engine knock or rattle, search continues... FOUND IT! Options

[malcolm2]

Let me ask......

Has anyone had an Alternator that knocks?

I have been searching for a random knocking or rattle noise. I thought for sure it was internal, maybe a rod or piston. The sound is random tho. I figured an internal noise would be timed with rotation.

Also thought it was from the passenger side.

I spent lots of time under the car with a stethoscope this weekend and I would bet a nickel it is not internal. Seems to be the fan, fan housing, or alternator; 'cause with the scope on the fan housing or alt. I can really hear the random knock. On the block, anywhere, all I hear is a faint consistent click of valves thru the case.

The fan is torqued and aligned, the belt has proper tension and the alternator was rebuilt 7,000 miles ago prior to my first start. Not sure what all the rebuild included, but I will try to find out. Thinking bearings, maybe?

I have had one suggestion.... remove the fan belt and start the car and listen. Can't think of any problems with that. Are there any?

Any thoughts or comments very much welcomed.

Clark

[pilothyer]

It would be perfectly safe to remove the belt from the alternator and fan and start the car and see.........You would never want to disconnect the battery with the car running though....you would be replacing diodes in the alt.

[Dave_Darling]

I've had one or two things fall into the fan or into the fan shroud over the years. The worst was an alternator pivot bolt that worked its way out. It was grabbed by the alternator belt and thrown across the engine bay--HARD. Lucky it missed the battery, because I'm pretty sure it would have put a hole in it.

--DD

[rhodyguy]

i chased a loosening belt issue and a weird rattle to find that the alt bracket was loose at the case. loosen or remove the belt and see if you can shake the alt.

[saigon71]

Have you done anything with the heat flapper boxes recently?

I had a random rattle this spring. After some searching, I realized that the passenger side heat flapper box was hitting the engine mount bar occasionally, causing the rattle.

[malcolm2]

Have you done anything with the heat flapper boxes recently?

I had a random rattle this spring. After some searching, I realized that the passenger side heat flapper box was hitting the engine mount bar occasionally, causing the rattle.

I did remove one HE and took out the damn little flapper on the btm of the fan housing on the pass. side. It was stuck open. Drivers side was stuck closed. Was able to wedge a screw driver in and break the driver's side flapper free. I'll crawl under and check those boxes tho.

[rgalla9146]

Check the belt itself.
I had a mysterious noise a few months ago on a friends car.
It did sound knock-ish, turned out to be a flap on the belt !

[larryM]

I have been searching for a random knocking or rattle noise. I thought for sure it was internal, maybe a rod or piston. The sound is random tho. I figured an internal noise would be timed with rotation.

you need to better describe the noises and when they occur if you hope to get quality opinions on this from 914 community

who have heard & resolved every noise there is

[malcolm2]

I guess I'll take what comes. This post got more action than the ones with actual videos of the problem. This was a question about the ALT and if anyone has had a noisy one. So i hope i am narrowing it down.

youtube COLD knock

There is a hot engine video on my channel too. Much less knocking.

[yeahmag]

Man... If that CHT is accurate on the "hot" video your heads are WAY hot. Have you checked the valve lash yet to see if there is anything funny there?

If you suspect the alternator I agree with Jerry. Remove the belt and see if the noise goes away. While you are at it make sure the fan hasn't come loose. That's a really strange sound on the "cold" video.

[era vulgaris]

Man... If that CHT is accurate on the "hot" video your heads are WAY hot. Have you checked the valve lash yet to see if there is anything funny there?

300F on the CHT? That's perfectly normal. If it were 400F, that would be cause for concern.

Why is your oil warning light on at the beginning of the "hot" video?

[somd914]

I have a little piston slap on my 2056 when it's cold, but doesn't sound like that, more like a rod knock. It kind of reminds me of when my fan came loose - some random "knocking" every now and then, especially on acceleration. But it only took 25-30 miles for it to go from an occasion knock to a loud racket and threw the belt.

Agree, check the belt as the next step...

[TheCabinetmaker]

Sounds like crankshaft walk to me.

[somd914]

Sounds like crankshaft walk to me.

This is a new one for me from a diagnostics standpoint. I would assume if the crank were walking there would be bearing or other wear leaving metallic residue in the oil. If that is the case, should the OP drain the oil and look for particles or have an analysis performed? The other option I assume would be to drop the tranny and measure end play. Just curious, thanks.

[malcolm2]

I don't discount the suggestions, but wouldn't a rod or crank sound come thru the case? Originally I felt like that was it too. But I have had the mechanics stethoscope all over and the sound is loudest when the scope is touching the fan housing or alternator.

I have had the Tranny out 3 times since February. During the first missing Tranny month, I did check end play and it was fine.

I have 1 more home project to attempt to complete this evening. I have been working on the damn tile back splash for 4 weeks now.... Time to grout.

Then I will do as Jerry suggested and remove the alternator belt and see if the sound goes away.

[malcolm2]

Man... If that CHT is accurate on the "hot" video your heads are WAY hot. Have you checked the valve lash yet to see if there is anything funny there?

300F on the CHT? That's perfectly normal. If it were 400F, that would be cause for concern.

Why is your oil warning light on at the beginning of the "hot" video?

.

Normal running CHT on this car is just below center of the gauge (350*F). Everything I read tells me that is normal. I have verified the gauge with an IR thermometer. The sender ring is under #3 spark plug.

On the HOT video, I had just returned home from work, about 20 minutes on the interstate.

OIL WARNING LIGHT: The sender has 2 connections, one for the light and one for the gauge. I hooked the OEM OP light (wire) to the VDO sender connection for the light. I also have a mechanical OP gauge in the engine compartment.

From all indications, the VDO sender lights the light at about 10 PSI. At warm or hot idle the green dash light will come on. But the mechanical gauge and the VDO show about 10 PSI. it is kind of annoying, but I have gotten used to it coming on at stop signs, etc...

I have read that that is normal. I would and will be concerned if the dash light comes on cruising down the interstate.

Thanks

[McMark]

Not uncommon for the lower alternator pivot bolt to lose the nut on the back. When you're under the car, check that. It can knock.

[euro911]

I watched your videos. My wife's 1.7 had a similar noise - ended up being from the alternator tin. A little tin readjusting and re-tightening the bolts took care of it.

[malcolm2]

I watched your videos. My wife's 1.7 had a similar noise - ended up being from the alternator tin. A little tin readjusting and re-tightening the bolts took care of it.

FOUND IT VIDEO

Well the stethoscope did not lie and Jerry's suggestion proved it.

Probably didn't need to start the car with the belt off. Once I got the belt off, I grabbed the ALT pulley and CLANK. I could pull it in and out with about a 1/2' to 1" of movement.

Damn that thing only has about 7000 miles on it.

Next question where do I get a new one that is correct and will last?

During my rebuild I got one at AutoZone that was not going to work. It would not seal up, and other crap I can't remember, so I took the OEM one downtown and had it rebuilt. I am sure they won't honor their work, but I'll try.

Prefer a new one tho.

Thanks for all the suggestions.

Clark

[euro911]

Check with Mark (McMark) ... maybe the high-output alternator kits are ready? (IMG:style_emoticons/default/biggrin.gif)