Timing Belt Tension Poll....

[355]

Belt whine is typically caused by the balance shaft belt, and happens when the belt is toward the high end of the factory spec and/or tighter than the spec. Keep the 18mm balance shaft belts toward the lower end of the range (3.0) on the factory tool and they won't whine. If you set it to the higher end of the range (4.0), it will definitely whine, at least for a while.

I read about it being the balance shaft belt being too tight is what causes the whine so I played around with the tension a bunch while the car was still on my lift and ran the engine with the timing covers and accessory belts still removed. I even tried loosening the belt so far that is was just flapping about and the pitch and volume of the whine never changed so I'm pretty sure it is the cam belt on my car making all the noise. I keep inspecting the belts each time I have the car on my lift and nothing appears to be going bad with any of the timing components or water pump so I've just come to accept it as a normal sound from this engine. One good thing that has come out of this is I am getting really efficient at gaining access to the timing belts now!

[danmartinic]

Wow I never heard of a timing belt whine

[danmartinic]

You're missing an option for the poll: auto-set via the spring loaded tensioner (that's what I've been using since 2008 and over 120,000 miles of daily driving)

Seems to be work fine. I do take the tensioner off, clean and lubricate it before installing

I disagree with this, cause after 30yrs of age I do not think you should trust it to be accurate. I've since then seen issues with super weak ones being nowhere near spec.
Maybe ok on a personal car, but I always use a tool on a customer's car, and I keep records of everything being in spec.

A good survey might be "Have you ever experienced a timing belt failure?"

With so many variations on the tension setting, I wonder what the failure rate really is.

Personally, I am guessing that the design allows some variance.

When I first got my 951, I was young and scared, so I had a Porsche mechanic change the belt. When the time came for the next one, I did it. It was then that I learned about the re-tension at 1500 miles. The mechanic never suggested I come back for this.

I daily drove a few years with an 'out of spec' belt.

There must be some safety tolerance in it

[Latitude48]

For those with 944 S2 TSB #9208 was issued in 1992 to address "Camshaft Drive Belt Noise," which can be an issue in the 1800 rpm range. It recommends tensioning the belt using the 9201 tool to a scale value of 4.0-4.3.

On another note, I'm curious what tensioning mileage intervals most people follow after the installation of new belts, and for the interval between changes. In the past I've used 2500 miles for the first recheck goal after installation of new belts, then each 15,000 miles, thereafter, give or take.

[danmartinic]

Tension rechecks continue after the first one?

Change interval on vintage car usually dictated by necessary other service in the area

I haven't gone 5 years or 50,000 kms without being "in there" anyway yet

[blade7]

You're missing an option for the poll: auto-set via the spring loaded tensioner (that's what I've been using since 2008 and over 120,000 miles of daily driving)

Seems to be work fine. I do take the tensioner off, clean and lubricate it before installing

I disagree with this, cause after 30yrs of age I do not think you should trust it to be accurate. I've since then seen issues with super weak ones being nowhere near spec.
Maybe ok on a personal car, but I always use a tool on a customer's car, and I keep records of everything being in spec.

If you fit a new water pump every 2nd belt change too, I'm glad I'm not a customer.

[Darwin]

Nice. I'm not saying all tensioners are bad, but I feel like relying solely on something like that when literature doesn't say to do so is potentially asking for trouble. I'm sure with the manufacturing variance in springs, you can check to see where the tensioner puts it, but to say they all put it where it needs to be is a little too trusting IMO.

I've checked my tensioner against my 9201 as well and it consistently tensions my belt to about 2.0 to 2.2 on the gauge. I give it a little nudge to tighten the belt and can often get it in spec on the first try. But that only works because I know MY tensioner vs the factory gauge -- and the amount of tension these things apply does seem to vary from one tensioner to the next. I assume the factory was shooting for them to put the belt within the spec, but corrosion, wear, grime, etc. all conspire against it over time. Even though my tensioner always seems to need a little nudge to be spot on, I always check with the 9201 anyway, since I have it, and since I'm convinced the one time I don't check it will be the time the tensioner hangs up on something and is way out of spec (although I'd probably notice that by feel, but paranonia knows no bounds.... ).

AFAIK none of the fancy tools figure in the engine expansion, when it heats up. The cam belt gets tighter, and knocks out the waterpump bearing prematurely. That's why I back off the cam belt tensioner, until I can just turn the waterpump pulley by hand. It's never going to jump when cold, and as soon as the engine heats up, the belt gets tighter. Changing the waterpump every 2nd belt change is nonsense really.

I would assume, at least with the 9201, that this is taken into account based on the FSM stating that tensioning should only be done on a cold engine.

12317216-5213-4B99-9708-A8FF3EEFC0FF.jpeg (49.3 KiB) Viewed 1994 times

[Tom]

I've checked my tensioner against my 9201 as well and it consistently tensions my belt to about 2.0 to 2.2 on the gauge. I give it a little nudge to tighten the belt and can often get it in spec on the first try. But that only works because I know MY tensioner vs the factory gauge -- and the amount of tension these things apply does seem to vary from one tensioner to the next. I assume the factory was shooting for them to put the belt within the spec, but corrosion, wear, grime, etc. all conspire against it over time. Even though my tensioner always seems to need a little nudge to be spot on, I always check with the 9201 anyway, since I have it, and since I'm convinced the one time I don't check it will be the time the tensioner hangs up on something and is way out of spec (although I'd probably notice that by feel, but paranonia knows no bounds.... ).

AFAIK none of the fancy tools figure in the engine expansion, when it heats up. The cam belt gets tighter, and knocks out the waterpump bearing prematurely. That's why I back off the cam belt tensioner, until I can just turn the waterpump pulley by hand. It's never going to jump when cold, and as soon as the engine heats up, the belt gets tighter. Changing the waterpump every 2nd belt change is nonsense really.

I would assume, at least with the 9201, that this is taken into account based on the FSM stating that tensioning should only be done on a cold engine.

12317216-5213-4B99-9708-A8FF3EEFC0FF.jpeg

Agreed. I'm not in the camp that think it has to be right just because Porsche said so, but I can't imagine Porsche would overlook something as basic as thermal expansion.

There's a ton of people using the twist and feel method to set the tension, and it's highly unlikely that they are all getting the tension within the tiny little window that Porsche specs, so it seems pretty well established that there is a wider range that will suffice for most people, as a practical matter. The question I'd say is whether the 'set-by-feel' motors are wearing out water pumps faster, or seeing more belt or roller failures, etc. That's a tougher question to get good data about, expecially since most DIY types end up keeping a closer eye on their belts, changing them more often, etc. The factory needed to make specs that resulted in reliable cars with nothing but owners manual servicing intervals across every environment imaginable. Setting a belt a little loose/tight in Los Angeles may be way less of a big deal than doing the same in a climate with extreme temperatures.

[Darwin]

Agreed. I'm not in the camp that think it has to be right just because Porsche said so, but I can't imagine Porsche would overlook something as basic as thermal expansion.

There's a ton of people using the twist and feel method to set the tension, and it's highly unlikely that they are all getting the tension within the tiny little window that Porsche specs, so it seems pretty well established that there is a wider range that will suffice for most people, as a practical matter. The question I'd say is whether the 'set-by-feel' motors are wearing out water pumps faster, or seeing more belt or roller failures, etc. That's a tougher question to get good data about, expecially since most DIY types end up keeping a closer eye on their belts, changing them more often, etc. The factory needed to make specs that resulted in reliable cars with nothing but owners manual servicing intervals across every environment imaginable. Setting a belt a little loose/tight in Los Angeles may be way less of a big deal than doing the same in a climate with extreme temperatures.

I agree. Seeing as I was not amongst the engineering team that’s designed this engine (and also have no formal engineering education to speak of) I tend to follow established literature when it comes to my maintenance, and advise the same when asked about methods/practices. Probably my aviation background coming out, lol.

[stitch2k1]

A good survey might be "Have you ever experienced a timing belt failure?"

With so many variations on the tension setting, I wonder what the failure rate really is.

Personally, I am guessing that the design allows some variance.

When I first got my 951, I was young and scared, so I had a Porsche mechanic change the belt. When the time came for the next one, I did it. It was then that I learned about the re-tension at 1500 miles. The mechanic never suggested I come back for this.

I daily drove a few years with an 'out of spec' belt.

There must be some safety tolerance in it

I grew up working on airplanes before I ever knew what a Porsche was, so I have that mentality. If something is not correct to spec I will correct it. Today I messed with my Arnnworx tool and found that my timing belt was out of whack by about 15% on the loose side, even after following the Porsche method to re-tension a timing belt after those break in miles. I attached a picture of TSB 8820 which detailed that process. Maybe back in the 80's these worked fine as automatic tensioners, but I am not going to trust one. Laziness is not worth the price of a new cylinder head, especially on a 16 valve engine.

TSB 8820.png (499.05 KiB) Viewed 1977 times

For those with 944 S2 TSB #9208 was issued in 1992 to address "Camshaft Drive Belt Noise," which can be an issue in the 1800 rpm range. It recommends tensioning the belt using the 9201 tool to a scale value of 4.0-4.3.

On another note, I'm curious what tensioning mileage intervals most people follow after the installation of new belts, and for the interval between changes. In the past I've used 2500 miles for the first recheck goal after installation of new belts, then each 15,000 miles, thereafter, give or take.

I have been trying to fight a whining noise on my S2, I wonder if this might be what happened. I run a 4yr/45k mile interval on the TB & BSB, water pump replaced every other belt/10yrs. Attached a copy of TSB 9208 for future reference.

TSB 9208.png (791.78 KiB) Viewed 1977 times