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Land Rover Tdi Engines used in Defender
and Discovery like many other
turbo diesel engines can suddenly overheat due to loss of
coolant or cooling.
Tdi engine is a somewhat stressed engine that uses an alloy head on a
steel block. The engine relies heavily on good oil pressure and good
cooling.
If the oil pressure or cooling is interrupted or removed for even a
short period, the engine
will very quickly burn out.
Common reasons for this happening are:
- Radiator hoses fail or come off due to improper fitting or hose
damage
- Plastic thermostat and radiator plugs disintegrate without warning
- Serpentine belt breaks, leaving the water pump stationary
- Broken or seized Power steering, idler or air-con pulley leading
to main belt failure and stationary water pump.
- Accumulated sediment in the radiator.
- Low cooling fluid level due to negligence or leakage
- Incorrectly torqued head or Air cleaner mounting bolts
- Incorrect Diesel mixture or timing leading to high Exhaust Gas
Temperatures (EGT)
As preventative measures, always ensure the above items are taken
care of - never assume anything or try "just make it home",
you will be sorry. The plastic radiator plugs can be replaced with solid
brass plugs as originally fitted to Range Rover engines.
It is becoming increasingly common that people assume the Tdi to be
an extremely expensive engine to repair after a burnout.
The main reason for this is that it is believed that the cylinder head
cannot be skimmed and if not within spec, must be replaced - this is an
expensive chunk of aluminium - in the region of R 8000 !
When a Tdi engine overheats badly for what ever reason, the following
things happen:
1) Cylinder head warps - by as much as 2mm over the length
2) Two middle pistons start to heat seize to the bores - the alloy of
the pistons sticks to the steel sleeve.
3) Outer two pistons also heat seize and the cylinder head may
actually crack.
There are 3 different thicknesses of cylinder head gasket available
for the Tdi - This is to accommodate differing head thickness after
skimming.
If the head has been skimmed before or the
warp age of the head is so
severe that the head is too thin the head is believed to be useless as
the thickness does not determine compression but determines the
valve to piston clearance measurement. If this clearance is too
little, the valve will hit the piston crown causing severe damage to the
valve train and piston.
It is possible to have the cylinder head metal sprayed, such
that it is back to the original new specification.
The procedure entails heating the head up and spraying molten aluminium onto the head surface, the surface is then re-machined back
to new - original spec, the valves are re-seated and the head is as good
as new. This procedure costs less than 1/8 of the price of a new head
and is as good as a new head.
It may also be possible to have head cracks repaired in this way as
it involves heating of the entire cylinder head and effectively
resurfacing the head, this however has not been tried yet.
Generally speaking, if the engine overheated due to water or cooling
trouble, the bearings and general sub assembly is still fine and need
not be rebuilt. Disco Tdi
Overheating
Overheating of mainly Discovery
Tdi vehicles due to the failure of a variety of components. To complicate
matters more it appears that the temperature gauge did not alert owners of
the problem, resulting in severe engine damage.
There are really 3 components in question:
The first is a the standard flexible gasket (ERR3284), that has
subsequently been replaced with an improved aluminium version (PET100790).
The second has to do with the radiator hose coming loose or even failing.
Then lastly the over tightening resulting in damage or stripping of a
plastic radiator filling plug.
Installing an
engine monitoring system like the Madman EMS
(available from
LandyOnline Retail) will provide peace of mind
on engine monitoring and performance and alert you
before it is too late.
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