Background #
Water Pump Replacement is an eventual maintenance task. If you are having a coolant leak then other than checking hoses, the water pump is the next possibility. Also the heater valve. You may also experience noise or rattling from the engine. A stethoscope (or long screwdriver) placed on the water pump carefully while the engine is running may confirm bearing issues. With the engine off, you can grab the pulley on the water pump and check for movement. Not in the circular direction but side to side. There should be no movement.
Introduction #
If you determine there is a need for a water pump replacement then you’ll need to go through a few things. This experience is from the 1977 and later cars where the radiator is further forward and the electric fans are used. Early cars have the same general process but you will almost certainly need to remove the radiator. You will have little to no room to work if you do not. Also you will risk damaging the radiator.
The Process #
The cooling systems will need to be drained and you need to be ready to collect about 2 US gallons of anti-freeze/water mix. Removing the water pump itself is not difficult but you may have to fight with various hoses if they haven’t been touched in some time. Check and consider proactively replacing the coolant hoses while the system is going to be drained. Take your time removing and reinstalling parts. Take pictures to remind you of where things go and this can be a quite straight forward maintenance item/repair to do a water pump replacement.
Step 1 – Draining The System #
On the later cars the radiator generally doesn’t have a drain or petcock. As such this will be a messy process so plan ahead. If you have a drain or petcock this will be easy to start the drain process and capture the coolant.
Without a drain or petcock, you can remove the clamp from the bottom radiator hose at the radiator. If necessary break the hose free by rotating it, not pulling it. You may need to insert a flat screwdriver or other tool to separate the hose. Inserted far enough may make enough space for coolant to start to drain. This can help with directing the coolant to your container. Do NOT remove the hose completely unless you are somehow ready to capture 2 gallons of coolant coming out of an approx 1.5 inch hose fitting on the radiator! Manage the drain process until the radiator, and therefore the majority of the cooling system, is empty.
Step 2 – Remove Belt(s) #
If your car has an air pump still, there are 2 belts to deal with. The air pump sits above the alternator and has its own tension bolt and adjustment mechanism. However, as you may need to get to the alternator mounting bolts you will likely find it easier to remove the air pump. Undo the mounting bolts, disconnect hoses and also remove the tension adjuster mechanism bolt. The belt can then be easily removed.
All MGBs have a belt for the water pump, engine crank shaft pulley and alternator. To remove this, loosen the nut securing the alternator (generator maybe) adjustment mechanism. Use a 9/16th socket. The nut is just below the alternator and you’ll see the sliding adjuster. Once loose, push down on the alternator towards the engine block. If it will not move, loosen the nuts and bolts mounting the alternator to the block. Once the alternator is moved this will give just enough slack to remove the belt. You may need to rotate the belt/pulley as you do this as the belt has very little slack.
Step 3 – Remove Pulley From Water Pump #
It you have the air pump there will be 2 pulleys to remove. The earlier cars will have the fan attached holding the pulley in place. In both cases there will be 4 bolts to remove. If you are removing the fan from an earlier car pay close attention to the orientation. You will not want to put it on backwards during reinstall.
With the bolts removed you will then be ready to remove the pulley and fully expose the water pump on the front of the engine block. If you have not already, remove the inlet hose from the water pump.
Step 4 – Removing the Water Pump #
On the 1977-1980 cars there are 4 bolts and the bolts are not all the same length. Note which bolts come from where as you remove them. I like to either lay out the bolts matching the way they are installed or even draw a little diagram and keep the bolts on the diagram. Use the method that you like to use to keep track.
With the bolts removed you may be able to remove the water pump with pulling on it. You may need to break it loose with a few taps with a rubber mallet. If it is really stuck then some prying may be necessary.
Step 5 – Clean Engine Block Mating Surface #
As with any mating surface and gasket use, any old gasket material must be removed. Use your favorite gasket scraper, or razor blade and get the mating surface really clean and smooth.Carefully finish with fine (400 grit or higher) sand paper if necessary. Just take precautions not to get crud into the engine block
Step 6 – Prepare To Install New Water Pump #
Your new water pump should not require any preparations but always check. Also check the gasket fitment first. You may need to expand the gasket by soaking it in water to expand it. The gasket needs to align perfectly on the water pump and the bolt holes need to be completely clear.
My approach may be overkill. With hind sight I may have used too much of the Permatex 2B non hardening gasket sealer for my water pump replacement. However, I wanted to ensure no leaks. As the pictures below show I used gasket sealer on both the water pump and the engine block.Once you have prepared this and are ready you can move on to install the new water pump.
Step 7 – Install New Water Pump #
Have 1 or 2 bolts close at hand. Now fit the gasket on the water pump and then align and insert the new water pump into the engine block. Use one or 2 bolts to hold the water pump in place, just tighten with your fingers.
Check the fitment and then using your fingers get the remaining bolts started.
If you have an air pump remember to install the tension bracket as part of the bolting up of the water pump. You want to avoid having the remove a water pump bolt to address this later.
Tighten all bolts evenly and consistently. Ideally use a torque wrench to achieve the factory manual specified amount of 17 lbs ft.
Step 8 – Reinstall and Wrapping Up #
You can now proceed to put everything back into place. Note that it is possible that the new water pump may weep a little on initial use. Run the car for 50-100 miles before being concerned about any minor coolant leakage.
Make sure the belt(s) are properly adjusted for tension. Use new coolant (and hoses if needed) and connect everything that was removed.
Do a test drive and check for leaks and keep an eye on the temperature gauge while driving. Hopefully everything is fine and you will have completed your water pump replacement.
Other Materials #
I’ve built this website and spent time on the knowledge base to bring together a lot of information I have collected from around the internet. The intent is making it easy to find rather than having to know about and have skills with search engine query terms to get what you were looking for. Please make use of the knowledge base.
