HELP! Internal antifreeze leak on my 2007 ZR6 engine

[Donbayers]

Boy, I hope someone can help.

Problem: Loss of antifreeze within the closed cooling side of the engine (2007 ZR6 6.0L PCM). Nothing is leaking externally

What is happening: I fill the reservoir and drive for a bit (under an hour). engine temp comes up. I have to stop and add more antifreeze.

What I have checked: I checked the oil to see if antifreeze was going into the engine. All perfect. I checked the plugs, all perfect and the engine runs perfect. I took the heat exchanger off and to a shop to be cleaned and tested thinking that has to be the problem. It checked out fine

So now I'm thinking about the exhaust manifolds and the risers.

Question: Is there any antifreeze running through the manifolds or the risers? Externally I see no hoses (other than raw water) that attach to the manifolds externally. Could there be block antifreeze somehow circulating through the manifold/riser that has a leak and causing loss of fluid which then is going out the tail pipe??

Lastly. I have records that the manifolds were replaced before and about a year ago I replaced the gasket between the top of the manifold and the riser but I don't recall seeing antifreeze there.

Ask more questions please if I haven't provided enough info

And IF there is no antifreeze going through the manifolds/risers then what in the world could be happening?

Best regards

Don in Vegas

[jpwhit]

On that engine, I don't think there is any coolant in the manifolds. All the excess raw water goes through the manifold and then out through the exhaust to cool and reduce noise.

You could have a blown head gasket between a cylinder and the water jacket. You wouldn't likely see anything on the plugs because it burns off almost instantly. You may see white smoke in the exhaust under the right conditions. Doing a compression and leak down test may tell you something.

I have to think more about other places the coolant could be going.

[Jonny Quest]

Keep an eye on the oil. Any "milky" oil or oil that looks like chocolate milk is an indication that coolant is finding its way into the oil system. If the oil system continues to look good, then it sounds like there may be a leak in the heat exchanger. The heat exchanger acts much like a radiator where the raw water cools the coolant/anti-freeze. A similar heat exchanger is your transmission cooler (tranny cooler is much smaller). A leak in the heat exchanger can easily pump the coolant into the raw water stream that eventually exits through the exhaust system.

Unfortunately, a new heat exchanger is a bit spendy:
https://nautiqueparts.com/heat-exchanger/


JQ

[Donbayers]

Thanks Jonny, I thought the heat exchanger would be my issue but it checks out fine. and the other cooler only has raw water through it.

[vision]

Does the oil cooler have raw water circulating through it or anti-freeze on that year motor?

Do you have a heater?


Sent from my iPhone using Tapatalk

[Donbayers]

Does the oil cooler have raw water circulating through it or anti-freeze on that year motor?

Do you have a heater?


Sent from my iPhone using Tapatalk

The only other cooler is the trans and that only has raw water going through that. I do have the heater option but that runs lines up to a radiator and has nothing to do with the raw water. Since you mention it I think I will go back and double check that nothing is leaking from up there, but I've not seen any antifreeze in the bilge.

[Donbayers]

Keep an eye on the oil. Any "milky" oil or oil that looks like chocolate milk is an indication that coolant is finding its way into the oil system. If the oil system continues to look good, then it sounds like there may be a leak in the heat exchanger. The heat exchanger acts much like a radiator where the raw water cools the coolant/anti-freeze. A similar heat exchanger is your transmission cooler (tranny cooler is much smaller). A leak in the heat exchanger can easily pump the coolant into the raw water stream that eventually exits through the exhaust system.

Unfortunately, a new heat exchanger is a bit spendy:
https://nautiqueparts.com/heat-exchanger/


JQ

My oil is perfect and this problem just didn't start, it grew over time so I'm confident that nothing is going into the crankcase. Thanks for taking the time to chime in

[Jonny Quest]

Heater…yes, that certainly is a potential source for coolant leaks. If the heater system is leaking, you should be able to smell the coolant or find a wet spot near the heater. Try running the engine in your driveway on the hose. Carefully look for coolant drips around tthe heat exchanger, hoses, fittings, etc. Report back what you find.

JQ

[SilentSeven]

The classic automotive mechanic method to check for cooling system leaks is to run a pressure test. If not familiar, you use a special tool that connects to the reservoir tank that puts about 15psi pressure on the cold cooling system. You run two checks from this - first, you run a time based check to see if the system looses pressure over time. If yes, then leak. You also can inspect the pressurized system for drips / leaks / puddles as coolant should leak from the bad area.

Your local autoparts store might loan pressure testers.....

That's where I would start.

[Rednucleus]

That would have to be a big heater leak to lead to overheat condition - would expect a huge puddle if that was the case.

[core-rider]

Donbayers How much coolant are you replacing in you given "hour" of runtime?

As mentioned earlier, you can rent a coolant system pressure tester from most auto parts stores like O'Reilly or Autozone. I'm not sure they have adaptors to fit the reservoir though of your boat though, so I suggest taking the cap in with you to check. If it works test the pressure over duration of time. You could also put it on while the engine is running to see how much pressure is built up in the system... this might point towards compression leaking into the system i.e. head gasket failure.

You can also get combustion gas test kits to check for combustion gases in the coolant which would also point towards a gasket failure.

Another thing you can do to check for head gasket failure is to remove the sparkplugs. If any of them are basically new looking, as in clean, then that is a good sign you have coolant leaking into the cylinder as well. It could be leaking from the coolant passage into the cylinder and burning up out of the exhaust which will be hard to see because we normally always have "steam" in the exhaust.

Aside from the heat exchanger which you're already checked or an external leak there really isn't another place for it to go that I'm aware of.

[SilentSeven]

Edit / nuts, wrote all this and then see this "I took the heat exchanger off and to a shop to be cleaned and tested thinking that has to be the problem. It checked out fine". Oh well.


+1 for question on 'what's your coolant loss rate'.

Also, you can overheat due a partially filled system that has a big air bubble. There's typically a system bleeding procedure to make sure all the air is out. I would follow that and make sure your system is actually correctly filled before getting too deep into other considerations.

Soooo...if it were my boat:

1. Verify correctly filled.
2. Monitor coolant loss - if you are indeed loosing...
3. Run a pressure test

I don't find the cooling diagram above very helpful - the diagram co-mingles raw water cooling with the contained system making it confusing. Here's how I think your system works relative to raw water. 1) cold water for engine and exhaust cooling is pulled in and run through a dedicated raw water pump (part 19) 2) that pump sends cold water to the reservoir/heat exchanger tank (part 9). In that tank, there's a water embedded radiator where hot engine coolant from the closed system is circulated within a submerged heat exchanger surrounded by cold raw water. (This is how the engine heat is transferred out of the coolant). 3) Then the now hot raw water then leaves the exchanger tank and flows (lines 1 and 12) to each exhaust manifold where it exits the boat.

Sooo...thinking out loud again - one more place to check for a leak would be for a crack in the heat exchanger within the tank. If this is cracked, hot pressurized engine coolant would flow into the raw water side and then out the exhaust via the raw water. This would be really had to detect IMO. You'd see a pressure drop on the pressure test but never would see a leak. I'm almost half betting now this is your issue.

Edit: new heat exchanger tank. ouchie! https://nautiqueparts.com/heat-exchanger-6-0-ho-half/

Edit 2: If you think this is occuring, pull the tank and take it to trusted local radiator shop and have them check it. They should be able bench test the tank and....maybe....just maybe...fix it.

[bturner]

You can loose a bunch of coolant from a loose line going to the heater core or from the heater core itself and not notice it IF the core is draining into the bilge but then you should be smelling it or seeing it in the bilge. If you want to eliminate the heater core you can pull the panel, remove it and pressure check it as well or check to see if it has been leaking when you pull the panel.

Either way, the best advice I've seen here is with a pressure test. You can do this with a leak down test on the cylinders as well to check for a blown head gasket. My money based on your Las Vegas location on your post profile unfortunately is going to be first with the head gasket and then with the heater core. It only takes one overheat to mess up these newer engines.

Best of luck getting this under control. Please let us know what you find to resolve the issue.

[imonabout]

The exhaust manifolds on this motor pictured are 100% water. Next step go to auto part store and pressure test system as noted above, watch for leaks and pressure drop. also verify coolant mixture. the motor BLOCK is 100% antifreeze. so a internal leak could only be into oil or combustion chamber. so yo can also google and get a loaner tool, "cylinder leak down tester". but if you leaking as much s you say you are, I doubt you have a internal leak. which leads to a external leak, hose, heater, or just big air pockets. these can be a big pain to bleed the air out of the system. whats the back story. how long have you had the boat and how long has this been a issue, when did it start?

PS I have a lot of spare parts for this engine, I scrapped 2 engine blocks and kept most of the bolt on parts, heads, manifolds, intake, injectors, etc, I will be selling parts soon.
good luck.