Water pump

[Jonat127]

Hello,
This is my first post. Recently bought my stag and am doing some maintenance and service work before putting it on the road.
Previous owner thinks I am bonkers as I drove home a perfectly functional car and now it is in my garage in many pieces! But, I like to give my classics a proper going over before I use them so it is getting a full service, cooling system inspection and overhaul and new brakes all round, plus a good cleaning and waxoiling underneath and in the cavities. I will then be happy to use it.

So my first question relates to the water pump. I have removed the pump and it is a 6 vane one. However, the upper housing is in poor condition mainly corrosion on the pipe fittings where the hoses clamp on. So, I was thinking, if I need a new pump body anyway, why not change to a 12 vane pump?
The question I have is regarding the pump shaft. Is it just a matter of fitting a 12 vane head (plus bearing & seals of course) to my existing shaft or is there a difference between shafts?
All advice gratefully received.

On another but related subject, I need to helicoil one of the manifold threads in the head, all the threads are stripped out (it wasn't me I found it like that!)
Can sombody please confirm the thread size so I can buy a helicoiling kit.
Thanks

Jon

[Guest]

I'm not sure a 12 vane is better than 6, I think there was an issue with cavitation? I could quire easily be wrong. The experts will be along shortly to advise. If Kryten replies heed his advice, he's a little daft but knows what he's talking about.

Jason

[nib]

Welcome Jon
I have read up before now that the six vane water pump is better at stirring the coolant around than the twelve vane,I have a six vane water pump on my car and the only reason I know that is there was an invoice for a new one in 1997 when I bought the car, never been any trouble in my eleven years of ownership. Also in the past there have been a lot of duff brand new pumps on the market that I dare say are still coming up for sale. Definitely keep your one and when that gives trouble get it repaired rather than buy new.
The thread size is 5/16 unc and when I've done mine in the past I didn't drill out the hole, just tapped the thread and inserted the helicoil.
Mark

[Seaking]

Hi Jon
Be aware that the (pump bodies) Are different between a 6 and 12 vane water pump they look the same from the outside in are machined differently on the inside.

Cheers Glenn

[Jeff]

Appears from what I have gleaned the 6 is better than the 12.

I have a 6 and no problems.

Jeff.

[robbo]

Mine is a 1976 car so should have the 12 vane fitted but when doing the head gaskets last year on checking mine is fitted with a 6 vane. No problems touch wood.
Cheers.
Rob.

[DJT]

Welcome, and good luck with your new purchase.

Over the years I've come to the conclusion that there is little difference. My Mk1 had a 6-vane and it ran cool. My current Mk2 has a 12-vane and it runs cool. It is critical to ensure that the block waterways and radiator are clean and clear of sand/rust.
How did it run on your drive home? Hot, or cool?
As already said, if you change the pump head you have to change the cover too as they are different.

[GDPR]

Hiya

There is a body of opinion that a 12 vane pump is more effective at low rpm, but not quite so good at high. The opposite is said of the 6 vane. To be honest there isn't much difference, but I personally use a 6 vane in my late Mk2 engine and it works just fine. As has been previously mentioned it is much better to repair your existing pump than exchange as there are still some poorly hardened pump shafts out there and you could get one with disastrous results.

Get a pump kit from Peter at LD parts, with the ceramic seal (you will need to get the impeller machined) and find a decent S/H 6 vane cover then get on with enjoying the summer in your Stag

And welcome to this little pot of madness Jon

Russ

[Nigel W]

You may find the attached video from Rimmers helpful https://www.youtube.com/watch?v=VklGz6-U0Xw

[fussydave]

Hi Jon,

From my experience, i would avoid buying a new pump at all costs. I did just that and ended up having my engine rebuilt because of the poorly hardened shaft disintegrating and seizing the jack shaft in the block. If you know your existing pump shaft is a good hardened one, have it refurbished, or you could consider fitting an external electric pump as I have decided to do to avoid this happening again.

Dave

[Jonat127]

Thanks everyone.
So, I will stick with the 6 vane and buy one of these http://socspares.co.uk/store/36-wate...thermostat?p=2 which looks reasonable plus the necessary parts & machining from LDpart.
Excellent, better get on with it then!