1.8T timing belt tension & stretch

[relative4]

Halfway through the timing belt & WP job. Last thing I did before bed last night was install and tension the belt. I set the gap at 8mm and torqued the nut to spec. When I got up this morning, the gap was 10mm. I can only assume this is due to several hours' stretch on the new belt. Should I take it that the 8mm spec is for a new belt that hasn't stretched yet, or should I readjust the tensioner to 8mm? Thanks!

[old guy]

Halfway through the timing belt & WP job. Last thing I did before bed last night was install and tension the belt. I set the gap at 8mm and torqued the nut to spec. When I got up this morning, the gap was 10mm. I can only assume this is due to several hours' stretch on the new belt. Should I take it that the 8mm spec is for a new belt that hasn't stretched yet, or should I readjust the tensioner to 8mm? Thanks!

The spec is 6→10mm so you are still fine. If you really want to adjust it in place I can give you a few pointers.

[jacobsen]

Halfway through the timing belt & WP job. Last thing I did before bed last night was install and tension the belt. I set the gap at 8mm and torqued the nut to spec. When I got up this morning, the gap was 10mm. I can only assume this is due to several hours' stretch on the new belt. Should I take it that the 8mm spec is for a new belt that hasn't stretched yet, or should I readjust the tensioner to 8mm? Thanks!

Make sure you use a brand new nut with some red loctite. The oem nut is soft and not at all suitable for a second use. A fellow az'r lost his tension and completely destroyed his motor when he reused the tensioner nut. It fell off into the timing belt and that was that. 10mm is a good place to set it as long as its tight. I suspect the piston has forced its way out more... turn it by hand a bunch if times before you start it. Mark the belt at tdc and check the time before you turn it. Get a nice hard nut from the hardware sstor before you set it and forget it.

Sent from my SM-G920V using Tapatalk

[relative4]

Thanks! I thought the nut looked pretty soft & crappy, but I figured if it were an issue Gates would have included a replacement. Foolish and naive of me. Thanks for saving me from myself! Good nut installed with blue loctite, I'd rather not use a blowtorch for my next timing belt job. Gapped to 8mm and holding, feeling much better about the work now.

People like you guys make these forums amazing resources. Thanks again, looking forward to bugging you again soon.

[customa4]

Not sure how far you've gotten but this should help if you're still working on it. Click

[diagnosticator]

Halfway through the timing belt & WP job. Last thing I did before bed last night was install and tension the belt. I set the gap at 8mm and torqued the nut to spec. When I got up this morning, the gap was 10mm. I can only assume this is due to several hours' stretch on the new belt. Should I take it that the 8mm spec is for a new belt that hasn't stretched yet, or should I readjust the tensioner to 8mm? Thanks!

Timing belts do not stretch any measureable amount. The design and construction of synchronous timing belts is specifically to prevent stretching. If timing belts stretched, the camshafts would lose timing with the crankshaft.

[relative4]

Timing belts do not stretch any measureable amount. The design and construction of synchronous timing belts is specifically to prevent stretching. If timing belts stretched, the camshafts would lose timing with the crankshaft.

Good point, thanks. Glad I re-did it with a better nut. After resetting it last night, I let it sit overnight again and double-checked it this morning, not a hint of change.

On a related note, the old tensioner, with about 90K miles and 8.5 years on it and the belt, was at 18mm. Is that a normal gap after that amount of mileage/time?

[old guy]

The total travel in the adjuster is ~19mm so you were right at the limit. Essentially playing with matches….

[diagnosticator]

Good point, thanks. Glad I re-did it with a better nut. After resetting it last night, I let it sit overnight again and double-checked it this morning, not a hint of change.

On a related note, the old tensioner, with about 90K miles and 8.5 years on it and the belt, was at 18mm. Is that a normal gap after that amount of mileage/time?

Timing belt tension will loosen due to wear on the belt toothed side, and wear on the sprockets. Belt tension is also effected a very small amount by the thermal expansion of the engine. This is why a dynamic tensioner is required.

[Audine]

I would like to ask about that gap between TB tensioner and tensioner pulley tab. Should it remain constant 6-8 mm all the time? I am asking this, because that gap is changing on my car. It is like 2-3 mm after driving on hot engine and after I crank the engine it returns to like 5-6 mm. And one point which is worrying me that I can pull that pulley tab up by finger and rise up to 8-11 mm, however I can't compress it back (it comes back to 6 mm by itself after some time though). Timing belt tension is good, belt is not loose. Is it normal tensioner and pulley behavior?
I noticed that after leaking water pump change (I am not sure how it was behaving before work, as I just measured it on cold and it was 8 mm). My mechanic left old timing belt on, tensioner was not removed. He just loosened that pulley, removed tensioner bearing and removed the belt only from crankshaft and the pump. Timing was set OK. However one thing was not completed as it should: the tensioner was not compressed before putting the belt back.. gap was like 12-13 mm with the belt on and when we cranked the engine by hand few times it became ~8 mm.
Many thanks for the answers.

[old guy]

It sounds like you have a weak hydraulic tensioner. Do yourself a big favor and replace the old style hydraulic tensioner system with the new style Liten's spring loaded tensioner. Clicky click®

[Audine]

Thank you for suggestion, old guy. I just ordered updated INA 530054610 kit, I regret that I did not research about that updated version before my current water pump change :(

But for now I still drive the car and I would like to know how that hydraulic tensioner should function properly? Should it retain this 6-8 mm gap all the time?
On my cars engine there is a decent gap (looks like 6 mm) when my engine is running, that gap reduces in 1-2 minutes after the engine stops (yesterday that gap was: 0 mm, today: 3 mm). if I crank the engine gap opens...
That tab on roller - is it normal that I can rise it higher just by pulling it with my finger or it shouldn't move at all?
I saw some videos with A4 TB change and I saw that mechanics slowly compress this tensioner for reuse before removing TB belt.. my friend mechanic did not compress it and maybe that way its hydraulic mechanism was damaged...(loosened too fast)?
There was a thread about this here: https://www.audizine.com/forum/showt...ing-10-minutes
Thanks