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How long can an engine be safely run without coolant?

158
97
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
I ask because I'm in the midst of several mods and just completed an oil cooler install. I wanna test it for any leaks but I've still got the cooling system apart. I'd rather find any leaks now while things are more accessible.
Related question:
Will a thermostatic sandwich plate allow any oil to pass to cooler before reaching temp? I'd like to get the oil cooler system full and under pressure before overheating a no-cooling-system engine...

...Or maybe this is just a bad idea???
 
Last edited:
95
87
Exp. Type
HPDE
Exp. Level
3-5 Years
Arizona
I ask because I'm in the midst of several mods and just completed an oil cooler install. I wanna test it for any leaks but I've still got the cooling system apart. I'd rather find any leaks now while things are more accessible.
Related question:
Will a thermostatic sandwich plate allow any oil to pass to cooler before reaching temp? I'd like to get the oil cooler system full and under pressure before overheating a no-cooling-system engine...

...Or maybe this is just a bad idea???
Yes, both the Mishimoto and Setrab units I've used will send some oil to the cooler even when cold. With a big cooler it can take a freakin long time for the oil to heat up on the street.

You should only need to idle for a few seconds to get oil pressure and heat won't be an issue that quickly. I just put a new cooler in my car and it had oil circulating through it by the time I climbed out of the driver seat and climbed underneath to check for leaks.
 
I don't run any engine for any length of time without the cooling system flowing water. Not even my old 300 Inline 6 truck that could probably take a 3000 mile trip with no fluid of any kind in it. I'm probably WAAAAY too picky about that, and I will freely admit that, but I just think it's good practice.

I had no belt on it after we locked a power steering pump at Hallett in June. I ran it long enough to load on the trailer and that's IT. Maybe 15 seconds. I am always worried about hot spots on the cylinder heads, something they hammered into us in auto shop back in the day. Is that likely to happen? No, probably not.

Still, this is a forum and the internet, and that's my opinion/personal practice; I would hold off, get it back together, then do it. I don't know about you, but my $15,000 engine ain't worth leaving the cooling system apart to test for leaks. I don't have that kind of money to blow just because I got distracted by a squirrel (maybe not everyone has that problem, though).
 

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618
882
Exp. Type
Time Attack
Exp. Level
5-10 Years
Bay Area, CA
If the engine is cold like it is in this case, you could run it for several minutes at idle without issue. The electrical/charging system will be more unhappy than anything in the engine without coolant.
 
158
97
Exp. Type
HPDE
Exp. Level
3-5 Years
25 min. to 1½ hrs. from Sonoma (ugh... traffic!)
If the engine is cold like it is in this case, you could run it for several minutes at idle without issue. The electrical/charging system will be more unhappy than anything in the engine without coolant.
I ran it for 30-40 seconds and the heads were barely warmer than ambient. The exhaust manifold, well... don't ask ;)
 

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