Jumping toothed belt

Montemar

Montemar

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Joined
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Dorset
www.voltloudspeakers.co.uk
A friend has replaced the water pump and drive belt on a Volvo 4.3litre V6 GXI petrol engine in his Dell Quay Ranger. The new belt appears to be correctly in line but under load it keeps jumping off the pulleys for no apparent reason. He has tried adjusting the tension but to no avail.
Can anyone shed any light on this please?
 
It's the "appears to be correctly in line" bit that is most likely the problem. The belt needs to line up with all the pulleys when viewed from above, but also the axis of each pulley needs to 90' to the direction of belt travel. If the water pump is even slightly wonky, or there is any play in one of the pulleys, the belt will go "walkabout".

Could also be a duff belt, but unlikely if an OEM part or better.
 
Thank you.
Presumably the old pulley would be fitted to the replacement pump so maybe that is the problem.
He has now joined the forum so can search through the accumulated boating wisdom himself.
 
Montemar said:
A friend has replaced the water pump and drive belt on a Volvo 4.3litre V6 GXI petrol engine in his Dell Quay Ranger. The new belt appears to be correctly in line but under load it keeps jumping off the pulleys for no apparent reason. He has tried adjusting the tension but to no avail.
Can anyone shed any light on this please?
Click to expand...

Do you really mean "toothed" belt? Could it be a Poly Vee (multi vee) belt? Anyway, the most likely cause is missalignment and either you were supplied with the wrong pump/pully assembly or if you have reused the old pully on the new pump maybe the pully has been fitted back to front. If the pully has an offset betwen flange and rim if you reverse the pully the offset goes the wrong way resulting in misalignment. Can you provide photographs?

Www.solocoastalsailing.co.uk
 
Has he got the correct tooth profile? there are many tooth profiles such as squared, tapered square, round, etc. If you get the incorrect profile such as replacing a tapered square profile with a round profile they will not fit the sprocket correctly and jump.

Most commonly it will be a dealer or supplier mix up where they have the same part number for two identical belts which have different tooth profiles with identical parts numbers and a letter, they get mixed up because although they are identical in every way and have the same part number someone has ignored the tooth profile letter and mixed them up in dealer stock.
 
The volvo flat hyvo belt is a bit unusual as its also has teeth cut into it.
I would take a good hard look at the tensioner first, Im assuming its an auto tensioner?
The oe belt is quite expensive.
 
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