Disappearing coolant....???
 

New engine with about 100 miles on it and it is loosing coolant at an extreme rate.

I took the car for a drive 3-5 miles, got on it a time or two, and by the time I get back home it's out of water. There's no water in the oil and no visible leak other than the overflow tank overflowing. My best guess is that all of the water is getting pushed into the overflow tank until there is nothing left in the engine.

Head gasket leak? Cracked head???
Video of the overflow hose

Jeff,
Lets see your coolant routing.
Anything on the ground besides over flow bottle?
Sure looks like oil mixed in that tube.
I see a lot of hose clamps on over flow tube maybe obstructing the cap from fully seating Also maybe the cap is no good.
I like to fill the engine right down the thermostat housing then install the stat with a hole drilled in the side and finish top off.
then I slowly rev motor so it will draw the coolant down and top it off before letting off the throttle
Jeff

I've tried 2 different radiator caps (18lbs & 16lbs) thinking that the original was bad & got the same results. Caps are seating properly.
The tube is just old & dirty. Antifreeze & water is the only thing in the system.
Oil level is remaining constant.
There is no thermostat. It was the first thing I pulled when it started overheating.
I top it off the same way.

The only thing about the cooling system that is "different", is that there is a hose from one head to the other on the rear with a tee going to the heater core.

There is good water flow & the engine stays cool until it runs out of water. Since there are no external leaks on the engine or hoses & radiator caps are good, the only thing that I can think of that would "push" out all of the water would be compression entering the cooling system pressurizing it.

It’s either leaking it or burning it..... Make sure you’ve purged all air and simply aren’t getting goofy readings as well...

Pull the plugs.... look for spotlessly clean ones, could indicate a head gasket failure

Missed the overflow reservoir overflowing in your post....combustion(head gasket), failed cap(unlikely),?.... are your temps acting goofy as well?

99% of the time, your situation is caused by combustion gases entering the coolant.
 

Actually, it's probably really 100%.

Leaking gasket (doesn't need to be blown). Did you re-torque the heads?
Cracked head or block or ??

You can verify with one of those test kits where you drain all the coolant, put in straight water with their chemical additive and then let the engine idle.

If combustion gas is present in the water, the chemical changes color.

Good luck.

If it was burning the coolant, it’s hard to believe that it burned 2-3 gal of coolant in “3-5 miles.” Or that you missed the huge smoke clouds following you. I’d leave it in the driveway,, and rev it up while looking under the hood. You won’t be able to miss a leak that big. (Or the smoke clouds.)

It doesn't take very long to push all the water out thru the overflow tank.
 

The bubble stream in the overflow hose is a huge clue.

You said you "got on it a time or two" when you drove it. Think about the volume of air being pushed into the cooling system if just ONE cylinder is venting into the cooling system at, say 4k or 5k RPMs.

Even a 'little' 400CID engine has 50 cubic inches of volume in one cylinder. At 4k RPMs, with a 4-stroke system, and presuming that the leak only occurs on the power stroke, that becomes 50,000 cubic inches of air in sixty seconds. Even if only 50% of the air is making it into the coolant, that is still 25,000 cubic inches of air!

Doesn't take long to blow all the coolant out thru the overflow tube and then thru the overflow or lid on the tank.

We lost a head gasket on our 440CID (428 + .060) race engine and it blew out practically ALL the coolant in just about TEN SECONDS..........

Was the overflow tank lid still on when you got back home, or was it loose / pushed off ?

Which heads?
Which head bolts?

I had a shop miss a cracked cylinder wall many years ago, and it acted just like what you are now putting up with. If you can find a smog shop willing to wave the sniffer tube that samples exhaust gas over the filler neck you will have an immediate answer. There will be no reading from steam even with the antifreeze mixture. If there is exhaust gas escaping the meter will climb right up.

While I drove to the smog shop and waited for the engine to cool down so I could pull the radiator cap, I really don't see why waving the sniffer over the overflow tank wouldn't give good results.

If you are running anti-freeze, it should have a sweet smell from the tail pipes with the engine running.

Do you have a radiator pressure pump? It goes on the radiator where the radiator cap goes. Pressurize it and see if it leaks down

Most of the national cars parts dealers (NAPA, AutoZone, etc) will loan one.

Easy way to check for compression entering the cooling system is drop the end of the overflow hose in a cup of water with the engine idling. You'll see a constant trail of bubbles coming from the hose end.

You don't have to borrow any pressure tester, and you'll find out almost instantly.

The brown bubbly fluid in the clear overflow hose certainly looks to me like combustion gases are getting into the cooling system. In other words, a blown head gasket. It shouldn't look like that.

Autozone rents the coolant pressure checkers. I would start with that.

I missed the link to the overflow hose video on the first read.

Having seen this symptom many, many, times over 50 years of working on cars and engines as my profession, you have a head, or head gasket leaking. A distant possibility, would be a cracked cylinder in the block. No need to look further, pull the plugs and you'll find which cylinder, as the plug will be steamed cleaned and have zero deposits on it.

I worked in a Buick dealership for 3 years and ran in to at least a couple dozen buicks with blown head gaskets. Common on 455 and 350 buicks, and the short lived 4.1 V6, basically a overbored 3.8.

I couldn't tell from the video if you had cast iron heads, but the later cast heads had a propensity to crack between the valves. SBC cracked in the same area.

Finding no evidence of coolant in the oil doesn't really pinpoint anything, I've seen buicks with blown head gaskets so bad you could put a garden hose in the radiator and couldn't keep water in them, yet show little, if any trace of water in the oil.

Thanks for the responses! This is first time that I've run into this problem so I wasn't sure exactly what was going on.

I'll try re-torquing the heads with a different torque wrench. (I'm beginning to think mine is off.)
I'll also check all of the plugs. I pulled a couple to get a reading & they looked good.

To answer some of the questions above:
Heads are 16 large valve.
Cometic gaskets.
No cloud of steam or sweet smell from the exhaust.
Air was purged from system by topping off at a fast idle & burping the upper hose.

Sure sounds like a head gasket with a new engine you should torque the heads, then torque again the next day, then after the engine has ran some and is completely cool torque again. A re-torque could fix it or you may need t replace the gasket if a re-torque doesn't stop the leak. If it is the head gasket then you either didn't do the re-torque or you could have a warped cylinder head.

I had just such a leak in my daily driver Subaru.
It was a head gasket and a very very small leak into a cylinder.

My coolant over the course of 5 days of a 74 mile round trip to work and back would go down by a little over 1/4 of a gallon, just enough to use up the reserve in my overflow tank.

It never steamed or smelled out the tail pipe either atleast at hot idle.

I got lucky and 3/4s of a tube of the Brass and Aluminum powder fixed it.

probably a head gasket. or....cracked head...one way to check is with a cue tip. let the car sit, crank it over with the fuel line plugged(no gas) do this for a minute. pull your plugs one at a time. put the cue tip in the hole.... then pull it out and see if it smells like antifreeze. weird method but it works..