KV6 Front Belt Tightness
 

Has anyone ever come across a front belt on the KV6 that is too tight ?

Has anyone came across a failed KV6 tensioner ?

Here's my story so far.
Removing the front upper left and right timing belt plastic covers, I tried twisting the belt but to me it seems there is not much movement if any TBH. It does not seem typical of a KV6 and there is a general low pitched whine about the engine at idle that disappears when revved. The roller tensioner is free to rotate on its fulcrum. All other idlers or water pump pulleys are new and were replaced using original INA components (ie the original stuff that MGR fitted) Despite the new components there is a distinct idle speed whirr that I know should not be there.
I can eliminate the engine because itself because this one is a replacement, the only common denominator is that the old engine had just recently had the same (new) timing components on it and it too had this low whirring noise, so there is something in common that I have carried over from the old engine and its not going away.

As a comparison I have recently changed another KV6 timing belt system of late and the running tension with new belt fitted is what I would class as normal, and of course it is whisper quiet as one would expect.

Many years ago I recall changing a belt on a K series with manual tensioner where I had inadvertently applied too much tension to the belt, and the noise with the engine running was similar to my ear anyway. That's why I am suspect of this fellow below in the KV6, but find it hard to understand why that design of tensioner can lead to over tensioning as I assume it is just a simple plunger and spring arrangement. (perhaps some hydraulic damper arrangement also?) Surely the failure mode for this would be to not tension enough rather than over tension?

https://image.ibb.co/cPC3hU/LHP100610.jpg

I would of thought the hydraulic plunger wouldn’t cause it but more the adjustable tensioner pulley that sits against it. What’s the gap like of the pin to body of the part pictured? Once tensioned you should be able to refit the pin, I’ve found this isn’t always the case but as long as the pin isn’t overly extended or the arm close to the body there isn’t an issue or noise.

I don't know right now will probably have to look at taking front end of engine off again to satisfy my curiosity. The tensioner was set up with nice gap and engine turned over etc a few turns then checked again, socket head screw tightened up for sure and small locating pin for tensioner piston slid out nicely as per usual.

Would like to understand if tensioner is hydraulic and spring or just spring, if hydraulic perhaps a check valve or visco jet inside playing up inside it which is inhibiting the plunger returning giving high tension due to fluctuation in belt tension as the engine turns :shrug:

I’ve never had a KV6 one apart but the Hyundai version that looks exactly the same has oil in it. If you put it in a vice and wind the pin in too quickly to fit the locking pin they pop and loose oil

If I remember correctly there is a grommet in the casing in front of the unit, not sure if you’d see the length of the pin though as I’ve never removed it to look

I see thanks for that info, so potentially could be a suspect. I am planning to renew the hydraulic tensioner anyway next time I open her up.

BTW this is in my sons (ie, hard driven ZS180), but it still goes very well apart from my concern over the belt too tight.

Oh that's right an oblong sort of shape grommet, probably need a mirror to see it. Or perhaps the big rubber at the back could also reveal something?

https://preview.ibb.co/jRfH99/IMG_1126.png

don't know why the jockey wheel uses an allen key type bolt(I use threadlock there).they can turn the bearing inwards to touch the outer edge of the casting to create a similar noise.but these should be set by yourself and tightened before fitting as they are sometimes not tight enough as you are probably aware.once the pin is released and the engine rotated manually you would have had a good idea if there was enough reserve travel left on the pin to be reasonably sure of it having enough. I did have the auxillary belt roller give me this noise in the past but managed to repack with grease LIGHTLY after removing it from the car. its done 25000 k miles since and still quiet. this was more of a whirring noise as you describe. please don't be offended if I have mentioned the obvious as I know you are more than competent ! but sometimes it doesn't hurt to recheck. regards xsport.

another thought is that its idler or waterpump bearing. Im unclear if you used the timing tools or not. if you didn't and left them static then its possible that there is far too much tension on the belt either side of the waterpump.there are many variables to take into account between belt swops and components used on the job each time. once the two bolts are undone this allows the floating cams to give a much more balanced tension throughout the belts length. if not it puts the bearing under duress.this is one of the reasons I use the tools. many members have done this job without the tools successfully. its still a lottery without as many have then gone on to complain of waterpumps failing early sometimes this could be part of the reason. there is also the issue of nearly dry bearings from new. i.n.a or not things aint what they used to be !! keep us up to date if you find anything else !! regards xsport

Yes timing tools used as I can achieve better alignment/fine tuning on the rear timing belts using the them. Plenty of gap between the hydraulic tensioner, and the roller tensioner which I checked and checked again after rotating the engine.

Of course the roller tensioner factory setting was an issue many years ago when the it came preset and the installer was not supposed to have touched the adjustment. Lesssons learned since then resulted in a bulletin from INA helped make for more reliable installs.

One other thing which makes me suspect over tension is the manufacturers writing on the belt has vanished in the space of perhaps 6,000 miles, i would normally expect to see some faint writing even on a belt way past it’s sell by date.

Doesn’t sound like a bearing tbh. Possibly my imagination but a higher than normal tension on the belt is my thought, by a belt that is singing to me, but caused by?

Interestingly I understand that there may be a ultrasonic based tool available to the professionals that can monitor belt tightness?