I recently purchased a 97 Disco SE with about 160K on the clock.
The truck ran well except the temp gauge would climb and fall seemingly at random. I found this website (LRF.com) and took some advice and corrected the belt routing and problem solved!
Ran it for 30 miles and the gauge stayed right in the middle.
Then...I decided to "fix' the gurgle behind the dash which I guessed was air trapped in the heater box. Sounds like a water hose emptying into a bucket.
I thought if I parked the truck on a slight incline the air would better find its way to the open radiator cap during bleeding.
That didn't work. Now I have no heat and the temp gauge is up and down again.
Before I flush the system, I thought I ask for some wisdom and see if there is a simple way to correct this.
Here is exactly what I did last.
1. Parked on a slight incline (3%)
2. open the radiator plug (on top)
3. Open the cap on the reservoir box
4. run the truck with the heater on
5. Capped the plug when fluid ran out with no bubbles
6. Waited a few minutes (no heat)
7. The gauge started indicating hot so I capped the radiator (reserve) and turned it off

I tried again on a flat surface when it cooled off with the same result.

In case it helps, here is what has be done to the truck based on the records from the last owner.
Stuff that’s been done….
2007
Oil pump
Head gasket
Timing cover gasket
Timing chain
Timing chain camshaft & crankshaft
2005
Waterpump
Serpentine belt
Pipe to manifold gasket (rt)
2004
Alternator
Thermostat
Exhaust gasket
Front rotors
Repack front wheel bearings
2003
Starter

Next time...I'm going to quit when I'm ahead!
Any suggestions?

 

The air needs to come out, that is what is causing your problem.

You can try revving the engine to 2000 rpm as you bleed the system.
Rev it and hold at that engine speed for a few min, leave the plug in the radiator but the cap off the overflow while doing this.
You can stay in the truck and keep a eye on the temp gauge as well as feel for heat.

If that still does not work let us know as there is one more thing to try.
But that usually does the trick.

 

Thanks. I'll try that in morning.

 

That did the trick.
Thanks!
I'll try to come up with something more advanced next time.

 

Glad that worked.

And I hope so, that was to easy. LOL

 

Spike, What is the next trick if that don't work?

 

The next trick Danny is to switch the heater hoses so that the supply is now the return and vise versa.
By doing that the water pump will force the air pocket up and out of the heater core instead of down and out.
Coolant flows through the heater in the same direction as the radiator, top to bottom.
A stubborn air pocket in the heater will come out if you reverse the flow but then you still need to put the hoses back in the correct order once that has been done.