How hot is too hot?

I have a feeling i may have cooked my motor.

It was running about 275 before i noticed it.

Gimme a break, my fan sure did!

 

If it's not knocking, pinging, or rattling, it should be ok (***uming it didn't do it before Ha-ha). Chances are very good that no hard parts were damaged. Without getting too technical on the issue, I would change the oil for sure.

 

Will it turn over? Check for water leaks. Do a compression test. If it is does start don't run it too long. Change the oil and filters.

 

As long as you stopped it, rather than it keep going till it stopped it's self,
I would be real surprized if any damage had resulted.
Even when I have got a motor hot enough to start to 'nip up'
prompt shut down has meant the engine still ran fine once cooled down again.

 

In 2000 Jack Costella had my 3 liter Nissan in his streamliner. On the first run he forgot to turn the water on. It was trying to die pretty soon but he flogged it thru the 5. Melted the electrodes off the spark plugs. Went about 120. It turned over OK so I bumped the timing 10 and the fuel 10 and ran it with the water turned on. It went 231. On record return # 1 rod gave up. Don't know if that was because of the overheat.

 

Its never good to overheat a motor and usualy it does damage. If you went to 275 there is no telling but it should have some problems. Not many survive those high temps without something going wrong. If it runs well after this consider yourself very lucky

 

The big question is how much water did you lose. Running it with the water boiling out is when you start to warp and crack parts. If you see it getting that hot and shut it down your probably OK. If you drive it a few more miles to get home that's when you toast them. If you fill the radiator back up and it runs fine then you should be good to go.

 

I lost about a gallon plus of water in my 400 Chevy once. It did not have a recovery system and would loose that gallon on every major hill. The outside temp was over 100 degrees. I was about 200 miles from home and the engine temp would not go under 230 for the whole trip and ran as high as 260. I had no choice but give her hell. I changed oil and added a friction reducer when I got home and it ran great. The only thing I noticed that it would use about a quart of oil in 500 miles after that. It would not smoke from the tailpipe but I had a hot MSD ign. in it. I figured I had toasted the oil rings. Pulled the motor and sold it as a core to a kid that put it in a daily pickup until he could rebuild it. Ran fine for him for a couple years too.

 

Your not going to know until you drive it or pull it down. If it's a daily I'd change the oil & filters, Replace the anti-freeze, replace the thermostat and check all the hoses. Drive it for awhile close to home and check to see if your oil gets muddy or you lose water. Any seepage under the head down the block? For sure you didn't do it any good by letting it heat up but you might get lucky and you can keep on driving.
If it's intended purpose is to run hard on the street or track, I personally would pull it down and take a real good look.

Terry

 

You didn't say what kind of motor and Yes that can make a difference. Flathead I would say all kinds of problems.
I had a 460 in my Crew Cab Dually and was towing the Race Truck home from Vegas when the by p*** hose came apart. We were on a long (17 mile) grade and almost to the top when I noticed the temp gauge pegged. Figured we were almost at the top so I could cost the 16 miles down the other side to the rest stop and get it cooled down (didn't know it was a hose yet). Well we got to the rest stop and the damned thing would even shut off! It was so hot the plugs were like glow plugs! Being an automatic couldn't kill it either. Pulled the coil wire, got zapped, and it kept running. We started pouring water from the ice chests into the radiator and after about 40 minutes is finally cooled enough to shut off. Took 3 hours to get it cool enough to hold any water. Fixed the hose, fired it up and towed the race truck the rest of the way home. Seemed to run fine.
Called a friend who worked for Ford and he said SELL IT! His 40 years of Ford Engineering said that the rings would have lost tension but more importantly the head bolts would have crystallized and would break off if we tried to remove them.
Drove it to the dealer and traded in a on a nice new E350 Van the next week.

 

If the head gaskets haven't already blown you're probably fine. But the oil is ruined right now. It may also become a leaker, old gaskets don't always appreciate getting that hot. Good luck!

 

Ok did it boil over? Mechanical or electric gage? Any symptoms of it being hot as a couple of the other guys asked?

If it still runs I'd run a compression test and see what the compression is. If it is up were it is supposed to be and fairly even you may have not done any serious damage.
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My bet is the rings are gone, as hotroddin says it takes the tension out of them. i overheated my 454 going up the g****vine years ago and same thing would not shut off, the exhaust manifolds were glowing for 10 minutes after i finally got it shut off. other than the rings and a few broken head bolts it was still good, and the damn thing had 4 sleaves and none of them pulled! i thought for sure one or more was gonna be pop'd.