should I change the timing belt or not that is the ???????
 

should I change the timing belt or not that is the ??????? I have a 1980 928 66k miles runs perfect I bought the car from the wife of her passed on husband. She has no records with the car but the car has new brakes new tires and new Borla exhaust. Theres no rust and the car looks perfect. I drive it twice a month. I don't beat on the car at all. My question is without knowing if the car had the belt replaced what would happen if the belt did go, how much damage could it do the engine? I dont want to just replace engine parts just because. I usually go by the theory that if its not broken don't fix it. What would you do and is there anyway to tell if its time to change it or should I just drive it and stop worrying thanks

Change the TB and Water Pump while your at it. No history, just do it. Non-interference engine wont break anything but you'll be stuck and embarrassed on the side of the highway with the 911's laughing at you. Wow, 66k on a 1980, you scored!

With an early non interference motor, I would inspect it, but if all looks fine I would wait until time for some other repair has you getting into the area. Its not like you are just going to replace a $35 belt when you open it up, so maybe don't go looking for trouble.

Inspection should include checking the tension, and belt tracking, as well as generally snooping around as much as possible on the whole front of the motor. Don't forget to check the oil in the tensioner.

Respectful dissent
 

I respectfully dissent in part, AND concur in part with my esteemed colleagues, Do the belt, inspect the components,Rebuild the tensioner, and inspect the WP

My rationale is that I have heard that timing belts if sitting for a while "set" and may cause WP trauma. Also, they tend to age a bit even if you don't put the mileage on the car. IMHO you should probably go looking for some problems before they find you. A low mileage WP MIGHT be good, give it a good peek and make the call. Replacing a perfectly good WP might be excessive. Rebuild the tensioner (replacing the boot)

Yes, Non interference engine. belt failure is a nuisance rather than a catastrophe, but, still a nuisance.

Have the car appraised by a good 928 person.

recommended changeout for TB is 5 years or 50,000 miles.

if you have no records, then yes, a changeout is a good thing.

as it has been said here, your non interference motor probably won't break/bend any valves when (not if) the belt breaks.

count on about $750 in parts for the standard TB/H2o pump kit, plus labor.

if you are going to do this, I would recommend Porken's tensioner kit as well. replaces the tensioner with a modern Audi unit that requires no servicing like the Porsche tensioner does. just plug it in and go.






--Russ

Belts don't break from being old, they break when some part of the rest of the water pump and pulley system sieze. If the tension is ok on the belt, and it tracks fine, and nothing else on the front of the motor needs attention, then I think your needlessly opening a can of worms. I'm not suggesting to defer the job for more than say about a year, but to plan on it, and do everything related.

Drive the car a bit, enjoy, find the distinction between beating on it, and driving it like a Porsche. Then once you know you like it, plan the big project after the first snow next fall. Pull the motor and reseal, new motor mounts, pan gasket, all the stuff it needs for the next five years.

If the car sat for a long period, you may find that the water pump will start weeping after a few long drives.

TB failure on your car will not hurt the engine. What hurts is when you replace the TB, and the water pump goes the next week, you replace that, and you find that the cam or main seal leaks. Then you do that, and the TB skips a couple of teeth because you never rebuilt the tensioner.

It would be even more painful if you paid someone to screw up like that.

Belt set?
 

Correct me if I am wrong here, I was under the belief that when a TB belt sits for a while the belt "sets" in. That is to say it gets used to being in one shape. When you run the engine the uneveness of the belt creates a strain on the WP and WP trauma results, which is why when a car is run after it sits the WP goes south. This phenomena is especially pronounced on a belt that was overdue for a change to begin with.

This is why I recommend changing out the belt immediately and holding off on the WP IF it seems good.

Never heard of that one.

The belts are supple, very flexible, and STRONG, the previous owner used the VERY old belt off the 86 motor I bought as a lifting strap to pull the motor. Each time it would hang up on something the whole front of the car would get lifted a bit. They are crazy strong and the contact with the water pump is off the smooth back of the belt.

Over tensioning is the big killer, followed by pump seal leaking and bearing failure.

Hmm..
 

Yes Dangerleb: I agree that the belts are strong and they are flexible. That is after all what they are designed for. My impression was that they would settle into a shape. Similar to Tires getting flat spots if they sit too long. When you start the engine up again the set belt would (presumably) create an uneven load on the WP pulley as well as the idlers as it spins around. It is just a theory. I wish I could remember who said it. Anyhow, It is my rationale for changing out old belts that have sit for a while if they are past the 4 year mark.

Your position, to drive the car for now and put off the belt job for later holds validity as well, In that, flat spots can be driven out of tires by simply moving them around and exercising them. It also has the advantage of just getting the car out there and driving. There is an abbreviation "JDTFT" that comes to mind.

I will try to remember where I heard that theory. I think I heard it just recently and it echoed something an engineering professor told me about belts years ago.

These guys are right. With the 928 and all of the issue that cant arise I would take the precaution when you are ready to replace the belt and have the WP checked out. The recommendation is 50,000 miles or five years like someone said earlier. I learned the hard way but now I know I bought an old Porsche (which I love) and it needs to be looked after. Save yourself the headache and have someone knowledgable look it over.

The rubber in all belts lose flexibility with age. When that occurs they will crack and stretch. On the 16 valve engines a broken belt probably won't bend the valves but a loose belt can break the nose off the drivers side cam. BTDT :(

Also, installing a new belt can damage the seal on an old, seemingly serviceable, waterpump when the retensioning takes place. Unless you like tearing down the front end more than once, I would recommend a new or rebuilt waterpump, front main seal and a rebuild of the tensioner with each belt replacement.

I don't see the big deal made about just replacing the Water Pump. Your already in there and the Water Pump is not hard to change once the TB is off and not that expensive. I think I paid around $150 for mine. To me, it's not worth it to have to loosen the Timing Belt and remove a bunch of crap to replace it later. To me it's a peace of mind and convenience thing. IMHO

I can't believe you're considering not doing it.... 1st thing I do on any 928 without records
while the potential for valve damage is quite small with the early cars it does happen, so do old belts breaking, I've even seen 1 split right down the center into 2, and skip 3 teeth in the process
the potential damage to other parts, ie cams as noted above, alone should be enough to convince you to do it
the job is not that difficult, especially on an early car.... get the parts and invite the local 928 crowd over for a tb/wp party

928srock, fill in your location. maybe we can get a tb/wp party at your house.

I still think a good inspection and you will be fine. When I bought my 83 the timing belt checked out fine, and didn't go fubar for about a 1000 miles.

It would also be nice to skip to the next gen water pump, whenever that is out.

I never have considered belt set, but I have seen many waterpumps fail because they sat too long and the shaft corroded, causing the seals to fail.

Not that I am proud of it, but I did wind up doing the belt multiple times on my first 928 because I didn't do it all the first time. Sitting for long periods plays havoc on waterpumps, belts and seals. If you are in there for the belt, do it all and be done with it. Once you know the history of the WP, rollers, etc., you may elect to skip renewing them on the next belt change.

OTOH, I have seen and heard of many Miatas that are still on their first TB/WP, and these cars are almost twenty years old. If you are driving around locally, I don't see a big concern. My only suggestion is that you do the entire service ONCE.

I suppose it is possible to own a 928 for a short period, neglect all maintenance, and sell it to the next sucker. But there is a reason why routine maintenance is also called preventative maintenance.

Consider all the people who own 928s and think that they are unreliable pigs that never get out of the driveway.
Consider also that there are others who drive their 928s on a daily basis, and never experience any letdowns. Having been the former, I would reccomend the latter.

If I can chime in.. I'm about to change my water pump and belt sometime this spring.. as my water pump has started to whirr and hum.. I replaced my belt (only) 10 years ago and then the water pump 9 years ago without replacing the rollers, etc.
I'm going to do the pump and belt, rollers, guides, etc. the whole shebang when I do the pump this spring.
10 years, even with being a daily driver between timing belt changes. Granted I've been a slacker.. but I haven't beaten it either and have kept down the miles.
And of course it's a 79' so there's no paranoia about a belt failing or skipping.

I say check it out, enjoy it and if the water pump leaks in a couple of months or the belt fails while driving... do the entire service at that time. Just this peanuts opinion in the gallery.

Curt
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79 928 5sp silver/blk
02 boxster 5sp blk/blk

My current belt was installed in December 2003, and has since seen about 16,000 miles.

-I was going to replace it this year, but I check the tension each month and it is consistently perfect. The belt appears in good shape, so I think I'm going to wait another year.

My understanding is that the failure mode of the M28 timing belt does not involve the belt breaking. What happens in most instances is that the belt either jumps a tooth due to looseness, or it actually shears a few rubber "teeth" off. Based upon this, and also based upon a set of Bridgestone tires that I put on the car about 5 years ago and that FLAT SPOTTED LIKE CRAZY....I kind of wonder if the notion of the belt sitting in one position for a period of time might not cause a "set" to one small section of the belt, and then the sudden start-up of an engine who's oil film has largely disappeared [more friction than normal] might be enough to shear the teeth when the belt bends.

When in doubt....change the belt. Good insurance, and you're going to have to do it eventually anyway.

N!