I currently losing my mind trying to figure out the discovery 2 coolant out the exhaust. I bought it a month ago and it was blowing white smoke out the exhaust. I changed the head gasket and when I took the heads off I couldn’t find any cylinders steamed cleaned or spark plugs that were fouled by coolant. I changed the timing cover then cause I thought maybe it was leaking into the oil there. I put everything back together and when I started it back up it ran hot and was still blowing white smoke, but seemed like it was running great. No misfires and seemed like it had all 200 hp. Which was surprising for the amount of white smoke coming out. I took the heads off again and they still had no steam cleanest to them. I want to think it’s a slipped liner or cracked block but I can’t find anything that really points to it. It almost seems like the coolant is leaking straight into the exhaust somehow. The coolant is disappearing fast but it isn’t showing up in the oil.

 

White smoke in the exhaust is typically fuel and coolant mixed in the combustion chamber - if it continues after the engine is fully warmed up and 15 or so minutes.
If you have a cracked block you likely have water in the oil, you can get this from a head gasket leak combined with warped heads as well if the head gasket damage is towards the water passages

Now for a few questions

1. Is your cooling system over pressuring - does coolant spew out the overflow hose.
2. Did you get the heads checked for true
3. How hot is running hot
4. is there yellow/white under your oil filler cap

 

I got no signs of water in the oil. And I had the heads milled before I put it on. I got an obd gauge on it but it said it only got up to 197 but I don’t think it was reading correctly, and it doesn’t take long for it to get to that to that 197, less than a few minutes. Which is why I’m thinking the coolant is getting exhaust gas’s into it. Also I put a new 180 thermostat in but the lower hose would stay cold. I’m thinking I’m getting air in the hoses is the reason, but I’m picking up a new one just to see if the other one came defective. There was white under the cap is why I change it the first time, but I do like in North Dakota so it could be from condensation.

 

Not all cracked blocks put coolant in the oil, some just put coolant in the cylinder. In fact, I believe that is the more common occurrence.

How long have you run the engine since the rebuild? Fully warmed up, took it for a drive?

That said, here are the steps I recommend for troubleshooting:

1. To help troubleshoot, remove the thermostat from the system. If you have the factory one either put an inline in or just put a temporary hose splice (autozone) in the stock location and run the top rad hose directly to the manifold outlet. It will have a funny bend but it will work temporary. Run truck with radiator cap one full turn loose from full tight.2. Run cold pressure test on the cooling system, let sit 24 hrs. You can borrow a pressure test kit from advance or similar. If it drops pressure, you have an issue. Turn engine over by hand one full turn before attempting to start truck in case it has filled a cylinder with coolant. Report back on results.
3. Start truck, let it get to operating temp. Re-run #2 above.

 

When you cold start the engine, how long does it take to build pressure? If you get gases into the coolant, the hoses get stone hard already when they are lukewarm only. I have a similar issue (overheating, white smoke, oil looks fine). The engine is toast, I will know more when I rip it apart.

To make sure there is no water in oil, you can also do the crackle test:

 

If it was leaking into the cylinder it should at least clean the cylinder it’s leaking into or at least have fouled plugs right? All the cylinders look like the same for cleanness and the plugs looked good. I took it for a few 10 minutes drives hoping that it was just antifreeze in the exhaust from the HG replacement. But it seems like it’s blowing more smoke now. And thanks for the pressure test tip! I’ll have to try it when I put it back together again.

 

The steam cleaning is not a definitive sign. A small leak may create white smoke without steam cleaning.