Since I can't drain more than 5 quarts of coolant out of my 11+ quart capacity Buick, I am now wondering: how much coolant does an engine need to run successfully? 75% capacity? 50% capacity? I would imagine that air bubbles would start forming at some point...

I can't find this via Google .

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

A lot more than half the capacity. If its a quart down it will start to suffer I would estimate.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Did you drain the engine block? There will / should be a pipe plug on each side of the block near the bottom. I use 1/4" pipe drain valves and press in a short piece of 1/4" tubing. ( you need to get the type with the drain hole between the wing nut. )

This allows for easy draining and less mess since you can slide a piece of hose over the tubing.

Another hint go to rock that sells parts auto, enter your car, look at the engine section / long block. You can see pictures of your engine from all sides to locate the block drains.

Re-winding back to the question

What do you call "run successfully"? How long does the engine have to "successfully" run until it overheats and starts to seize?

{Ignoring air cooled engines}

It is possible to start and to run an engine without coolant. Some modern engine management systems will stop you from doing this though.

If you have anything less than the correct amount of coolant in a liquid cooled engine you could be in trouble. The definition of "correct amount" is described in your owners manual. If you don't have enough coolant in the system you will find that voids (lack of coolant) will be in the system - sod's law dictates that these voids will end up exactly in the least ideal place => at the top of an engine.

So the answer is don't run the engine (for longer than a few minutes) unless you are sure there is 100% of what should be in there.

If you have the problem of not being able to take out what you expect should be in there then you will find (as mentioned above) that there is probably a drain plug on the side of the engine and there will probably be coolant left within the heater core.

If you know the system is dry and you can not get as much coolant as the book says it needs in the system then you have a (air) bleeding related problem. Some cars have a bleed screw for this. You run the engine at idle and open the bleed screw - don't forget to open your heater controls to hot.

OM617s seem to be thought of as difficult beasts to bleed / expel the air from their cooling systems. I've read that some people put the front of the car on ramps and do a lot of jiggery pokery trying to "burp" the system.

(I hope this helps and it isn't too too patronising big boy)

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Actually, what I was trying to figure out is if the car could have possibly been running well on a 50 minute highway trip or a 20 minute city trip with that little coolant. Since the answer is no, and I did both of those with the Buick just before parking it (where it has leaked zero coolant, at least externally), I will assume that I have an issue of not being able to recover the coolant and not an issue of the car losing coolant .

Fortunately, the bleeding on this car is pretty close to dirt simple. No witchcraft or casting spells involved.

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"Senior Luna, your sense of humor is still loco... but we love it, anyway." -rickymay ____ "Your sense of humor is still loco... " -MBeige ____ "Señor Luna, your sense of humor is quite järjetön" -Delibes

1982 300SD -- 211k, Texas car, tranny issues ____ 1979 240D 4-speed 234k -- turbo and tuned IP, third world taxi hot rod

2 Samuel 12:13: "David said to Nathan, “I have sinned against the Lord.” And Nathan said to David, “The Lord also has put away your sin; you shall not die."

Coolant won't affect the way a motor runs until the headgaskets pop.

If you think the motor is running poorly because you were running it really hot, you damaged something.

Personally I think you're being far too anal about this coolant situation. Put the intake back on, refill it, and run it. It will be fine.

Drain and refill a couple of times after that if you're really that bothered by the coolant color.

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Well that's no fun

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

It depends on the temperature. At 20 below zero it probably doesn't take much coolant to keep the engine going. At 100 above zero it will take a lot more.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Even though the system is pressurized, I have to imagine that a 50% coolant level means that certain parts of the engine aren't being properly bathed in coolant, and hot spots would develop. While perhaps this may be less pronounced at lower ambient temperatures, I hope that you don't need an operating heater or defroster, as there is no way that the heater core, fed with relatively high-mounted hoses, will consistently flow coolant at such a low level.

It will run great right up until it never runs again

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Coolant in the engine won't do much good unless it can circulate. Without circulation it is just sitting in the engine's water jacket passages and heating up like the rest of the metal in the block.

The coolant needs to be almost full for the water pump to create circulation. You have probably read several threads on this board regarding high engine temperatures due to an air bubble and the need to "burp" the systems to purge the last of the air.

The Cadillac Northstar engines claims to be able to run with low or no coolant. Its engine management system severely limits the power output and shuts off cylinders to keep heat created to a manageable level. It is supposed to do this for short distances, like to get you to a safe place.

Coolant will thermosyphon if the thermostat is open and air flow across the rad will keep temps somewhat controled. Not for heavy load / low ait flow through.

It shuts off the injector to different cylinders but keeps the valves operating to pump air through the cylinders offering some cooling. This effect is also why it is bad to idle a diesel as it leads to wet stacking.

You've got maybe a minute or two without coolant. I've moved more than one heap without a water pump & dry block.

If you've been running it half empty around town it would be fried.

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Thats what you think

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2012 BMW X5 (Beef + Granite suspension model)

1995 E300D - The original humming machine (consumed by Flood 2017)
2000 E320 - The evolution (consumed by flood 2017)

GM cars of that vintage are notorious for weird cooling system designs.

I changed the radiator in a V6 Grand Am (94 IIRC) and got less than a gallon of coolant out. The block drains yielded more, but there was still quite a bit in some of the pipes and hoses and heater core and recovery tank. The actual bleeding process wasn't the worst thing in the world once I got it pretty close and found a good ramp to pull the car up on, and there was still quite a bit of air in it at that point.

But to answer your question, no, it's unlikely it was dramatically low before you changed it.