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new cam belt walking off


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#1 thegoat

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Posted 23 September 2018 - 06:38 AM

hi folks

this has been a pain, tried to fit a new cam belt yesterday, ( 2.0 HDI  05 reg ) done a few before various cars not had a probelm

but this is driving me mad, 

fit the belt

tension so i can just twist the belt to just under 90 dgrees

remove timing pins

turn crank (about 8 full revolutions)

check the pins

belt is walking off the cam pulley

 

redo it, same again

 

did web search " maybe too much torque on tensioner bolt" or " tension too tight "

 

any suggestions



#2 thegoat

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Posted 23 September 2018 - 12:22 PM

think i've found the probelm, getting the old tensioner off was hard as there was not much space between engine and engine bay, maybe i burring the end of the tensioner shaft ? all I know is it has slight burring.

when I fit either the new or old tensioner there is very little shaft going into the tensioner (but its up against the block the other end.  even with the bolt nipped up (no belt on) as soon as you turn the tensioner (as if trying to tension belt, the tension moves off the end of the shaft

think I need a new tensioner shaft if you can get them ? or the engine part no ?

 

the tensioner is not solid it bears on the shaft at the bottom and top, ( even on the tensioner I took off it only bears on the top end by a few mm

 

 

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#3 thegoat

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Posted 23 September 2018 - 03:16 PM

had a look at some citroen software says part is

Screw column 0820 17         M8 x 125(2)

 

anyone know if these are citroen part nos



#4 discv

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Posted 24 September 2018 - 11:13 AM

I fail to see how the tensioner can move on the shaft once the bolt is tight.

Let's make sure I'm on the right hymn sheet-

 

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#5 discv

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Posted 24 September 2018 - 12:03 PM

Attached File  2.0 Cam JPEG.jpg   136.29KB   0 downloads


C4 Grand Picasso 1.6 HDi 16V FAP/DPFS 110, -Auto (DV6 - 80kW) (C4) (DT) (2008)

 


#6 thegoat

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Posted 25 September 2018 - 06:22 AM

its part no 8 pillar screw, that I think is my problem

as I said the tensioner only bears on the "Pillar Screw" at the bottom and top, the middle of the tensioner is empty 

the top end of the tensioner bearing point appears to be a tapered wider inside the tensioner then thinner on the outside ( both old and new tensioners will not fit on to the pillar screw in reverse (but go on ok the right way round)

looking at the wear marks on the old tensioner it appears that the top end was only on the pillar screw max of 2mm

 

I've put a small T square against the pillar screw it looks ok

when I put on the new tensioner (without a belt) tighten bolt hand tight, then turn tensioner, it felts like it slips off/comes out of square, 

I've ordered 2 new pillar screws (extra 1 incase) £7 +vat

 

my thoughts are that with the tensioner not square against the belt allows/assists the belt walking off the cams (a youtube video from KS tuned says similar)

 

I can't see it another way, but i'm open to help



#7 thegoat

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Posted 25 September 2018 - 06:41 AM

if you look at photo this is the top end of the old tensioner, inside the bearing hole there is a darker line that is way i believe the pillar srcew shaft ends

(the yellow paint are marks by me to make sure that tensioners are not mixed up)

the photos of the tensioner in post 2 is the rear/bottom of the tensioner (end against the engine block)

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#8 Avon

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Posted 25 September 2018 - 11:12 AM

Is the belt coming off completely, or just centering itself?

I doubt tension itself could cause this problem, one of the pulleys must be out of parallel with the others for the belt to come off or spaced too far sideways for the belt to move over.


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#9 discv

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Posted 25 September 2018 - 11:27 AM

Avon makes a point- maybe we are focused on the tensioner too much. I wonder if the different options for the cam pulley varies the belt for example.


Edited by discv, 25 September 2018 - 11:31 AM.

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#10 thegoat

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Posted 25 September 2018 - 01:16 PM

its walking off the pulleys, 

i can see it moving off the cam pulley first then the fuel pump, then then slowly off the crank 

i've not touched anything on the cam or fuel pump pulleys (single bolted cam pulley)

 

its not the tension from the tensioner, I think its because the tensioner is not on the top of the pillar screw so the tensioner is not square on the back of the cambelt

so there would be more pressure(tension) on the inside of the cambelt, less (if any ) tension on outside, thus allowing it to walk

that is my best stab at it

if you watch that KS tuned youtube video I should it says the same,  



#11 discv

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Posted 25 September 2018 - 03:53 PM

So if I understand correctly, the tube that screws into the block is too short and does not enter the outer face of the tensioner. I wonder if unscrewing the support tube a little, then securing it with loctite might help.


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#12 thegoat

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Posted 25 September 2018 - 06:53 PM

yes that's it

the tube (pillar screw) is not going far enough into the outer edge of the tensioner, so even when the tensioner bolt is tighten up the tensioner outer edge can/does slip off the tube (pillar screw)

 

the end of the tube (pillar screw) feels burd, and as I said there appears wear/running marks inside old tensioner outside bearing plate but they are only about 2mm inside the old tensioner outside bearing plate, so originally there was not much supporting the tensioner outside plate

 

I'm still awaiting the new pillar screws I ordered

 

the tensioner bearing is like a wheel hub, the wheel hub bearings touch only the ends of the stub axle (not all the way along it) and that's like this tensioner bearing (hope that makes sense, )

 

 



#13 Thunderbolt

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Posted 25 September 2018 - 06:59 PM

I had a similar problem on a Merv, turns out the the wheel was off by about 5°,drove me nuts. Once I got it on square, no worries, (touch wood).

#14 thegoat

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Posted 26 September 2018 - 04:52 AM

I had a similar problem on a Merv, turns out the the wheel was off by about 5°,drove me nuts. Once I got it on square, no worries, (touch wood).

so you think i could be right that the walking is due to the tensioner not being square on the stud (pillar screw)


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#15 discv

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Posted 26 September 2018 - 08:59 AM

You could try backing off the tension, do not let engine start!, to see if this reduces/stops the 'walking'.


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#16 thegoat

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Posted 26 September 2018 - 10:23 AM

i've ordered these pillar screws but awaiting PSA main stores to send them to local dealer

 

having tried setting it up about 8 times, i'm sure its the pillar screw, only way to prove it by getting new one

 



#17 thegoat

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Posted 27 September 2018 - 06:44 AM

the probelm i'm thinking about now is how to remove the old pillar screw, 

i've been squarting it with plus gas, to try to relase the thread grip

thinking about using freeze spray to break the grip just as I'm about to try to undo it

do you thing screwing a bolt in to the pillar screw (stud)  then tightening 2 nuts against the pillar screw, then trying to undo the bolt would unscrew the pillar screw ?



#18 discv

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Posted 27 September 2018 - 10:58 AM

Something has changed here. It was all working, the support pillar did not get shorter by itself.

Stupid thought- the tensioner was rotated in the correct direction??!


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#19 thegoat

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Posted 27 September 2018 - 04:43 PM

looking at the pillar screw there is a burr at the end, don't know if it was on there before I took old tensioner off

but when I took old tensioner off there was not much room to remove it, and I had to jiggle it about, so maybe I caused the burr

I've tried without the belt (just the tensioner) with the tensioner pushed home there is no space between the engine block and tensioner, tighten the bolt and I can fill its slipped off the end of the pillar screw

 

 



#20 thegoat

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Posted 27 September 2018 - 06:57 PM

Something has changed here. It was all working, the support pillar did not get shorter by itself.

Stupid thought- the tensioner was rotated in the correct direction??!

just re-read this

 

do you mean was i getting the belt tension tighter when i turned the tensioner (if that is question Yes belt was tighter)

 

the tensioner has the pillar screw shaft offset and the adjustor offset so there is an 180 drg turning/tensioning 

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