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magnetman

BMC 2.5 (Thornycroft) water pump pulley

9 posts in this topic

A friend of mine has a Thornycroft marinised BMC 2.5 from the 1970's and the pulley on the engine cooling pump has worn out and come off. a new one is needed. its the engine cooling pump as opposed to the raw water pump.

 

The boat is in the Reading area and the part is needed asap.

 

Anyone know anywhere in the area to get such a pulley? Apparently the pulley itself is in two parts, I hope to be able to post a picture of a little later.

Edited by magnetman
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DSCF0781aa.jpg

 

 

DSCF0783aa.jpg

 

 

someone suggested getting a whole new water pump complete with pulley but again where from?

 

 

DSCF0782aa-1.jpg

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someone suggested getting a whole new water pump complete with pulley but again where from?

 

 

The pictures look like a standard BMC vehicle pulley (if there is such a thing) and I think the drive flange that is normally fixed to the shaft has come away with the pressed metal pulley still attached. I think you will find that if you undo the four hexagon setscrews/bolts you will have a light metal pulley and a heavy drive flange.

 

Looking at it I suspect the drive flange was originally pressed onto the pump shaft (Its the first one I have seen that has fallen off) so I think this will be easy to solve as long as the shaft/drive flange has not worn too much.

 

If you can find you have to tap the flange back onto the shaft with a soft hammer or mallet then I suspect a de-grease of the surfaces, a generous application of Loctite stud & bearing lock and leave to set will solve the problem.

 

 

If the flange slides over the shaft but is still a fair fit it might be worth centre punching the shaft all around it and along it length to "increase the shaft diameter". Then tap the flange on with Loctite as above.

 

If the shaft is a sloppy fit and centre punching is ineffective then I fear it will require the flange to be welded onto the shaft. First tacked and checked for truth and then welding.

 

ASAP Supplies list the pumps and the drive flange should be fitted when you receive it. www.asap-supplies.com 0845 1300 870 or 01502 711 680. They are in Beccles.

 

Edited to add:

 

PS if you want me to have a look ring 01189874285.

Edited by Tony Brooks
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ASAP Supplies list the pumps and the drive flange should be fitted when you receive it. www.asap-supplies.com 0845 1300 870 or 01502 711 680. They are in Beccles.

 

Edited to add:

 

PS if you want me to have a look ring 01189874285.

 

They list 4 here

http://www.zippy-images.co.uk/asap-images/...ection_1_13.pdf

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thanks for the suggestions. We found a replacement (2nd hand) pump complete with the pulley at Chertsey Meads Marine. They can also do a new replacement if required. Chertsey Meads Marine is a cool place, one of those old fashioned yards where there is nothing but boats, boat bits, boat engines and boat engine bits and the occasional 'lesser spotted human being' interacting with an unusually boaty type of environment.

 

Re Tony Brooks' comment, the internal boss on the pulley is too worn to be worth re-using, there has been a suggestion that it was 'sweated' onto the shaft i guess that means heating it up a lot, dropping it on and the contraction caused by cooling results in it locking onto the shaft. the pulley, as suggested, is a standard 4 bolt BMC type. I like the suggestion of centre punching the shaft to increase diameter, thats a good idea.

 

thanks for the suggestions and advice.

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thanks for the suggestions. We found a replacement (2nd hand) pump complete with the pulley at Chertsey Meads Marine. They can also do a new replacement if required. Chertsey Meads Marine is a cool place, one of those old fashioned yards where there is nothing but boats, boat bits, boat engines and boat engine bits and the occasional 'lesser spotted human being' interacting with an unusually boaty type of environment.

 

Re Tony Brooks' comment, the internal boss on the pulley is too worn to be worth re-using, there has been a suggestion that it was 'sweated' onto the shaft i guess that means heating it up a lot, dropping it on and the contraction caused by cooling results in it locking onto the shaft. the pulley, as suggested, is a standard 4 bolt BMC type. I like the suggestion of centre punching the shaft to increase diameter, thats a good idea.

 

thanks for the suggestions and advice.

 

If it was sweated onto the shaft, then it had failed before and been bodged by a previous person. Sweating is the term used for fastening something together with soft solder. A flange like that would have been pressed onto the pump shaft.

 

Richard

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If it was sweated onto the shaft, then it had failed before and been bodged by a previous person. Sweating is the term used for fastening something together with soft solder. A flange like that would have been pressed onto the pump shaft.

 

Richard

 

Hmm. I did wonder about the terminology. I was thinking this thing should be interference fit but I haven't seen it 'in the flesh' and hadn't heard the term 'sweated on' before. Either it was previously bodged or the person who used the term 'sweated on' didn't actually know what it meant.

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Hmm. I did wonder about the terminology. I was thinking this thing should be interference fit but I haven't seen it 'in the flesh' and hadn't heard the term 'sweated on' before. Either it was previously bodged or the person who used the term 'sweated on' didn't actually know what it meant.

 

I think the flanges were a press fit because when we overhauled the pumps (in general, not this one specifically) you either had to push the shaft out of the impeller (unless it's French, then they remove themselves :lol: ) or push the shaft out of the flange.

 

Having looked at the pictures again it looks to me as if the shaft might be slightly wasted which suggests the flange has been moving on the shaft for a long time. If this is so I fear any attempt to fix it with Loctite will be short lived.

 

I can not recall even seeing a pump that was new with a blued or browned flange that would have indicated that it was shrunk onto the shaft and I very much doubt the whole pump was dunked in liquid nitrogen to make the shaft smaller because of the rubber gator on the seal.

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I think the flanges were a press fit because when we overhauled the pumps (in general, not this one specifically) you either had to push the shaft out of the impeller (unless it's French, then they remove themselves :lol: ) or push the shaft out of the flange.

 

Having looked at the pictures again it looks to me as if the shaft might be slightly wasted which suggests the flange has been moving on the shaft for a long time. If this is so I fear any attempt to fix it with Loctite will be short lived.

 

I can not recall even seeing a pump that was new with a blued or browned flange that would have indicated that it was shrunk onto the shaft and I very much doubt the whole pump was dunked in liquid nitrogen to make the shaft smaller because of the rubber gator on the seal.

 

The shaft looked damaged to me from the picture which I agree suggests it has been moving for some time. I wonder, are the alternator and pump pulleys aligned properly?

 

I can't see any reason why the drive flange would be anything other than an interference fit onto the pump shaft. It hasn't got a lot of work to do and would be cheaper to make and fit that way rather than using a shrink fit. After all, this is essentially a car component where cheap is an important factor!

 

Richard

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