300Tdi vacuum pump rattles
WHEN LAND Rover reworked its long-serving four-cylinder diesel engine for the last time, simplifying the design to reduce costs, one of the least welcome changes in what became the 300Tdi engine was the replacement of the nearindestructible rotary brake vacuum pump with a rather less durable plunger-type pump. I am not a fan of these pumps. They leak oil from the end cover (held on with pop rivets that stretch slightly over time), are awkward to change (especially on the Defender where the air cleaner bracket and stay are perfectly positioned to obstruct access) and will eventually wear out and stop working. This event is normally preceded by a rattling noise that sounds exactly like a badly-adjusted valve. When the pump fails altogether you will know about it: 300Tdi Defenders have disc brakes all round, and without servo assistance it will feel as though someone has jammed a block of wood under the brake pedal: almost no travel and precious little stopping power unless you really stand on the pedal.
This kind of failure is not always the fault of the vacuum pump itself. The pump is lubricated by a spray jet positioned just under the camshaft. The jet is of very narrow bore. In theory this should not be a problem as it is fed by filtered oil from the main engine lubrication system. However, on engines where the oil has not been changed on schedule, sludge can start to build up inside the oil passages, and the first oil passage to be blocked as a result will probably be this little jet.
When you remove the vacuum pump, the area immediately behind the mounting flange on the block should be absolutely swimming in engine oil. If it is not, it is a good idea to remove the jet (10 mm slimline socket, and make sure you don’t drop it as you withdraw it or it will end up in the sump) and blow it through to remove any debris. You might then want to run some flushing additive through the engine to tackle the sludge build-up before it causes worse problems, such as blocking the jets which spray oil onto the undersides of the pistons.