as temps. I like to see mine running below 200 but that is nowhere near any temp that could bring anything to a "failure". I know that some of the modern GM engines will run in the 220 range normally.

 

Totally normal, think that's HOT....hell, try my work truck here in Florida...that thing you could easy cook steak on....serious BBQ time...

it starts and runs fine, drags the starter a bit, but it lights off....

for a big block vette in the desert, that's FINE.....

what did you do for rad/fans??? never spotted the final outcome??

 

weimer, mine will cruise at about 190-195F but will rise to 200-205F in a stop and go traffic, thats on a 100F day and A/C off, add at least 10-15F to each with A/C on.

mrvette, I installed a Dewitt radiator and dual spal elec. fans combo. its working real good compared to the stock system, but I am still looking for a better results. I know our environment is so brutal for a big block corvette! but I still have a hope that I can drive it with A/C on and still with in a safe engine temp. range.

my 6.2 engine Yukon will run right at 210F all the time no matter what the outside temp is. can I still apply that to a old chevy big block and consider it as a safe normal driving temp.?

 

In my '72's owners manual it states "During normal operation, guage will indicate around the 230* mark." I know I wouldn't be comfortable with that but I think it shows that if your car is running over 190* you don't need to freak out like alot around seem to believe.

Greg.

 

You're "good to go". Even with the A/C on in stop and go, you'll be fine. The temps that you are specifying are not dangerous levels IMO.

 

I am amazed at how many people don't know or notice that their engine gets hotter after they shut it off. That's why some cars have those annoying electric fans that stay on after you shut the engine off. I would often blow an old radiator hose after shutting the engine off. That's when I first noticed the phenomenon - when I was 16.

That is also a reason to use a battery cutoff switch after you shut the engine off. That superheated turned off engine can melt 30 year old insulation and start an electrical fire several minutes after you shut it off.

 

So its normal the engine will get warmer after its turned off. Then why we dont see that on new cars? is it due to a more efficient cooling systems? in my yukon the electric fans will turn off right when I turn the engine off, and still I dont see that rise in engine heat. I am not trying to proove any one wrong, but I just want to have some knowledge, I am not comparable with most of you guys!

 

chances are your vette has a mechancial temp gauge that continues to read after you shut it off. newer cars are all electrical gauges so they shut off when the car shuts off, so you never see it. as far as normal, totally, as soon as you restart the car and coolant starts flowing again it'll cool right down.

 

OK, last question (I promise). would the block and heads stand that rapid heat change without cracking or deforming?

 

I'd bet on your Yukon, if you left the key on, you'd see the temp gauge rise after you turned it off. As mentioned, it's electric, so you won't see it rise. My Z28 used to get close to 250 after being shut off for 10 or 20 minutes in the hot summertime.

 

Without a problem. When you shut down, the heads and block are not actually getting hotter. In reality they are cooiing down. That's why you see the water temp going up. The heads and block are simply tranferering the heat in them to the coolant. In order for the heads and block to get hotter after shutdown you would need a heat source i.e. combustion taking place. Heat requires a source of energy. With the engine off, no energy- no additional heat. Your temp gauge is reading only coolant temp, not real engine temp. You heads in particular are much hotter than your coolant temp during operation. Point an ir heat temp gun at them during operation and you will see this is the case. Believe me, you're fine.

 

I have a separate electric fan on mine in addition to the main fan which is on as long as the key is in the "on" position. If I'm running hot I can just shut it off and leave the key in it to keep that fan going. I was actually thinking of wiring up a timer for this exact situation, something so when I shut the motor off the electric fan will continue to run for a couple minutes and then shut off.

Wouldn't be hard to do, a couple bucks at radio shack.

 

easier yet, and to get the same result, i just open the hood when i shut the car off. a fan running on the rad isn't going to do much as the coolant is not flowing. open the hood and it'll let the heat out of the engine compartment.

 

That's fine for when you're home and in the garage, but if I run out to the store or something I'm not leaving the hood up when I go in

The electric fan is between the rad & motor (right behind the normal fan), blowing toward the motor, not toward the radiator. I've got a laser thermometer somewhere, I'll have to check the temp differences with it on and off and post them.

 

Very normal. Just for basics, these V8's are "water cooled." So, while the engine is running, there is water flowing through the engine & cooling system, coupled with the fact that the fan is keeping cooler air circulated and while driving, more "fresh" air gets added to the equation.

So, when you shut the engine off, you are eliminating the cooling system from running its course & the fan stops. You simply have a very hot slab of iron, slowly cooling itself off by dissipation. Hence, why the engine reads hotter when you shut it off.

For a big block with old school technology, especially in the desert of Doha, your car is reading very safe readings of 200 to 220. Do you know what your temp. thermostat if fact set at? I have a 180* thermostat in my Small Block here in Oregon and it's just fine. It'll read up to 200 or a tad above if it's over 100 degrees and I am stuck in traffic.

If it makes you feel more secure, always keep a fresh coolant system in the car (semi-annually change the coolant) and hell, why not even make sure you put new hoses on at that time too! You are in the desert

If it does ever go above the 230 to 250 area, don't shut the car off...Just put it in Neutral and slowly rev the engine to around 2500RPM to let the coolant system bring the temps back down.
(ask me from personal experience on that one)

 

You can also turn the heat up to MAX inside the car and turn the fan to high. The extra flow through the heater coil will help to bring the temps down in an emergency.



Rick B.