355 front of engine rattle

HELLO -- Post #23 buddy. They disconnected the drive alt belt and the noise was still there.

 

You forgot "end of story".

 

I think Brian was onto it way back... when he said about hydrastatic tensioner...

If the drivers side belt was "scary loose", chances are either the tensioner unit and NOT the bearing itself, has either been allowed to fully extend and therfore not been set correctly, or it has failed.... making the swinging arm that supports the bearing bounce on it's little stops and make the rattle noise...

Has it been confirmed that the tensionsers (NOT the bearings) are working correctly.. ie.. were the little pins used as part of the procedure to set belt tension, and did it take "reasonable" force in a vice to press them back enough to fit the little pins..

 

The belt was not "scary loose," although it was not quite as tight as the passenger side belt. Terry replaced the belt after using the pins (in this case a small drill bit) to control the tensioner extension and verified that the tensioner force was in the proper range. We started the car yesterday afternoon and finished it up today. No noise...

More soon.

 

ok, I was just going on what he said in post #18....

Hold it closer to the internet... I'll have a better look....

 

ok

Too loose, no use
Too tight, not right
Nice and greasy, slips in easy

 

Reminds me of the philosophy that i use for women word for word

 

It could be a fuel pump that is rattling around on its mount.

 

That's possible. It is now completely apparent that the noise emanates from an area between the foward engine bulkhead (the removeable flat alloy panel with tabs to hold it in place) and the interior bulkhead behind the seats, basically in the fuel tank area. It is a metallic screeching, scratching noise of some light gauge sheet against something else, not related to engine rpm, only to body resonances duplicatable only when the idle goes way under normal and only in the first 30 seconds to a minute on the first start of the day. We've decided we'll look into that at the next oil change, but for now, we're satisfied that Actionfigure can enjoy the car without the sword of Damocles hanging over him!

-Peter

 

...that's what she said.

 

Jeeez.. you guys are driving me nuts, LOL. Read post number 9 it's one or both of the belt tensioners. They can do that for a few seconds when the car is cold and stop after some heat gets to them(strange sound and irritating). I know this first hand because mine did it before I changed them. If you have a parts manual (Nov. '97)for a 355 look at Tav. #6 part 26 can touch part 22, that what makes the rattle, when it warms up a bit the 2 move away from each other and no more rattle.

Oh and by the way the fuel pump(s) can't rattle, it's inside the tank, the cover plate that holds it in is attached with 8 nuts and has an Oring gasket between it and the tank also see the parts book on that too and you will see what I am referring to. Regards, Vern

 

Vern, are the belt tensioners hydraulic, mechanical (ie. fixed after adjustment) or spring loaded???

 

Hydraulic. That is probably the reason they can rattle sometimes they seem to compress slightly not much but just enough to get the 2 parts noted above to touch, until heat expands them apart. When I had my engine out last year my left tensioner was touching I took a hair dryer to it to warm it up and it moved out. I think it also has to do with proper adjustment of the belts. Regards, vern

 

Thanks! So that would mean that the tensioner does not imediately apply full pressure to the belt, until the oil pressure gets there...right??

 

They don't have engine oil pressure in them... they have a spring to set belt tension, and oil to dampen the vibrations. The oil is self contained, if it gets out they're toast.

I had a 355 a while ago that had a noise at sub idle (like when fans kick in for a split second etc)... turned out it was just the tin cover over the RH shock top/battery cable junction.... from in the car it sounded like it was right behind your head, but nope....

 

Ok from reading on here this is what I understand.... there are two major parts to the belt tension mechanism.

1. the bearing with eccentric adjustment and has no oil (except for bearing lubrication)

2. the tensioner which contains oil only for damping purposes. but is spring loaded.

Now my questions:

a. what holds the oil in the tensioner?

b. how far does it collapse if the oil "does" leak out?

c. does it collapse enough to let the belt jump teeth?

d. is there an after market tensioner that does not have oil that may leak out?

 

a. seal
b. if adjusted correctly about 2mm
c. no. read above
d. no. I don't think it is common for the oil to leak out.

 

Vern, I love ya, but your suppositions are not correct on this jewel...

It would be clear if there was any "dampening oil" loss on the tensioner assembly, it would be just like when a shock starts leaking, you can see it, clear as a bell. Also, to make the noise, the tensioner would have to be an awful lot more compliant than the ones on this car are. There is a way to get the stethoscope in that area, even on to the fastening hardware near the tensioners, and there was never noise in that general area. Sorry...

I'm with Phil on this one.

 

The tensioner is very much like a hydraulic valve lifter in a car. It is full of oil that expands when hot to maintain constant belt tension when the belt wears and can contract when the motor expands (which is a rather large amount).

The tensioner can be bad even if the oil is still in it (I have never seen one leak to any degree that counts). As I said it is like a lifter and has an internal check valve mechanisim that can go bad and that is the cause of many metallic rattles when the motors are cold. They have bled down in exactly the same way a lifter can. Being able to judge the bleed down rate is an important part of being able to properly service these motors. There is no spec or instructions for it. Other wise the only way is to hear a rattle, know what is causing it and pull the motor to deal with the problem. Better to just be able to make that judgement call when the motor is out for routine service. Also a very important part of knowing how to properly service them is if the belt is tensioned correctly and there is a complete failure of the hydrostatic portion of the tensioner the worst that will happen is a rattle. The belt will not come loose enough to slip.


Also they have long abandoned the pin in the hole method of tension setting. It is now done with an electronic tensiometer. Far better and more consistant method.

 

Just for completeness, would that same statement hold true for stock 348's?

 

The system is different in every way except for the material the belt is made of.

348 has a mechanical tensioner that is set and forget. If it comes loose your goose is cooked.

 

Thanks. That explains quite a lot about the two. Is the 355 tensioner not mechanically set, then...perhaps remotely similar to a Porsche 928 tensioner?

 

Don't know about the P Wagen but the 355 is manually set and locked but the hydraulic portion does have the ability to compensate for engine thermal growth and belt stretch.