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[polilara]

Hello all

When I start my V6 I hear something which I do not like. With Idling speed about 600 rpm I hear three sharp noises on regularly basis. The noises last together about 0.5 second and then there is silence about 0.5 second, during next 0.5 second I hear again these three noises etc. Just calculated that crank sprocket has 23 teeth and timing belt has about 10 times more teeth so while crank is rotating 10 rounds/second the timing belt is rotating one round/second.

But what it can be? If something in tooth side I should hear something 5 times/second and without brake. If something in back side I perhaps heard something three times/sec (without brake). When engine gets warm the sound disappears. That happens every day.

I changed timing belt + other parts about 500 km ago. During first wekks I did not hear this noise. Perhaps better to open cam cover and see. Any ideas??

[zirk]

First thing I would do is to pull the Aux Belt off and run again briefly, that will eliminate, Aux Tensioner and Pulley's, Alternator, Power Steering and Water Pump, then go from there.

[polilara]

Yes, thanks. That is something to be done first but I am afraid that it is not the case. Aux belt is rotating much faster than timing belt so difficult to imagine what else will cause a frequency that I hear once a second when engine idling. But I'll do that. Let's see.

It is difficult to explain this in English but if you divide one second to six parts (1,2,3,4,5,6) I hear a 'click' in time 1 and a 'click' in time 2 and a 'click' in time 3. Then in time 4, 5 and 6 I do not hear anything. Like there was a loose tape in outer surface of the timing belt which touches the cam cover in top corners etc. But what happens when engine is getting warm.

Today I take my bike when going to work...

[polilara]

Good to have a bike!

Removing aux did not change situation. Took cam cover away. Timing belt seems to be a bit aside of cam sprockets.

1. In bank 1-3-5 I can see about 3.5 mm cam sprocket teeth in front of the belt and in bank two maybe 3 mm. So belt is a bit "back".
2. Belt seems to be against rear flanges of the guiding rolls. Rear flanges slightly polished.
3. All old belts I found have GM number 9 128 500 39 while new one (Gates) is GM 95522522
4. Rotated engine manually 15 rounds, nothing abnormal can be seen in teeth or back side.
5. Tensioner have same SKF numbers than previous, Guiding rolls seem to have same SKF "main number" other markings differs.

Should I assemble everything back except cam cover and start the engine to see something or just buy a new belt with GM number 9 128 500 39.
Can a new belt be noisy when cold, never heard
What this really can be?

[terry paget]

Some years ago I had noise problems on my V6 Omega after fitting new belt and pulleys. I had bought the belt kit from a Vauxhall main dealer, so I returned it and got another one. That was similarly noisy, so I returned that one and bought an SKF kit, which was silent. The noise was not the same as yours, it was a whine varying with engine speed. My theory is that the belt slipping through the V-pulley whined at certain temperatures.

I have since fitted a variety of cam belt kits, but never had any noise problems.

If you still have the old belt, fitting it on your new pulleys would prove whether the belt is the problem.

[Lincs Robert]

I had a similar problem a few years ago. Turned out to be a small leak in the exhaust manifold gasket. The clicks were the gas escaping through the leak, when the engine & manifold were hot something must have expanded & the problem stopped!

Try listening in that area.

[polilara]

Thanks for comments, I try to start the engine today without cam cover just to see whether the frequency (of the three clicks) really is once in a time belt round. Estimation is that when idling 600 rpm timing belt rotate once/sec and crank 10 rounds/sec. There is a text and number in the outer surface on the timing belt. If I hear the sound allways when the text part of belt is in the same place then the reason can be the belt itself. Can it be bent when tensioned so that it touches e.g. to the steel plate/cover behind the cam sprockets.

Test with old belt is a good idea. Have to study those leakages in exhaust, too, even it is difficult to understand that as when Idling 10 rounds/second each cylinder has power stroke 5 times/sec so I guess leakage sound should come much more often than once a second. But let's see, usually I think in a wrong way...

[polilara]

Hello

Started engine without cam cover.
Seem to be once/belt round Have to study more.

Is it normal that about 3 mm cam sprocket teeth are "free" in front of the belt. Is it possible that the guiding rolls locate the belt too far to the rear side.

[cam.in.head]

You have definately fitted the pulley spacer washers behind the correct pulleys havnt you. The lower pulley (central or eccentric type )has a thicker spacer than the top eccentric pulley

[polilara]

Hello

I bought a "Timing Belt Package" in a big box with GM-logos and texts. Also all boxes I found inside the package had GM texts. The package included the base plate where both upper guiding roll and tensioner we ready installed. Then there was another smaller box including lower guiding roll and spacer for that.  I have old parts still lelft so I can make a verification.

[ffcgary1]

i had a gm kit fitted last time out and it made a chirping noise like a baby bird (chick) it died down after a few thou miles. also removed the aux belt and it made no difference, cam
belt cover also removed still the same. i put it down to the white lettering on the belt passing over the pullys

[polilara]

Baby bird chirping noise is exactly what it is. This noise is coming from top like cam sprockets did not like the teeth in certain part of the belt. Then silence, that part continues down to lower idler, crank, tensioner and up again and the noise starts again etc.. Can clearly seen as noise starts always when white text in back of belt is in certain place coming to cams 3&4. So it is not when text is against idlers or tensioner.

[polilara]

Look at this

https://youtu.be/2oA3VBB6hGA

Chirpy Chirpy Cheep Cheep

[polilara]

Did anybody see my video?

I today started the engine again (noise was there) and during the engine running I injected some drops of water to the timing belt back above cam 1 sprocket. As my hands were shaking some drops fell to the sprocket teeth, too, and after one second all noises disappeared. Remember in 70' when some deposit was knocking between piston and head some water through carburetor when engine running helped in seconds.

So should I lubricate the belt with silicon or just assmble everything back and forget the whole thing?

[polilara]

I checked once again the belt tooth by tooth. It is perfect. On tooth is a bit white in the bottom. Perhaps the seam area or is this seamless?

I should assemble it today to be able to drive tomorrow. Understand it is difficult to give any recommendations in this case but what you would do:

1. New Belt
2. Light lubrication with silicon (both sides)
3. Just leave as it is

Please comment
https://youtu.be/2oA3VBB6hGA