Noise, Check Engine Light, Bucking while driving

[moparknighthawk]

I have been experiencing the above off and on for a few weeks now. I was getting a screaching noise under the hood (since it has got cold out), now its turning into a whining noise. For an added bonus, I get a check engine light for a bit then that goes out. When the CEL comes on, I get a bucking while driving , then its gone. Listening under the hood, it seems the noise is coming from the altenator, or at least that is where its the loudest. I have not seen a battery light come on to indicate a problem with the electrical system either. Any ideas of where to start? BTW, my Ranger is a 1994, 4.0 V6 with 5 speed manual with 107,000 miles. It gets used about 5K mile a year. Thanks.

 

[moparknighthawk]

Need something: How do I check the codes on a 94? I have a OBDII scan tool, but I don't think that can be used on a 94. (I think it was 96 and up).

 

[RonD]

I would remove the serpentine belt and spin all the pulleys manually, yes, most likely the alternator.
The alternator has the most "drag" after start up, recharging battery.
The alternator has 3 "fields" that generate AC power, only 1 "field" passes to the Battery Light, so if there is a problem with the other 2 "fields" then Bat. Light wouldn't come on.
If you have a volt meter you can test the alternator.
Connect voltmeter to battery, engine/key off
You should have above 12.4vDC, below this means battery is getting older and I would look for the next sale , especially if you live in a cold area.

Turn off all lights, fans or any other electrical devices, start engine.
Voltage should now be 13.8vDC or higher.
Now turn all electrical devices on, headlights, driving lights, Fan on high, radio, even cigarette lighter.
Voltage should drop down then pop back up to 13.8vDC or above.
The down and up is the voltage regulator responding to changes in current draw.
If voltage is 13.8 or better then alternator is working so noise could be a bad bearing inside it.

If voltage is below 13.8 then 1 or more "fields" is not providing power, this will slowly wear down your battery, especially if you drive at night.

If alternator is found to have a problem I would fix that first.
The CEL coming on briefly could be from engine misfiring and that could be from a low voltage situation caused by the alternator.
A bad alternator can pull power as well, depending on the failure point, that could cause intermittent misfiring.

 

[moparknighthawk]

Thanks RonD. I'll give those things a try. The battery was put in last August so its fairly new. I think I replaced the alternator about 2 to 4 years ago. Its hard to remember without looking for the repair receipt and since I only drive the truck a few miles a week, time gets away more than miles. Not much has been replaced on my Ranger besides maintenance items. Being an 19 year old truck, she is holding up very well. Anyway, I'll try things out. Thanks!

 

[moparknighthawk]

So far I have spun the pulleys. The alternator has a squeak in it, the others spin fine as far as I can tell. I do remember hearing a squeak every now and then a few months ago as the temps started getting colder. Also, there is a date on the alternator of 2007. I have to track down a voltmeter to do more testing. Any more advise is greatly appreciated. Thanks.

 

[RonD]

Squeak is not good

If you look here:
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

Then scroll down to the Charging Diagrams, the first one is for the 4.0 alt. although I think most are pretty much the same.
You can see the 3 "stator fields" and how only 1 feeds the Charge Light, via the jumper wire for the regulator, in theory it should report any under voltage but it doesn't always work that way.
Check all the alt. wires for any signs of corrosion or "hanging on by a thread" connections

Most auto parts places will test an alt. for free, although you get what you pay for in some places.
But with the squeak I might just replace on spec.
Squeaks never seem to get quieter, lol.

 

[moparknighthawk]

Ok, so I took the alternator off so I can get it tested tomorrow at my NAPA place. They have some in stock too if I need one. I tell you, the shop that replaced that alternator little over 4 years ago must have hired the 800 lb. gorrilla that the car manufacturers use to put oil filters on new cars. LOL Those two bottom bolts were on REAL good.