Timing belt idler pulley

Colin Aitchison · 22-01-17, 11:45 PM

Hi, I have been having problems fitting a timing belt to my 7A 20v engine that I am rebuilding,
I have fitted dozens of timing belts to Audi 5 cylinder engines in the past 26 years, but this one just didn't feel right, even got a second new timing belt to make sure that there was a problem with the first one, but today solved the problem, when stripping the old engine that I never had running the idler pulley bearing was noisy so measured it (74mm) and ordered it and fitted it when fitting new oil pump when it came to fitting the timing belt with the flywheel on '0' and the cams on '0' you need to fit the belt clockwise round the crankshaft pulley then anti-clockwise round the idler pulley the clockwise round the camshaft pulley and the timing belt teeth should fit into the camshaft pulley with no slackness in the belt, any slack should be on the water pump side where you adjust the tension via the water pump but the timing was 1/2 a tooth out with both of the belts, so after a minute of thought today my solution was to fit a 68mm idler pulley and hay-presto the timing belt fitted into the camshaft pulley with no problem, so, still had the old bits from the engine in a box and measured the old noisy pulley again and is was indeed 74mm, just thought I would post this for information.

mikes2 · 23-01-17, 08:17 AM

7A is supposed to have the 74mm pulley

John. · 23-01-17, 08:32 AM

Interesting? While it was a few years ago since I did the belt on my car, I'm wondering if the water pump only fits one way.....and would it be possible to fit it differently causing the timing issue?

I wish I had the room for "an engine room"!!

Maybe one day.

Colin Aitchison · 23-01-17, 08:46 AM

Thanks for the reply's, this may sound daft but this may turn out to be an oil pump problem, I will need to remove the timing covers from the other engines in the garage to have a look see at the size of the idler pulley.

sinbin5t · 23-01-17, 03:29 PM

Quote:

Originally Posted by John.

I wish I had the room for "an engine room"!!

Maybe one day.

You're not on your own there John

23-01-17, 08:17 AM	#2
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	7A is supposed to have the 74mm pulley __________________ 1991 90 quattro 20v sport 1991 90 quattro

23-01-17, 08:32 AM	#3
John. 4 ring whore! Classic Audi Club Member Join Date: Mar 2011 Location: Scottish Borders. Posts: 7,540	Interesting? While it was a few years ago since I did the belt on my car, I'm wondering if the water pump only fits one way.....and would it be possible to fit it differently causing the timing issue? I wish I had the room for "an engine room"!! Maybe one day.

23-01-17, 08:46 AM	#4
Colin Aitchison Senior Member Classic Audi Club Member Join Date: Dec 2013 Location: Back home in Tillicoultry Posts: 1,342	Thanks for the reply's, this may sound daft but this may turn out to be an oil pump problem, I will need to remove the timing covers from the other engines in the garage to have a look see at the size of the idler pulley.