From running great one day...to a knock/rattle noise and dead battery the next

[Jbwalsh76]

Of course my Bronco sat for a bit this summer (AZ), but fired right up and I drove it around town a couple times in the recent (all went well).

I had the oil changed last week and the wheels fell off the bus so to speak. Yeah...I know I should have done it myself, but I was being lazy as its still north of 100 out here in the desert.

From a cold start last Saturday...I noticed the battery struggled a bit to fire up the engine, but it fired up and the engine sounded fine...so I went inside for a min to let it warm up a bit.

Maybe 5 mins later...I heard a rattle/knocking noise (after the engine was warm). I first thought the noise was coming from in front of the engine, but now I'm thinking it may be from the block.

This may be a completely separate issue, but my battery was dead this am as well. I had to jump it in order to shoot the below video.

Link to short video. https://photos.app.goo.gl/kCmw97jMyckE54UF7

Again, the Bronco was running smooth until I had the oil changed last week...

Just figured I'd bounce this off you all, before taking this somewhere to get looked at.

Thanks!
JB

 

[Pops68]

Have you checked the oil level??? Is the drain plug installed??? Filter on tight??? NOT trying to be a smartass or anything, but these seem to be simple checks especially since you just had an oil change.

 

[Jbwalsh76]

No offense taken...I did check oil level and just double-checked filter and plug. All are good...

 

[fluffybunny]

Watching the video, it looks like the tensioner below the alternator is jumping around. Maybe pop the belt off and start it see if it's a tensioner rattling. Check the balancer too to see if it's separating.

 

[m_m70]

it looks like the tensioner below the alternator is jumping around. Maybe pop the belt off and start it see if it's a tensioner rattling.

agree with this.......pop off the belt and try again.

 

[Jbwalsh76]

Thanks guys...will pop the belt off and see if that fixes the problem.

 

[DirtDonk]

Went through this with a friend’s bronco a couple of years ago.
I heard a horrible death rattle from the engine that was half rattle half knock, and figured the engine was on its last legs. Mechanic looked at it and took the belt off in the process of diagnosing and the noise was 100% gone.
Don’t remember what they found as the actual problem, but no noise since.

Let’s hope yours is that simple and uncomplicated, but even if not it’s still a good first place to start.

 

[DirtDonk]

Did you have the oil changed at a large chain store? If so Google their name and oil problems to see if any others crop up.
Even though I’ve never heard of it happening, it’s not out of the realm of possibility that there is an oil problem with their source.
Or sometimes when people change from standard oil to synthetic in a high mileage older engine that has lots of caked on burned on deposits inside, some of those deposits dissolve and work loose and get churned up in the engine.
Generally not a good thing!

 

[71 CA Bronco]

My guess is alternator bearing, or tensioner pulley. Like others have said you should be able to tell its front dress related by removing the belt and starting. If the noise goes away then spin the alternator and/or belt tensioner to see if there is an issue. Good luck.

 

[Jbwalsh76]

So I went to pull the belt off last night, but fired up the engine to see if I could hear the noise and of course I couldn't....

Only thing different...is that the battery had been on a charger for a day and a half.

Took it out this morning for a short drive around town and it drove/sounded fine. Weird...I just checked the battery and there was no draw when the engine was off and alternator was charging at 14.4 volts when running.

I guess I'll keep the battery on the tender for now...

FYI - oil was changed at a reputable shop (not a large chain).

 

[DirtDonk]

With the battery being low there was a much higher load on the belt because of the alternator putting out a high amount of amperage to recharge the battery.
I don’t know that this could cause any of your noise, but it is something that would’ve been different between a low battery and a fully charged battery.