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Cracked block or radiator?

1986 Isuzu pup pickup truck

Was running hot. Parked and inspected radiator. Empty.

Refilled with coolant. Started engine. No visible leaks. Immediate billowing of white smoke from tailpipe.

Seriously breeched headgasket. Engine might be ruined. Cracked blocks are highly unusual.
Too bad you weren’t doing a better job of monitoring your fluids. This might have been avoided.

Pull out your engine oil dipstick.
Does the oil on the dipstick look like oil, or does it look like coffee?
Is the engine oil level higher than normal?
If it looks like coffee, you most likely blew a headgasket.

Looks like oil. By that I mean it dosen’t have the appearance of coffee grounds if that is what you mean.

I didn’t mean coffee grounds, actually.
So the oil doesn’t have a milky color, I gather?
Can you have someone do a coolant pressure test?
You may want to consider having a block test done, as well.
That coolant definitely went somewhere . . .

No milky color. When it first overheated, there was a small amount of steam under the pressure cap on the body of the radiator. Less than perfect but still useable seal I suppose. The reservoir tank was boiling. That leads me to believe there was adequate pressure in the tank itself. It’s currently stuck on my army base until I can get a tow. I pulled over because when I accelerated it billowed more white smoke, making a hazard for.other drivers.

Very little smoke at idle/very large quantity of white smoke from tailpipe upon acceleration.

“The reservoir tank was boiling. That leads me to believe there was adequate pressure in the tank itself”. I don’t think there should be pressure in the reservoir tank.

OK so I don’t know much about reservoir tanks. Or cars. That’s why I’m here.

It still sounds like you’ve got a blown head gasket.
You also need to get that cap replaced.

Will do on the cap. I plan on getting it towed this week.

Definitely blown head gasket, possibly cracked head. Cracked blocks are extremely rare, but given the circumstances, a cracked head is a real possibility. Don’t just swap the gasket out, have a machine shop inspect the head, unless you pull it off and see cracks, then just get a new or rebuilt head. They usually crack around the valve seat, typically between the valves to form a “bridge”.

If this type of overheating has been done numerous times, you may consider just replacing the engine. Severe and repeated overheating can damage your engine’s bearings. It would be a shame to do all that work and end up having to rebuild the bottom end or replace the entire engine soon after.

I’m fortunate to be a soldier in the army so I can take my truck to a shop on post that caters to soldiers and their families. The mechs there are fair and accurate and they don’t start work until you know and understand exactly what’s wrong.

I’ve been told that I can put radiator stop leak and oil in my oil fill in order to get a temporary seal that will keep down the level of smoke to a point that I can drive it 2 miles to the shop.

Any experience with this type of fix?

"The reservoir tank was boiling. That leads me to believe there was adequate pressure in the tank itself"

If with ‘boiling’ you mean bubbling, you definitely have a breached head gasket. Those bubbles consists of exhaust gas, finding another way out of the engine. The white smoke out the tail pipe is another dead give away.

Bubbling would be more accurate. It seemed to be coming from one area rather than a rolling boil as would a pot OJ the stove.