1.9 Dci Timing Belt Problem?

[pastymuncher1]

Hi Guys

Just half way through changing the timing belt on my car have got the dowel in flywheel and marks all line up as they should, have put belt on and tensioned. The marks on the belt(white lines across width) are all on the timing marks on all pulleys(cam,crank and fuel pump). When i rotate the engine over 2 complete cycles on crank as instructed the timing marks return to tdc and dowel will enter flywheel,however the white lines are then 1 tooth round to marks on all pulleys but engine is at tdc, keep rotating and it moves round another tooth(after 4 turns of crank) and so on, obviously eventually they will return to marks after a lot of turns but is this correct??
cheers
Stu

[AlexB]

Starting to read at p.187 here:
https://www.uas-bg.com/meganii/eng/MR364MEGANE1.pdf

There is no mention of repeated checking the belt marks. I guess, they are only needed for the initial installation.

[pastymuncher1]

Hi thanks for that..

The marks are all lined up at initial fitting of belt but like i say after every cycle of the engine(2 turns of crank) they have moved 1 tooth from timing marks??? never noticed this before on other cars that i have done, even other french cars but this just does not seem to stay with timing marks. its still turns over no problems but i am very wary of sticking it all back together and starting it for it to go bend bang crap!!
Have been using a haynes manual which is almost identical to that manual you suggested but i would have thought it is quite important and someone would mention it when instructing how to do the job?
Could do with a Renault mech's advice (unless thats what you are?)
will keep a copy of that manual though looks very handy!
Thanks again

[davelowe]

Crap, and I was starting to psych myself up for this job too. Hmm. What is the belt up to??

[AlexB]

pastymuncher1,

If the belt is OEM (check it!) and it is not jumping teeth in your experiment (double check!), then there is not much one can do. In fact, there is something wrong with your description. The crankshaft pulley is half size of the camshaft pulley. If you crank the engine twice, the belt advances by twice the number of crankshaft pulley teeth or exactly the number the camshaft pulley teeth. If the same timing mark returns to the reference point after this, then the belt must have the same number of teeth as the camshaft pulley, which is not the case! It may happen that you are looking at the different markings...

On the other hand, there exist a well known method of making the belt/pulley wear more uniform. It is possible to select the length of the belt so, that every time a tooth returns to a pulley (within some period, of course), it catches a different pulley tooth. For this, the number of the belt teeth must be a co-prime to the number of teeth in either of pulleys. So, it is also a possibility.

[pastymuncher1]

Hi Alexb
Yes tha belt is a genuine renault belt that i purchased, I dont quite follow your explanation as yes the crank is half the size so crank does two revolutions cam one revolution and timing belt one complete revolution and should return to the same position?
whereas mine is moving one tooth around on all pulleys every two revolutions of the crank, but it is definately not jumping. Have had on other cars where it been a tooth out on say the cam due to tension gaps between pulleys but never on every pulley and timing marks on engine still line up.

confused!!

[AlexB]

Hi pastymuncher1,

I'll explain.
First, I don't think that the belt can do a full round trip within two turns of the crankshaft. More turns are required.
Second, If you keep turning the crankshaft until the belt makes the full round trip and its marking comes back to the initial position with an n-teeth (one in your case) offset, then it can be an intended behaviour. They do it to prevent a particular tooth of the pulley from always meeting the same tooth of the belt. If the numbers of teeth on the belt an on each pulley are co-prime to each other, then the effect will be as you've observed. This is intentional and designed to equalise the wear of the belt. You can count the teeth in order to test this theory...

[pastymuncher1]

Ah...i see
Still got sleep in my eyes i think...after reading again initial reply...
I have contacted renault to see what they say if they will say!
Thanks again Alexb for your help,
if i get a reply from renault i will let you know how i get on..but not holding my breath..
cheers
Stu

[pastymuncher1]

Got a reply....

White lines will advance as belt rotates they are used for initial set up, providing timing marks on engine line up and crank pin can be entered then it ok.......................................Hopefully

[AlexB]

Well done, it makes sense.

Sorry for the confusing explanation, I was typing with my left foot while being drunk. What you've observed is clearly done on purpose to make the belt wear uniform.

[davelowe]

So, if the idea is that the initial set up marks are correct, and with no jumping, the belt will deviate from this position until a set number of crankshaft rotations have taken place, for example 4/8/16 revolutions until it returns back to normal? Is this the theory behind the even wear system that is intended to prevent the same tooth coming into contact with identical parts of the belt on every revolution?

Sorry if I'm being thick...

[pastymuncher1]

Well its all back together and running like a dream, but is peaking every now and then raises from 800rpm upto 900rpm and then down again after 30 second s or so but like i say runs fine...
can i just mention that coles of cookstown have been blinding with their help and parts cheaper than anywhere i could find for genuine parts...think their in ireland an im in cornwall but all parts arrived lightning quick and made good savings......
Alexb thanks to you also for your advice and reassurance...cheers bud
All filters cambelt waterpump and oil done...trouble free for a short while i hope!!!!
120k onwards and upwards.....

Stu

[triumph2.5man]

Stu, I'm interested to know how you set the final tension of the belt before tightening the tensioner - or do you have access to Renault tool MOT1273?

Cheers, Mike

[pastymuncher1]

Hi

No i dont have access to tooling i just set tension by pressing on belt on its longest run between crank and tensioner so that i can get between 45 to 90 degrees of movement with moderate pressure with my thumb.Then turned engine over manually a complete revolution then check again and adjust if needed.
Not the preffered renault way but hey ho!! it works on any other car so why not this...
Im sure some will argue i m risking it but like i say other cars its ok so ill give it a whirl and it seems ok so far!!touch wood

[triumph2.5man]

Thanks Stu. You are quite right, for years this was the normal way to tension a belt and I don't think you will encounter any problems. The mystery is why Renault decided that a little (and expensive!) tensioning tool was needed to do the job. Why did the Renault engineers not fit the 1.9dci with a spring-loaded tensioner as they did with the 1.5dci??
Cheers, Mike