Idler pulley, tensioner, torque.

I have a 2001 996 (I forget that 1.1 or 1.2 thing - mine is the earlier one) The lower idler pulley broke the other day. I ordered a new one on Ebay (cheapest I could find - $34, by Dayco). I was planning to replace the tensioner pulley and belt anyway, so now I have TWO of these Dayco pulleys on order and the belt. The pulleys and tensioner LOOK the same to me, and on the Ebay page, the Dayco chart indicated the pulleys were compatible with my car, but said nothing specific about whether they were pulleys or tensioners...(that I could find). So; 1; are these pulleys and the tensioner interchangeable? 2. Am I committing a horrible sin by installing a Dayco? Some of the more expensive pulleys were shown with some inside bracing, presumably to strengthen them, but there were also pulleys that looked EXACTLY like the Dayco - with no bracing either - that were going for $80 or $100 or more. I'm on a budget, and it seemed unlikely the lack of bracing would cause the part to disintegrate... in fact the one that broke, in my car, had that bracing. Thanks for helping... PS I'm going on the assumption that these parts ARE interchangeable, so I'll have installed them by FEBRUARY 24th or 25th, most likely, so it won't be necessary to post replies after that, unless you think I'm heading for disaster. Thanks, Chris

Interchangeable? Just because it says it will fit, doesn't mean that it's of decent quality (or the same quality as the original part). I think the fact that you bought "the cheapest one you could get" is a good indicator of your mindset when it comes to maintaining your car... Who knows, you may get lucky but my experience with parts is that you generally get what you pay for. This is not to say that you must always use Porsche branded parts, but going the "cheapest" route is usually looking for trouble - i.e. you may be doing the job again in a few months or a year. Anytime you're using a part that includes bearings (idler pullies/tensioners) cheapness is not kindness! Good luck

^^ Well said dporto. If you ask me, if you skimp $$ on your Porsche (1) you are headed for disaster and (2) I find it is always best to use Porsche OE replacement parts on moving objects. You own a Porsche and you want to save $$ on moving engine parts? How in the world are you going to afford that next tank of gas? Do it once and do it right. Just my 2 cents...and you asked.

Ouch. Here's my thinking, though; I think MOST people consider taking your car to a dealership to be needlessly expensive, and not necessarily a guarantee of any better work done, than that of an independent shop. I guess I'm hoping this is true of parts manufacturers too. I should have noted that the photos of the differently-priced pulleys looked like stock photos, and to my understanding, sometimes a single manufacturer will sell parts to many sellers, who can price them as they choose.... but they're the same part. I'm GUESSING that this is the case here, though without ordering one from each seller, I won't know for sure, obviously. BTW, I haven't been particularly impressed with some of the parts my car came with... nor Porsche's choice of plastic in places where metal would have been a much better choice. On my other question... is the tensioner pulley the same as the idler pulleys? THANK YOU.

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Did the pulley itself fail, or was it the bearing?

The pulley - the bearing is still there. BTW I notice that the other pulley is a Sebro - I think that's an expensive brand - but I'm not sure if the one that failed was Sebro too -

Deleted as post was of no help!

Well I don't know if that was a stock part or not. As I mentioned, the other one is a Sebro - do those come stock on 996's? Looks like I'm 0 for 3, so far.

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I'm going to try to answer some of your questions. I'll also be a little up-front with my thoughts. 1) I believe the pulleys are interchangeable. The best place to be sure is the parts catalog (PET). Porsche has them available on their website. The tensioner is a different part and may not be what you think it is. It does not make contact with the belt; only the pulleys do. 2. You may not be committing a sin by using Dayco parts. You mention you are on a budget. Would you mind explaining this? You are skimping on a very basic part. What will you do when you need to replace something serious? If you don't mind, can you provide us with some details of this car? What did you pay for it? What's it's history? Did service records come with it? And maybe more importantly - tell us why you bought this car? You've come to the right place to get information. The impression I get from your post, is that you may not have done much homework on this before jumping in. We're here to help - but you've got to help yourself too.

Well not an apples to apples comparaison, but i used dayco pulleys and bearings on my truck with a 5.9 cummins. That motor puts a heck of a lot more torque and hp through the system but not the rpm. I got over a 100k miles out of them before i swapped new of the same as preventitive maintanence. Dayco is not a bad supplier. i would say its your money and your car, do what u want. I put less then 3k miles a year on my car and im betting even the less expensive pulley would be fine in my car.

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I am doing the same myself. I have an upper idler pulley that needs replacement, as well as my tensioner pulley. Went ahead and purchased two idler pulleys from RockAuto ($25ea) to replace my upper and lower. If you look at the part numbers, they match the requirement. They so happen to be Dayco. However, I couldn't find part number matching for the tensioner pulley, so I reverted to buying the OEM off Pelican Parts ($80). Hope that helps!

I went one step further than buying the cheapest rollers.......I removed the old bearings and replaced them with new ones. This is just a pulley and the only thing that matters is the quality of the bearings. These bearings are standard off the shelf parts so as long as they are of good quality, it doesn't matter how much the complete pulley costs. There is nothing wrong with a cheap pulley as long as the bearings are good quality.

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You don't do much wrenching do you?

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This seems to make good sense, given that replacement bearings cost around $8.

I'm from the old school of do it once and do it right. I never want to second guess myself after spending a lot of time and effort on a job and found out things are not working because of inferior installed parts. This is not to say all non-OEM parts are bad, but personally I've been there in trying to save a few bucks by installing some cheap parts from China and then regret the frustration encountered later.

Thanks - I'll try to answer all your questions. It had just been inspected as of 12/18 - new brake pads but not much else. The guy had records back to 2016 - I haven't bothered to get the Carfax. It's had the IMS bearing installed - I think at 90,000 miles, & new clutch at that time. The records show regular oil & filter changes, & some repairs - spark plug things (I forget what they're called) window motor, new tire, etc. My impression is that he did what was necessary & no more. I removed the "muffler delete" system and reinstalled the original mufflers myself. I replaced the old cabin filter & engine filter (Both in terrible condition) & found that the front left strut spring was broken right where it meets the bottom plate. I bought a used one on Ebay ($100) + new bump stop - haven't installed them yet. A week ago the pulley blew apart; that's why I posted my questions - I'm going to install the new ones & new belt as soon as they arrive. Anyway - I CAN spend thousands, or even spring for a replacement engine, if it comes to that - I'd just RATHER not, if possible, and plan to do as much of my own work as possible. I'm new to the Porsche world - that's why I'm asking people opinions on Porsche vs. independently made parts. I get the argument about buying known & reliable parts; I guess I don't trust that it's necessary to do that... IF I can save money, I'm willing to take a chance on used parts, or off-brand, now & then. Maybe I shouldn't have posted; even if I hadn't already ordered the Dayco pulleys, I suspect I would have used them anyway. As I said - they LOOK exactly the same - same stock photo - as the more expensive ones. I'm confused by your remark about the tensioner - I'll look again, but I'm pretty sure mine definitely is part of the loop the belt makes - w contact. & it LOOKS exactly like the idler pulleys - though I haven't removed it to make sure, yet. There you go - thanks for the suggestions -

In my own experience, the idler bearing and the tensioner bearing are not the same part. The tensioner pulley comes with a couple washer, spacer, and a bolt that has red Loctite on it. The idler pulley does not come like that. I cannot tell you if the pulleys themselves are the same, but I don't want to save a couple dollars and have a mess on my hand. I rather let the part(s) vendor do that leg work for me. The tensioner is a spring loaded assembly sitting behind the pulley and that is different. On the other hand, changing the pulleys (all 3 of them) every 60,000 miles is preventive maintenance (as well as the water pump) so that they don't break and leave you stranded. Therefore, change them with the right parts and forget about them for another 60,000 miles is the way to go. Good luck.

Christopher: I learned a lot by going to my Indy and talking to him. If he�s not receptive but a good mechanic, I�d try to schedule an appointment and discuss all this�IOW, money talks. This site is an invaluable resource with nearly unlimited 996 expertise but I�m much better at face to face explanations. Maybe try that and you�ll be able to better integrate the info you�re getting here. TC

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Christopher - thanks for the complete return. Sounds like you've got a good car that needs a good look-over. There's a maintenance document out there on the web. I'll post the link, if I find it again. Regarding that document - that's been a significant guide for me in getting my 'new' car ready for spring driving. I'm a little ahead of you on accumulated miles and digging into what should be checked, fixed, or replaced. I started a thread on it about a month ago when I bought the car. Here's a link to a page that covers a lot of the belt, pulley, tensioner parts you are discussing in this thread. You may find some useful information and tips: https://rennlist.com/forums/996-foru...tune-up-5.html