Rattle During Idle with Ac On

[Zander]

I bought a 97 ranger 2.3 2wd 5 Speed and it has a strange rattle when idling in neutral, but it's only audible with the ac compressor is on, and is louder if the headlights are on. So in other words it seems to be when there's a load on the alternator. And it goes away when I push in the clutch. I don't notice it when the truck is driving around. I got under the truck with it running hoping it was a heat shield or something simple but after using the old screwdriver stethoscope method the rattle seems to be loudest in the bellhousing of the transmission. Anyone have any ideas? I'm hoping someone has run across this before. I posted a video of the sound under the truck on YouTube, I'll link it below. Thanks in advance for any help!https://youtu.be/x4IT6fh6oho

 

[RonD]

COLD Engine
Loosen and remove fan belt from crank pulley
Spin each pulley to see if there are any obvious failing bearings

If not start engine, you can run a COLD engine for 2 minutes without the water pump, Battery Light will stay on, no alternator.

Engine bay will be very quiet with no fan, see if you can ID the rattle
If no rattle then problem is a component being drive by fan belt, so check each again
Shut off engine as soon as possible, no use running it if no rattle


bellhousing rattle can be starter motor gear not retracting all the way, its loose and hitting ring gear now and then

 

[rednik]

I also have a 97 2.3 2wd 5speed that rattles I’m neutral with the ac on. I used to have the equivalent 93 an it did the same thing. My theory is that it was the input shaft bearing since hitting the clutch while in neutral would allow it to stop. It never really bothered me much since both of mine weren’t perfect an had worse problems lol.


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[Zander]

I also have a 97 2.3 2wd 5speed that rattles I’m neutral with the ac on. I used to have the equivalent 93 an it did the same thing. My theory is that it was the input shaft bearing since hitting the clutch while in neutral would allow it to stop. It never really bothered me much since both of mine weren’t perfect an had worse problems lol.


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Interesting. I didn't have time to do any testing today but will tomorrow. I'm just worried that if it's something like the input shaft bearing that it'll fail on the interstate when I'm far from home. I was hoping that someone would comment that had the same issue but figured it out lol.

 

[rednik]

Yeah I was too for a bit but it's been 20k since I noticed on my 97 And I put 10k on my 93 with not issues. I'm due for a clutch soon so I'll check out the trans more than


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[Zander]

Sorry about the delay I finally got around to taking the belt off and it still does the same thing. I listened around with a stethoscope and the rattle definitely seems to be coming from the transmission, specifically near the front of the bellhousing. Any thoughts? I also have a dry bearing kind of sound all the time. It's especially noticeable when coasting in neutral with the engine off. Doesn't matter if I push the clutch in or not it's always there unlike the rattle which only occurs when the clutch is not pushed in. Anyone have any ideas or past experience with this type of thing?

 

[1990RangerinSK]

That sounds to me like it's your clutch release bearing. I'll let (ask?) somebody else chime in and tell us whether or not that's fatal. All I know is that I've had vehicles with that rattle in them in the past, and I drove them like that for thousands of miles.

 

[Zander]

That sounds to me like it's your clutch release bearing. I'll let (ask?) somebody else chime in and tell us whether or not that's fatal. All I know is that I've had vehicles with that rattle in them in the past, and I drove them like that for thousands of miles.

If it were the clutch release bearing wouldn't it only make noise when the clutch is pushed in? Because mine only makes noise when the clutch is not pushed in and it goes away when I push in the clutch

 

[Zander]

So I noticed something else today. The rattle is also present when the headlights are all turned on at once. So it seems to me that it's the extra load from the accessories (ac and alternator) that's causing the rattle. And like before it goes away when the clutch is pushed in.

 

[Uncle Gump]

Well if you removed the accessory drive belt and the noise is still there... I would rule out the accessories. Sounds like you have it narrowed down to the bell housing area anyway.

A clutch release bearing with the clutch pedal not depressed still contacts the pressure plate lightly which is rotating at engine speed. This will make the bearing rotate at engine speed too. Once you depress the clutch pedal the release bearing is "under load" with the forces of the pressure plate pushing against it. This "load" is probably enough to make the bearing go quiet. So... release bearing free wheeling... noise. Release bearing under load... quiet.

I would start to worry about it when the release bearing makes noise under load or pedal depressed.

 

[Zander]

Well if you removed the accessory drive belt and the noise is still there... I would rule out the accessories. Sounds like you have it narrowed down to the bell housing area anyway.

A clutch release bearing with the clutch pedal not depressed still contacts the pressure plate lightly which is rotating at engine speed. This will make the bearing rotate at engine speed too. Once you depress the clutch pedal the release bearing is "under load" with the forces of the pressure plate pushing against it. This "load" is probably enough to make the bearing go quiet. So... release bearing free wheeling... noise. Release bearing under load... quiet.

I would start to worry about it when the release bearing makes noise under load or pedal depressed.

OK wow I was under the impression that the bearing wouldn't spin unless the clutch was pushed in. Not sure where I got that idea. Is what you're saying true across the board with all manual transmissions? So if my truck has a bad throwout bearing then that could account for the dry bearing sound I'm hearing while coasting in neutral with the clutch pedal out right?

 

[Uncle Gump]

I think in theory the throw out bearing wouldn't touch the pressure plate until the pedal was depressed. In reality... I've replaced a few throw out bearings that made noise without the pedal depressed. Tolerances are close... everything has to have end play. Things move... contact is made... bearings spin and make noise.