Technical Auxiliary belt tension.

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Technical Auxiliary belt tension.

Robin Banks

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We have a Rapido motorhome based on a Ducato X244 2.8JTD registered in 2007. According to the paperwork, the van has only been worked on by 'professionals'. I am in the process of changing the timing belt and have found a broken centre bracket on the upper belt cover, The timing belt tensioner mounting bolt was finger tight (I kid you not!) and the washers on the tensioner roller were fitted the wrong way round - damaging the lower belt cover - so much for professionals.
Anyway, can anyone tell what the correct tension for the auxiliary drive belts (also, both being changed) should be? I'd been told many years ago, that such belts should be able to be turned through ninety degrees (just) when tensioned. Before the belts were removed, I checked the tension this way - and it proved so - I could just turn them. Bearing in mind the above comment about professionals, this could be right or wrong. Is the 90 degree test viable - or is there some other way to determine the correct tension?
 
We have a Rapido motorhome based on a Ducato X244 2.8JTD registered in 2007. According to the paperwork, the van has only been worked on by 'professionals'. I am in the process of changing the timing belt and have found a broken centre bracket on the upper belt cover, The timing belt tensioner mounting bolt was finger tight (I kid you not!) and the washers on the tensioner roller were fitted the wrong way round - damaging the lower belt cover - so much for professionals.
Anyway, can anyone tell what the correct tension for the auxiliary drive belts (also, both being changed) should be? I'd been told many years ago, that such belts should be able to be turned through ninety degrees (just) when tensioned. Before the belts were removed, I checked the tension this way - and it proved so - I could just turn them. Bearing in mind the above comment about professionals, this could be right or wrong. Is the 90 degree test viable - or is there some other way to determine the correct tension?
Sounds like you were very lucky, I have heard of several 2.8 owners who have had the cam belt replaced as a precaution and a few miles down the road, catastrophic failure as when belt fails it tends to bend the con rods at the same time as the valves. Often the spacer incorrectly fitted as you describe is a major factor.
Most of my work was on those engines fitted in Iveco Daily vehicles.
The 90 degree test many use re auxiliary belts, but does depend on the length of run between pulleys and the strength of thumb pressure, I just use general feel from many years in trade, basically if too loose it will squeal from cold on a damp day, especially if headlights on, ideally don't make it too tight as alternator bearings etc. are punished.
 
Thanks for that. Yes, lucky - especially as the timing belt was last changed in June 2020 - hence it's being done now. I get what you mean re the auxiliary belts - it's the criteria that's used when replacing primary chains with toothed belts on classic motorbikes - tight enough to drive, without overloading the bearings in what it's driving.
 
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