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Rising coolant immediately upon shutting engine off
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Author:  eh3civic [ October 12, 2017, 3:33 pm ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

I've done a leakdown test, but not yet a co2 test. I'll pick up one of those kits. I like to think I shouldn't need another radiator as well, but so far nothing else seems to be working. Maybe the co2 test will reveal an issue that the leakdown test couldn't detect.

Author:  rx7locost [ October 12, 2017, 5:12 pm ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

A second radiator will not be required unless you see temps rising noticeably higher then your thermostat or > 240 deg.

50/50 ethylene glycol mix and 15 psi cap will not boil until 265 deg F.

Simply said, your problem is elsewhere.

Author:  eh3civic [ October 12, 2017, 5:37 pm ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

rx7locost wrote:
A second radiator will not be required unless you see temps rising noticeably higher then your thermostat or > 240 deg.

50/50 ethylene glycol mix and 15 psi cap will not boil until 265 deg F.

Simply said, your problem is elsewhere.


Going much over 240 with Aluminum heads sounds like a recipe for disaster, and I'd rather not test that. Regarding the mix, I've gone with a lower percentage of antifreeze, a bit of waterwetter, and the rest distilled water. I'd think that once the engine is turned off, the coolant is very likely to reach very high temps while it sits in areas of high temps and is no longer flowing with the waterpump.

Author:  rx7locost [ October 12, 2017, 6:56 pm ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

I'm not recommending that running at 240F is OK mind you. Only that the 50/50 antifreeze coolant should not bubble over like you are seeing until over 240F.

Altitude and pressure affect the boiling point of water. At an altitude of ~6,000 ft, water boils at ~200 deg F, not 212F. Just suppose you are a) using 100% water, b) your thermostat is rated to open at 190 degrees and c) your are running no pressure radiator cap as in trying to remove air pockets, then turn off the engine, then I can easily see boil over happening inside the engine and pushing out cooler colant. A 2nd radiator won't fix that.

From my limited experience, I've never had issues like what you are seeing. There is some other problem that a 2nd radiator will not fix.

Author:  davew [ October 13, 2017, 8:43 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

Could you possibly have the wrong water pump [blades in the wrong direction]. dave w

Author:  eh3civic [ October 13, 2017, 10:25 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

Water pump is in the right direction. Removed that a long time ago to check, and went ahead and replaced it while it was removed.

Author:  a.moore [ October 13, 2017, 11:00 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

Don't recall you mentioning it - what is your timing at idle?

Author:  horchoha [ October 13, 2017, 11:04 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

What is your timing at idle vs 2000-2500 rpm?
LOL a.moore beat me to the question

Author:  eh3civic [ June 3, 2018, 10:43 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

Just a heads up, the cooling problem is fixed. Previous radiator just wasnt sufficient. It cools in 90 degree days on hot new pavement now. The new radiator was custom built and required moving the nose forward 5 inches.

Author:  Miatav8,MstrASE,A&P,F [ June 3, 2018, 11:45 am ]
Post subject:  Re: Rising coolant immediately upon shutting engine off

FWIW, I've had a 5.0L ranger since highschool.

Not to beat a dead horse, but it didn't look unusual to me in the video since the system was not under any pressure from a cap.

I have not seen any pics but you should have an over flow even if you have an expansion tank, unless you keep the expansion tank half full or less. Hot coolant expands and has to go somewhere, particularly after shut off.

I have an expansion tank on the trike but only because I needed a high fill point since the raditor was so low.

An overflow is any vented container that will catch the fluid and the hose from the cap is always below the coolant level in the overflow so it will return to the radiator when the system cools, so no loss of coolant with each thermal cycle.

Just fyi.

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