Is my head gasket either blown or "blowing"?

[1949plymouthdeluxe]

Its been awhile since I have been on here. But here's the deal. I have a 1949 Plymouth Deluxe. I've been driving it for around 6 months. When I got it I changed everything including the coolant. When I changed the coolant a TON came leaking out of the overflow because I guess I overfilled it. Recently my MIL moved across country to live nearby and until we get her a car of her own, she is borrowing my truck. So that means I'm daily driving the Plymouth. Well, the other day after I pulled it in I noticed it sort of smelled a bit like coolant. Thats when I noticed a little coolant had dribbled out of the overflow tube and onto a part of the frame. I didn't think a lot about it. Just for the hell of it I pulled the dipstick and there isn't any coolant in the oil. There also isn't any seepage around the head. Its also not overheating. 

 Today I went to the store. Its not super warm here.  Its maybe in the upper 50's. So the car didn't get exactly hot. Like 150-160. I pull into the garage and it had done the same thing: dribbled a little coolant onto the frame.  This is puzzling. I looked online and there is mention that if your head gasket is leaky it can put exhaust pressure through the coolant system and then force some coolant out. But again, I don't see any obvious signs. I guess worse comes down to worse it doesn't look like its nearly as bad to replace the gasket if I have to.

Anyway.... thoughts?

Edited December 20 by 1949plymouthdeluxe

[Dave72dt]

It's a non pressurized system so you can run it with the cap off.  Warm it up with the cap off and observe the coolant.  Bubbles in the coolant are an indication of compression seeping into the system.  There is also a chemical solution that can be purchased for testing for exhaust gas contamination.

[53windsor]

It will puke coolant if overfilled too. There seems to be a level where its happy, well below the very top.

Been here, done this.

[1949plymouthdeluxe]

Thanks. It was still hot from coming back from the store so I ran it for around 10 minutes, got it up to 165 or so. No bubbles. The overflow tubes ends up right over the cross member in the front. A thought that came to mind is that I'm now taking the car out on longer trips whereas before it was just for short little trips. So maybe it still had a bit too much coolant. I dunno... the car otherwise seems fine. Maybe time to install an overflow tank.

[Sam Buchanan]

Don't fill the radiator past about an inch and a half below the filler neck. That should keep it from sloshing out through the vent tube.

[Sniper]

7 hours ago, 53windsor said:

It will puke coolant if overfilled too. There seems to be a level where its happy, well below the very top.

Been here, done this.

 

This right here.  If you fill the radiator fully it will puke the excess out until it's happy.

[Pep48]

You can test for combustion gasses (head gasket, head/block crack) with a tester

Harbor Freight sells them and Autozone rents the (you have to buy a special chemical...about $10.00). You attach the tester to the rad filler neck when the engine is hot, and the solution changes color).

[JBNeal]

If ya know anything about Y2K-ish Subarus, you'd know that they had a head gasket design flaw that would eventually fail if the coolant was not flushed every 2 years.  As the coolant aged, it's pH level would change to the point where it would erode the head gasket, exposing the design flaws that would leak exhaust gas into the coolant system.  Eventually, the coolant would start to smell like tailpipe and turn brownish green, but by then it was too late and overheating was an inevitability.  These are pressurized systems so the other telltale sign would be a low coolant level in the reservoir when cold but nearly overflowing when at op.temp.

 

These flathead head gaskets typically are far more robust than the Subaru design, so they can take some abuse.  The only failure that I have seen was an abused flathead and the gasket split on the siamesed area, but that did not seem to affect the coolant as much as it was smoking and backfiring.

 

The long gone radiator guy in town told me to fill an empty system to about an inch below the neck, drive it around for a week, fill to below an inch again, and repeat until it didn't need topping off...he said sometimes it takes weeks to get all of the air out, but not to worry about it, as these flatheads were not gonna blow up if they were a little short on coolant...he even made the offhand comment that ya could drive a flathead without any coolant in the top tank visible, but ya didn't want the inside of the rad.cap to be dry, something about keeping the radiator wet like a good date--if it's dry you're in trouble, but if it's too wet, then you're also in trouble but in a different way...not sure what he was getting at cuz I was a dumb teenager at the time 🤔