Diagnosing Engine Whirr

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nm9stheham

nm9stheham

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Engine is a 225 slant 6, original 1962, 60,700 miles.

Issue is a 'whirr' or vibration in the engine that cyles on and off at 1-2 seconds intervals; it builds up and dies off and then does that over and over. It seems most pronounced when warmed up, and the intervals are somewhat erratic.

Using a tube or long screwdriver to listen to the block whiel idling, it seems to be towards the front. I was thinking possibly a loose pilot bushing or trannie input bearing but for this. Water pump was changed and there's no change in the sound; no impeller marks in the block or on the old impeller.

The nature of the sound and the location makes me thing timing chain has a lot of slack and it is slinging out and rubbing on something, but I can't say I ever heard this before with several /6's in the past. The only other thing that pops into my mind is the front cam bearing but how that would do this is not making sense.

Anyone have any similar experience to share on this? Thanks!
 
You need to figure out for sure whirr the noise is coming from.


Those timing chains were not very good and stretch easy. It wouldn't hurt to get a double roller. You can get them from NAPA, but have to order the gears and chain separately. It could be possible that the chain is your problem.
 
Numb'ha Whon step is to listen for a short time with the belts off. Have you done this?
 
You can readily check timing chain stretch by turning the engine over by hand while watching the distributor rotor. Reverse and see how many crank deg of dead-zone before rotor starts turning. Over 10 deg is pretty sloppy.
 
Del: Have not tested with belts off....I have been going the assumption that since the whirr did not change with the water pump change, then it is not the water pump. And it is not the alternator; those bearings are a bit worn but not the same noise at all. But I might just try that.

Bill....good idea. I guess I am so used to tensioned chain systems that that did not occur to me to try.... duh! Easy to do.... and I need to look under the distributor cap anyway.

Will report 'whirr' this ends up....
 
OK, so I did the crank vs distributor rotation check, and my initial 'eyes closed, seat-of-the-pants' assessment was 'whoa that is loose', based on prior experince and before even looking the rotor button; at first I thought maybe I had a broken crank or worn key or keyway! (And I suppose it could be the key or keyway...) Using the crank timing indicator, it has about 5-6 degrees of crank rotation before the rotor button moves. I suspect there may be a degree or so in the distributor gear backlash but the majority presumably is in the chain, based on the 'feel' results.

Does anyone have a /6 cam timing gear to give me the outer diameter? It would be the median tooth diameter...or the diameters to the tips of the teeth and also to the valleys between the teeth, and those 2 numbers averaged. My FSM says that with the crank fixed, a chain link at the end of the cam gear away from the crank should move not more than 11/64" (.172"). I am trying to reverse calculate what that .172 cam gear movement figures up to in degrees and relate that back to crank degrees.

And yeah, I about 99% sure I'll replace the chain, but I want to relate the FSM number to actual degrees. Tnx!

And any other ideas on this whirr source are still welcomed.
 
Put that screwdriver on your alternator, any idler pullys and power steering pump while it's running and I'd bet you will find it.
I find it a lot easier and faster than removing the belts and using the screwdriver for a stethescope can pinpoint it.

One of the best clues was that it is worse when warmed up. (probably a bearing in something)
 
TrailBeast said:
Put that screwdriver on your alternator, any idler pullys and power steering pump while it's running and I'd bet you will find it.
I find it a lot easier and faster than removing the belts and using the screwdriver for a stethescope can pinpoint it.

One of the best clues was that it is worse when warmed up. (probably a bearing in something)
Click to expand...
Tnx! .... I've done the stethescope thing, and my son has done the same, and is how we determined that it was up in the front of the engine. The alternator bearing whirr has a much different sound than this. No PS and no idlers, just wasserpumpe und lichtmaschine.

And I'll update one thing: this eve it was there even when starting cold. I probably just have not noted it cold, or the switch today to full synthetic made it different. I keep going over possibilities (like a badly worn front cam bearing...??), but nothing is registering as probable based on what I have seen/heard before.

I will say that I have heard something similar before. My wife's cousin Donnie stopped in years ago and while visiting, he mentioned he was losing a lot of oil and had a noise out of the front of his van's 350. I checked it running.....and the timing chain was so loose that it had worried 2 grooves in the side of the timing cover!! I patched it with epoxy and warned him about the nylon gears being prone to strip ..... but old Donnie just kept drivin' it 'til the gear stripped.
 
nm9stheham said:
Tnx! .... I've done the stethescope thing, and my son has done the same, and is how we determined that it was up in the front of the engine. The alternator bearing whirr has a much different sound than this. No PS and no idlers, just wasserpumpe und lichtmaschine.

And I'll update one thing: this eve it was there even when starting cold. I probably just have not noted it cold, or the switch today to full synthetic made it different. I keep going over possibilities (like a badly worn front cam bearing...??), but nothing is registering as probable based on what I have seen/heard before.

I will say that I have heard something similar before. My wife's cousin Donnie stopped in years ago and while visiting, he mentioned he was losing a lot of oil and had a noise out of the front of his van's 350. I checked it running.....and the timing chain was so loose that it had worried 2 grooves in the side of the timing cover!! I patched it with epoxy and warned him about the nylon gears being prone to strip ..... but old Donnie just kept drivin' it 'til the gear stripped.
Click to expand...

It's not the fan is it? :D JK

It very well may be the timing chain and sprokets like you said.
Did you happen to notice any chunks of the gear in the old oil?
 
Fortunately, no gear chunks in the oil... at least that flowed out! Hmm, never thought to look at the fan for cracks or a loose blade or rivets .... will do.
 
Whirring noises can mean a lot of things. Since you know the timing set is somewhat worn might as well go ahead and change it. While you have it apart you can make sure it is getting proper lubrication. Listening with a hose or dowel or screw driver should make identifying this noise fairly simple. If taking the belts off doesn't stop it you could try a little water on some of the rotating parts. If you think the noise is caused by moving air, look to the fan blades. Are they straight, tight and all there?
 
nm9stheham said:
Del: Have not tested with belts off....I have been going the assumption that since the whirr did not change with the water pump change, then it is not the water pump. And it is not the alternator; those bearings are a bit worn but not the same noise at all. But I might just try that.

Bill....good idea. I guess I am so used to tensioned chain systems that that did not occur to me to try.... duh! Easy to do.... and I need to look under the distributor cap anyway.

Will report 'whirr' this ends up....
Click to expand...


I hope you figure out the puzzle, and I'm not making light of it, but why am I thinking Jetson's here?

Have you at least determined an area from which it is coming.


Del: Have not tested with belts off....I have been going the assumption that since the whirr did not change with the water pump change, then it is not the water pump. And it is not the alternator; those bearings are a bit worn but not the same noise at all. But I might just try that.
Click to expand...

No, but it could be the fan, alternator, heck it could be a funky belt. That's a good place to look.
 
The Jetsons///that's it! LOL I know the sound you are thinking about.... wish it was that! Yes, it is from the front; the stethescope shows it loudest on the front of the block.

Again, if anyone can supply the OD on a /6 cam timing gear, I can figure up the number of crank degrees that corresponds to my FSM's info for stretch limit.
 
I was getting strange noises from my 6 banger and it turns out it was a cracked flex plate. 3 of the 4 holes holding the torque converter on were cracked and about to break apart.
 
nm9stheham said:
The Jetsons///that's it! LOL I know the sound you are thinking about.... wish it was that! Yes, it is from the front; the stethescope shows it loudest on the front of the block.

Again, if anyone can supply the OD on a /6 cam timing gear, I can figure up the number of crank degrees that corresponds to my FSM's info for stretch limit.
Click to expand...

I have a brand new aftermarket timing set in the box if you think the dimensions would be the same?
 
cudajim said:
I was getting strange noises from my 6 banger and it turns out it was a cracked flex plate. 3 of the 4 holes holding the torque converter on were cracked and about to break apart.
Click to expand...
Tnx! Manual 3-speed here. I was thinking it could be the pilot bushing but that should not whirr with the clutch engaged, which it does. And then I was thinking input bearing in the trannie, but the noise is loudest in the front per the stethescopoe tests.
 
Just straight across the outer diameter from one tooth to the opposite tooth. I think I figured the whirr is not the timing chain (see below), but I would still like to calculate the crank degrees that correlate to the chain slack service limit in my FSM, which this dimesnion will allow me to do. Tnx!
 
And now for the latest...I think this is sol-ved. I took 67Dart273's suggestion and took off the fan belt and ths whirr seemed to be gone. Put the belt back on and made it tight; the whirr was low but steady. Loosened the belt and it became louder and erratic.

With the belt really loose and the engine off, I examined the old stock 4 blade steel fan and water pump pulley; all tight. I tapped the fan blades so see if I could find any loose blade rivets (none) but noticed that the whole fan/pulley/water pump shaft had dull ringing tonal quality when tapped as this whirr.

So, my conclusion is that the teenine, tiny looseness in the new water pump bearing is allowing the shaft to rapidly wobble just a tiny bit, and when that wobbles, it is exciting the dull ringing tone in the whole fan and pulley assembly. The wobble is variable with the fan belt doing its usual small amount of movement, and thus the 'whirring' comes and goes, and varies with belt tightness too. I'll visit NAPA someday when I am ready to chage the coolant again, and see if this very tiny looseness falls under the water pump warranty. I just might have to go through a couple to see if there is one with no bearing looseness.

Like many things like this, it led me to know that my timing chain is getting pretty slack, so all this rigamarole will have the benefit of me deciding to put in a new chain set; that ought to make things run just a bit better by eliminating most all of what appears to be about 5 degrees of cam timing retard.

Thanks to all for your input!
 
nm9stheham said:
Just straight across the outer diameter from one tooth to the opposite tooth. I think I figured the whirr is not the timing chain (see below), but I would still like to calculate the crank degrees that correlate to the chain slack service limit in my FSM, which this dimesnion will allow me to do. Tnx!
Click to expand...
3.072 let me know if you would like a picture

This is a Rollermaster double row sprocket. Just opened the wrapper
 
I think I would remove 4 nuts. I would remove the fan and pulley look at how clean and flat the pulley sits against the water pump then the fan to the pulley. There could be a burr there somewhere. I would expect everything is going back in different holes and tighten those 4 nuts up evenly. The whirl might just disappear.
 
1930 said:
Sorry for that, yes 6.072 would be cam gear

Confirmed very carefully. 6.072 O.D tooth to tooth straight across
Click to expand...
Thanks! The stock gears might be a bit different (I got one coming), but that dimension and 11/64" chain movement at the cam gear at the service limit works out to about 3.1 degrees cam slop and so a bit over 6 degrees of crank movement for the service limit. Good to know, IMO.
 
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