I did definitely get boiling coolant when I pulled over the last few times.

Ok, lots of great advice. I will do some tests this week and see what I can find out -- pressure test, oil change and check for coolant, check for moisture in plugs, and get a machine shop to look at heads for cracks and straightness. Also to steam clean piston heads if they are worth saving.

As for likely repairs, it looks like probably new heads, head gasket, liners. Dealing with the cooked rings and obviously the coolant system needs to be fixed.

I will be tackling the oil change and pressure test first. Will update this thread once I get those results.

 

than if all goes well get the inline thermostat from extinc and get those temps down to 190 lower temps means less pressure in the coolant system means less leaks

 

​​​​​​​Yeah, was hoping to have that done before the trip but was waiting on parts :/ Should I do the pressure test before or after I swap it in?

 

Actually you misunderstood the steam cleaned piston part. The intent is to look at your pistons for steam cleaning... If one or more do appear to already have been steam cleaned that is an indication of coolant in the combustion chamber. You don't actually steam clean them.

 

you have to find your leak or cause of your overheating first.

 

Probably not. Because there was no pressure the boiling point was likely lowered to something like 230. The block is the lowest point in the engine/cooling system, so as long as there is coolant in there the boiling/phase change limits the maximum temperature. A boiling pot on the stove cannot exceed 212 degrees, but once the pot is empty the temperature can skyrocket. The problem is the temp in the heads would have been superheated steam if it got to 280. The basic problems with Discos is that they don't overheat (assuming good thermostat and not pulling a load) until there is so little coolant that the pump cavitates, and then the coolant boils and the temperature skyrockets.

 

Haha, OK thanks. Definitely misunderstood.

 

Even if the block maintained a reasonable temp (which it didn't) the heads were boiling hard at those temps with no pressure. The heads constitute the majority of the combustion space and carry most of the heat away. When your heads can't cool the chambers because they are running on steam it overheats the whole system, so I'm sticking by my statement 100% here

 

Got the inline thermo mod installed and all air removed from the system. Currently running without a thermostat since I am also flushing all the coolant from the system. I let it idle to temp and drove around for a bit on local roads. Temp didn't get above ~170.

I also rented the autozone pressure tester kit today and pressurized the coolant system to 15 PSI. Found a few leaks where the hose clamps weren't tight enough. I did see some dripping from the drivers side valve cover, but after reading through some threads on here and going back to confirm, the leak is definitely coming out from the throttle body heater gasket. That seemed to be the only leak left I could find. In half an hour, I lost 2 PSI (15.5 to 13.5).

Found a disco near me at a local pick-n-pull where I got a few cosmetic / trim pieces. It did have the upper intake plenum all together so I may grab that and see if that one leaks before I buy the part from roverparts.com.

 

Just bypass the TBH using ATF hose direct from intake manifold to the bottle.