Audi 1.8T Timing Belt Problem.

-=Maxed=- · 28 Feb 2006 at 00:19

Last month a work friend was driving home in the above car and getting a loud banging from the engine..
He was only driving a short distance to get home (less than a mile)

We have looked into the problem and it seems the cam belt tensioner has gone so the timing may have skipped a tooth or two..

The ECU is coming up cam error..

What sort of damage could have been done? the belt is still on and has SOME tension but i wouldnt of thought enough to stop from skiping.

Any idea would be great..

Cheers

Dandle · 28 Feb 2006 at 00:35

The engine is an interference engine so the pistons will wack the valves if the belt snaps. He may be very lucky though and the belt may just be looser than it should with the tensioner working properly. Causing the engine to notice the cam timing is out the banging could be caused by the timing being out. The only real thing to do is replace the belt and tensioner then turn the whole engine over(by hand) with the plugs out and see if anything is fouling. If not try the car and see, you could also do a compression check if he has the equipment. If that doesnt work its a head of job to check for damage.

-=Maxed=- · 28 Feb 2006 at 00:48

what would the compression test tell us? that a valve has been bent?

We have turned the engine over by hand and it dosnt seem to have much trouble but we will check again!

The belt hasnt snaped but has become a lot losser... there is no tension being aplyed to the belt.

Dandle · 28 Feb 2006 at 01:01

You may be lucky like I said and just the timing is out a bit. Or might have wacked the valves, this is what the compression test will tell you. If the belt is really loose and you can turn it over with the loose belt then chances are valves have come in contact with the pistons. It all depends on your description of the belt being loose as they arent so tight that you cant flex them under tension when fitted ok.

-=Maxed=- · 28 Feb 2006 at 01:09

Its lose enought to move a good half an inch freely...

So the only way to see if it needs more work is to compression test and if there is none then a valve is bent and need more work.

Dandle · 28 Feb 2006 at 01:31

Is the half inch movement on the long run of the belt? Correct tension as a rough guide is that you should be able to turn the belt 90 degrees on the longest run of the belt on cars with manual tensioners.

One thing i should have mentioned earlier is that you could check the timing marks on the cams and crank to see if they are out, that will give you some idea of how much it is out.

-=Maxed=- · 28 Feb 2006 at 01:35

You can turn the belt much more than 90 degrees...

The tensioner is a strange little thing.. its uses a spring and a metal rod to pull down on a cam witch pushes the belt in and gives tension..

I will try and get a compression test done and ill go from there.

Cheers

One thing i should have mentioned earlier is that you could check the timing marks on the cams and crank to see if they are out, that will give you some idea of how much it is out.

How much would be too much?

Dandle · 28 Feb 2006 at 01:44

The marks wont be exact but they should be within 4-5mm or so of alignment on each cam pulley if the crank is lined up. Any more than that and the belt may have slipped. Whatever you do dont drive it or start it now though until its all checked out. Its sounding more likely that the valves may have contacted if the belt is as loose as you said though.

-=Maxed=- · 28 Feb 2006 at 02:09

Yes i think thats what its going to be... we have a endoscope (if thats how you spell it) at work so were going to try that in and see if there is anything that we can see.

There is a scratch on the piston 4 that ive noticed as well...