Colleagues, I could use a little help here.

Vehicle – 2004 Discovery SE, 70,000 miles, owned for 1 year.
The problem – Overheating when driven and I am aware of thehistory of slipped liners, bad water pumps, bad thermostats etc.

Last week and out of the blue, our Disco overheated and violentlyvacated all of the Dexcool coolant through the coolant reservoir. I initially replacedthe thermostat. Now twice, I’ve refilled, purged all of the trapped air as per theD2 workshop manual, bled any residual air when cold and topped off thereservoir as necessary. Both radiator fans (viscous and auxiliary) areoperating and seem to be in good condition. Our Disco does not leak any coolanteither. The engine oil is good with noevidence of cross contamination due to a blown head gasket.
After I refilled, purged and prepped, she runs fine in thedriveway and for hours. During this I will rev her up to 2000 – 2250 rpms onoccasion to help purge the heater core. During the driveway test, hot air is comingout of the heater, and as soon as I drive around the neighborhood and put aload on the engine (<5mins) the heater will go cold, the temp gauge beginsto rise and I have steam injected back into the coolant reservoir.

Yes, she has always had a tick at idle, however it seems togo away under a load. The only new noise seems to be coming from the front ofthe engine (water pump?) and sounds like a stretching fan belt. Which is also ingood condition. Again, she isn’t leaking any fluid and I spent a couple ofhours looking for coolant leaks all to no avail. Overheating is only under aload.
I can’t get into our mechanic for another 10 days and amhoping that a member can assist in getting to the root cause here.

 

So the heater going cold, before it overheats seems to be the key here. My brain ask is the heater going cold because it is expelling coolant first? If that is the case then it isn't significant because your heat is going off because you are low on coolant, which would rule out the thermostat. however if it goes cold first in is should be a stat issue.

so lets go with that, take a photo of the stat and how you have in connected just to make sure it is on right.

However, if it is not the thermostat i would my concern would be exhust pressure purging the system, so bet it pressure tested.

now i am rambling is the coolant circulating, threw the system, all coolant lines warm while running, you see it moving in the res, and coolant flowing out of the purge valve?

 

Your alternator could be going bad - the bearings in the alternator are locking up. The belt slips.

Or the water pump bearings are going bad.

Or pulley bearings. You need to figure that out first.

For heat up under load you need:

1) Low temp genuine Land Rover thermostat 180 degrees.

2) New Nissen's radiator from RockAuto Parts Catalog

then you'll be set.

 

All the above. And a scanner that shows live data - the factory temp gauge points at 50% from about 130 - 240, so it is almost useless. As an example, the Ultra Gauge shows you are starting to over heat a lot sooner (which I bet you are).

Note in the two pix the gauge reads the same. Also, if you have been running Dexcool then it is quite likely that Dexmud has formed in the lower rows of the radiator. An infrared thermometer will show cooler rows on bottom, because they are restricted. No flush will get it all out. A new radiator is best path.

Oh, almost forgot - have mechanic run a chemical test for exhaust gas in coolant first. Cracked block or HG can be injecting that steam, boiling out coolant from over pressure. Test makes a fluid change color from exhaust gas in coolant, a kit that does maybe 15 tests is like $60.

 

Savannah,

Many thanks for the note and insight. Outstanding photos too! A picture is worth a 1000 words.

All the best

Far North

 

I am curious if you determined the cause? I am having the exact same problem in my 2002 Disco II

 

Folks,

Thanks to all you have replied and provided insight. Unfortunately, I've confirmedthat my No. 6 cylinder liner has slipped allowing combustion gases to enter thecooling system. With a $5,000 engine replacement price tag, I'll be putting herup for sale or auction.

Far North