Cooling System - Overheating Engine

303-15

XK8

DATE: 10/97

Cooling System Bleed Lines - Correct Routing - Model Year Differences

MODEL
1997 MY-ON XK8 Range

VIN
001001-ON

Issue:
There are differences between the routing of the cooling system bleed lines between 1997 Model Year vehicles and 1998 Model Year vehicles. Incorrect routing at the coolant reservoir connections could lead to air remaining trapped in the cooling system, resulting in overheating of the engine.

Action:
In case of a customer complaint of engine overheating on an XK8, check that bleed lines are correctly routed as detailed.

1997 Model Year Condition VIN 001001 - 018107

^ Reservoir: Part No. MJA 4400AC for 1997 MY only.





^ Bleed line R, Illustration 1, from radiator is connected to front fitting on reservoir Illustration 1).

^ Bleed Line T from thermostat is connected to rear fitting on reservoir.

1998 Model Year Condition VIN 018108 ONWARDS

^ Reservoir: Part No. changed to MJA 44OOAD for 1998 MY.





^ Bleed Line T from thermostat is connected to front fitting on the reservoir (Illustration 2).

Note:
There is no bleed line from the radiator. This has proved to be unnecessary.

^ The rear fitting of the reservoir (not connected) is plugged.





RESERVOIR INTERCHANGEABILITY:
It is permissible to use the 1998 MY Reservoir Part No. MJA 44OOAD on 1997 Model Year XK8 Models provided that the bleed lines are reversed at the reservoir from the original layout (Illustration 3) as shown:

^ Bleed Line R from the radiator is connected to the blanked off rear fitting on the Reservoir (Illustration 3). ("This is satisfactory, since air will vent from the radiator by routes other than this bleed line).

^ Bleed Line T from the thermostat is connected to the open front fitting on the Reservoir, as in Illustration 3. THIS VENT CONNECTION Is MANDATORY. Trapped air in the cooling system cannot vent if the thermostat bleed line is connected to the plugged rear fitting.

DIAGNOSIS:
In any case of high coolant temperature/coolant loss, check that the bleed line from the thermostat is always connected to the correct (open) fitting of the reservoir, especially if a 1998 MY Reservoir may have been installed in a 1997 MY vehicle.

Warranty Information
This Technical Bulletin is issued for information only, to aid to diagnosis.