Replacement water pump - studs too short?

[Sloop]

Just replaced the water pump on my 1960 TR3 (allegedly on its third engine...) because the pulley on the old one was loose on the shaft and the woodruff key had knackered the slot.  The new unit, from Rimmer, appears to have exactly the same dimensions as the old one, and I used only the paper gasket supplied.  However the threads on the two studs holding the pump to the housing only come slightly more than halfway through the nuts.

Even stranger, the thread on the shaft carrying the (supplied) pulley doesn't even reach the nylon ring on the nyloc nut supplied.  I'm confident that the pulley is fully seated on the shaft.  Everything seems to line up properly and the pump works well.  

The nuts on the old unit were claggy and I didn't notice that the studs didn't go right through the nuts - but they must similarly have been, apparently, too short.  

Anyone else had a similar problem?

 

 

[BlueTR3A-5EKT]

Does your original pump fit satisfactorily?

How thick is the flange of the old one compared to the new?  is that the problem?
How far does the impeller protrude from the mounting face?  Is that stopping the pump from fitting deep enough in the housing?

Is it seriously different?  

Then throw it back as more untested unsuitable product.

[John McCormack]

I had a similar problem with a Moss unit. It wasn't the pump but the nyloc nuts. I used plain nuts with spring washers.

 

Edited December 6, 2021 by John McCormack

[james christie]

It just so happens that I have two species of water pump on the bench. The County has run its bearings after about 4 years and 2500km.

Thanks to Brexit, Royal Mail, Covid et alia, I have been waiting for a replacement  3/8 UNC X 2-3/4 bolt for 4 weeks now, the original having corroded beyond my comfort level.

I have made some measurements this morning, which may help you in the diagnosis of where the problem lies:

The two studs on the housing protrude by 20mm

On the County the thickness of the pump casting is 10mm whereas on the Powertune it is 8,2mm - measured where the 2 studs and the bolt pass through.

In both pumps the ‘nose’ of the impellor is 30mm proud of the face of the casting. I haven’t measured it, but from memory the Workshop Manual says the impellor should be 85mm (edit: er hmm, 85 thou in. - thanks Ian) from the face of the casting.

Good luck

james

Edited December 6, 2021 by james christie

[Ian Vincent]

A small error James, 85 thou not 85mm. 

[rcreweread]

Hi all - I have just checked my small stock of original OE pumps which have been refurbished by EP Services ( they come with a lifetime guarantee) - on the one I measured, the three pump mounting flanges measure 7.80, 7.83 and 8.25mm respectively in depth of casting, the depth of the impeller from the back of the casting is 31/32mm and the gap between the pump body and the underneath face of the impeller is 0.080 inches.

I also have a pump to block casting, and the two studs on that are 20.71 and 20.82mm  - there is no third stud as this is usually a bolt. 

By my rough calculations, this leaves about 12mm for the nut and spring washer ( usual fitment) or a nyloc, so that should be plenty - hence why OE parts fit!

Some photos to illustrate the above attached. Hope this helps

Cheers Rich 

[BlueTR3A-5EKT]

5 hours ago, james christie said:

It just so happens that I have two species of water pump on the bench. The County has run its bearings after about 4 years and 2500km.

Thanks to Brexit, Royal Mail, Covid et alia, I have been waiting for a replacement  3/8 UNC X 2-3/4 bolt for 4 weeks now, the original having corroded beyond my comfort level.

I have made some measurements this morning, which may help you in the diagnosis of where the problem lies:

The two studs on the housing protrude by 20mm

On the County the thickness of the pump casting is 10mm whereas on the Powertune it is 8,2mm - measured where the 2 studs and the bolt pass through.

In both pumps the ‘nose’ of the impellor is 30mm proud of the face of the casting. I haven’t measured it, but from memory the Workshop Manual says the impellor should be 85mm (edit: er hmm, 85 thou in. - thanks Ian) from the face of the casting.

Good luck

james

James,  Do you have a spare TR2-4A cylinder head with the rocker pedestal studs fitted? (Pt No TE506241 - 3/8" unf/unc 3" long stud)  If so you can use one of the rocker pedestal studs in place of the bolt.  

[james christie]

Yes indeed, I have the original block and head under the bench. T’is wisdom like this from an ex parts man that helps over come these local difficulties!!

I owe you a beer in January…if I get there

james