Long story short, we bought an '02 Disco II a couple years ago as a hauler for very very cheap. When we got it home (I'm not sure how it survived the 600+ mile trip), we discovered that the head gasket was blown and couldn't drive for even a few minutes without losing all the coolant.

Since the cost of a head gasket replacement is more than what we paid for the poor guy, and he's got a number of other problems as well, we decided to just try and see if we could repair it with the goop (been using the K&W Fiberlock). It's worked pretty well since then, but every 6-9 months it starts to throw cylinder misfire codes which lets me know that coolant is leaking into the cylinders and it's time to add more goop in through the top radiator hose.

During our latest round of treatment, I made the stupid mistake of leaving it unattended for an hour or so while circulating the goop through the coolant system. I didn't realize what was going on until my wife pointed out that coolant was spraying from the pressure cap. I had severely cooked my LR! I immediately turned it off, and then carefully tried to cool the system by alternating periods of running the engine to circulate the remaining coolant and shutting it off to cool the engine (not sure if this was a good idea or not, but I didn't want to crack the engine by letting it cool too quickly). I believe my mistake was forgetting to bleed the coolant system this time after opening it up to add the goop.

Ever since then, I've had significant overheating issues. Driving in town, full sun, 80F outdoor temperatures for 10-15 minutes while running the AC brought me in excess of 232F as per my Pocketscan readings. The dash gauge was just starting to rise when I got to my last destination, where I had to park under a tree and leave the hood open in a desperate attempt to bring the temp down. Turning the AC off and cracking the windows seems to help a bit, but the temp is still far above the reference values other people are citing.

What I've tried so far:

- Pressure-tested for leaks a few months ago. The system held pressure, and the fact that the pressure cap valve opened up during the latest incident suggests that the system as a whole is sealed and holding sufficient pressure.
- Removed, cleaned and tested the thermostat with a pot of boiling water. It appears to open in boiling water, but is it possible that it's not opening enough? I'm not sure what the possible modes of failure are for the t-stat and whether it's possible for it to function suboptimally vs catastrophic failure.
- The radiator was replaced about a year before we bought the LR, but I thought maybe it could have been clogged by the goop. I disconnected it and flushed it with a garden hose until it ran clear with no residue from the goop. I can see with my IR thermometer gun that there is a clear temperature gradient from the top to the bottom when the engine has warmed up. This suggests that coolant is flowing easily through the radiator. Exterior of the radiator appears to be clean and free of obstructions.
- Disconnected the manifold outlet hose and briefly ran the engine. Coolant comes pouring out of the engine block, suggesting that coolant pump is working and there are no obstructions in the engine channels.
- Viscous fan appears to run, but I'm not sure how to test if it is running at sufficient speeds.
- Electric fan appears to kick in once the temperature exceeds its threshold.

Every time I have tested something, I have made sure to refill the coolant and bleed the air from the system.

The only components I haven't tested are:

- Heater core. Since this system runs "in parallel" and is relatively small, I can't imagine it plays a significant role in rejecting heat from the system overall. I can't easily test it since my LR uses an ECU to automatically control the air mixer temperature and it is currently summer where I live. I'd have to remove the center console and take the temperature of the core directly.
- Throttle hoses. Again, this is a relatively small component that I don't expect would impact the overall coolant temperature significantly.
- ECT (engine coolant temp) sensor. Maybe I fried the sensor and am getting false readings?

I'm not really sure what my next step should be at this point. Try a new thermostat? Test the performance of the viscous fan somehow? Remove and clean out the pump? Drain the cylinder block and look for sludge?

 

I’m sorry you are not meant or deserve to own a disco 2

 

The problem is you over-heated this is an all aluminum engine with steel sleeves, so you may have done a bunch of damage to one or more of the things below

• Clogged cooling passages with the block sealer - it is not uncommon
• The head gasket is shot - a combustion gas test may prove this
• Heater core is clogged - you can bypass that to test
• Cracked block - least likely but possible
• Warped the head pretty much the same as a head gasket just way more expensive to fix
• Thermostat could be flakey from the quickseal

My money is on the heads or head gaskets

 

Yes unfortunately this engine is often times a one-and-done with regards to overheating. You have probably warped the head, or if you are lucky just terminally failed the head gasket. Been there with my first disco. As I'm sure you know by now, overheating is one of the things that a disco owner dreads the most, and we go to great lengths to implement as many cooling system improvements as we can. If you plan to keep the truck you really have to budget for a head gasket change if you don't feel comfortable doing the job yourself. Start with the cheapest options tho, get a 180 degree thermostat and change temp sender, you might be right that it's gone wonky, never know.

Rhys L.

 

Don't underestimate the heater core. On steep mountain climbs on payment I can take the engine temp from 215 to 195 in a few minutes on a 90+ day. Not bad in the trees with the windows down. Idle in the summer - 206 is the magic hold temp for mine. If you do need to cool it down, pull under a tree and put your heat on high for a few minutes then turn of the engine.

Without properly fixing the heads you have a real gamble. Also that repair stuff can partially plug the heater core and radiator.

 

All of the above are correct... You will need an entirely new cooling system in addition to head gaskets now... If that works is still a gamble after you failed at the basic level.

Just because you got it for a low price does not mean you have a "cheap" car and should not treat it as such. Fail number one actually, but common for those just seeking to get a formerly expensive ride on the cheap.

You CAN NOT take cheap short cuts with these. Frugal maybe. Save money by doing your own work with quality parts... Don't have the money, time, or care to learn? Time to eat the loss and buy a Japanese car.

Luckily you came to the right place if you want to actually attempt to address your issues or at least ascertain where you now stand.

Lots of willing help here for even the stupidest questions. As long as you are a willing learner.

 

Thanks, I'll try the thermostat and sensor, and maybe next the radiator and water pump in case anything is clogged there. If the head is warped, wouldn't I be experiencing coolant leaks, loss of pressure, and misfires due to coolant seeping into the cylinders? I'm not getting any codes atm.

At any rate if I can't fix it with these steps...anyone want to buy a totaled Disco 2? 😂

 

@alexw You can have a warped head and leaking head gasket without coolant leaks, it largely depends on where the leak ends up and how bad it is.

When my head gasket went it was a tiny crack, the only sign was a slightly overpressure cooling system, no overheat no codes.

But at some point my Disco had been overheated by a PO the heads were so warped they could not be reused.

The reality is spending money on radiator etc is a waste, the thermostat and bypassing the heater are worth trying, if it still overheats assume the worst head gaskets. Then either fix the problem or scrap it trying to nickel and dime it will not save it.

 

Alright, got a new thermostat coming some time this week! How do I bypass the heater? Do I just disconnect the hoses at the firewall and shunt them together?

If I do decide to scrap, what do y'all recommend? LR parts aren't cheap and I'm sure it has plenty of salvageable parts. Would be nice to get some money back on it.

 

Thermostat & bypassing the heater core is NOT going to fix your problem. You have blown HG’s. If coolant is getting into the cylinders = HG.

Get the 80-100.00 HG kit from say Lucky8, and tear it down. The HG’s will tell you instantly what is going on along with any cylinders that appear to be steam cleaned. Also check your heads for being warped and either have them fixed, or get another set from a salvage yard.

The thermostat is the least of your problems IMHO. With all that goo you slapped in there I’d start over with all new cooling parts and flush the heck out of that engine block!!