Probably an unpopular opinion regarding cam belts

[yokomomr4bx]

I appreciate what I'm going to say/ask opinions on is probably going to be quite unpopular, but I'm curious as to thoughts on the topic. Also this is all in relation to my rev 3 turbo. So, I'll be coming up to changing my cam belt for the 3rd time (1st after purchase, 2nd after an extensive period off the road). Both previous times I replaced all pulleys, the tensioner, water-pump and thermostat and even though I do it myself, the cost of the parts alone does rack up a few hundred quid. Both times previously I used high quality components and replaced all the above mentioned.

This upcoming third replacement is due to it coming up 6 years since I did the job last, and I'm thinking of just replacing the belt alone.

My justification is as follows. I've changed a lot of cam belts on lots of different cars and honestly the only times I've felt justified changing the pulleys and water-pump is on French and German engines which use a lot of composite components in these parts and I've seen these fail - I will find a photo I took years ago of an Audi A2 cam belt which had an idler pulley that had disintegrated and belt was running on the outer race of the bearing. All metal (i.e. metal pulley/housing/bearing) bearings I've changed have always felt as solid and smooth as the replacement part I was fitting. I unfortunately do not have my old Autodata book but I feel like I read that pulleys/tensioners are not required to be changed at each interval - only every other interval i.e. 12 years or 200,000km.

So given the cost of a belt being around £30 vs 10x the cost for the full kit and caboodle...I'm going just for a belt this time round. What are your thoughts/experiences with this?

EDIT: Here are the photos of a failed cam belt bearing. The 'pulley' to the right and above the crank pulley at the bottom of the picture is just the bare metal bearing which used to be surrounded by a plastic pulley. In both photos you can see what this idler pulley should look like when you compare it to the tensioner and upper idler. The bottom photo also shows the loss in belt tension as a result of this pulley disintegration, though it should be noted that this was not why the customer brought the car in, it actually ran and idled very smoothly despite this failure. It was only brought in because of the rubbing noise the remnants of the pulley were making.

[abovetherim]

I'm with you on this one

If you know the water pump and pulleys are only say 20-30 k miles old and they feel smooth but with a little resistance when spun then they should be good til next belt change.
The only caveat being check the front and rear of each pulley as even supposedly quality pulleys can loose grease out of the seal on the bearing. I had a set of Continental pulleys do this on my Subaru.

As for the old adage of "if you're in there anyway it's not much extra work to change em for new". This would only apply if you were paying someone to do the job. Your time is free to a certain degree and personally I don't think it's that much of a pig to do if you have the right kit.

[MartinF]

I'm with you on this one

If you know the water pump and pulleys are only say 20-30 k miles old and they feel smooth but with a little resistance when spun then they should be good til next belt change.
The only caveat being check the front and rear of each pulley as even supposedly quality pulleys can loose grease out of the seal on the bearing. I had a set of Continental pulleys do this on my Subaru.

As for the old adage of "if you're in there anyway it's not much extra work to change em for new". This would only apply if you were paying someone to do the job. Your time is free to a certain degree and personally I don't think it's that much of a pig to do if you have the right kit.

Yes, agreed as well.

If you know the history then these sorts of decisions are easier. Also if it's not your everyday car you can inspect when stripping down and still order up if you find excessive wear.