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300TDI thermostat replacement

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Replacing the thermostat on this engine is very easy and straight forward - very little coolant is lost, there's a minimum of tools needed, there's no gasket as such, and you barely get your hands grubby.

Make sure the engine is cold before starting work.

The thermostat is right at the top/front of the engine sandwiched between the top radiator hose alloy elbow, and the thermostat housing:-


Remove the top radiator hose, and disconnect the thim bypass hose and tuck it out of the way.

There are also two plugs underneath the alloy elbow, carefully unplug them - the wire connections are quite fragile and will snap easily, so be careful.


Two 10mm head bolts hold the elbow to the thermostat housing - they are fairly accessible, although the bottom one is tucked away a bit. These bolts are usually quite tight, so 3/8" drive at least to undo them.


With the two bolt out, a gentle tap with a soft mallet or a bit of careful leverage, and the elbow will come off. The thermostat will be either stuck in it or still in the housing.


There's no gasket, but a rubber ring that sits on the lip of the thermostat. This seal is reusable if it's not damaged.

Thermostat with rubber sealing ring still on it.


Put the rubber seal (or a new one) on the new thermostat, then fit it in the housing - NOT the elbow. It will only fit in a certain position, so make sure it sits flush in the housing before re-fitting the elbow. Coolant loss is minimal, so a small top up is all that's required. There's a plastic bleed screw of the same type as the radiator on top of the thermostat housing - these shear off very easily, even when being careful. If you feel that you should bleed out the minimal amount of air that might get trapped at the top of the thermostat housing, they buy a replacement plastic one, or X-eng sell a metal replacement item that will last.

Les. :)

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