Belt Tensioner mystery
 

Like countless others, the belt tensioner on my 2014 Stingray started leaking hydraulic fluid, so I just got a replacement.
All other tensioners I have seen just had a spring to maintain the tension, so I was curious how the Corvette tensioner worked.
I pulled the rubber boot off the top and inside was just a spring with some fluid in the body of the tensioner... As far as I can tell, the fluid did not provide any hydraulic tension or dampening, and it just ran out when I removed the boot..

Anyone have any ideas on the purpose of the fluid, and if it really hurts anything if some (or maybe even ALL) of the hydraulic fluid eventually leaks out (other than it just makes a mess on the tensioner and spring below)
Also, when they "go out" and start making noise in v4 mode, what fails that causes then noise?

Here are a few photos....

Tensioner, bracket, and pulley (which has a sealed bearing)



https://cimg0.ibsrv.net/gimg/www.cor...2450062550.jpg


https://cimg6.ibsrv.net/gimg/www.cor...e5c151d25a.jpg



Spring and hydraulic cylinder-Note it does have a TOP arrow on the body, probably just to keep the fluid from running out even faster! :D

https://cimg8.ibsrv.net/gimg/www.cor...d99d09a909.jpg

You can see all the way to the bottom with the fluid drained out, and it does not appear to have any hydraulic piston or reason for the fluid.

https://cimg9.ibsrv.net/gimg/www.cor...228c7e59da.jpg

Looking at the last pic showing inside of "piston" it appears the fluid would simply be a lube for the spring so I don't know why they wouldn't use something thick such as wheel bearing lube.

Does anyone know what changes if any were made to the belt tensioner after the 2014's. It seems the 2014's had all the failures. :ack:

I just posted this on another forum:

The bearings in the enclosure of the tensioner. My wife was hearing this whining noise at 37,000 miles. (I can't hear you know. Just ask her. http://www.stingrayforums.com/forum/...d_till_5am.png) She took it in and it was the belt tensioner. The service manager just walked up to her after she pulled into the service writer area, and without a peep from her, he said they better replace the belt tensioner. He was familiar with it I guess from some others going south.

So the hydraulic fluid leaking from the tensioner has nothing to do with the failures that cause noise? I hope GM improved the bearings for the new part number.:(

Mine wasn't leaking...just the whining noise. The 2014 model year had issues right out of the shoot, above average with going out, but they put a different design into it. But yes, the leaking issue and noise issue were independent of each other.

Anyone know if there was a running change to the tensioner in the 2014 model year or was it corrected in 2015?

Very interesting. Sorry I have nothing to add that will help, but subscribing to see an answer to OP's question.

There is a service bulletin about possible premature failure of tensioners and my 2014 was supposedly built after the date range (March 15, 2014), but mine still started leaking... I still see reports of even 2016 models that have had failures...Note, the bulletin says if it is leaking it will need to be replaced.
In looking externally at the new part number I just bought, I cannot tell of any change.
(The bracket, bolts, pulley and sealed bearing were fine. Too bad GM does not sell just the tensioner:()

https://cimg1.ibsrv.net/gimg/www.cor...de966d7fcc.jpg

As a bonus, I found this photo of where the tensioner is located and how the belt runs... You cannot really get a wrench on the bottom bolt from above, so it must be removed from underneath the car.. You can tell from the photo why.



https://cimg8.ibsrv.net/gimg/www.cor...53d412f000.jpg


https://cimg9.ibsrv.net/gimg/www.cor...5495dcc149.jpg

All I can say about that routing of belts-OMG! Certainly won't be me changing it out if it fails.:eek:

TEXHAWKO, My C7 was built in May 2014 sequence # 26624. I've had no problem with my belt tensioner so far..

Thanks. Mine never started making noise like the early ones, but it did start leaking. You might want to check your tensioner from the bottom for fluid leaking.

Since mine never got noisy is one reason I am trying to determine the function of the fluid.
Makes me wonder how may people have tensioners that are leaking and just do not know it yet.
I read a post last week about a guy that did not know his was leaking until a track day inspector pointed it out.

Thanks TEXHAWK0. Mine was built July 16 but I’ll keep an eye on it anyway.

I bought mine in April of 2014. I believe it was built around 3/7/14. My tensioner has been fine without issue up to now. I have 53K miles. Great homework on all this by the way, Tex. :cheers:

Ant

Mine failed on my 2016 1LT Stingray at about 39,500 miles. I don't think it was leaking but it had quite a whine.

Mine failed at 27,000 miles on 2015. Warranty covered it and it was the last month of that.

Very loud whine!!

Sounds like there is more than one problem going on.:lol:
My original question was what is the function of the hydraulic fluid, but mine was not making noise..

If the updated part number fails by making a whining noise, that sounds more like the pulley bearing is failing...I think I will hold on to the pulley that came on mine since the bearing appears to be ok.

There was a change made after the 2014 model year and there still is an issue on later years. Just had my car in for repair at Kerbeck. 2016 Z51 convertible with around 24,000 miles. Sounded like a rattlesnake was in my engine compartment at 1500 rpm while in V4 mode. Belt tensioner was the culprit.

GM needs to redesign this part.
Some leak, some whine (more like a bearing), and yours has the rattle when in 4 cylinder mode that first showed up back in 2014.:(
Glad I never have to use ECO mode.:yesnod:

Anybody come up with why the tensioner spring needs an oil bath?
:rolleyes::confused2: