Timing belt, fact or Internet folklore?
09-17-2015, 03:52 PM
#31
Team Owner
Join Date: Oct 2009
Location: one thousand, five hundred miles north of Ft. Lauderdale for the summer.
Posts: 28,704
Received 212 Likes
on
153 Posts
there's some truth in what he says... belts have improved.
Gates belts will go the distance (up to 60k miles) and perform flawlessly.
one problem; some don't change their rollers/tensioner or their pumps seize.
took my advice, went back 6 years and opened up to page 550....
what do we got but, 3 engine failures in the op....
(page 550, fourth thread, opening post)....
944 pulled from his cold dead hands....
you can't make this stuff up.
I remember that one (ugly).
did they read the signs? I read the signs.
I have them archived.....
all the departed.
moment of silence.
https://rennlist.com/forums/924-931-...ngine-bay.html
Gates belts will go the distance (up to 60k miles) and perform flawlessly.
one problem; some don't change their rollers/tensioner or their pumps seize.
took my advice, went back 6 years and opened up to page 550....
what do we got but, 3 engine failures in the op....
(page 550, fourth thread, opening post)....
944 pulled from his cold dead hands....
you can't make this stuff up.
I remember that one (ugly).
did they read the signs? I read the signs.
I have them archived.....
all the departed.
moment of silence.
https://rennlist.com/forums/924-931-...ngine-bay.html
the number of death cards drawn is truly damning.....
to date, we've had over 1600 timing belt failures separate from 800+ complete engine failures. here on the forums...
also: 22,000+++ no starts usually leading to junked 944s.
go back 6 years and look at the avatars.
yep, they're all dead sir.
nobody gives up their 944s unless you pry them from their cold dead hands. RTFM
look on the bright side.....
you can still blast Stevie's pretty voice over the stereo paid for with help from blowing off the scheduled re-tension.......
www.youtube.com/watch?v=U_aYibUx1B8
to date, we've had over 1600 timing belt failures separate from 800+ complete engine failures. here on the forums...
also: 22,000+++ no starts usually leading to junked 944s.
go back 6 years and look at the avatars.
yep, they're all dead sir.
nobody gives up their 944s unless you pry them from their cold dead hands. RTFM
look on the bright side.....
you can still blast Stevie's pretty voice over the stereo paid for with help from blowing off the scheduled re-tension.......
www.youtube.com/watch?v=U_aYibUx1B8
Last edited by odurandina; 09-17-2015 at 04:45 PM.
09-17-2015, 04:05 PM
#32
No, they are told to do the belts as it a 944 problem only. Not trying to knock the guys here. The advice given is some of the best. But I'll tell you this, a friend of mine had a towing business back in the 90's. 1/3 of his calls was for flats and the other 1/3 was for (can you guess?) timing belts. He never recalled any one car worst then another. Now l may be unlucky but l get flats about every 25000 miles. So should l say the brand of tire that went flat is problematic? If l do the math, all belts fails. It's the wording that's use that perpetuates the Internet folklore.
09-17-2015, 05:46 PM
#33
Drifting
The only reason a timing belt will fail is due to old age, high mileage, or a mechanical failure. A tire has many hundreds of thousands more obstacles then a timing belt. I had a spark plug sent thru the side wall of one of my tires once. I won't see that with a timing belt. However if a timing belt and all the components are replaced when they are supposed to then only the belts will need to most likely be addressed the next timing belt change not the rollers or water pump. The rollers get changed every other time if the bearing don't make noise the first change. I had a brand new tire only last 3000 miles because it took on a nail at a gas station and I was traveling across country. My belt didn't break because I replaced it when it was time. What ends up happening in most cases is people don't have the money to do the job so they try and drag it out as long as possible, that procrastination is what leads to most timing belt failures. Money can be the cause of tire blow outs as well with people taking there tires past the "may pop" zone with no tread to the, when your friend says "dude your wire is frying and popped on your tire" zone. Never in my life have I had a timing belt problem because I alway due the maintenance required when it's time.
09-17-2015, 06:02 PM
#34
Drifting
I would like to add that nowhere does the Porsche manual tell you to replace the fuel lines. That's why a newbie is told that. So one day when there driving there car and get to a stop sign their car doesn't catch on fire. If they know how to read a manual and follow the rest of the maitanace that these cars need then they shouldn't have a problem.
09-17-2015, 06:06 PM
#35
Rennlist Member
Re: fuel lines
There was actually a recall on them for late cars. I forget the details but I think it had to do with the swage fittings. Regardless, they fail due to age primarily... it's ridiculous to risk a total loss just to save $100.
There was actually a recall on them for late cars. I forget the details but I think it had to do with the swage fittings. Regardless, they fail due to age primarily... it's ridiculous to risk a total loss just to save $100.
09-17-2015, 06:27 PM
#36
+1 for Gates belts, but their alternator belts tend to run small. I had an issue on another car as well with TIGHT alternator "5V" belts. Subaru DOHC belts are probably twice as long as a 944 belt but the also have a hydraulic tensioner. The DOHC comment I don't believe applies in the 944/968 since they use a single gear and chain. With all that said change your belts for gosh sake, nothing stings more than regret. Especially when there is a immobile sports car involved. Learn to do your own work. "Experts" are no smarter than you are and anything can be learned.
09-17-2015, 07:41 PM
#37
One other factor is that these cars have a pretty hot underhood enviroment and that also shortens belt life.
That said, even if you follow the "rules" sometimes you get unlucky like i did, the cam belt on my 968 engine (hydro tensioner was still good) failed after 2.5 years and about 25k..... While on vacation and 1,000 miles from home. I got lucky and did not bend any valves, but it did break some teeth off the exhaust cam which i had to replace. it was a fairly intense job while on the road.
I should really get around to posting a thread about that experience lol. It was only just last month so i was kinda letting stress of that one fade away a little bit..
That said, even if you follow the "rules" sometimes you get unlucky like i did, the cam belt on my 968 engine (hydro tensioner was still good) failed after 2.5 years and about 25k..... While on vacation and 1,000 miles from home. I got lucky and did not bend any valves, but it did break some teeth off the exhaust cam which i had to replace. it was a fairly intense job while on the road.
I should really get around to posting a thread about that experience lol. It was only just last month so i was kinda letting stress of that one fade away a little bit..
09-17-2015, 07:48 PM
#38
Team Owner
Join Date: Oct 2009
Location: one thousand, five hundred miles north of Ft. Lauderdale for the summer.
Posts: 28,704
Received 212 Likes
on
153 Posts
not related to the above post.....
but, do rollers and tensioner with the belts every 50~60 k miles along with the water pumps.
they make this junk in Mexico now....
at 50 k miles, everything, (with the possible exception of the belts) are pretty much, toast.
but, do rollers and tensioner with the belts every 50~60 k miles along with the water pumps.
they make this junk in Mexico now....
at 50 k miles, everything, (with the possible exception of the belts) are pretty much, toast.
09-17-2015, 07:51 PM
#39
Three Wheelin'
The only reason a timing belt will fail is due to old age, high mileage, or a mechanical failure. A tire has many hundreds of thousands more obstacles then a timing belt. I had a spark plug sent thru the side wall of one of my tires once. I won't see that with a timing belt. However if a timing belt and all the components are replaced when they are supposed to then only the belts will need to most likely be addressed the next timing belt change not the rollers or water pump. The rollers get changed every other time if the bearing don't make noise the first change. I had a brand new tire only last 3000 miles because it took on a nail at a gas station and I was traveling across country. My belt didn't break because I replaced it when it was time. What ends up happening in most cases is people don't have the money to do the job so they try and drag it out as long as possible, that procrastination is what leads to most timing belt failures. Money can be the cause of tire blow outs as well with people taking there tires past the "may pop" zone with no tread to the, when your friend says "dude your wire is frying and popped on your tire" zone. Never in my life have I had a timing belt problem because I alway due the maintenance required when it's time.
To me the key factors are:
1. 4-cyl torque pulses at idle (as you say) which is why the 944 driver's manual specifically states "do not let the car idle but immediately drive away". Cambelts see most stress at idle.
2. The factory tensioning procedure is subject to misinterpretation. A lot of people miss the difference between the spring tensioner procedure and the tension roller procedure since the WSM is translated from German and it is assumed a certain level of training...
3. Age vs mileage can vary considerably on these cars.
I'm changing my timing belt this weekend, at 105,000km (65,000 miles). Not worried.
Cheers,
Mike
09-17-2015, 07:55 PM
#40
Three Wheelin'
I would like to add that nowhere does the Porsche manual tell you to replace the fuel lines. That's why a newbie is told that. So one day when there driving there car and get to a stop sign their car doesn't catch on fire. If they know how to read a manual and follow the rest of the maitanace that these cars need then they shouldn't have a problem.
Fuel hoses do not have a fixed-time changeout specified because it is assumed that the Porsche service technician will inspect these every 20,000km as per the service schedule and change them out on condition.
Timing belt condition is difficult to assess which is why they are on fixed time/distance schedule.
newbies don't always realise this...
09-17-2015, 07:55 PM
#41
IIRC Romania on the last set of INA rollers i had.
09-17-2015, 08:24 PM
#42
I did my belt a few weeks ago
My only trouble is I keep having to redo the alignment because after tensioning the belt the crank is off. Usually the third time is the charm.
I don't even bother using special tools anymore
My only trouble is I keep having to redo the alignment because after tensioning the belt the crank is off. Usually the third time is the charm.
I don't even bother using special tools anymore
09-17-2015, 09:07 PM
#43
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Join Date: May 2001
Location: Hotlanta - NE of the Perimeter
Posts: 12,269
Received 267 Likes
on
154 Posts
Heat no doubt plays a major factor in belt longevity.
The rubber loses essential oils, which are baked out by the heat in the engine compartment. The loss of these essential oils results in a lack of flexibility, then cracking.
No doubt the torque in the gear train and tensioner plays a factor - however I would submit that the torque is the system parameter that, when it exceeds the ductile behavior of the belt, results in exceeding the tension strength of the belt - which results in catastrophic failure.
In addition to the heat, chemical attack (motor oil and anti-freeze) can also degrade the ductile behavior of the rubber belt material.
Even if the belt is preserved, the other factor regarding abrasion due to the metal tooth of the gears and the rollers eventually wear down the cord, resulting in failure.
Just my observation...this and $2.29 will get you a medium coffee at your neighborhood Starbucks just about any day.
The rubber loses essential oils, which are baked out by the heat in the engine compartment. The loss of these essential oils results in a lack of flexibility, then cracking.
No doubt the torque in the gear train and tensioner plays a factor - however I would submit that the torque is the system parameter that, when it exceeds the ductile behavior of the belt, results in exceeding the tension strength of the belt - which results in catastrophic failure.
In addition to the heat, chemical attack (motor oil and anti-freeze) can also degrade the ductile behavior of the rubber belt material.
Even if the belt is preserved, the other factor regarding abrasion due to the metal tooth of the gears and the rollers eventually wear down the cord, resulting in failure.
Just my observation...this and $2.29 will get you a medium coffee at your neighborhood Starbucks just about any day.
09-17-2015, 09:20 PM
#44
Quick question:
I had my new to me 86 turbo belt, pump and rollers done 1.5 years ago. Car had 96K miles. Well maintained, documented history. I drive it infrequently maybe 2Kmiles/year.
Do I follow the 3yr interval, or can I push it further because along further?
I had my new to me 86 turbo belt, pump and rollers done 1.5 years ago. Car had 96K miles. Well maintained, documented history. I drive it infrequently maybe 2Kmiles/year.
Do I follow the 3yr interval, or can I push it further because along further?
09-17-2015, 09:26 PM
#45
Three Wheelin'
Heat no doubt plays a major factor in belt longevity.
The rubber loses essential oils, which are baked out by the heat in the engine compartment. The loss of these essential oils results in a lack of flexibility, then cracking.
No doubt the torque in the gear train and tensioner plays a factor - however I would submit that the torque is the system parameter that, when it exceeds the ductile behavior of the belt, results in exceeding the tension strength of the belt - which results in catastrophic failure.
In addition to the heat, chemical attack (motor oil and anti-freeze) can also degrade the ductile behavior of the rubber belt material.
Even if the belt is preserved, the other factor regarding abrasion due to the metal tooth of the gears and the rollers eventually wear down the cord, resulting in failure.
Just my observation...this and $2.29 will get you a medium coffee at your neighborhood Starbucks just about any day.
The rubber loses essential oils, which are baked out by the heat in the engine compartment. The loss of these essential oils results in a lack of flexibility, then cracking.
No doubt the torque in the gear train and tensioner plays a factor - however I would submit that the torque is the system parameter that, when it exceeds the ductile behavior of the belt, results in exceeding the tension strength of the belt - which results in catastrophic failure.
In addition to the heat, chemical attack (motor oil and anti-freeze) can also degrade the ductile behavior of the rubber belt material.
Even if the belt is preserved, the other factor regarding abrasion due to the metal tooth of the gears and the rollers eventually wear down the cord, resulting in failure.
Just my observation...this and $2.29 will get you a medium coffee at your neighborhood Starbucks just about any day.
Good point on the abrasion. New gears are available.
Cheers,
Mike