Stumped, air bubbles in coolant not combustion gasses

JEEPSTER401 · Nov 12, 2020

So I am working on a friends 7.3 Excursion. It is puking out of the coolant bottle. I put my combustion gas detector on it, it’s bubbling but not changing color. I initially drained all of the coolant and put straight water in with dye in the fuel thinking it was cracked injector cups but it didn’t push dye into the cooling system. The cooling system will pressure test out fine for hours. Anyone have any ideas? Thanks

Petro · Nov 12, 2020

How bad is it puking? Does it all the time or just when under a load?

ghohouston · Nov 12, 2020

Have you replaced the coolant reservoir cap with q new Ford cap?

JEEPSTER401 · Nov 13, 2020

It would puke at idle and all the time that I have had it if I let it get that far. I didn’t put a new cap on but I did monitor pressure on my tester. After 12 minutes of idling it was at 14 PSI of coolant pressure. Coolant was rather cool yet, I’m in Michigan. I was going to get new additive for my combustion leak tester but in the past when it gets old it changes color in the bottle. It is still bright blue. If I run it with the cap off it will eventually just overflow, turn it off for a while, it will gurgle down to where it was prior to starting. And of course no heat, ever. There is a ton of air coming from somewhere.

6.0 Tech · Nov 13, 2020

JEEPSTER401 said:
It would puke at idle and all the time that I have had it if I let it get that far. I didn’t put a new cap on but I did monitor pressure on my tester. After 12 minutes of idling it was at 14 PSI of coolant pressure. Coolant was rather cool yet, I’m in Michigan. I was going to get new additive for my combustion leak tester but in the past when it gets old it changes color in the bottle. It is still bright blue. If I run it with the cap off it will eventually just overflow, turn it off for a while, it will gurgle down to where it was prior to starting. And of course no heat, ever. There is a ton of air coming from somewhere.

We had one here recently that had a cracked block that was very similar. It would build pressure in the cooling system cranking it over with the starter solenoid.

I would be leaning towards head gaskets though. Personally I dont trust the combustion leak detectors...

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JEEPSTER401 · Nov 13, 2020

6.0 Tech said:
We had one here recently that had a cracked block that was very similar. It would build pressure in the cooling system cranking it over with the starter solenoid.

I would be leaning towards head gaskets though. Personally I dont trust the combustion leak detectors...

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This one is not that bad. Head gaskets on the 7.3 are just not very common and this truck is bone stock, but it is high mileage. With the amount of air going into the leak detector it should turn color in no time.

PDT1081 · Nov 13, 2020

JEEPSTER401 said:
This one is not that bad. Head gaskets on the 7.3 are just not very common and this truck is bone stock, but it is high mileage. With the amount of air going into the leak detector it should turn color in no time.

I think I'd be looking for a small crack that opens up with heat. Have you done any oil analysis?

JEEPSTER401 · Nov 13, 2020

It doesn’t take much heat to start bubbling. It will do it rite off the bat. I was thinking the same thing. That is why I ran it with the coolant tester on it. Once I shut it off, as it cooled down I kept the pressure up to around 14 PSI thinking I might get some in the oil or on top of the piston, nothing. I have not done an oil analysis but it is not overfilled and looks fine. I know a lot of people don’t trust the combustion gas tester on top of the overflow bottle but I have used it for years with great luck.

Petro · Nov 13, 2020

I ran into this a few years back, i never found the solution but a reply to this thread said he fixed it with injector cups. Heres the thread. http://powerstrokearmy.com/forums/showthread.php?t=63685

JEEPSTER401 · Nov 14, 2020

Petro said:
I ran into this a few years back, i never found the solution but a reply to this thread said he fixed it with injector cups. Heres the thread. http://powerstrokearmy.com/forums/showthread.php?t=63685

The only thing that doesn’t make sense if it were cups is that I don’t see fuel in the coolant and the block test isn’t changing colors. So if it were cups one would have to have a crack from the bottom part in the combustion chamber up into the water jacket. So in theory I should at least show gasses in the coolant. You would think that would affect the way the cylinder/s with the effected cups would run. This thing runs great. If the bubbles aren’t combustion gasses I have no idea where they would come from. I can’t see it pulling outside air in under an area of vacuum to built that kind of pressure in the cooling system. When I say it bubbles in the cooling system it is excessive, like 20 bubbles a second. It is also strange that it hold a pressure test for hours without dropping pressure.

Petro · Nov 14, 2020

JEEPSTER401 said:
The only thing that doesn’t make sense if it were cups is that I don’t see fuel in the coolant and the block test isn’t changing colors. So if it were cups one would have to have a crack from the bottom part in the combustion chamber up into the water jacket. So in theory I should at least show gasses in the coolant. You would think that would affect the way the cylinder/s with the effected cups would run. This thing runs great. If the bubbles aren’t combustion gasses I have no idea where they would come from. I can’t see it pulling outside air in under an area of vacuum to built that kind of pressure in the cooling system. When I say it bubbles in the cooling system it is excessive, like 20 bubbles a second. It is also strange that it hold a pressure test for hours without dropping pressure.

The one I worked on was the same. No mixture and according to the block test, there was no combustion gases present in the coolant. I didn't risk it, I scrapped both heads and the block and started from scratch. Lost my ass on it but such is life.