Oh, and chubbs, mine also has a tapping that sounds line sleeve movement. It only gets loud when temps are above 190

 

Is your coolant level changing after you've repaired the leak? Does it stay pressurized overnight? Does it smell like gas vs just plain anti-freeze? Are the hoses rock hard when it's completely warmed up?

It could be as simple of a problem as a stuck thermostat, or a Head Gasket issue.

I've been around LR's since 1990 and honestly the 3.9, 4.0, and 4.2L engines really didn't have the issues the 4.6L did. Also the 3.9L & 4.2L in the RRC had a massive radiator along with the GEMS 4.0L in the D1. The D2 went with a smaller plastic tank aluminum radiator for starters, swapped over to Dexcool/HOAT Coolant, removed the oil cooler (03-04) and they had to have it run hotter to meet the current emission laws with an engine that dates back to the 60's. Then in 03-04 SAI became pretty much standard (I have seen some none SAI 03-04's but I never verified if it was factory). That in my opinion was a disaster...

I honestly prefer 99-02 D2's with a 4.0L without SAI. I've owned 5 03-04 D2's and the two I bought new lasted well past 100K without any head gasket issues and back then we all just went by the gauge on the dash. I can guarantee you I was seeing 210-225F in both my 03 D2's. I went thru brittle spark plug wires like crazy, wire loom covers dissolved into nothing, and I even had the OEM hard plastic lines melt or completely break like glass when touched.

Now with my 99-02 D2's I don't have that (none SAI), 180F Thermostats, and better fan clutches. So I've improved on what originally rolled off the factory floor and it shows.

Replace your thermostat, flush the cooling system, and monitor the temps afterwards. Sounds to me like a stuck thermostat.

 

No, the coolant level has not changed in over a week now. It would drop fast when we drove even a small bit on the highway, and after 2 separate 2 hour trips, we are still at the exact same coolant level.

The hoses are resistant to compressing when hot, but they are not rock hard. I can squeeze them down a little, but not like when the engine is cold.

No antifreeze/ coolant smell that I can tell.

 

it is diverse info but I provide examples with the info as well. All you have to do is take some time to read through the threads. I just read in 1 of the recent posts that a guy has owned 4 discos and 3 of them had a block failure either due to cracks or the liner coming loose; it's that common. Most of the time the problem isn't confirmed until the cylinder heads are removed and evidence is found that a liner has broken loose.

To answer your question about the pressure test: it is a fact that a COLD block WITH a crack will hold pressure. A HOT block will NOT, most of the time. This goes back to the law of dissimilar metals expanding at different temp. When the aluminum block expands at temps over 200f and the steel sleeve is no longer held tight within, the coolant escapes through the crack and begins to leak behind the liner, up & over into the combustion chamber. It just depends if the liner is loose enough, how severe the crack is. It's a well known problem of Rover V8s, but people continue to lose thousands of $$ because the block passes a pressure test, the top end is rebuilt along with everything else in the vicinity, then the engine overheats again driving home from the shop. Only then does the owner pull the engine, strip it all down, bake the block, remove 8 sleeves, hook up the compressed air & discover the crack in the cylinder wall. That's how far you have to go to confirm a cracked block if holds pressure cold but still overheats when running. If a cylinder liner is really loose, the cracked block is sometimes discovered with a pressure test but the cylinder heads are removed. Even with the heads off under pressure, a cold block will not always leak under pressure; once again the cyl with crack would need to have an especially loose sleeve. Your block isn't cracked. If it was cracked it would not hold a 220 deg operating temp. It would overheat and boil the coolant straight out of the overflow maybe even blow a hose off of the fitting. You probably need a radiator along with the thermostat. Hell, even the water pump or fan could be going out. Just start with the Tstat. If the top hose and top of radiator is hot, and the very bottom exit radiator hose is much cooler, then the radiator is stuffed.

Edit just to clarify: cracked block and faulty cylinder head gasket are 2 completely different subjects with somewhat different effects. I've said all I can say about the cracked block which doesn't apply to you. I just said what I know about the subject since you posed the question. As for a faulty cyl HG, it will not hold pressure 95% of the time. BUT under circumstances like my bad HG which wasn't broken, it will hold pressure most of the time even under controlled conditions like a pressure test. Then other times, I look underneath and see a drip! WtH? It's just 1 of those Rover things. Eventually it gets bad enough there is no denying the HG leaks & you repair it before you encounter a complete failure. Stand at each side of the truck in front of your windshield and shine a bright LED flashlight very back of the engine into the bell housing. From the passenger side you can see a very back HG leak without moving anything. On driver side there is more in the way or the bulkhead design slightly obstructs the view of bell house.

 

Chubbs, thank you so much for taking the time to explain that!! It makes perfect sense! I would assume that even with a cracked block, if you can keep the sleeve in place by a cooler operating temp, then it would at least prevent the issue from getting worse??

I will keep a very close eye on my coolant levels to make sure we aren't leaking somewhere that is not visible. I plan to change the water pump as well, but I think I would want to do the fan as well at that time. My upper fan shroud was missing the two bottom screws to hold it in place, so the fan was rubbing the top. It shaved down a good size section, but didn't make it through before I fixed the bottom brackets. So I think the fan might not be balanced, and I would think that would have an effect on the viscous type of fan clutch. But maybe not??

 

If u plan on changing the fan clutch you'll need a 99-02 fan blade/fan clutch setup. I'd recommend the Dorman 620-112 cooling fan and any 99-02 fan clutch. 03-04 units are one piece. If the fan isn't balanced it could be a sign that your waterpumps main bearing isn't doing so good.

 

That's absolutely correct that in some cases pertaining to engine noise and cylinder sleeves moving you can remedy the situation by lowering operating temps to that of 200f or less. In this instance the block is not expanding at the rate at which the aluminum seperates from the steel.
When I got my temps low enough that the noise stopped, I continued pressing forward as the benefits of lower coolant temps were undeniable so I went all the way down to 180f.

On another note, if you have the impression that the fan is moving in an oblong motion or wobbling, the water pump bearing could be faulting, but it wouldn't have originated from the viscous fan. If you suspect this the water pump and viscous clutch should both be replaced, or so I have read. I've been through so many crappy aftermarket fan clutches that I'm currently running somebody else's original unit (fan clutch) for the past few months.

The fan/radiator shrouds are essential to engine cooling and should never be overlooked. It's best the shrouds are secured in the event water pump goes as the fan hits whatever and splinters throughout the bay or slams into the hood. Bad things have been documented so I like to keep as many guards around that fan & belt as provided LoL.

 

Out with old and in with the new 180 Soft Spring Tstat today and temps are astoundingly better. Old night driving twmps were still at 215ish, now not over 188. Tomorrow during the hot day will be the real test, but it is already running a lot cooler.





i also flushed and switched to Peak green coolant and added a few ounces of Purple Ice. Has anyone tried this from Shell? Says its ideal for high temp conditions and reduces damage to aluminum.





I think I found another reason for the high temps. Far right tstat hole is completely blocked. WTF!?

 

After doing this swap my temps have not exceeded 194F even in the hot FL weather.

Thanks guys!

 

Glad you found the usual problem.

Often here, people jump to the cracked block as a diagnosis, and 215 for any length of time will not crack the block, or loosen the liner.

The most common thing to look for is the plugged holes in the stat.

If you did a pressure test and it held, you usually can eliminate all the major issues.

You can test a fan clutch, if it works, it works. You can borrow a motor scope at the local auto place and drain your rad and see if it's clogged.

The technology that built this engine is waaaay old, people make them harder to work on then they are.

Remember KISS. Keep it simple stupid.

And no, you don't need thermostat relocation mods, new fans, duct work tunneling air into your rad, your truck is running just the way it's supposed too.

Also, running your truck too cool, can lead to a multitude of problems, truck running to rich, changed air fuel ratio, carbon buildup, poor fuel mileage, and new catalytic converters.