Okay, fixed the cylinder 4 misfire issue with a new coil and was finally able to actually drive the disco. noticing a vibration between 25 and 30 mph, both up and down speed. grabbed both drive shafts and have no play there... (not what this thread is about, but mentioning it anyway)

but then it started to heat up (not overheat, because I'm paranoid like that and didn't let it) when I stopped, the small tube from the filler tank to just above the radiator hose had popped loose and was spewing all over... crap... head gasket... but a combustion gas check showed up negative...

filled up the reservoir, drove home (8 miles) with no heat up, but coolant low about half full mark when checked... so, what the heck? and go.

 

"Heat up" how much?

 

not even to 3/4, but I'm a freak about anything above normal. truck is new to me and this is the first time I've driven since fixing the cylinder 4, dead coil misfire. no smoke, no real smell to speak of and it seems to run great, other than the vibration between 25-30 mph and a slight ticking sound (maybe like a sticky lifter?)

 

You may have just move and air bubble to the reservoir?
There are ways to get the air out of the coolant system correctly, do a search you will find many.

Put you should pull the front driveshaft and check it on the bench.
It is hard to find a bad centering bearing on the truck.
If you break that driveshaft you'll be buying a transmission.

How many miles are on your rig?

 

121k on the disco.

 

Well you are really about to have a panic attack because I'm telling you right now that the dash gauge doesn't "gauge" accordingly. If the needle even starts moving up toward the red zone, your coolant is already over 240 degrees. You should do a lot more reading bub. Everyone buys an aftermarket gadget to read coolant temps because the dash gauge will only reflect cold, normal, and hot is already overheated. I bet when you get something that plugs into your ECU via the OBD hookup under the dash, you will find that your coolant temps are outrageous. You can F*%+ up a Disco2 so fast with operating temps over 200 and you are running around at 220-260

 

Start checking everywhere for external leaks, and get something like an Ultragauge to get a reading of your real-time coolant temps. At this point it could be a bad head gasket or the block is failing altogether. Could be an internal coolant leak so check the motor oil consistency on the dipstick and see if you smell it coming out of the exhaust. Make it your priority to get it figured out and find out if this fixable. One of the more common coolant leaks as at the throttle body where there is a little plate within that circulates it to keep the throttle from sticking in cold climates. The gasket there will corrode and the plate will also warp. It can be bypassed if you find any coolant pooling on top of the DS valve cover. If you can't get a visual on the coolant leak, you will have to order an adapter from Rock Auto and rent a pressure-tester from your local big-box parts store. If you don't get anything leaking externally under pressure, then...internal?

FyI that ticking sound is usually a symptom of high coolant temps, as well. Mine was ticking after I bought it. Did some reading on here and found out I should be getting a real-time reading on my coolant temps. Turned out to be 220 F at idle when I plugged up the OBD scanner. I replaced a bunch of stuff, got the temps down to 190's and the ticking noise went away. Sometimes that sound is a cylinder liner moving up and down inside the engine bore because the engine temp is too high and it comes loose. I first looked toward the lifters and valve train for the noise, did a bunch of stuff but that wasn't it. Scary, right?

when you figure out where your idle, highway, and operating temps altogether are, you should flush the cooling system, especially if it still has the Red DeXCool-type antifreeze still in it. That stuff ruins everything from the inside out. There are several methods to flushing but you want to end up with green antifreeze diluted with distilled water. You need the $80 gray Land Rover brand thermostat and also check the viscous cooling fan that it has resistance and still pulls air well. When they go out on the '03-04s everybody switches to the earlier 2-piece fan instead of the 1-piece assembly so that you can put a heavy duty fan clutch on it. We haven't even got into the upper and lower radiator hose assemblies. The red coolant destroys the hose and fittings from the inside out. Def order a new Tstat though.

 

thankfully never even got to 3/4... just noticed it climbing above the normal just below halfway and shut her down. the oil looks good, not milky... will take a sniff of the tail in the morning, but haven't noticed any smells. picked it up for $2500 and figured I'd have to do some stuff, so I'm not super bummed... yet

 

a quick under hood look turned up something funky... looks like the throttle body heater (?) has been bi-passed. watched a video on something else and two hoses were removed from it... I've only got one... dunno if it has anything to do with it, but pretty sure it's not supposed to be like that

 

There are 2 outlets from the intake manifold for heated water. One of them goes to the TB and back to the overflow tank via brittle, plastic OEM tube. If the throttle body leaks or the hose breaks, most will run the line directly from the manifold to the tank, bypassing the TB and swapping the plastic line for a new flexible hose, and never get around to replacing everything back to OEM. Plus, the TB heating just isn't useful in our climate here. Like I said, most replace both hard plastic lines with new tubing but VERY carefully as the spigot attachment to the radiator will break right off and you will be buying a new radiator with that $10-worth of hot water tubing. A healthy cooling system is so paramount and vital to the D2 because it under-performs as it is, plus the engine is just so poorly manufactured that it cannot tolerate higher than average coolant temps. This is a fact. It's nearly 100 deg in TX now and even with all-new cooling system components, it just barely keeps it within a healthy range. Even when the AC is turned on, that does nothing as it only pulls in hot air on top of hot air with the condensor fan. Where cooling temps stayed between 183 and 187 a month ago, it gets up to 194 no problem now with even some moderate modification. So you can see where the problem lies. There are some $1000 radiators on the market that are supposed to keep it within a few degrees at all times, but the OEM rad really has a hard time keeping up in hot weather. An all-original setup will create an environment for engine temps to go up and down (mostly UP) maybe 30-degrees influctuation and it is hell on the block and cyl heads. They weren't made for that to begin with, and combine that with loose tolerances and you get a recipe for disaster.