4.2 in a Mk2: Water pump?

Saloons
1

For those of you that put a 4.2 in your Mk2, which water pump did you use?

I have a MkX 4.2 and I can buy a new E-type pump for the cost of rebuilding a MkX pump. Does it matter which pump? Does one mate up better to the Mk2 radiator?

2

I used the MK2 pump on the front of my 1975 3.4 XJ6 Engine , in my 240 , the MK2 pump Impeller is a few mm smaller , but I have had no heating issues !
I do have a uprated Rad core !

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1 Like
3

Yes it matters because the outlets from the pumps changed over the years, and the incorrect one for your radiator will cause big headaches

4

Tony, can you elaborate? Is it the sizing or the angle or something else? I don’t think anything else will fit, so I assume I’ll end up with an aftermarket aluminum MK2 radiator or a recored original. I don’t have a radiator right now.

So you’re saying I need a MK2 3.8 pump, and that it will fit the 4.2 timing cover?

5

Also, the Mk2 pump has 2 outlets whereas the MkX only has 1. Where does the smaller pipe go on a Mk2… or rather, where would it go on a MkX 4.2?

6

There is main 3 issues

  • What size, number and orientation of pipes are on your MK2 Radiator

  • will that match up with the WP you propose to use

  • will a 3.8 MK2 WP fit a 4.2 MX engine

Dealing with the last one first, if you have the original 3.8 WP, you can check

Otherwise I would check the Parts Manuals of the major suppliers, they have diagrams

I can say for sure there was at least 4 iterations of MKX radiator/WP, and not easily compatible, as the inlet and out let pipes were altered for rad and heater

You can usually plumb up a water pump to work with adaptors, but a perfect match is ideal

7

My Mk2 came without a radiator or engine. The 4.2 came without a radiator, so I’m flying blind without much to go on for comparisons. The major suppliers list one WP for all Mk2s and only 1 radiator that I see. From the diagrams, the MK2 pump goes straight down and the MkX is at an angle, and then a series of pipes and hoses pieced together. Very different radiators.
It seems like the 4.2 swap is common enough that there would be a common solution. I just don’t want to spend a lot of time reinventing the wheel.

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8

Well you know you must obtain a MK2 radiator, so if you are not in a hurry, I would buy that and see if everything will fit ok.

Note the steel bent pipes to hook up the MKX parts.
That is the mid-iteration of the MKX cooling systems

My personal opinion is fitting a MK2 WP to a MK2 with a MK2 rad would be the most straightforward (Ian said he did this)

Are MK2 WPs not readily available new or rebuilt ?

Also worth checking the archives, as others have done it before

The gasket part number may help tell if they are the same