Water pump preventive replacement

Dear Jag- lovers, I am in the process of repairing the gearbox of my car and, since the engine is removed from the car I wonder if I should take advantage of it to preventively replace the water pump, in order to improve the reliability of my car.
From experience, what are the failure modes of the water pumps and reasons to have them replaced ?
Do they progressively deteriorate or can lead to a sudden failure and car immobilisation ?
Kind regards.
4.2 l 1966 S1 FHC

Hi Christophe

It is wise to consider replacing the pump when the engine is out.
Given the time it takes to replace the pump with engine in place, I recommend it.

Dennis 69 OTS

And just in case you haven’t thought of it, replace all the hoses, belts and engine mounts too. Inexpensive parts than can be a challenge to fit otherwise, and will add to the cars reliability considerably.

If it’s been awhile, also consider pulling the radiator and having it flushed. Also inexpensive and much easier to do with the engine out.

Right after that, have @69Cat help design a rotisserie!



Thank you very much all.
I will certainly follow your pieces of advice.

I agree that the water pump should be replaced.

I recently installed a unit manufactured by XKs Unlimited and it is excellent.

There is better flow and now the engine does not overheat.

No core charge.


I deleted this post…

Thank you Bob, for your comment. I ordered it, as well as the hoses, jubilee hose clips, belt and engine mounts.
Kind regards.

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I’m sure you’ll think of this but – after I replaced mine with a new one while the engine was out I put the old pump in the boot (inside the rim of the spare) as it was working well when removed.

Can’t say I relish the thought of replacing the pump in a motel parking lot… at night… in the rain - but given how far from home I sometimes get, it is at least an option.

Packed with that spare pump is a new gasket and a chart (courtesy of Mike Frank) showing which bolt goes where.

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IIRC we had someone do that on the last Oil Leak. Not a bad idea at all, besides it ensures that you will never have a water pump failure if you pack it (pretty sure that’s a corollary to Murphy’s Law).

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Et tu, Fuel Pump Boy?


So true…
LLynn :slight_smile:

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I have this one as well on my 3.8 - in place four years and all good.

On my side, following a break down, I installed 2 fuel pumps in parallel, with a switch to activate one or the other.

Do you really consider replaceing the water pump as preventive maintenance…if its making a noise or leaking ok your replaceing a faulty part…you wouldnt think about replaceing the oil pump whilst the engins out would you?..if it aint broke dont fix if…just my opinion…Steve

I suppose the difference is that I have never had an oil pump let me down but have had many water pumps that have failed.

Sure, they have always given a lot of warning by leaking or making noise or both… but installing a quality replacement is so much easier while the engine is out. I was already carrying that replacement as a spare – now I have a fresh pump and still have a workable spare should it be needed.

And in addition to the historical failure rate George mentions, a water pump has a rubber seal that will, as a matter of course, fail at some point. The oil pump does not. The oil pump is constantly lubricated with a supply of oil. The water pump is typically a sealed bearing, with no replacement oil.

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Some suppliers/rebuilders, Coventry West and maybe others, also offer a pump with an enhanced impeller. Moves more water per revolution, IIRC. That in itself, along with the piece of mind of having a new unit in place might be worth the nominal cost.

Geo - Can I get a copy of that chart?
Thank you

How long does a water pump generally last? A new one was put in place four years ago when my engine was rebuilt. My 4.2 engine is not out, but I don’t have a spare for the long tours and like Geo sometimes the distances traveled are very long – like around 5,000 miles.