They have a good tendency to block inside. Take it out and have it rodded out
by a competent rad shop. This should only cost around 50-70 US$ and will give
your rad a second live. Have at the same time installed a release valve to empty
the rad next time. Another good idea is to have 2 fittings installed for a possible
later installation of thermo switches. One can activate an electric fan while
the other may switch an warning light.
Range Rover rads are even more vulnerable as they have a side-to-side flow
while the Defenders have a upper-lower flow.
You can check the rad easily by feeling for cold spots when the engine is warm.
Any difference in temperature indicates a weak spot.
There are several different sizes of interchangeable radiators with different
cooling abilities. Some have an intercooler built in, others have an oil cooler.
Some even have both. From the engineering point of view it's not the best idea
to mix tasks. If you want to go for the maximum water cooling get an rad that
only cools water. I believe early Turbo Diesels had the biggest ones but I may
be wrong on this. Talk to one of the rad specialists for Land Rovers and they
will surely tell you what's the best. An oil cooler for engine oil is is normally
not needed but can be fitted as an aftermarket unit below the radiator. If you
have an automatic box you must use an transmission oil cooler. This one can
be mounted in front of the normal rad but it will block off some air and heat
up the other rad- not the best idea. But you haven't much choice.
The Intercooler needed for the TDi engine is another story. The factory ones
are WAY too small to reduce intake temp to good levels. If you get an aftermarket
unit it will lower the air temp by up to 40 degrees Centigrade allowing for
12% more power without other modifications except adjusting mixture.
Those can only be mounted in front of the radiator but heat output on the TDi
is much lower than on the V8 and generally no problem at all.
3. The thermostat
An ugly little piece that hides behind the distributor and has a tendency to
stick. If you suspect it junk it out. They aren't expensive and can stick in
any position. You can get them in various ratings, the lowest being 74°C.
But remember that an engine is more efficient the hotter it runs (but not boiling).
You can even get aftermarket thermostats with a buil-in safety. It's a small
metal tube that extends when the engine overheats and forces the thermostat
to open and stay open. You might to have to shop around a bit to find them and
they are almost double as expensive as standard units but worth every Penny.
And they must be replaced once the engine overheated as the unit can't close
4. The ignition timing
The V8's are sensible to ignition timing. If the timing is about 4-5° off
you will get an overheating engine. I've set mine at 8° BTDC at 800 rpm
(for an 3.5 EFI).
5. Corroded block
The aluminium block is very vulnerable to corrosion if the wrong coolant is
used. You MUST use coolant designed for use in aluminium engines. Corrosion
can partially block the water galleys and make an insulation that prevents heat
transfer. Once you have this corrosion you have a problem that can only be resolved
by stripping and dismantling the engine. Corrosion can even make holes inside
the cylinders, allowing the water to leak inside.
6. The cylinder head gasket.
Hey, that's my favorite one. The Rover engine has a special design fault in