Water Pump Cam Wear

[LONG_KEELER]

I have had overheating issues with a Volvo 2001. It is raw water cooled.

I think I am nearly there to solving to solving the problem.

Thanks to this forum, I remembered to look at face plate wear. The plate was noticeably scored and reversed it as suggested. This made a big difference and the alarm only sounded in the very hot weather at high revs after quite some time motoring. Taking the engine cover off and slightly less revs got me home. The washer the other side of the impeller looks unscored.

The pump has a renewable Pump Cam. I am wondering what to look for with regards to wear.

I assume the impeller vein need the best 'spring' it can get off the cam.

There is slight scoring and the ends feel very 'sharp' .

Would be grateful for any things to look for.

Thanks in advance.

 

[Modulation]

I had an overheating problem a few years back in my Yanmar 2gm20. Turned out to be the water pump too. I took it to the London boat show to the French Marine stand and they confirmed that the inner pump body had worn where the impeller van ends rub along it i.e. all the way around except where the cam is. I found it hard to believe that a nitrile vane could wear away brass to such an extent so I took it home and looked at it with a powerful magnifying glass - and they were right. There was a tiny space between the vane and the pump body. As the engine had done only 350 hours I was not pleased especially as the pump is unrepairable and costs around £400.
Luckily I found a 2nd hand pump from an earlier Yanmar which was fine and has now done 700 carefree hours.
Yours could be a similar issue.

 

[glsg91]

Take a look at the pictures at this thread: http://www.zeilersforum.nl/index.php/Forum/79-motoren/431394-volvo-penta-2001-impellerhuis

The first pictures are with wear. Half of the thickness of the cam is gone because of wear.
At the end of the thread you can see the pump with the cam is replaced.

When comparing you can see the difference.

 

[charles_reed]

I had an overheating problem a few years back in my Yanmar 2gm20. Turned out to be the water pump too. I took it to the London boat show to the French Marine stand and they confirmed that the inner pump body had worn where the impeller van ends rub along it i.e. all the way around except where the cam is. I found it hard to believe that a nitrile vane could wear away brass to such an extent so I took it home and looked at it with a powerful magnifying glass - and they were right. There was a tiny space between the vane and the pump body. As the engine had done only 350 hours I was not pleased especially as the pump is unrepairable and costs around £400.
Luckily I found a 2nd hand pump from an earlier Yanmar which was fine and has now done 700 carefree hours.
Yours could be a similar issue.

Interesting but generally a soft, resilient surface mated with a hard one will usually wear the harder surface away. Tribology and all that stuff.

Usually, by machining the inside of the pump body, one can get about another 2K hours out of it.
The Johnson pumps, fitted to later Yanmars, are far easier to refurbish than the Jabsco ones. I soon took to carrying a spare raw-water pump, rebuilding the old one at leisure.
The parts, that I get direct from Johnson, cost about 35% of the Yanmar official prices.

 

[Poignard]

I found it hard to believe that a nitrile vane could wear away brass to such an extent so I took it home and looked at it with a powerful magnifying glass - and they were right.

It isn't the nitrile that wears the brass - it's the abrasive grit that becomes embedded in its softer surface.

My father (who worked as a mill engineer) told me he had seen a lineshaft in a woollen mill that had had a grove worn in it by a length of cotton and rubber flex. The machine operator wanted the lamp above his machine moved nearer to him so he draped it over the rotating line shaft. It took many years before the flex wore through and blew a fuse, by which time the shaft was badly scored.

 

[vyv_cox]

There is an interesting case history on cam wear on this page of my website http://coxengineering.sharepoint.com/Pages/Waterpump.aspx Demonstrates how what appears to be a small amount of wear will reduce water flow considerably.

 

[Talulah]

There is an interesting case history on cam wear on this page of my website http://coxengineering.sharepoint.com/Pages/Waterpump.aspx Demonstrates how what appears to be a small amount of wear will reduce water flow considerably.

I had issues with insufficient cooling. Having seen vyv_cox website I replaced the raw water pump with a new one I bought off ebay a couple of years ago. Problem sorted.
Just glad I bought the spare pump when I did as it saved a fortune.