I see lots of q's on here about whether the hydraulic tensioner should be changed when the belts changed.

What's the general opinion? Does someone have a definitive answer for me, as I'm about to change my belt (once I source one!)

Has anyone had, or heard of a tensioner failing? :happy:

Wouldn't hurt to, it is rare for a tensioner to fail, but when it does, it costs a fair bit to rectify when you could of spent a small amount of money getting it replaced when yuo got your timing belt done :)

I'm leaning that way; but I really would like to know if anyone's heard of a failure. There's a big price difference betwixt just a belt and the full kit.

Speaking from experience, if you do not have a start up rattle in the mornings, dont bother spending over $200 on something you dont need

The only tenisoner that is worth getting is genuine, it is not such a big job to change it either, I have done a few here, did one this week while the owner waited for the car lol

Is that a metallic rattle, or otherwise? I'm just wondering how a 'rubber' belt can create a rattle.

metallic rattle..

also depends who you get to do job i had to get one or they would not give a warranty on timming belt etc

A question on "Hydraulic Tensioner"... The timing belt tensioner I have changed as far as I know has no hydraulics in it. It seems just like a very tight spring. If it is hydraulic, there seems to be no connection with the engine oil pumping system - where does the "hydraulic" come from?

also depends who you get to do job i had to get one or they would not give a warranty on timming belt etc

Then they are not that good lol,

I always state that if there is an issue with the belt i fit it will be fixed, if the tensioner does start to play up however this is a separate part so is not something I can cover

As for not being connected to the engine oil system, it uses fluid to dampen it

A question on "Hydraulic Tensioner"... The timing belt tensioner I have changed as far as I know has no hydraulics in it. It seems just like a very tight spring. If it is hydraulic, there seems to be no connection with the engine oil pumping system - where does the "hydraulic" come from?

As above, it's fluid filled but I would guess there is a weak spring in there too as the plunger moves out when it is off the car. Only replace it if it is leaking, or it doesn't extend the plunger, or offers little resistance when a vice is used to push the plunger in so the holding pin can slide in.

As above, it's fluid filled but I would guess there is a weak spring in there too as the plunger moves out when it is off the car. Only replace it if it is leaking, or it doesn't extend the plunger, or offers little resistance when a vice is used to push the plunger in so the holding pin can slide in.

That is not the cause of the noise at all, springs have no bearing on the way this works

It is pressure driven, a little bit like a damper. When the engine is stationary for any time the cams will move as some of the lobes are being pushed by half open valves through the rocker gear, this can cause movement and thus the back of the belt will tighten up. The tensioner will move the arm that the adjuster is attached to and take up that slack. As soon as you crank the car, the front of the belt takes up again leaving the back loose, the tensioner is meant to take up this slack immediately however if a little fluid has been lost over time the tensioner can be slow to move thus the rattle. THis is why when you crank the motor first and then start you will get no noise as the tensioner has had the time to take up this slack.

Above is a very breif description only as is hard to explain in a forum lol

I get the feeling it's a spring activated, fluid damped (probably silicone oil) unit. It's not connected to the main oil system as some other units have been.

Still don't have an answer to my question as to whether anyone has seen, or had one fail......

Sorry mate you are not correct.

I have been working on these cars since they came out, I have also seen enough of these tensioners broken apart to know how they work

They are spring assisted however the main function is carried out by valving, just like any damper is set up. The fluid is a hydraulic fluid of some sort, may be silicone based

As I stated before and in many many other posts here on AMC (search helps occasionaly) they can fail, they will start to get a little tap in the mornings and eventually they will get worse over time. Will generally be in the mornings when cold as once the engine has had some heat in it for the day the fluid thins

I have seem them go on 60k motors and I have seen other motors with 300k still running the original

Could the tensioner be responsible for a tick/rattle when hot and at idle? (but not when only just warmed up)

I have a Pajero and a Magna. The Magna never gives any rattle, but the Pajero rattles on startup - but not consistently. Sometimes it is like a machine gun, especially when itis cold. Randomly, often when it is really cold, it is absolutely quiet. I blamed the valve lifters, but even with fresh oil the thing can rattle - occasionally even when the engine is warm. When the engine is warmed up, no problems. It is annoying/frustrating/embarrassing, but so far nothing has gone BANG, so I assume it is OK. At the next timing belt change, I will replace the tensioner, but both cars are 70000 km away from that

if its rattling, try turning it of f then restarting it, does it go away? if it's doing it every morning then one morning before you start it, take off the top cam belt cover and look at how loose the belt is. don't forget to put it back on. Then when the car has been running and has no noise, with the engine OFF, take off the cover again and look at the belt tension. You don't want to be running around with an engine constantly making that tapping sound and running with a loose belt. mine began the noise at around 60,000kms, I made quite a few previous posts about it. until I got it fixed every time it made that noise I would turn the car off and restart it, and for the most part it stopped the noise. I had check the belt tension a few times and I knew once it had been restarted and the noise had gone that the belt was tensioned again and was ok. I remember seeing a 380 at a mitsi dealership at the time and it had thrown the cambelt ... pretty rare and the car was fairly new, but not good for the engine or your wallet.

SteveJJ:
Thanks fro your comment. I seem to have hijacked this thread a bit, but there are others who are equally interested. Each time I have replaced the timing belt, I have stripped the covers back after about 2000 km to check the tension - it has been OK. Having said that, the belt on the Magna was "loose" when I last replaced it (200000 km). By "loose", there was slack between the 2 camshaft pulleys - presumably one cam had rocked off the peak of the lobe. The slack was not enough to threaten a total slip, but was enough to scare me. I will check the Pajero - have done it before but there was no slack. Shutting it off and then restarting doesn't seem to help. The noise goes away after 30 seconds. The spring in the Pajero tensioner seems much stiffer than the Magna one.

I suspect that the fluid inside is to quell any resonance because these springs are very stiff. Their natural frequency would accordingly be rather high and I imagine that under certain operating conditions one could hit resonance and have the tensioner oscillating in time with the belt and thus potentially creating all sorts of hell. The fluid would certainly damp that out.

What is all this discussion about fluid and springs, I really wonder why I spend the time trying to explain to you guys sometimes how things work, I would be better off just taling to a brick wall

I have posted up many many times how to check if the tensioner has issues, add to this, many many here have brought cars into me here to have the tensioner replaced and has fixed the issue so is not all puff and wind either

Of course there will be slack on the belt between the pulleys, that is exactly how the system works, even a brand new motor stopped in the right place can do this FFS

If you want to waste your money on a new tensioner then by all means go right ahead and do this but as I have stated over many threads, if it dont broke, dont fix it. No need.....

I agree. If it's not leaking or physically damaged no need to replace it. Make sure it is set up correctly, that's just as important as having one in working order. I imagine even a new one not set up as per the manual will rattle.