Timing Belt Tension

[Strm Trpr]

This is on my 2g GSX... with all new OEM Mitsu parts.
So, I set the tension, and rotated the crank 6 times and everything lined up.
Waited 15 mins, and I measured the gap and it was at .168".
It's within the .150" - .180" spec.

Called it a night.
Woke up the next morning and decided to check my handy work, and I rotated the crank 6 times and everything lined up.
I waited 15 minutes and rechecked the gap, and it was .155".
It crept .013".
I haven't checked since, and it's better to be tight than loose, so I chose to run it. So far so good.

I recently did a T-Belt on my friends 6-bolt with all new OEM Mitsu parts, rotated the crank 6 times, waited 15 minutes and the gap measured .155".

So, after 3 months of working on it, and doing upgrades, the day finally came, and we fired her up.
We wanted to take the upper T-Belt cover off to check for leaks and to check the belt slack, and then unthinkable happened.
We noticed that one of the thin t-belt cover gaskets wasn't in the cover WTF.
So naturally, we panicked and we decided that the covers had to come off so we could retrieve that POS.

So, last night he pulled the covers off and removed the pesky t-belt cover gasket, and he decided to check the gap on the auto tensioner.

It was .078"...

A mitsu tech would do a t-belt job, turn the crank 6 times, wait 15 minutes, check it, and if it were in spec, he'd button everything up and call it a day.

So, given everyones experiences with dreaded T-Belt changes, has anyone ever come across this phenomenon of the t-belt tension changing over a period of time?

 

[FORMONTOYA]

I've personally never re-checked it afterward. I've been one of those that did the initial checks, everything looks good, button it up and called it a day.

Interesting result. Although it is a hydraulic tensioning device and it should move within spec throughout it's life. Was this on a NEW tensioner?

 

[luv2rallye]

And did you measure with the camshafts and crank in the exact same place each time?

 

[Champ Masters]

And did you measure with the camshafts and crank in the exact same place each time?

It's my 1g that Strm Trpr is talking about. And now that you mention it, no, we did not measure it at the exact same place the second time. When we first measured it, it was at TDC. When I measured it the other night, it was somewhere before TDC. Does this make a difference? I thought that the tensioner arm gap stayed the same no matter where the engine is at. Am I wrong? Thanks for the replies.

 

[luv2rallye]

Depending on the camshafts (lobes) position, the belt tension amount will vary slightly going CW or CCW (just check the belt deflection between the camshaft sprockets at various positions to see this) and some of this will get transmitted to the tensioner. So you really need to do multiple measurements at the same position. I check tensioner at TDC and camshaft sprocket holes up position.
Note: A non factory belt or leaking/weak/non factory tensioner can also cause different tensioner measurements. (Also note this warning: Of course if you use a non factory belt/tensioner you almost certainly will be paying big time later).

 

[Strm Trpr]

Thanks for the replies guys.
We did use all factory OEM parts on both jobs.
I reused my waterpump on my 2g 7-bolt, because it only has 56k miles on it (crosses fingers).

We will check the gap on his 6-bolt after the motor has been cranked to TDC, and we will wait the 15mins.

We didn't think it mattered where the crank was when you measured the gap, we assumed the tension would remain the same, but you know what they say about assumptions....

Assumptions make an ass out of you and me.

Thanks Nick, next time post your own Noob question...