22 November 2022
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This job is often made more difficult by the effects of corrosion
: credit: © Alisdair Cusick
Replacing a coolant pump should be simple, but when bolts and studs shear, there’s big trouble. Alisdair Cusick explains how to fettle them
Need to know
Time: 2 hours.
Difficulty: 4 out of 5 stars.
Models: Most Land Rovers up to 2002.
Tools needed: Spanners, welder, grips, screwdrivers, funnel/watering can, impact gun optional.
Parts needed: Water pump (269974) £54.01; fixings kit £21.48; sealing ring (RTC1975) £2.18; fan belt (STC3673) £34.86.
Work safely:
• Use the right tool, for the right job.
• When using welding equipment, wear protective overalls and gloves in addition to the correct face mask.
• Always be fire safe in the workshop.
• Allow the coolant system time to fully cool and depressurise before releasing hoses or any other work. Release the pressure cap with care in case of residual heat and pressure.
• Bleed the system only when the coolant is cold and depressurised.
• Always disconnect the battery before welding on a vehicle.
• Get an expert to do the job if you’re in any doubt about it.
Thanks to: James Holmes for his help with this feature.
Regardless of fuel type, capacity or age, all our Land Rover engines use a water pump to circulate coolant. It’s belt-driven, usually off the crankshaft, and the drive belt will usually power the alternator, power steering pump, or air conditioning compressor, too. Impeller blades inside the coolant pump push coolant around the sealed coolant system, through the engine water jackets and passages, to the heater, through the radiator to cool, and back into the engine block in a continuous cycle, and at a flow-rate controlled by the engine speed and thermostat.
Water pumps can last for decades if drive belts are correctly tensioned, and if the correct coolant dilution is used and changed at the specified intervals. But they are a moving part, using bearings for the shaft to spin on. Those bearings wear, and can allow movement in the shaft. If left in that condition, bearings can lock up, with the potential for catastrophic engine failure from overheating. Failing bearings are probably the most common reason to replace a water pump, and they create a telltale whining sound. Beyond that, gasket leaks and impeller corrosion can also be reasons for changing a water pump.
James Holmes show us how to change a water pump on this Series I’s 2.0-litre petrol engine, but the process and principle is broadly similar on all Series, Tdi Defender and Discovery, Range Rover Classic and P38A models. Later engines are more tightly packaged, so can be slightly more involved, though the basic principle is the same, and the likelihood of shearing bolts is greatly reduced.
The one key thing we’re pointing out here is how to deal with the most common issue associated with this job: corroded water pump fixings shearing off while trying to undo them. It’s a nightmare when we feel them shear, but the solution isn’t too troublesome, and it’s very effective.
In this case, we’ve already drained the coolant system after letting it fully cool and, unusually, we’ve removed the fan, radiator, front panel and wings on this car, to aid photography. Usually, this is a job done leaning down into the front of an engine. Fixings are usually easy to reach that way, and the area offers plenty of room to work – though not to photograph.
Diagnosing a failing pump
There are a couple of ways to spot problems with a water pump, besides the obvious gasket leaks. First, use your ears. Bearings on their way out will start to whine, or even grumble. Any unusual noise warrants a further check. The way to do that, is to use your hands on the pulley shaft and feel for any side-to-side play. It should be tight, but rotate smoothly. Any wiggling in the shaft, or rough spots when rotated, mean it’s time for a new pump.
Removing the old pump proves tricky
Removing a coolant pump should be a simple job on this Series I, with excellent access and room to work. However, the old problem of corroded bolt threads plays its part, always demanding great care during initial release and subsequent winding out.
Unbolt with caution: Choose a water pump fixing with good access. With a well-fitting spanner or socket on it, force is applied. Hopefully, we feel it come free and rotate.
Moment of dread: With a crack, this fixing shears in half just at the end of the threaded section. Will they all do the same? Only one way to find out…
Avoiding the snap: Sometimes, a little heat can help. Using an oxyacetylene torch, James carefully applies heat to the head of a fixing for 30 seconds, then tries to undo it.
Four out of eight: Using this technique, four of the eight fixings come out in one piece. However, the other four shear. We now have to extract those from the engine block.
Where to start? The four broken bolts have barely a thread or two standing proud of the engine block. It can look daunting, but there’s a way to get them out.
Make it a bolt: James deftly TIG-welds a nut onto the stump of the fixing. A spot-weld first attaches it, then he fills in the nut centre with weld for extra strength.
Voila! The finished job: Effectively, the remains of the sheared fixing now becomes a bolt. The nut doesn’t even need to be squarely attached, just welded with good penetration.
Will it come out? James uses an impact driver, thinking a little extra shock may help coax it out. With a few measured taps from the gun, the fixing spins straight out.
Result: This is the result. Because it threaded out cleanly, there’s no further damage or swarf in the engine block, unlike using a drill, which needs great care.
Engine face: Now, there’s just one remaining stud to remove, then the gasket face will be carefully cleaned and, if necessary, flattened before fitting the new pump.
Installing the new pump
Gasket is important: With all the sheared studs out without further issue and a clean mating face, we’re ready to fit the replacement parts. First, a quality gasket goes on.
Old and new: The old pump and the new replacement. It sounds basic, but check the new part
is correct. I always check the mounting hole positions are identical before fitting.
New seal: Now is the time to change any other minor seals around the pump. Here, we fit a new rubber O-seal for the water pump/thermostat housing joint.
On it goes: The new pump is offered into position. I don’t use sealant because any that comes loose internally can clog a heater (usually the smallest passages in the system).
Fix it in place: New bolts are used, with lock washers, and torqued up. Note, there may be varying bolt lengths around the pump. These are BSF thread, being a Series I.
Anything else? Connect any surrounding feed pipes such as this water pump inlet pipe,
which has its own gasket. We fit a new one of those and use new fixings.
Important part: Especially on SI, check the fan for cracks – a fan shattering can take a radiator out. Satisfied, refit the fan, pulley and belt. Don’t over-tighten the belt.
Hoses: Consider the condition of coolant hoses and belts. Replace any remotely suspect, and don’t forget the heater feed pipes, too. On a Series I they are copper pipes.
Fill her up: Refill the system with the right mixture of antifreeze to water. Check the refilling instruction for your car; some fill through theradiator, some through the coolant reservoir.
Bleeding a coolant system
Any air needs to be removed, or bled, from the system, otherwise it will collect at high points and restrict the flow of coolant. Every engine is different, some bleed more easily than others, and design may affect how you fill the system in the first place. Check the workshop manual for your vehicle.
This Series I fills from the radiator, and self-bleeds very well. As the radiator is the highest point in the system, air moves there as the engine runs. However, a late Rover V8 system, particularly Discovery 1 and Range Rover soft dash (1992-96 models), can be troublesome to bleed. In those vehicles, air can become trapped inside the heater matrix, as evidenced by little or no heat from the heater.
To help bleed a coolant system, normal practice is to have the heater set on maximum heat and run the engine. Repetitively squeezing a top or bottom hose (but only with the engine stopped) can help coax air upwards, or unbolt the coolant reservoir from its mountings and run the engine while holding the reservoir raised up 10cm or so. The extra height can help encourage air up to that point. It’s important not to run the engine too long or allow heat and pressure to rise while using any of these techniques, especially while the filler cap is off. A couple of minutes is enough.
Some engines, such as early 3.9-litre V8s and Td5s, have a bleed valve conveniently placed high in the system. These are much easier to bleed, for with the engine running, you simply loosen the bleed valve, tightening it up again when coolant flows out.
Ed Evans adds: As Alisdair says, you may hear coolant pump bearings whining or rumbling. You might also notice a drip of coolant from the tell-tale hole in the pump casting. This indicates that the seals at the bearings are damaged, and the usual cause of this is bearing wear which allows the shaft to run off-centre, thus distending the seals which then leak. Either way, a replacement pump is needed.
Setting the fan/drive belt tension is critical. A belt that is too slack may not drive the pump at its correct speed, risking the engine overheating. If too tight, it will put side force on the bearings, wearing them prematurely.
It’s worth noting that on the 300Tdi engines, the gasket between the coolant pump and the engine block tends to leak, producing a drip (and a stain from antifreeze) down the front of the engine. The coolant pump is probably okay, but the gasket needs replacing before the block face starts to corrode.
The coolant pump on Td5 engines is difficult to reach at the rear of the power steering pump. This coolant pump is driven from the steering pump shaft at the back, and the connection can fail, leaving the coolant pump static, and quickly resulting in overheating.
Any risk of engine overheating should be avoided as, whilst early engines can deal with it up to a point, or be repaired, later engines including the Td5 cannot be re-machined if warped.
Moment of truth: Having bled the system, start the engine (heater set to maximum), run to operating temperature, switch off and check for leaks. If happy, road test briefly and re-check.
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