Sooo, I took it to a shop and they were kind enough to let me look over their shoulder when they did the testing on the 4.4. They tested the gasket by applying pressure to the cooling system and immediately identified a coolant leak that was bad enough to make it impossible to pressurize the system enough to see if they could force any coolant into the engine. To get the leak, they removed the intake manifold and there is a coolant hose connection under there that they repaired. This morning, we tried a different test, which measures if exhaust gasses are escaping into the coolant system. I ran the car for about 5 minutes and the test was negative. Great sign!

The mechanic said that due to [insert a few technical things I don't really remember] we couldn't figure out 100% whether there is a head gasket leak without pulling the intake manifold and spark plugs again (expensive-ish) but his hunch is that it's more likely a cooling system problem that my have presented as a head gasket to an inexperienced mechanic. Today, he's going to bench test the thermostat. If the thermostat is bad, we'll repair/replace it and go from there. I'm really hoping not to do a bunch of band-aid repairs at like $75-$150 each just to find out the thing DOES have a head gasket leak, but that may be a little bit of what I signed up for. Thanks again for all the help so far!

 

Thanks! The mechanics did mention something about that yesterday. Also, when I tested out the car, I shifted it in to low gear but now it's stuck there and won't shift back in to normal drive. I know there could be many reasons for that but is there anything that is known to cause that issue in the LR3 specifically?

 

I don't get why they pulled the intake manifold. Makes no sense at all. FYI, I hope they used new gaskets if not they will have to be replaced. I also don't get why they did not just do a compression test. That is the first thing that should have been done, then move onto coolant testing.

 

As DakotaTraveler pointed out, a bad PCV can cause smoke and poor running, like to where the vehicle will barely move. I have seen this first hand on a 4.4 AJ in a Range Rover. As for the gear shifting problem, look to the shift cable adjustment and movement. My "broken" LR3 would only shift into reverse and not into drive until I had lubed and adjusted the cable at the transmisson end.
Engine failures on the AJ 4.4 are rare, and ebay has used ones for + or - a thousand.

 

If you are relying on a shop to do all the work on this rig its going to get expensive very quick, you'll need to start getting your hands dirty or the money pit will bleed you dry.