[daly]

Is it possible to see the timing belt to check wear without removing parts from the engine?

Partial Post: Please Login or Register to read the full post.

[flash]

not really - there is a tiny inspection port at the top of the distributor, but you can only see a very tiny portion of the belt - to really see it you need to pull the covers on the front of the engine



just a note: if it's been 30k or 2 years, whichever comes first, you're overdue for at least an adjustment of the balance belt, and really should pull the covers and at least inspect everything

Partial Post: Please Login or Register to read the full post.

[sasilverbullet]

My Porsche shop, Jones Autowerks, been in business since 1961 - says replace both belts every 30K miles or every two years. With a balance belt retension every 10K miles. Anything outside that and you risk a head job.

Partial Post: Please Login or Register to read the full post.

[flash]

personally i agree, but 45k seems to be the accepted norm for replacement - why the book says replace at 60k and check at 30k is beyond me

Partial Post: Please Login or Register to read the full post.

[sasilverbullet]

Jones used to go by the 45K rule, but with all the 944 series cars they work on, they had about 3 belts fail in the 30K to 45K range. They said they've not had any belt failures below the 30K range, except for one belt that broke in about 5 miles! They did the head job for the customer for free.

Partial Post: Please Login or Register to read the full post.

[sbdrivingdotcom]

If no one has heard of a belt failure below 30K then why the two year addition to the rule? I know rubber dries out but if it's in a climate controlled garage and driven sparingly, I think two years is a bit dramatic. I could understand 6-8 years or less in an extreme environment but two years? My belt has 10K miles in five years and after opening it up and looking at it, my mechanic, a 968 specialist as he used to own one, said there is no need to replace it at this time. The rubber is fine. Any ideas?

Partial Post: Please Login or Register to read the full post.

[PorscheDude]

[quote name='sbdrivingdotcom' post='36646' date='Jun 8 2007, 02:12 PM']If no one has heard of a belt failure below 30K then why the two year addition to the rule? I know rubber dries out but if it's in a climate controlled garage and driven sparingly, I think two years is a bit dramatic. I could understand 6-8 years or less in an extreme environment but two years? My belt has 10K miles in five years and after opening it up and looking at it, my mechanic, a 968 specialist as he used to own one, said there is no need to replace it at this time. The rubber is fine. Any ideas?[/quote]







$40 belt vrs. $2000 head job...... <img src="/forum/images/smilies/968/blink.gif" class="smilie" alt="" />







I'll go with the $40 belt

Partial Post: Please Login or Register to read the full post.

[flash]

there is math to work out the aging and such of rubber, but that one is long lost to me - i remember that it has to do with heat cycling and plastic memory



while i don't think they need to neccessarily be changed at that interval, but they should be at least inspected, and the balance belt retensioned



but remember that no belt is intended to go beyond 5 years - that is the maximum that the manufacturers of the belts will warranty, so i figure they have a good reason for that



mine won't be let go that long, in fact, at 24k and 4 years now, i am going to change them soon as a pre-emptive measure - they look perfect, feel perfect, and the car does not see big temperature or humidity swings, so i have no reason to suspect them, but age is age, and i am not inclined to fall into the category of those who have guessed wrong and paid the price

Partial Post: Please Login or Register to read the full post.

[wingers]

Now i am getting to worry,to-morrow i will be on the track.

Does any engine damage occur when just the balance shaft belt lets go.

Partial Post: Please Login or Register to read the full post.

[flash]

it has happened - it has also caused no problems



there have been a variety of occurrences, from nothing happening at all to the belt getting caught up in the timing belt and snapping it and bending every valve in the head, to the vibrations rattling the oil pickup tube and breaking it, causing spun bearings from oil starvation



not worth the risk to me personally, but you have to make that call yourself



"do you feel lucky? well? do ya?"

Partial Post: Please Login or Register to read the full post.

[wingers]

Yep i feel lucky but if i do not post anymore you know the worst has happened!

Partial Post: Please Login or Register to read the full post.

[flash]

i'll sacrifice something to the porsche gods for you tonight (read as "hoist a glass of cabernet")



good luck - shiny side up

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

I have several questions/inputs on the subject of our car's belts. First, regarding the balance shaft adjustment. I replaced by balance belt about a year ago (a previous mechanic had put a narrower 944 belt in, so I suspect the walking this narrow belt must have done along the sprockets shortened its life pretty dramatically), and, with the help of a neighbor who has had a lot of experience working on/rebuilding 944 engines, adjusted its tightness to the point that it whines a little when cold, and the sound goes away as the engine warms up. It was a major pain to get it to this point, but it seems pretty much perfect. The sound has not changed in the year the new belt has been on. I keep hearing these things need to be re-tensioned after a period of time, but it doesn't seemed to have loosened at all, based on the sound it continues to make, so what's the point of re-tensioning it, given that the tensioning mechanism is one wretched contraption to have to deal with?



Second, on the topic of timing belt replacement interval. In any modern engine, the recommended timing belt swap interval is in the 75K - 100K range. It strikes me that a 48K interval, let alone 30K (!), is uttelry ridiculous. Are we to believe Porsche uses inferior materials for their belts? I can't believe belt materials have improved dramatically since the early 90s, given that timing belts have been common practice for many decades now. And by modern standards, our engines' specific output is pretty modest, not that that should have a huge bearing on belt life anyway. So what gives with these absurd recommended belt change intervals? A timing belt change on these engines is a major job that takes many hours, so its cost is WAY beyond the $40 price of the belt itself. Please understand, I fully comprehend the risk/reward tradeoff of replacing the timing belt at a sensible interval vs. the risk of destroying the engine.



So, I'd like to see a show of hands - Is there anyone out there who has ever had a timing belt snap on a 968 engine? And if so, how long had it been in the engine? Sorry to sound like I'm ranting, but it seems that we (myself included) tend to put Porsches on a pedestal, believing that they require special treatment, but a belt is a belt, and if Honda, BMW, Toyota, ad infinitem, can have their belts last up to 100K miles, why should we beleive that we have to fork over major bucks (or hours of our time and skinned knuckles) every couple of years to replace ours?

Partial Post: Please Login or Register to read the full post.

[flash]

i don't mean to sound like "the sky is falling" but there is a real issue here



it's not the belts, but the mechanism that leaves a lot to be desired on this car - add to that the extra torque of this engine that is applied over its predessor and you get stretch - remember, we have a lot more torque than the 944, and are using essentially the same parts - the belts are very long, with uninterrupted distances and non roller surfaces to rub against - i'm not surprised we have a problem, as this is the frankenporsche after all, made up largely of leftover parts from previous cars



even the manual says to retension it, first a couple thousand after installation, and again at 30k - they wouldn't do that if they didn't think that it might snap - no way they wanted to get into a warranty engine - obviously they knew something was in need of attention to prevent that



yes, i know of a few people that have, for one reason or another, snapped their timing belt - howard did it, bill did it, just here in l.a. - if you do a search on the sites, you will find another 3 or 4 who have had it happen in the last 2 years alone that posted their woes - it happens - it's not every day, and not every car, but it happens



i drive mine very hard, and stretch the belts pretty quickly - i've had to adjust the balance belt twice, but the timing belt has been fine due to the hydraulic tensioner - others may not wear it that quickly, and certainly there are an overwhelming number of those who have not had the problem, but i'm just not inclined to take the chance



but, feel free to let yours run as long as you like, and we will still be bummed if it happens to you, and curse those danged german engineers



lol - so, i'll be sacrificing a second glass of cabernet to the porsche gods tonight, this one in your honor

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

Thanks for the toast - hopefully the Porsche gods are listening, but I don't feel that I'm anywhere near the danger point yet, as my timing belt was replaced at about 75K, and I now have 98K on the car. Agreed, it must be a pretty crappy design if far "lesser" cars can go twice as long between belt changes as ours.



As far as the question about re-tensioning the balance belt, I still don't understand why I would need to do it if it's still whining when cold, to about the same degree as when I first installed it. Maybe I overtightened it initially (though it felt awful loose). The first time I put it back together, it whined like crazy even after it was warm, so I spent over an hour fiddling with it until I got it to the point it is now, which, as I said, seems to be just about perfect, as the whining goes away after a couple of miles. In other words, I can understand the need to re-tension if it has gotten too loose, but this doesn't seem to be the case with my car. I don't drive the car particularly hard on the street, but I have taken it to four DEs (with a 5th scheduled for mid July), where it's another story. I'm just afraid I will make it worse by going in and messing with that infernal tightening mechanism again. Talk about a crappy design!

Partial Post: Please Login or Register to read the full post.

[sasilverbullet]

The first time I tensioned my balance belt without the tool I thought it was too loose. Come to find out it was too tight!



At about the center of the long run of the balance belt (with the idler removed) I can twist the belt 90 degrees pretty easily. This was then checked with the tension device and was okay.



Another thing that hasn't been mentioned yet on the balance belt that I got wrong the first time was the amount the tensioning cam was turned. I had it too far out at first.



Moral of this story is that our cars are pretty complicated in the balance/timing belt area and require a good bit of know how to get it right.

Partial Post: Please Login or Register to read the full post.

[Cloud9...68]

[quote name='sasilverbullet' post='36688' date='Jun 8 2007, 11:07 PM']Moral of this story is that our cars are pretty complicated in the balance/timing belt area and require a good bit of know how to get it right.[/quote]



Agreed! That's why it's so infuriating that Porsche recommends such a ridiculously frequent change interval.

Partial Post: Please Login or Register to read the full post.

[flash]

lol - this morning i am feeling the pain of that second glass (or was it the third?)



as for the belts, i was stunned to find that you can actually go past the correct position and orient the danged thing wrong - looked like it would work and all that, but this then makes the belt rub against one of those guide plates - made a racket like it was too tight

Partial Post: Please Login or Register to read the full post.

[Duckman]

I had been planning on having the belts replaced at 40k, along with a water pump, etc., but didn't make it that far. My timing belt gave up at a little under 40k miles. Yep, I had to rebuild the top end.



Was I really, really, really unhappy about it? You guess.

Partial Post: Please Login or Register to read the full post.

[unknown4u]

I do have another question about the mainbelt.

When the engine is cold. There is no noise at all.

When the car is hot I have a wining noise.

I'm pretty sure it comes from the main belt.

The balancebelt is tensioned correct.



Does anybody have had the same experience?

Partial Post: Please Login or Register to read the full post.