924Board.org

[DON]

CAN ANYONE TELL ME, DO THE VALVES GET DAMAGED ON A 1986
924S IF THE CAM BELT BREAKS. THANKS Don.[/b]

[Chrenan]

Yes, the valves will collide with the pistons if the cam belt breaks as the 924S engine is an interference design (same engine as 944). This will at a minimum bend some valves. It may bend all valves, and it may damage the piston crowns.
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1987 951 - M193 Version for Japan

[DON]

Thanks Chrenan you just made my day. Don

[Chrenan]

Hmmm, I'm not sure how that news could make your day? Wouldn't that ruin your day?

Keep in mind there is also a seperate balance shaft belt. If only this belt breaks, no damage will occur but the engine will run "rough" and vibrate a lot...
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1987 951 - M193 Version for Japan

[gohim]

If the balance shaft belt breaks, and the engine is not stopped immediately, there is a very high possibility that the broken pieces of the balance shaft belt will get caught up in the path of the timing belt, and the timing belt will get thrown. This has the same consequences as a broken timing belt.

The sudden appearance of a bad engine vibration is cause for immediate engine shut down until the cause of the problem is found. Remember that bad engine vibration (at low rpm only) is also a sign of bad engine mounts, but the engine mount problem does not develop suddenly.

[DON]

Sorry Chrenan just local way of putting things, clearly not the best way of improving the day. even worse is the fact that I have taxed the car twice MOTd it filled it with petrol more than once, but have only driven it about 100 miles. due to the fact that my daughter borrowed it for a few days seven months ago, she has kindly given it back now cos it wont go.
On a more technical note there is every chance that it was the balance belt that broke up and took out the cam belt going by the nature of the debris in the front cover.
Don t suppose it makes a lot of difference still have to pluck the head of and fix it anyway, Don.

[gohim]

Make sure that you do everything on the front of engine service list, or you will be going in again in short order.

Someone from the RennList posted a message this morning that illustrates exactly why this is important. He wanted to know if he should replace the waterpump now, as it was leaking, and it "only" had 35K miles on it. After questioning, he admitted that he had recently replaced the belts, but saw no reason to replace the waterpump. The reason is MONEY. Now that guy is going to have to pay for another set of belts because they have been wetted by coolant which causes the rubber to rot, and pay another full labor charge to replace the pump. This is going to end up doubling the cost of the service, and it was not necessary, since he could have replaced the pump when he had the belts changed.

Somehow, I get the feeling (without asking him) that he failed to replace the front of engine oil seals as well, and we are going to here from him again.

[Manning]

[Paul]

Gohim, although I agree with your advice, how many front end services have you actually paid for?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

[gohim]

I actually do the work myself, so I don't pay for them. I don't drive my Porsches near as far as I used to (used to drive as much as 50,000 combined miles in the Porsches, so belt replacement for me is a matter of time, and not mileage. Last year I drove all of my Porsches a total of less than 200 miles.

The cost of the tools hurt. The only tool that I have been borrowing is the P9201 belt tool, as I have not been able to find one worth buying at a price that I am willing to pay, yet. And, the cost of the replacing parts that appear to be perfectly usable seems awful high, since I run that are similar in function until they show symptoms of failure on the VW engines (1.8L watercooled) and the 924 engines.

I don't reuse or sell the used belts, rollers, pulleys, or water pumps (I have given away some used water pumps that I have removed to be used as cores to be traded-in, if/when someone needed one so they could keep their old water pump when they were getting a rebuilt watp pump and needed one for exchange), as I have seen some people doing with the parts that they have removed. I do have a couple more used pumps sitting here (I can't make myself throw them out, and I am not going to put them back in), as well as one, or two, new water pumps (I am always on the lookout for more at swapmeets). It seems dishonest to resell parts for reuse that I would not trust to install on one of my cars.

I figure the cost of replacing broken valves would be much higher, than replacing the parts myself every three years, since I can't replace valves myself (don't have access to a machine shop), even though I have purchase a number of new Porsche brand valves (at a low price from swapmeets) and have them sitting here just in case (NO, I am going to sell any more of my new spare valves, no matter how poor you claim to be, so please don't ask).

I didn't buy my 924S until about four or five years ago. because I knew from reading about the problems with the belts back in 1983 (when the production 944 first hit the US shores), that I didn't to own one of these engines until I was ready to do the service on time, according to what a safe replacement schedule, and not what Porsche was claiming the replacement schedule should be. It seems unreasonable to trust the people telling you not to worry about the relatively short period between belt changes that is indicated by the number of realtime failures, when the same people will not stand behind the product when the the belts fail earlier than predicted, and the same people are ready to jump in with "ja, I can fix the damage for $3500-$4000".

Incase you were not around when it happened, I still remember what Porsche did when 944 clutches were failing in a very short time on new cars if you don't, which was "the clutch failed, and you must have abused it, or it would not have failed. So there is no warranty, here is a bill for $XXXX ($2500-$3000) for the clutch replacement.".

There is not doubt that the 944 engine is far superior to the 924 engine. But let's not forget that it initially supplied with some parts that were not the best choices for production cars, and how Porsche chose to treat thousands of people who trusted Porsche, and bought those cars, and strengthen Porsche giving it the finances to avoid from insolvency or merger, and fund the development of the new models.

[Manning]

So what, is the 944 motor just an inherently bad design as far as t-belts are concerned? I have never seen such rabid concern about timing belt change intervals until I started posting on Rennlist and here. I don't recall seeing such fratic behavior about belts when I was into 16V VW motors, or even with the Honda I have. Can anybody tell me honestly where this comes from? Did the original belts on these cars just suck outright, or the front seals or what? Frankly I would be willing to bet that a majority of failed belts or water pumps on these cars, at this point are either due to the fact that they are original and should have been replaced years ago, or have been overtightened when they were replaced.
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Michael Manning
1988 924S Undergoing weight loss program

[Manning]

Also, somebody would have to be an imbecile to buy and use a used timing belt.
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Michael Manning
1988 924S Undergoing weight loss program

[gohim]

A significant number of belts were failing when the 944 engine first made it into production. The belts have been changed numerous times, along with the pulleys, rollers, and waterpumps, in attempts to improve the service life and reduce the failure rate.

When the early cars suffered from belt failures, Porsche pointed out that many failures were due to the failure of owners to have the 1K belt retension done after the cars were first delivered, and after new belts have been installed. The inside of the belt cover had some reinforcement ribs that Porsche claimed were eating the belts when the belt became loose. Porsche changed the belt cover design, and tried ventilating under the belt cover, then gave up on that, then added the belt guide on the waterpump, all attempts at improving belt life.

There have been numerous documented belt failures below 40K miles, and the number of failures increases with age and mileage. Below 30K miles, there have been few unexplained failures. Over 30K miles or 3-years on a front of engine service, and the failure rate starts to climb significantly. That's why many independent service shops recommend and follow a 30K or three-year front of engine service interval.

You are welcomed to follow whatever service cycle you like, as you are the one who will be paying for the results of your choice. Yes, VWs with 16V engines are interference, as are later high compression 1.8L engines (When I bought a VW Jetta last year as a driver/beater for my daughter who just turned 16 YO, I specifically purchased a car with the lower compression non-interference engine). If the timing belt breaks on those cars, valves do get bent. But look at the cost of head repair or engine replacement on the interference engined VW cars. You can buy a VW factory fresh crate engine for less than the cost of a valve job on a 944 from some aftermarket importers.

People have a tendency to believe that a more expensive car should take more abuse, and last longer than a disposable, less expensive car (like many consider the VWs). Therefore, they complain more, and longer, when there is a failure, and the failure turns out to be expensive to repair.

Seems to me that as the old saying goes, you pays your money, and you takes your chances...

Personally, I really don't want to waste money on unnecessary parts replacements, BUT I don't want to eat the cost of an engine failure either. The $500-$600 cost of replacing the parts every 3 years or 30K miles seems cheaper to me, than the cost of driving the car until something breaks, and then getting stuck out somewhere, at a bad time, and having to pay through the nose to have a Porsche Dealer somewhere that I am not familar with do the repairs, or abandoning the car where it breaks down, or paying for a tow from the middle of nowhere to home, so I can do the repairs myself. I prefer to take care of what I would consider to be normal maintenance on my own schedule, and be able to drive the car anywhere I choose, without having to worry about whether I am cheating the Car Gods, and about to pay the price.

And apparently/unfortunately, there appear to be plenty of people who are stupid enough to buy and install used belts, pulleys, rollers, and water pumps. Don't believe me? Check the number of auctions on eBay for these parts, then check the auction history, and see how many of these types of auctions close with multiple Bidders/Buyers

[Manning]

[gohim]

Nobody will supply parts and labor for a full front of engine serivce for $500-$600. You would be extremely lucky to find a competent mechanic willing to do the work for that price, and you will end up paying for the return visit check the belt tension at 1K miles.

$500-$600 is what I pay for the parts alone. I only buy Genuine Porsche Parts, and even though I shop Authorized Porsche Dealers, I do end up paying slightly more for the necessary parts, than if I were willing to take a chance on generic parts. Which would some with anywhere from no-warranty to 10/10 warranty (10 feet or 10 seconds) and 90-180 days, I prefer the security of the Porsche 2-year warranty that will pay for replacement parts and labor to repair any damage that is caused if the Porsche branded parts fail.

Yeah, that right, Porsche replaces the parts, covers the labor to install the new parts, and repair the damage caused by covered parts that fail, if the Genuine Porsche Parts are within the 2-year warranty. Even if the parts were not originally installed by the Porsche Dealer Service Department, as long as it is not obvious that the parts were not abused, or improperly installed.

No generic parts supplier stands behind their products like that. While a generic parts supplier may be willing to replace the failed parts that were purchased, if the parts are within the warranty period, the cost of replacing the parts, and repairing the damage always falls on the car owner.

Like I wrote before, if you choose to run parts till they fail, just because you feel that that shouldn't fail, that would be your choice. You are the one incharge, and you are the one who will pay. Same thing when it comes to buying parts. Buy your parts where ever you feel comfortable, and at whatever price you want. BUT, know that buying less expensive parts from less reputatble sources carries some risk. AND don't bitch and moan, and post sob stories here, if and when, you get bit by deferred maintenance, and cheap parts from generic suppliers.

Personally, I have not seen any VW parts inside of the 2.5L 944 engine. Off-hand, can you list the VW parts inside of the 944 engine that are actually VW parts, and the same quality as the parts that are installed in the engines when they are built by Porsche?