The bearing in the water pump on my wife's car (2002 Vauxhall Corsa C, 1.2 Ecotec engine) failed - so I decided to make this my first Instructable! I'm keen to point out that I'm not a professional mechanic, and although this isn't the first time I've tackled a job of this nature, I'm sure there are better tools or techniques for elements of this task (and if you look closely at the background of some of the photos you might notice that I didn't necessarily carry out the steps in the order that they're published here!).
However, since replacing the water pump the vehicle has covered 500 miles or so without losing any water - so the fix appears to have worked so far.
I hope this is helpful to somebody.
Step 1: Diagnose / Confirm the Fault
The car had developed a rattling / grinding noise, which didn't seem to vary in pitch or speed with acceleration. The obvious thing to do here was to listen closely with the bonnet (hood) open while the engine was running. Having established roughly where the noise was coming from, I employed one of the mechanic's favorite diagnostic tools - the Listening Stick. Everyone has one of these in their tool box - even if they don't know it. It could be a length of wood, piece of plastic / metal - basically a stick of some sort which will allow you to place one end against your ear, and the other end against (in this case) the engine, in order to pinpoint noise / vibration. I used a long reach screwdriver, with a soft plastic handle. Placing the tip against various points of the engine, and the handle against my ear I was able to establish that the source of the noise was the water pump. BE CAREFUL what you're poking here, as there are moving parts nearby - in this case I placed the tip of the screwdriver against the engine block, very close to the moving water pump pulley in order to establish that this was the faulty bearing. If working under the bonnet with the engine running is unavoidable, make sure that any loose clothing is tucked in, and long hair tied back.
The water pump is driven by the top pulley of the auxiliary drive belt (the only moving belt you can see with the bonnet open), and is situated at the LH end of the engine block. On many engines, the water pump is driven by the timing belt, making it quite tricky to get at and involving a lot of work to replace (timing belt / tensioner are usually replaced at the same time). Luckily this Corsa's engine is an exception and the pump is easy to get at once you've removed a few bits.
Step 2: Remove the Air Box
The air box needs to be removed in order to allow access to work on the water pump. To remove the air box, first release the inlet / outlet hoses, loosening / removing hose clips as necessary. Unclip anything else attached to the air box - in this case, the 'MAF sensor' was clipped into a slot at the rear, and can be tucked away to one side once removed. The air-box itself is held in with simple rubber mounted 'push' fittings. Giving it a good yank will release it from these.
Step 3: Drain the Coolant
A small plastic drain plug is situated at the base of the radiator - I'm afraid the only picture I could get isn't great, but if you squint you can just about make it out. Place a large-ish bowl (I used an old washing up bowl) beneath the plug if you don't want to get your feet wet. (If it's a windy day, I learned that you'll still get your feet wet unless you put a brick in the bottom of your bowl.) Loosen the drain plug but don't remove it fully - if this can't be done by hand use a pair of pliers, but be very careful - if you snap it off there's no way to drain the radiator without removing it altogether. Don't remove the bowl yet.
Step 4: Remove Hoses Etc.
All inlet / outlet hoses / electrics etc., need to be removed so that the water pump is free. Use water pump pliers to squeeze the hose clips. It's often easier to push the clip further down the hose away from the spigot, allowing you to remove the hose freely, rather than trying to hold the clip open and pull the hose off at the same time. Water hoses will often be stuck tight with residue, but a blunt screwdriver or something which won't pierce the hose can usually be slipped under the edge to persuade the hose to part company. When you pull the hose away, any water still held in the system by vacuum pressure should trickle out of the open drain plug.
Inspect the hoses for any cracking / bulges, and replace if necessary. Tighten the drain plug.
Remove the water temperature sensor plug at the top of the water pump. I used a pair of pliers to carefully squeeze the plastic tab as it wasn't quite free enough to be removed by hand.
Step 5: Support the Engine and Remove the Engine Mounting
To gain access to the water pump, the LH engine mount must be removed. Before this can be done, the engine must be supported. I used a scissor jack to take the weight of the engine on the sump (in this case I had another jack handy, but if not, the jack from the vehicles tool kit would be suitable), and placed a piece of wood between the jack and the sump to spread the load. You're not aiming to lift anything with the jack, just to take the weight of the engine when it's mounting is removed. Once the jack is tight and can't be pulled out, it shouldn't be raised any further.
Two screws hold the engine rubber mount to the chassis of the vehicle. Another two screws hold the flexible mount to a casting which is in turn bolted to the engine block. I had to remove all the screws and fully disassemble to gain access to the pump. The lower screw of the casting bolted to the engine block is tricky to get at without removing the wheel and access trim, but it can be done. The screws are TORX (star) type, and should be removed with the appropriate sockets, but if you don't have a set you'll find that standard sockets will fit pretty well - although when re-fitting you may be unable to tighten them to the correct torque before the socket slips.
The engine mount casting can be tricky to extract - I found it was possible using a length of wood to lever the engine out of the way by a few centimeters.
Step 6: Remove the Auxiliary Belt & Pulley
The auxiliary belt which is driving the water pump pulley must be removed. With the belt still in place, loosen the three screws securing the pulley on to the shaft (the tension of the belt will make this easier - remove the belt first and you'll need an impact driver to do this). Place a socket on a power bar (long socket spanner/wrench) on to the nut in the centre of the belt tensioner as shown (this is a pic was taken during re-assembly without the pulley fitted, as the view of the tensioner is clearer). Pull the power bar towards you and you'll see the belt loosen. If you look closely towards the spring pushing on the tensioner, you'll see a small tab appear at the end of the mount as you release the tension. The tab has a small hole in which you can place a pin (hex key / screw / whatever is handy) to hold the tensioner in position. It might not be necessary here if you can slip the belt off the top pulley with one hand on the spanner - but either way, hold the belt somewhere away from any pulleys to avoid trapped fingers. Once the belt is off, the pulley can be fully removed, and you can now see the water pump.
Step 7: Remove the Thermostat
Remove the three screws securing the thermostat as shown. Once these screws have been removed, if the thermostat doesn't come away easily, a light tap with a soft faced mallet should free it up.
So, here's the water pump - held in place with nine screws, two being hidden in the photograph. (If you find ten, you've undone the trick one near the thermostat, so put it back - this one doesn't need to come out!) Undo these and the water pump should come free - if not, use the rubber / wooden mallet again. The screws are all different lengths, but don't panic - it's impossible to get them mixed up as a long screw in a short hole will bottom out too soon, and a short one in a long hole won't catch the thread.
When I was removing the screws, the head of one sheared off the moment I applied some force. I was tempted to make this into another Instructable if it became difficult to remove, but as it happened it was easily (and carefully I might add, as there is a mating surface here) removed with mole / vice grips. There might be a lesson to be learned here if it had been stuck tight and I'd been forcing it (bad idea), but in this case it was unavoidable as the shoulder of the screw was corroded where water had leaked out of the pump chamber. Sometimes these things happen, and that's what mole grips are for. If you encounter a similar problem, my advice is to have a cup of tea then sit down think carefully about the best approach before doing anything about it - diving in with the first tool that comes to hand usually makes things worse.
Remove any interchangeable parts from the water pump - depending on the type, it may have components fitted which won't come with the new one. Gaskets should be provided where necessary.
Step 9: Clean Up the Mating Surface
Remove the old 'gasket' (like a convoluted 'o' ring in this case). I have some handy dentist tools for this sort of thing.
Use ScotchBrite or wire wool to clean the mating face ready to accept the new pump. N.B. There's a video on Youtube of someone doing this job, and a razor blade is used to scrape the surface clean. Personally I'd avoid this as the engine block is aluminium and could easily be damaged with anything other than a plastic scraper.
Step 10: Fit the New Gaskets
The new pump should be supplied with new rubber gaskets - one for the pump itself, another for the thermostat, and any other joints.
There's probably different schools of thought on this, but I like to use a product called Form a Gasket # 2 which is designed to 'improve the sealing performance of pre-formed gaskets'. https://tds.us.henkel.com/NA/UT/HNAUTTDS.nsf/web/07AA5736D6BB3BDD882571870000D993/$File/Form2-EN.pdf. Silicone is another option, but I prefer this stuff as it doesn't set.
Spreading a little of this along the groove is enough to hold the gasket in place, and any that is pushed out as the joint is tightened simply improves the seal. Only a little is needed, as it's best to avoid having it squeeze out of the joint on the inside of the pump. Remove any excess with a finger / plastic spreader / lolly pop stick (eat the lolly first).
Step 11: Check Locating Dowels Are Correctly Fitted
Upon removal, one of the hollow locating dowels came away from the engine block and remained in the pump. These dowels are fairly thin walled and could easily be damaged if forced out with pliers, so as it seemed reluctant to come out I decided to use some heat.
A little heat applied with the blow torch to the aluminium pump casting near the dowel soon freed it up and I was able to remove carefully with pliers. Once cleaned up the dowel pushed easily into the correct location in the engine block.
Step 12: Re-assembly
The remainder of the re-assembly procedure is basically the reverse of removal so I won't go into great detail.
• Clean all parts as necessary, particularly screw threads & mating surfaces.
• Tighten all water pump mounting screws 'finger tight', then tighten the screws in an opposing pattern. The correct torque is 8nm (doesn't seem like much, but it's correct). As a matter of preference, I used thread-lock adhesive on the screws.
• Correct torque for the engine mount is 40nm.
• A small amount of Vaseline (insert your own joke here) applied to the inside of the water hoses allows for easy re-fitting. (Or, if practical the hose ends can be soaked in hot water to soften them.) Using new hose clips often makes life easier than struggling with the old rusty ones.
• Use fresh coolant / anti-freeze, mixed as per the instructions on the bottle. When re-filing the system add water slowly to avoid air-locks, and squeeze the hoses gently to push any bubbles to the surface.
• Take the car for a run to get it up to temperature and then check that the coolant level hasn't dropped. Check the level periodically for the first few hundred miles.