airtraffic

Hello everyone!

This was my first attempt at the timing/balance belt jobs on my '87 944. I was very nervous about tackling this, as it involved a lot of very important parts! I'm happy to say the job went without any damage to car or mechanic! Car seems to run very well. Here's the part that has me puzzled.

I'm using the Arnnworx P920x tool to measure the tension. The tool shows the balance belt right on the money.. The belt does whine a little, but I"m assuming that while will quiet down as the belt stretches/breaks in?

The timing belt is different.. I set up the belt as described in the instructions, a few clockwise turns then backing the timing cam to place the slack on the lower span of the belt. Measurement is at TDC. I have the "Automatic" spring tensioner, and it is NOT set to full tension, I have it pulled a little. At the current tension with a cold engine, I can NOT turn the water pump pulley by hand as many mention. I can just barely turn the belt to the 90 degress twist that I have read about on many 944 forums. The Arnnworx tool shows that it wants me to TIGHTEN the belt even further, which I am reluctant to do. My local indie shop mechanic says on cars with the auto tensioner, he just lets the tensioner all the way out and doesn't even try to set a specific tension. Says he's been doing it that way for years.

So my problem is, if it's too loose, I know I risk jumping a tooth.. Sure doesn't seem too loose! If it's too tight, I risk breaking a belt as the engine heats up and expands, or just limiting the life of the belt to way less that 30K miles.

Advice/opinions would be appreciated!

Van

IMHO, let the auto tensioner do its job.

porsche924-S

Hello,
I am a newbie, I am not expert porsche is too new to me, 2 weeks ago a member here in this forum (Dean924S) helped me step by step how to re-tensioning my belts by twist methods, timing belt I think all you have to do is release 2 bolts locking nut and locking bolt let the auto spring tensioner adjust by itself simple as that, mine car is running much better than before .

Todd

Fara

What you're reporting is not normal for these cars.

Are you sure you've performed the correct calculation for your tension?
Are you following the instructions properly?
http://arnnworx.com/Tools/944/920X-V...ctions_V53.pdf

John_AZ

Van,

I have never been satisfied with the results.

Porsche put out a TSB on the mechanical spring (auto) tensioner.



In addition, the auto tensioner spring should be relaxed to remove the possible memory of the spring. Loosen bolt A&B and "rock" the spring using the tension roller on the auto tensioner before tension begins.

Van, I have seen many of your excellent videos and the OP should search to understand the procedure.

John

royalschwarz

I'm with Van...always let the auto tensioner do what it does and never had a problem.

KevinGross

Unfortunately the automatic tensioner is not completely reliable. Springs lose pressure over time, the mechanism gets corroded and hampered by debris, etc. I use the factory tool and typically find that there is some manual adjustment of the auto tensioner needed to get the reading spot on. Whether that adjustment is necessary for safe operation, I can't say. Van's experience is that the auto tensioner is okay, so there's one guy for whom it works fine!

Since you have the Arnworx tool, you might want to remove the auto tensioner from the car, give it a thorough cleaning, then reinstall and see where it takes the numbers. And since you have the tool, there's certainly no harm and probably some good in indexing the tensioner to get the number spot on.

The factory tool is quite sensitive, in my experience, to where you use it on the belts. The same is probably true for your tool. For the factory tool, make sure its centred properly along the belt length, and across the belt. Do remove the roller per the factory bulletin before measuring. And take multiple readings, make sure they repeat properly. With the auto tensioner, make sure you roll the crank back 1.5 teeth on the cam sprocket before measuring.

Also note that the number for the updated 18 mm. wide b/s belt is different from that for the original 15 mm. b/s belt. Good luck.

John_AZ

I agree.

airtraffic,

IF you remove the mechanical spring tensioner, there are 3 nuts to remove...
and 3 washers behind the nuts. Do not just drop these washers down on the crank belt pullys.

They are easy to misplace and hard to find if behind the pullys.

I do not think Kevin means a complete disassembly of the spring tensioner. In fact do not change the factory setting for the spring at all. Do not take apart.

Just do a spray clean with carb cleaner or parts cleaner on the entire assembly.

GL
John

Van

All good info here. It would be interesting to devise a procedure to calibrate the auto tensioner. E.g. take it off the engine, clean it up so it's moving freely, put the base in a vice, put a torque wrench on the idler nut, and it should take xx ft. lbs. to move it 1"... or something like that.

Fara

The arnnwerx process actually calibrates your tension by combining the auto tensioner with a measuring tool. It's a pretty neat way to do it

John_AZ

To answer your concern,

The cam belt does need to be installed slightly tighter if the belt is new.
Even with the Porsche tension tool, the numbers are slightly tighter.

The belt will need a few hundred miles to fit/settle in the gear cogs.

Redo the tension with the Arnnworx tool. Follow the Porsche methods I posted above.

When I am finished adjusting the belt tension, I rotate the engine CW 4 revolutions to TDC , check the timing marks on the cam gear and the FW at the bell housing, and do the water pump pulley test you mentioned. Wipe the WP pully clean, clean your finger tips with windex and grab the pully. It needs to move with a strong grip-the engine still will expand a couple of thousandths of an inch when hot.

If you feel comfortable with the tension, finish the job and check again in a couple hundred miles--or a couple hours (on a cold engine) until you are satisfied.

GL
John

V2Rocket

The other day I did a belt job on an 87 with the auto tensioner, but someone had actually removed the spring mechanism so it was now manual. MUCH better to work with.

Of all the spring tensioners I've dealt with not one has been remotely close to any other in regards to spring effort...they are not to be trusted IMHO.

Had the tensioner sandblasted, got all new hardware with lockwashers/locknuts, set tension once and set it right, check it in a few months.

That said, if someone wants an 87 spring tensioner anyways, I have one spare that I don't have a use for...