Engine question for the smart guys.

[fastfredracing]

O.K. I have a dodge truck, 4.7 that came in the shop for a head gasket. This truck does not overheat, but when cold, and only for the first 250 yards, it does pour out some white smoke that smells like anti freeze. The customer stated that he has been adding small ammounts of coolant. There is also some staining around the muffler drain hole, that looks like ant-freeze residue.
I have checked with my combustion leak tester, cold/warm/and hot, and cold/warm / hot under load, and my tester shows no combustion gasses in the cooling system. I 100% believe that combustion gas testers do not lie. You either have a leak, or you do not. I have pressure checked the system, and it holds pressure for as long as I leave the tester on there.
So this is more of an automotive theory question. If there is indeed coolant getting into the cylinders from either a faulty head gasket/cracked head, or cracked block , then there should also be combustion gasses present in the coolant system. If you think about it, the cooling system pressure is only 15-18 lbs, where as the cylinder pressures are at least 150 psi.
The only way I can think of for coolant to make its way into the combustion chamber without also having the presence of exhaust gasses in the cooling system would be for it to enter somewhere before the intake valve. Be it maybe an intake manifold leak, or a crack in the head that lead into the intake port somewhere.
I have done 100's of head gaskets over the years, and cannot ever remember seeing coolant enter the cylinders without my tester showing the presence of combustion gasses.
Curious to hear your theories.

[kaisen]

Originally Posted by fastfredracing

O.K. I have a dodge truck, 4.7 that came in the shop for a head gasket. This truck does not overheat, but when cold, and only for the first 250 yards, it does pour out some white smoke that smells like anti freeze. The customer stated that he has been adding small ammounts of coolant. There is also some staining around the muffler drain hole, that looks like ant-freeze residue.
I have checked with my combustion leak tester, cold/warm/and hot, and cold/warm / hot under load, and my tester shows no combustion gasses in the cooling system. I 100% believe that combustion gas testers do not lie. You either have a leak, or you do not. I have pressure checked the system, and it holds pressure for as long as I leave the tester on there.
So this is more of an automotive theory question. If there is indeed coolant getting into the cylinders from either a faulty head gasket/cracked head, or cracked block , then there should also be combustion gasses present in the coolant system. If you think about it, the cooling system pressure is only 15-18 lbs, where as the cylinder pressures are at least 150 psi.
The only way I can think of for coolant to make its way into the combustion chamber without also having the presence of exhaust gasses in the cooling system would be for it to enter somewhere before the intake valve. Be it maybe an intake manifold leak, or a crack in the head that lead into the intake port somewhere.
I have done 100's of head gaskets over the years, and cannot ever remember seeing coolant enter the cylinders without my tester showing the presence of combustion gasses.
Curious to hear your theories.

It also could be a crack or leak that dumps into the EXHAUST port or area. Not part of the combustion process, so it wouldn't show via compression testing.

Perhaps when it warms up the crevice expands and seals the leak. Or it leaks small amounts constantly and pools, giving symptoms only at start up

[GH85Carrera]

Could it be a leak in the intake manifold? I fought with a leaky intake manifold that would seep out antifreeze on my old 305.

[krystar]

u mentioned no load and under load what about under engine braking?

[pwd72s]

Originally Posted by kaisen

It also could be a crack or leak that dumps into the EXHAUST port or area. Not part of the combustion process, so it wouldn't show via compression testing.

Perhaps when it warms up the crevice expands and seals the leak. Or it leaks small amounts constantly and pools, giving symptoms only at start up

Bingo..that's what happened to Cindy's Ranger. Exhaust port. I complained about minor coolant loss at 20,000. Dealership pressure tested, other tests. I was told "no leaks detected". Of course, when the problem got worse, I was past warranty...The independent who replaced heads & gaskets said the coolant was leaking into/onto the exhaust. He thought a casting flaw at first..that then became cracked heads.

[Laneco]

Fastfred-

Kaisen may be about spot on. We've had a couple (my company) of the 4.7 with a mystery coolant leak initally blamed on head gaskets that turned out to be something else entirely. The walls in the cooling jackets are pretty thin. We've had them leak into the exhaust (but usually into the cylinder). It's as if the coolant is as corrosive as battery acid...

That would explain it - leak into the exhaust - not consumed in the cylinder.

angela

[PFFOG]

Easiest way to tell if it it is entering the combustion chamber is to look at the plugs, if the antifreeze is the plug will look squeaky clean, with no carbon deposits at all.

[boosted 89]

Does it stumble or misfire on start up? I had headgasket issues with a Montana van which ran like crap on start up but quickly cleared up after 15 secs of running. Coolant was leaking into one cylinder during an extended cool down ie overnight or a 4-5 hour sit. Headgasket fire ring had a small split.

[Joeaksa]

Especially if they are not using the correct type of anti-freeze, this is prolly what Kaisen said. Look at the intake manifold and see if they run coolent through there to keep it warm. Wonder if thats where your crack/leak is?

Joe A