My RRS 2.7 has just done 130,000km and I am getting the fuel pump belt, the timing belt and oil pump done. I will also change the serp aux belt at the same time.

With the latter, do I also need to change the top and bottom tensioners? Noting that none of the auxiliaries the belt runs will be changed and their bearings will have as much use as the tensioners. If the tensioner do need replacing what is the reason?

Also I understand the plastic thermostat cracks over time so do I need to replace that at the same time all the belts are off.

Thanks

Garry 07MY RRS TDV6
Arctic Frost
Aspen Interior

It would not hurt to change the aux belt tensioner as they are know to give issues. Depends how much the part costs.
Doesn't need to be done at the same time as the belts.

The thermostat is at the bottom of the car, in isolation. Other that pulling a pipe off it to drain the coolant, there is no reason to change it with the belts

Be worth checking whether your engine has the less robust oil pump casting. If it has, change it to the later version when you change the belts. They are known to fail shortly after the belt is changed. Lots of info on disco3.co.uk. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

Thanks for the comments - I only mentioned the thermostat as I understand the plastic splits and you can have a catastrophic loss of coolant.

Yes as I indicated in my initial post the oil pump will be changed.

Thanks

Garry 07MY RRS TDV6
Arctic Frost
Aspen Interior

Ah yes, missed that, sorry  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

No problems.

What has always had me intrigued with the oil pumps is that the original pumps generally last quite OK with no failures when the pump is the one fitted when the engine was first built in the factory.

As we know these perfectly good oil pumps seem to fail about 20,000km after the cam belt is changed - so why do the original pumps last if the cam belt has not been touched but fail soon after a belt change? Is it that there is metal fatigue? or is the new idler over torqued causing the failure, is it the higher tension in a new belt and new tensioner? or is it something else? Would the oil pump fail if you didn't change the tensioner/idler (bad practice I know).

So what is it that makes the old oil pumps last OK until they are played with as part the belt change then fail - yes we know they dont have the reinforcing webbing but in theory the originals are strong enough until tinkered with. Any got a definite answer - I am sure there are plenty of thoughts but facts would be good.

Garry 07MY RRS TDV6
Arctic Frost
Aspen Interior

Maybe:

1 more tension applied by the new belt/tension setting

2 tightening the bolt

The metal casting is physically different and it's the casting that fails, not the pump. Changing the casting appears to have increased the chances of a heavy hand overstressing the casting. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed