Porsche Enthusiasts Club Forum

Hi everyone!

So, I'm finally doing the timing. I have the Arnnworx tool 920Xv6.1 ( http://www.arnnworx.com/catalog/index.p ... ustJC17Gv4 ) . and just can't get the timing belt right.

I have a brand new timing belt so assume that being a bit tighter than an older used belt the Auto tensioner needs to be a fraction looser....am I right?

1- With the feel and water pump pulley method:

Situation, with starter back on and at TDC I turn the crank round and back to TDC. I can then just about turn the water pump pulley by one hand. However, when I push down on the top of the timing belt the crank moves back ever so slightly..(1/8th of a tooth maybe) and I can no longer turn the water pump. I then turn the crank round again back to TDC and I can turn the water pump pulley by hand. I can also turn the belt 90 degrees at its longest run When I push down on the timing belt again it can just touch the bottom right hand side of the separation bar but not the left..photo below.

Question on this method: is it normal for the crank to move back a fraction when you press down on the timing belt?

2 - Arnnworx tool:

I can't get my head around the slack and moving it back to the top of the belt. When I use the above feel method and put my tool on the belt WITHOUT moving the slack back to the top by turning the crank back a tiny bit, the cam does not move, the tool is always spot on! However, the instructions clearly state that I have to move the slack to the top for a correct reading. When I do this the dial swings round about 150 degrees into the realms of super slack.
I then adjust the auto tensioner to tighten the belt up with the pin wrench to the readings set out and turn crank around back to TDC and I can not turn the water pump pulley at all...not even with two rubber gloved hands.

My thoughts are the problems are around the Auto tensioner....this is a piece that is over 30 years old..Clarks garage makes reference to it saying best to test tension rather trust it to get it right.

Having watched and read up on this topic with the feel, twist 90 degrees, turning water pump pulley methods I am happy that I have the timing OK.

However, with the special tool to zone in on the specific exact tension it seems I am way too loose......

So what do you think please?

All comment welcome....

Thank you,

Michael

It's been a while, but I used the water pump twist method. Let the tensioner do its job, then backed it off slightly, until I could just twist the water pump, all the time rotating the engine forwards. Don't recall turning the engine backwards at any point though. If you're struggling with the cam belt, the balancer belt might be a problem for you too.

Thanks for this. Strangely the balance belt is fine to check and spot on every time...so my tool must work...it's just when I follow the instructions exactly for the timing belt it is very tight, hard to turn 90 degrees and certainly can't turn the water pump with one or even two rubber gloved hands....will do some more research........

A while for me as well but I gave up with the Arnworx tool, it is a pain with the auto tensioner anyway. I used to use the Krikit

The cam belt will get tighter as the engine warms up and expands. There's a theory that is what knocks out the water pump bearing prematurely. I couldn't turn the water pump by hand when my engine was up to temp. I had to re tension the cam belt slightly after 1000 miles, the balancer belt whined slightly for a couple of seconds at start up for while, but it didn't need re tensioning.

Interesting Jim....I have had a proper play with it for the last 3hrs and I just can't do it. The problem I think lays with the Auto Tensioner. Doing it by feel, when I rotate the belt to TDC, I release the locking nuts for the Auto tensioner, depress it a couple of times then it springs back to default position...automatically......I then lock all nuts, rotate until TDC again and it is very hard to move the Water pump with one rubber gloved hand. So what I do, is let it tension automatically and then push it in a hair....as in slightly less tension...then bolt up, spin around to TDC. I can then just spin the water pump.

With the Arnnworx tool I can follow the instructions well but getting the slack up to the top is random and doesn't always work and then even with the nuts loose and with my pin wrench in the auto tensioner I can move it a down and up with a good 15cm of swing with the pun wrench and the gauge on the belt only move about 5........so somethings a bit adrift here.....

M

never turn the motor backwards when doing this, it puts the belt slack on the wrong side,

once set if you rotate the engine once, and then the water pump can be moved with quite a bit of effort with one hand, (all dependent on you own personal strength), thats about right, a new belt should not be any tighter or looser than the old belt, tension should remain constant.

you need the belt to grip the waterpump by friction, it needs to be able to pump without slipping, this is for two reasons, you want the water to circulate correctly, and you do not want the belt to slip as that will cause premature wear on the back side of the belt, also too tight will wear the waterpump bearings,

Thanks Waylander..

The instructions for the tool http://www.arnnworx.com/Tools/944/920X- ... _V6186.pdf indicate the crank needs to be turned back counter clockwise....but only like 1mm...certainly the cam does not move. This is to get the slack onto the top part of the belt...where you take your reading.....so the way the tool works is on the slack bit....

not sure how that works, as the belt will be slack along its entire length on the right hand side, you have to take into consideration what are you turning the engine with, cam or crank...

if you turn with the camshaft you are basiclly pulling the beltfrom left to right, so all the extra slack will be on the long run on the right hand side, if you use the crank you are pulling the right hand side tight and any slack will end up on the water pump side,

hard to explain in words but try it you will get what i am tring to explain

Thanks, all makes sense....but sadly the instructions, pdf, videos want me to turn the crank cc..i.e form right to left... a hair to get the slack on the top long run.....must be something I'm missing here....

M

ok so same principle applies, rotating the crank CC will put the slack on the long run, but depending on the effort will pull the belt tight on the water pump, so i would suggest that if you just give it a light tap CC test the water pump and then measure the slack,

sounds like your looking for a balance of tightness, once set if you just tap the crank clockwise to tighten the long run and see how easy it is to move the waterpump, that is the real test, with the long run pulled fully tight with the crankshaft, like what would be happening with the engine running the waterpump needs to be tight enough

Thanks again.....

Using the feel method is easy...and I can just turn the water pump by hand. This is after I turn the crank over a couple of times, clockwise...but no counter clockwise movement, like 1.5 teethe....and then I can just turn the water pump. If I move the crank back counter clockwise, 1.5 teeth, I can no longer move the water pump by hand..........jeez...thought it would be far easier with this special paper weight....er, tool........M

From memory with the auto tensioner I think you turn CW to the marks. Once lined up you turn the Crank backwards 2 teeth & then slacken & retighten the tensioner.
Everytime I did it I had the Porsche manual, Clarkes, Pelican & Arnworx documents to hand. I generally used the Krikit & set it up at TDC.
Generally I run it up to temp & then re-assemble. Recheck after 1000miles & then every 12K The Krikit has different numbers for a new belt vs a new one.
They all whine slightly & new belts whine all the time.

CW to the marks? Crank and Cam?
Sounds like a plan though, to set to TDC then cc the crank (1.5 teeth the manual says) then release tensioner...and let it do it's thing.
I'll give it a go tonight....determined not to be beaten......by this paper weight....

M

just remember the tension will switch sides as you move the crank one way then the other, with the engine running the main tension will be on the long run, the slack will be on the waterpump side