ABOUT how long can you run a 4 cylinder engine without the water pump turning?

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Old 06-09-09, 07:00 AM
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ABOUT how long can you run a 4 cylinder engine without the water pump turning?

This is in regard to my '91 Dodge 2.5L I have stored in the garage, whose head gasket is blown, or some crack. I periodically start it up. I would actually like to take it out and drive it a little to circulate transmission fluid also, and get the wheels turning, etc.

With water drained out of the radiator, I'm sure the temp gauge is not going to record the true engine temp. Hence my question.

I really am thinking of resurrecting this car. It runs like a top, even with the blown gasket that leaks so bad the cylinder fills up! It runs really smooth. I know a motorhead who maybe would love to do the job for me. Engine easy to work on because no junk is in the way. Plus his wife owned this very type car and he did a head gasket on her car.
 
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Old 06-09-09, 07:09 AM
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Not good to run any length of time at all. Without the water, temperatures will go up rapidly. I wouldn't go more than one minute.

IMO.
Bud
 
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Old 06-09-09, 07:35 AM
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That's all?? I've already run it about 4?(just a guesstimate) minutes at a whack. I was hoping for 15. I was hoping to crank it up, take it out of the garage, run it up and down a private roadway for over 1000 feet total, and park it back in the garage.
 
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Old 06-09-09, 08:35 AM
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I'm just guessing, but with no water to help distribute the heat, your head temps will rise very quickly and as you stated, there will be no temp guage to warn you. An outboard motor will be damaged rather quickly when the pump shuts down, and it still has water in place. You are asking it to run with no water at all. Better safe than sorry.

Bud
 
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Old 06-09-09, 08:56 AM
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Agree with Bud; with water in it a few minutes would not be an issue as the water would dissipate the heat until it reached boiling point. With no water everything would get really hot really fast.

Needs a tow job.
 
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Old 06-09-09, 10:35 AM
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As stated above it is a problem with the hot spots near the head. The local heat build up will do damage.
Think of taking a ox/acetalene torch to a pipe full of water.
No damage because the water rapidly carries away the heat.
If there is no water then the torch would melt the pipe very fast. Even with a running cooling system in good health the coolant flashes to steam at the hot spots. Hence the recomendation for ethyl glycol (higher flash point) as a coolant year round.
Ive run junkers for awhile with no coolant but I would not do it with my good car.
I think the combustion temps can hit 6500 F if I recall
 
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Old 06-09-09, 03:26 PM
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Originally Posted by frankiee View Post
I think the combustion temps can hit 6500 F if I recall
That much? You sure? When does cast iron and aluminum melt?


Hot sun surface temperatures.

I do not have water way up to the head anymore as I drained the radiator. I was surprised though that not all that much water came out. I'd have to go look again - but from what I remember, only 1- 2 quarts came out.
 
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Old 06-09-09, 04:54 PM
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melting point of aluminum 1220 F

melting point of cast iron 2150F -2360F


combustion temp ~1500F
 
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Old 06-09-09, 06:00 PM
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I think I was referring to a diesel engine when I guessed at instantaneous peak temps
Or I could be wrong at that number
The important fact is that the peak instantaneous temps can get very hot.
Usually not a problem, but if there is no coolant to carry the heat away...........disaster.
Below is a quote of some temps and pressures in today's equipment that engines have to endure without meltdown.



Dzl-Pep with AAT
In many of today's fuel systems fuel is used as a coolant and circulated back to the tank. Fuel temperatures have continued to rise. Average fuel temperatures have risen about 1000 Fahrenheit in the last ten years. Fuel is often pressurized above 20,000 PSI (over 30,000 PSI in some systems) and braised by temperatures in excess of 6500 Fahrenheit.
 
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Old 06-10-09, 07:03 AM
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Thanks nap.

I'll read that article, later, frankiee.

Anyway, it sounds like I'd better not run that car for as long as I was suggesting.

It could be kind of fun trying to restore that car engine. But at the same time, that is the car I have no heat in in the winter. So I'd need to find out if the heater core is the culprit, and if this is hard to change out on this car or not.

Why am I so hooked on these (junk, in some people's opinion)cars. Well, after seeing my neighbors new PT Cruiser where you can't see any belts or plugs - or my dad's car where you can't find the battery - I refuse to buy such vehicles, as these are bound to run up terrible mechanics charges for even the slightest thing.

And isn't it silly not even being able to quickly 'read' a spark plug to find out how your engine is running? I'm from the old school that way.
 
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