Can't find bearing noise

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AutoRicambi
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Can't find bearing noise

Post by AutoRicambi » Sat Oct 04, 2014 4:39 pm

I need help with a seemingly simple problem that has me stumped. The car is a 1971 Fiat 124 Spider with a 2 liter TC engine, mostly stock.
There is a noise that sounds like a bad ball bearing. Listening around with a stethoscope I could not find the exact source of the noise. I assumed it was external, so I replaced the 10 year old water pump/timing belt/tensioner. Noise was still there. I removed the A/C belt and tried a different alternator, but it made no difference.

After a lot of listening with a stethoscope and even with just a long rod, I found that the noise is loudest when I put the listening device against the right front oil pan bolt. It sounds like it's coming from inside the right front side of the engine, however there is nothing there! The oil pump drive is on the left front, but the noise lessens when I listen on that side.

I dropped the oil pan and checked #1 rod and #1 main bearings. Clearances were good, the only anomaly was that the #1 rod bearing had picked up a piece of debris which scored it all the way around, but not enough to feel a ridge with my nail.
I replaced the bearing, put it all back together and the noise is still there.

The only thing I can think of is that it has something to do with the oil pump or it's drive shaft (auxiliary shaft), even tho the noise is not coming from that exact area.
Any ideas?
Thanks,

Csaba
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Sun Oct 05, 2014 1:01 pm

is the noise at the same frequency as the crank rotation?

Or half crank speed?

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Re: Can't find bearing noise

Post by AutoRicambi » Sun Oct 05, 2014 4:10 pm

Neither, it's not that regular. It almost sounds like loose shied, loose pulley, or a bad ball bearing, but it's not a regular tap-tap-tap.
The only metal shield on the engine is the one between the bellhousing and engine and up front it only has the plastic timing cover. Once I rev the engine over ~2500 rpm in neutral I can't hear it with the hood open because of the engine noise, but I do hear it when I drive the car.

Csaba
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Sun Oct 05, 2014 5:02 pm

may be the layshaft not the engine...

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Re: Can't find bearing noise

Post by AutoRicambi » Tue Oct 07, 2014 2:08 am

You mean the transmission layshaft? Ii's not, I listened again today, and it's not coming from the transmission.
It's pretty loud when I put the listening device against the front crank seal carrier. Almost like the seal is turning in the housing, but if that was the case I think it would be dumping oil. Next time I look at it I will take off the crank pulley and see if I can see anything abnormal.
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Tue Oct 07, 2014 10:36 am

beyond the aux d/s hitting No.2 conrod Csaba I do not know,

I would pull the shaft out and take a look at the fuel lobe,

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Re: Can't find bearing noise

Post by AutoRicambi » Wed Oct 08, 2014 4:00 am

The fuel lobe has been cut off. I need to finish some other projects, but as soon as I dig into this I will post the findings.
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Sun Oct 12, 2014 5:11 am

I took the crank pulley off today. This gave me a chance to make sure the front crank seal has not come out of its place. It has not, but I did find some wear on the aluminum pulley caused by the belt. I recently switched to a 1" belt, but I wonder if there is enough space for it. Here is the pattern it wore into the pulley. Should I go back to the 3/4" wide belt?
I am not sure if this is the source of the noise, but I can't see anything wrong with anything else.
BTW, I also swapped in a spare transmission while I work on the original one, so it's definitely not the trans.
Thanks,

Csaba
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Guy Croft
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Re: Can't find bearing noise

Post by Guy Croft » Sun Oct 12, 2014 11:06 am

re belt - please study the attached,

offsets vary on the TC auxiliary driveshaft pulleys, some will pinch the 1" belt without mods, you have to check,

G
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Sun Oct 12, 2014 3:15 pm

I've run this engine with a 1" belt ~15 years ago, but at that time it had the stock crank pulley.

I am trying to remember if the noise was there before I changed to a 1" belt recently - I think it was, as the reason I changed the water pump and the timing belt tensioner was the noise. More diagnosis is in order...
Thanks,

Csaba
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miro-1980
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Re: Can't find bearing noise

Post by miro-1980 » Mon Oct 13, 2014 11:15 pm

It looks like you have to get inside.

If I understand what front crank seal carrier is, correctly I would think you need to take the sump off and see it form the inside.

My wild guess: lose conrod attachment to the crank (one bolt broke off or more likely got just a bit lose).

It would make sense for the crank to carry the vibrations and sound of a slightly lose crankshaft.

I had a similar problem years ago with Ranault Dauphine.

It will be very interesting what the real reason was.

Good luck !

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Will01
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Re: Can't find bearing noise

Post by Will01 » Tue Oct 14, 2014 11:02 am

If you are getting that level of wear on the flange of the pulley that could quite possibly be where you hear this bering noise from.
We have seen this before when carrying out tests. However we also normally do not use aluminium pulleys without being coated to help improve wear resistance.
Where the wear is evident, is that a vertical face or is it slightly angled?

The reason i ask, is if the flange is not designed correctly and the belt tracks onto the flange, the belt may try to climb up which further pulls the belt towards the flange due to tension. A belt mostly tracks towards tension, this constant rubbing noise would be noticeable in my opinion and it could possibly sound like bearing wear etc

Hope this helps
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Tue Oct 21, 2014 3:56 am

Miro,

> My wild guess: lose conrod attachment to the crank (one bolt broke off or more likely got just a bit lose).

I did take the pan off, but all the bearings and bolts looked good. I puled #1 rod cap and #1 main cap, measure clearances and it's all good.

> If you are getting that level of wear on the flange of the pulley that could quite possibly be where you hear this bering noise from.

Well, I changed the belt (and bearing + water pump) because of the noise, and the previous belt was narrower. It's possible the narrower belt was trying to walk forward, but it's been on for ~10 years and the noise appeared a month ago.

>Where the wear is evident, is that a vertical face or is it slightly angled?

Yes, it is, then it angles away right where the wear ends.

Putting a narrower belt on would be very simple, so I may just do that as an experiment.
Thanks,

Csaba
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AutoRicambi
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Re: Can't find bearing noise

Post by AutoRicambi » Wed Oct 22, 2014 3:16 am

I installed the normal width (narrower) timing belt today and the noise is still there.
Plan is to drive it and see if it gets worse.
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Re: Can't find bearing noise

Post by Guy Croft » Wed Oct 22, 2014 10:06 am

loose flywheel bolts or worn small end bush,

cannot rightly think what else,

I have exp of both and those give a sound response where the source is very hard to pinpoint on the engine.

G
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