355 hydraulic cam belt tensioners

I've gone for every other belt change along with the bearings. But then I do my belts every 4 years and some here do theirs every three years. With a 3 year frequency perhaps you could do it every third set of belts?

They are not cheap! (around €500 for a pair, inc tax). But I decided to go this way because I had one fail and rattle noise it made was dreadful.

 

The ferrari hydraulic tensioners are robust and if they fail they have a fail safe position.
This means that while the tensioners will make noise when failed, the belt should not jump a tooth.

Having said this I changed my tensioners in my 355 at my last belt change in 2009, at which point they were 14 years old.
They were in perfect condition so there was no need to replace them however I decided to replace them proactively.
Next change? probably in another 10 years.

 

The tensioner pulley (bearings) were perfect in my 355 after 14 years (and original)....but I replaced them at my last service , again just to be proactive (Hills Engineering).
I will be checking the bearings at my next service.....not sure if I will bother changing them though for 10 years unless I detect a problem.

 

When does the rattle occur? Is it constant? I have a rattle at start up which goes away when I'm up to temp. Am I being paranoid?

 

As I said, I've had a tensioner fail. A few others have too if you do a search.

That pretty much sums it up. Sounds like a death rattle when cold and goes away when hot. The rattle sounds like its coming from everywhere and anywhere, but I eventually isolated it using some garden hose as a directional "stehoscope". When I tore down the motor I saw the oil stain and corrosion inside the piston housing. 1st pic is the bad part, second pic are the nice new bits!!..
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no worries

 

I brought the car in yesterday. I have no death rattle. They believe it is an air pump that operates during warm up approaching the end of its life. Deemed a not to worry right now. It's only purpose is to reduce emissions duing warm up. No risk if it fails no point in replacing now. Sounds good to me. Another phycosamatic emergency averted. I have to stop reading these threads

 

I have the same rattle I was never able to find where it came from I just got my car this year and put on it 3000 km the rattle seems to go away but when the car is stopped for a week or two at start up I still get it. I was also wondering how to properly adjust the tension on the timing belts I usually set the belts take the slack out turn the bearing til the tensioner pin slide out easy is this the way it's don thanks

 

To set the tensioners you're supposed to measure the gap between the carrier and the stop/saddle. It's 3 to 5mm from memory, but don't quote me, my memory ain't what it used to be!!

Anyway, it's written in the WSM with diagrams, it's quite straightforward. I don't have it to hand, but there are a couple of sites where you can download the pages free.

Hope this helps.

 

Worth lifting up the car and listening to the front of the sump with a stethoscope. You might have the chain tensioner pad breaking up.
Also check aux. belt pulleys for slack....

 

It's 2.5 mm Bob. Some say that you get this by adjusting such that the blocking pin slides out easily. IMO (and one hesitates to say anything these days unless you are Rifledriver) the essential is to turn the engine over quite a lot to be sure that the gap settles near the 2.5mm mark. Some would say that this is obvious, but most things are unless one is in the minority!

 

Well, IMO you are right about hand cranking a few turns to check where it settles. That's exactly what I did (have done twice actually, since I've changed cam belts twice now) and it has worked like a charm both times.

So now we can both get flamed, but when all's said and done, the WSM tells you to measure that gap, not faff around till the pin comes out freely so I don't see how we can be wrong.

And dang my memory. 10 years ago I'd have remembered that setting with instant recollection. I'm developing brain fade...

 

My rattle seems to be really coming from the timing belt area it was really bad in the spring time the belts look tight no slack on them I was just hoping nothing would let go. Thank for the feed back guys.

 

If the rattle changes pitch or tone when you turn the A/C on, it can be the compressor, compressor clutch, worn compressor bushings, or broken bracket. All of these are surprisingly common.

 

I think that there was an internal Ferrari TSB for 1995 just as the 1996 cars started to show up. it dealt with an update of the originally installed tensioners being replaced with a new and improved(yadda yadda, yadda), version. As I also seem to recall, there was no direct specification as to: do it now, at time of belt svc, only when complaints of described noises were specific( I seem to require zone authorization required here in CA as it required messing with the cambelt/camtiming...also why in CA the belt svc period was upped to 52,500 miles...just out oif governmental mandated timing tampering limits(laws have since been "altered"...

I saw one once prior to reverting to vintage cars again, and seem to remember it rminded me of an Alpha 164 tensioner-any alpha guys out there care to comment?

ALL 1995 cars nneded this thing(s) replaced asap along with a laundry list of other notorious 1995 items(all well worth it once doen...a 1995 is almost a different model car IMO....)

I do remember a hallatious noise-breif, but horrifying...

 

I worked at an Alfa dealer in 92 and we use to change belt tensioners because they were Hydrolic and updated them to spring loaded ones we would get a kit that consisted of plugs and tensioner had to tap threads in the block to plug oil feed. but I don't recall them being noisy

 

It's a misconception that the 355 are hydraulically tensioned; they are not. The tensioning is provided by a spring.

In fact they are spring tensioners with hydraulic damping, simply a piston in oil with small orifice.

The failure mode that causes the rattle (at least on my car) was that the steel cap for the piston corroded, letting the oil out and thus the tensioner was no longer damped. The high frequency oscillation induced by the belt caused a rattle sound due to this lack of damping.

 

I thought that the role of the oil is to compensate for temperature (belt warms up, gets slightly longer) with the spring, as you said, providing the main tension. I can see why loss of oil could lead to a rattle. My theory was/is that even an oil filled tensioner could become sticky (especially, dare I say it, if the car does not do much mileage {like mine!}) but the piston will move out once the car warms up. This would explain the fact that many people talk of a rattle which stops after a few minutes. Hence more fuel for those that criticise the garage queens!
Anyway, good discussion.

 

I am doing a 355 engine out now I had heard the same noise and thought it was the air pump also. BUT the pump is electric and in front of the rear bumper Its the tensioner I removed the engine yesterday the belt was frayed tensioner was dead. Noise went away after 10 mins or so after start up. But I had a felling something wasnt right we work on aircraft so this is a standard process for us. Jim