Bearing noise on one bank

Well one thing is for sure. DO NOT START THE ENGINE ANY MORE!

The last thing you need is for a bearing to grenade and ruin even more stuff.

 

When in Doubt, Replace it!

 

Use a mechanic's contact stethoscope -- by touching close by and listening to each (and the good ones on the "quiet" side for calibration) you should be able to determine the bad player(s).

 

It might take and hour and a half to shift the A/C compressor out of the way, remove the timing belt cover and remove the tensioner for inspection. It shouldn't have rough spots as you rotate it and it should not make noise. Worst case, itfit isn't the bearing, you can slap it back together or just proceed to the next step.

 

Here is how to check all options.

With the engine running use the tip of the stethescope on the nut on the end of the tensioner bearing (if you have an extended steth you can do front and rear) they protrude through the cam covers.

If you can hear a significant difference then it is either the tensioner bearing or you have a lower drive bearing on the way out. FIrst one is easy to fix second one is a PITA!

if you can reach - put your index finger on the same spot on both tensioner bearing nuts. See what your fingers can feel. if you feel a vibration it is actually more likely to be a problem with the drive bearing.

There is one other possibility - if the noise changes with engine speed you may have a loose lower cam drive locking nut (happened to me!! and destroyed the woodruf key in the shaft and put the tolerences out on the drive gear on the shaft) - A major job to fix - engine out really! and you cannot tell it is loose until you take the cam belt off.

Hope it is just a tensioner bearing for your sake.

 

78,

My 82 308 developed an oil leak and then a singing noise so loud that I could hear it reverberate off of downtown buildings as I drove by. It was the outboard bearing and shaft seal of one of the cambelt drive pulleys. The outboard bearing and seal are common failure items. The outboard bearing and seal can be replaced in the car. I've done it. If you diagnose the problem as a bad bearing, I (or someone on this site) can help you through the repair.

Tom Treue

 

On a GT4, removing the timing belt covers is not a straight forward thing. You do need to remove the AC and swing it out of the way, or remove it altogether and put it in a box for the next owner. It does not work that well.

Then, you have to remove the bolts mounting the engine to the engine mounts, jack the engine up a few inches or more, then remove the cam cover bolts in order to maneuver the timing belt cover out of the way.

Good luck, I hope it is just the timing belt tensioner. The drive bearing is not going to be a pleasant job.

 

My '75 308GT4 is on the lift in the garage right now - I'm changing timing belts. You don't have to lift the engine to get the front cambelt cover off - just remove the rear wheel and wheel well, unbolt the A/C compressor and wire it up and out of the way, loosen the alternator and remove the belt, then unbolt and remove the cambelt cover. You may also have to remove the coolant pipe from the thermostat housing, which means draining the cooling system, but, hell, you needed to change the antifreeze anyway,... right?

 

78,

Understand that the outboard bearing is a SEALED bearing and the lip seal on the shaft is INBOARD of the outboard bearing, at least in my 82. In my case, the seal worked loose from its counterbore in the end cover and was spinning uselessly on the shaft, inside the cam drive gear case. Coincidentally, both seals on the outboard bearing also failed allowing the bearing to fail AND oil to leak out. It is conceivable that just the bearng's outboard seal could fail allowing the bearing's lubricant to leak out, causing the bearing to fail, without oil leaking from the engine.

Tom Treue

 

Just for information, there were at least two designs. In the earlier cars, behind the cam drive gear, there is an oil seal and a ball bearing behind this. This outer ball bearing is highly loaded and doesn't last too long, especially if the belts have been replaced and tensioned right up cos, let's face it, we're all scared of them popping off and destroying the engine.

On the later engines Ferrari tried to improve the situation by moving the bearing further outwards to the end of the shaft to lower its loading. Unfortunately it then had to be a sealed bearing and running right next to it is the hot exhaust. So these don't last for ever either

 

um, not to be the guy with the dumb questions, but you are SURE its not the alternator or alt. bearings making noise, and its reverberating thru all the structure and off the firewall?

been there, done that.

 

Just wondering about a quick clarification: It seems a few people recommended possibly replacing his tensioner bearing(s). I have been told by a few people that it is not recommended to re-tension a belt. In other words, if you take a bearing off to replace it (thereby releasing tension on that belt), that you have to go ahead and replace the belt as well.

Truth or myth?

 

Thanks for the lesson. I was under the impression the GT4 layout was similar to a carb 308 - shame on me for presuming!

 

I can't debunk that myth. I recall seeing somewhere in the thread that the belts were relatively new so I thought this wasn't an issue. My son's 944 calls for a belt re-tensioning at 2k miles so it seems that some blet systems can tolerate a re-tensioning. Bottom line is that the belts are probably the cheapest part of the job so its not that big a deal if they had to be replaced when checking the tensioners.

 

Very true....personally I would do the belts as well, just for the peace of mind. Like you said, if you are going to spend all the time to get to the bearings, it is no more trouble and very little additional money to just replace the belts too.

 

I have a 75 and changed the timing gear bearings twice with the engine in the car. Are you sure the 78's have a different outer bearing? I thought that was only on the later cars not gt4's but I could be wrong. When my timing gear failed you could see the lower gear moving off center about 1/4" it was very scary. If you put a stethescope through the hole in the cam cover on the tensioner bearing nut you can hear each one very well and they are noisy even when new. I think you could rule them out easy by doing this. Noises aren't what they always seem, although i track down each one just to be sure. I had a rattling sound in my step down gears replaced all of the bearings and still had it, turned out it was the idle speed below 1000 rpms made the gears rattle above 1000 they were fine...

I replace the belts every time I use one and run the car, even did it for a ten minute run, at $20 a pop it seemed like good insurance.

Rob