360 Question re: Hydraulic tensioners

I was looking back through my records trying to see if these had ever been done on my car and for what I have in terms of paperwork it doesn't seem mine have ever been replaced. Does anyone know if you can do these without doing the full belt service?

 

yes, as I remember tensioners were done on mine at full service

 

But can they be done outside of a belt service? Or does everything have to come off at least In terms of if you did a lock and swap?


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You can replace the tensioners without doing the belt service.

To replace the tensioners you need to remove both timing belt covers, which also means most likely disconnect the coolant hose to do the left one. Next you need to lock the cams, loosen up the belt tension etc, and after replacing the tensioners you need to set the tension correctly again. A lot of shops would just do that so it "feels" right to the finger, but of course the correct method includes setting TDC, checking the gap, engine rotation, belt frequency etc.

In other words, replacing the tensioners would be about 80% of the labor to do the belt service. And the belts are relatively cheap. So unless the belts and the timing belts pulleys (which are a bit more expensive) have just been replaced, I think it would be a false economics to replace the tensioners without replacing those other parts and doing a full belt service.

 

Totally makes sense and was kind of what I was thinking. I was hoping to just spread the maintenance costs over a couple years if it was feasible, doesn't seem worth it.

 

to replace the belts lock and swap style is only 30 minutes more labor after replacing the tensioner, for me.

 

I’ve asked before, but didn’t really get a consistent answer: is there a general recommendation for time or mileage in which the tensioners should be replaced as precautionary maintenance?

 

I've been investigating that as well and I don't think there is a clear answer. When I was asking the consensus was that those are reliable parts and could last a long time, maybe the life of the car. But should be checked at each belts change as they occasionally go bad.

The part I never understood was if and how they can deteriorate partially. If they totally collapse that's obvious, but if they are weak, how do we know if they are weak to the point of needing a replacement, while not yet collapsed?

I did experiments like aggressively driving the car with all the covers removed and watching the belts and tensioners while driving to see how they react but without having good reference points that was inconclusive.

 

When the tensioners start to get weak you will hear a temporary slight rattle at startup (1-2 seconds) as they build tension. They stop holding tension as well as they used to. I just did mine (17 years old). I think 12-15 years is a solid barometer for a replacement interval.


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Further question on this, I'm getting a parts order together for this job, is there any other parts associated with the tensioners that one would want to order in addition to the left and right pieces?

 

No, however there was an update to the left hand tensioner (driver side in lhd) where they added a locating insert. If your car does not have the larger hole for the insert a tab used to call for the panel needing to be replaced. It’s easier to just pull the insert with pliers and just install the tensioner. Unless your car is extremely late production it did not have the updated panel from the factory. (My car is March 2004 production for reference and still had original style tensioners with no locator)


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My car is a 99 so I am guessing that nothing is updated on it, especially since I can't find any record of them being done. So if I'm understanding you correctly, you buy the left hand tensioner and you remove an insert in a mounting hole for it? Apologies on not being super technical, I know enough to be dangerous, just not do the exact job.

 

https://ricambiamerica.files.wordpress.com/2016/01/tsb1315.pdf

You’ll see the locator in one of the photos


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Thank you!

 

The only difference between the Left hand (driver side for USA) tensioner and right hand tensioner is that
the Left hand has a rubber cushion around the hole

So I wonder if the LH and RH are interchangeable.

I did install a RH tensioner on the left and run the car for about 1000 miles and then feared something bad will happen, I replaced it with the correct one.

Reason for this is that the LH is much more expensive than the RH one.

 

New tensioner on left and old on right. The bracket is easy to remove, so I added a counterbore to my bracket so that it will be upgraded to the current version.
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Its a little tricky to add the counterbore because of the helical in the hole! You just have to go slow and careful. Fortunately, mine was installed deeper than typical.

 

When I had my belt service on my '03 we found a "bad" tensioner. I cannot recall what was bad about it: not collapsed but maybe not fully exerting tension on the belt (?). But what the mechanic did show me is that there is a stop that will not allow the tensioner to "collapse" if it totally fails. Which is a point of some comfort.
This was not the case on my previous older 911s--- which was a great source of consternation for 911 owners. As in the later 911s these tensioners were upgraded by Porsche to oil fed ones with a direct oil line to them. And in fact I did my own engines at the time and I always installed the "upgrade".

When my mechanic and I discussed the replacement of the tensioner, he mentioned that he couldn't really see how they would "fail" considering their design. FWIW.

I bought the one tensioner I needed to replace and it ran about $450. So you can see it will add about another Grand to the belt service-- if you choose to do it. Which I would since the belts are relatively inexpensive.
As always though, there are others here with a whole lot more experience with these engines that will undoubtedly offer very knowledgeable advice.

Regards, Ken

 

Wow. I would be very uncomfortable taking a drill to a major part of the engine. Screw that up and it's a real mess. Is there another alternative, like grinding down the nub on the tensioner? At least if that's screwed up, it's only $450 to replace it.

 

I ground off the "intrusion". It is mentioned in the FSM, actually
But, the "major engine part" you mention , isn't really a "major" part. It is less expesnive than the tensioner. It is detachable from the engine.

 

Thanks for that. If it comes off, then it can be properly machined. I can just picture myself with a drill in the cramped space of the engine compartment swearing to some unholy god for ruining a perfectly good component.

 

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