Question For VolvoPaul. KAD 300 A Circulation Pump Failure

[briggs]

I have a KAD 300A that has an issue with breaking Circulation Pump shafts. I have gone through 4 in the past 1500hrs. I have replaced everything!
Tensioners, belts, Harmonic balancers, and pulleys.
Nothing seems to help.
I initially was torquing belts to factory spec of 25-30 Ft/lbs. that made the problem worse- 250-300 hrs would break the shaft. Reduced torque to 15 ft/lbs and got 800 hrs out of the last pump.
I have heard that VP did have issues with bad shafts on those pumps. Am I just unlucky?
Shaft is breaking at base of hub.
Any insight would be appreciated.

 

[BruceK]

This wont answer your question as to why but may take the sting out of the problem

SP Water Pumps - engine water pumps for all makes and models

I believe you have the same pump as my KAD42. A complete overhaul which included a spray job for 85 quid. This included a new shaft and bearings etc. and a 1 day turn around. Quality of work is outstanding as is materials used. They even returned it with a new gasket and new mounting bolts. Who knows, probably last longer than the original if thats what you've been buying

 

[DavidJ]

Just for my records can you kindly give the SP number for your KAD42. Probably the same as for my KAD43.

 

[A_8]

You most likely have something creating a small vibration or alternating strain on the axle. I had a pump fail like this and when I examined it closely the pulley was not perfectly flat on the axle assembly. There was a bit of paint that had come between or it was not seated properly when it was painted. .

 

[BruceK]

Just for my records can you kindly give the SP number for your KAD42. Probably the same as for my KAD43.

Sorry I dont have that. They simply asked me for a photo and replied they can refurb it, 1 day turnaround, 85 quid including return courier. The receptionist was very knowledgeable and most helpful. I dont easily hand out praise for services rendered that I pay for. I expect it. They were brilliant though.

 

[briggs]

Volvo paul?

 

[BruceK]

Volvo paul?

Probably best to catch him on the Volvo FB groups these days

 

[volvopaul]

If you want my honest opinion I think they changed manufacturers, this is where the problem lies .

 

[briggs]

So I’m stuck with pumps that are unreliable?

If you want my honest opinion I think they changed manufacturers, this is where the problem lies .

 

[kashurst]

I don't think so. To snap a sizable steel shaft requires some force and/or intense vibration. I would go back and look at the associated components, fit etc as per A8s post
Consider getting the water pump pulleys balanced/trued.

 

[A_8]

In my example it was the larger pulley not being perfectly flat on the smaller pulley but generally all these surfaces need to be pristine. You also want to tighten them with neutral forces on the pulleys which might not be easy to do.

 

[briggs]

In my example it was the larger pulley not being perfectly flat on the smaller pulley but generally all these surfaces need to be pristine. You also want to tighten them with neutral forces on the pulleys which might not be easy to do.

I’m kinda thinking the issue may be that the supercharger clutch is grabbing to hard and causing the issue. As I have changed all pulleys, harmonic balancer as well as tensioners. I have followed the tighten pattern to a T. Problem continues. I am going to check tolerance on clutch to see if it is within spec. My feeling is that clutch should give a little to not shock the pulley every time it comes on. Any thoughts?

 

[A_8]

I think the clutch grabs pretty hard even if it was new or in perfect condition, IIRC it's metal to metal. Either way I think that is an unlikely explanation and maybe it's also like volvopaul says, some pumps may have slightly inferior metal quality in the axle. 800h is many years for most so perhaps if you just fit a new one it will last longer.

Perhaps find a way to measure how much the pulleys "wobble" when installed.

 

[kashurst]

I’m kinda thinking the issue may be that the supercharger clutch is grabbing to hard and causing the issue. As I have changed all pulleys, harmonic balancer as well as tensioners. I have followed the tighten pattern to a T. Problem continues. I am going to check tolerance on clutch to see if it is within spec. My feeling is that clutch should give a little to not shock the pulley every time it comes on. Any thoughts?

There are two things already in place that allow for that. The polly Vee belts themselves, they can slip albeit very slightly and the three metal straps riveted on the front of the clutch itself, they act as very stiff springs when the clutch engages. To snap a steel shaft requires a lot of energy either instantaneously applied or something is vibrating the shaft at it's resonant frequency (twanging a ruler on a table). I don't think pump shafts snapping is a common problem - I don't remember it being posted on here before so I would still be looking at sources of vibration as per A8.

 

[Portofino]

I,am not buying into this vibration , excess vibration or what ever being the cause of the shafts fractures.
Reason the impellers drop vanes and but n pieces and run for ever hrs and hrs .It’s only until you open the pump up and discover the worn impeller you notice .
Usually on its timed service or investigation into a cooling failure .
Not because you notice it vibrations .
^^^^ Ran for years without any shafts snapping Jabsco bolt on pump .Must have vibrated like hell .

It will be the recent change of manufacturers as VP said ^^^ .He ‘s immersed in Volvo Penta woes listen to him .

 

[kashurst]

I,am not buying into this vibration , excess vibration or what ever being the cause of the shafts fractures.
Reason the impellers drop vanes and but n pieces and run for ever hrs and hrs .It’s only until you open the pump up and discover the worn impeller you notice .
Usually on its timed service or investigation into a cooling failure .
Not because you notice it vibrations .View attachment 123473
^^^^ Ran for years without any shafts snapping Jabsco bolt on pump .Must have vibrated like hell .

It will be the recent change of manufacturers as VP said ^^^ .He ‘s immersed in Volvo Penta woes listen to him .

wrong pump.

 

[Portofino]

wrong pump.

Yes , but the point remains the impeller weight changes and it looses balance with use .
This is a huge common variable .

No need to pin this on a “thickness of paint “ a thou out on belt tensioner or what ever .

They should cope with a 0.002 g of paint on a stub axial at 4 o clock .

Another Yes it ain’t my problem.

 

[kashurst]

The small mass of paint is not the issue, it's the large outer pulley not rotating in line with the pump shaft that could be creating a harmonic resonance as per A8. Car stub axles can break if the discs are not fitted correctly.

 

[volvopaul]

Yes , but the point remains the impeller weight changes and it looses balance with use .
This is a huge common variable .

No need to pin this on a “thickness of paint “ a thou out on belt tensioner or what ever .

They should cope with a 0.002 g of paint on a stub axial at 4 o clock .

Another Yes it ain’t my problem.

You cannot compare an impeller pump to the Circulation pump in question .

 

[Croftie]

Same thing as fitting new disc's on a car, you must clean the hub surface else the disc will not run true, results in disc wobble that transfers pressure back to the brake pedal - you can feel it under foot. Can create hot spots on the disc that warps it making matters worse and worse.