Odd Humming Noise from Engine

[timtimtimajim]

I got in my Ex today and tried to fire it up. The first couple times it wouldn't turn over and finally after cranking it for 3-5 seconds it finally turned over. It started making this weird humming/kinda grinding noise and idling a little rough. Then when i shut it off the noise got louder and sounded like something was winding/spinning down. The noise lasts for about 2 seconds after i shut the engine off and comes from the driver side of the engine. The Ex was running completely fine yesterday, it was just all of the sudden this morning started giving me issues

I've read into the possibility of it being a timing chain but i'm not totally sure.

Any help is greatly appreciated.

 

[natenkiki2004]

First thing that comes to mind would be the fan clutch, it spins a bit after the engine stops. If a timing chain went, you wouldn't be able to start the engine at all. In our Ex's the timing chain is very robust, I'd rule it out. That said, the fan clutch wouldn't explain hard starting or poor idling, just the noise.

 

[Wolfie_85]

It's the fact that it continues after shutting down that stumps me. I would say vacuum leak with the rough idling, but that would be a sucking sound, fan clutch is a possibility (for noise), but wouldn't make it run poorly. Is your fan rubbing against anything? Check out your fan, fan clutch, and your vacuum lines. The fan should spin with just a little resistance, and vacuum lines can pop off or crack.

I wouldn't worry about the timing chain in the OHV in a '93, natenkiki is right.

 

[timtimtimajim]

Well the fan spins with little resistance and it doesn't look like it's rubbing on anything. Vacuum lines all look fine.

Would it be worth replacing the fan clutch even if the fan seems to be spinning fine? It's an easy thing to do and not really that expensive...

 

[natenkiki2004]

Only replace the fan clutch if the engine heats up excessively while idling OR you can feel in the front of it and feel a wet grease/oil in the center.

Take a look:
https://dl.dropboxusercontent.com/u/464376/vehicles/1991 Explorer/Pictures/IMG_20150419_135308.jpg
Old on the left (leaking), new on the right.

If the fan spins freely without contacting anything, ignore the fan clutch. I'm not sure of what direction to point you in now.

 

[Number4]

Well the fan spins with little resistance and it doesn't look like it's rubbing on anything. Vacuum lines all look fine.

Would it be worth replacing the fan clutch even if the fan seems to be spinning fine? It's an easy thing to do and not really that expensive...

If it spins without resistance, then I'd say it's bad. A good one shouldn't even rotate once doing a 'wheel of fortune' spin. Go to a parts store and check a new one out, you'll find out that they have quite a bit of resistance.

Edit, also replace the fan blade. Pay attention to wether or not you have the 9 or 10 blade fan. Most stores stock the 9 blade. Any of the blades missing? If you look where the blades connect to the center piece, you'll most likely see that they are cracking and getting ready to come off.

 

[timtimtimajim]

Edit, also replace the fan blade. Pay attention to wether or not you have the 9 or 10 blade fan. Most stores stock the 9 blade. Any of the blades missing? If you look where the blades connect to the center piece, you'll most likely see that they are cracking and getting ready to come off.

One step ahead of you. I replaced the fan blade last year (along with a new radiator and water pump) but i did not replace the fan clutch, i recall the fan clutch looking a lot like the one on the left in natenkiki's photo though. There was a lot of oil/grease on it.

 

[SuperKirby]

Are you sure the sound is from the engine compartment? Does it sound like something is turning or grinding, or more like an electric motor or something that's still powered?

 

[timtimtimajim]

Remember what i said about the vacuum lines being fine? Yah i was wrong. Found one that had fallen off of its connection that i missed before when i checked. The noise i was hearing is all gone and it's running smooth again!

 

[Wolfie_85]

Glad to hear! I had a feeling that would be it for at least part of your problem. A vacuum leak can make a pretty obnoxious sound, eh?

 

[natenkiki2004]

If that noise was caused by vacuum, I'd wonder if your brake booster one-way valve is bad, or maybe the grommet. Cheap fix at the parts store. If it's real bad, it'll hiss for a few seconds after shutting the engine down. A quick test you can do though, after a few hours of parking it, come back and press the brake pedal a few times. It'll sound hissy and be easy at first but then get hard to push after 2-3 strokes. If it's hard to push the first time, your booster isn't holding vacuum and you should look there.

Part number is UP 89000 at NAPA.

 

[vq5speed]

Haha sometimes a weird noise can be misdiagnosed. The other day I was checking my Tranny oil level pulling the dip stick in and out. After I was done all sudden I get this tap tap tap tap tap sound constant steady tap sound. Its really loud I rev the motor it doesn't go away. I think why are my rockers making all this noise all sudden. After awhile listening trying to figure out why my rockers or lifters is making a tap sound now. I then noticed I pulled up one of the plug wires slightly off the coil when reaching my hand back there. The tap sound was actually a Zapping sound of an electric spark jumping across the plug wire to the coil. I have a Screamin Demon coil that puts out 45,000 volts.

 

[timtimtimajim]

Glad to hear! I had a feeling that would be it for at least part of your problem. A vacuum leak can make a pretty obnoxious sound, eh?

Oh yah it's terribly obnoxious and a little bit freaky!

If that noise was caused by vacuum, I'd wonder if your brake booster one-way valve is bad, or maybe the grommet.

Brakes seem to be fine, havn't found any issue with them... yet

I have a Screamin Demon coil that puts out 45,000 volts.

All I can say is... WOW!

 

[natenkiki2004]

Brakes seem to be fine, havn't found any issue with them... yet

They will be fine when the engine is running. There's far more vacuum generated by the engine than what could leak at the brake booster. If this IS an issue, it's less a safety issue but more of an issue of your engine running slightly leaner on unfiltered air. Just a good thing to check, takes seconds.

The reason I bring this up is that the noise couldn't happen from the vacuum line being off. The upper intake plenum is almost instantaneously equalized when you shut the engine off due to the IAC valve. The only place vacuum would be stored is in the brake booster. Perhaps it was leaking back into the upper intake and the hiss was more audible with the vacuum line removed that you saw. It's a stretch, I know. But a good thing to check, cheap maintenance item at the age of our vehicles.

 

[timtimtimajim]

They will be fine when the engine is running. There's far more vacuum generated by the engine than what could leak at the brake booster. If this IS an issue, it's less a safety issue but more of an issue of your engine running slightly leaner on unfiltered air. Just a good thing to check, takes seconds.

The reason I bring this up is that the noise couldn't happen from the vacuum line being off. The upper intake plenum is almost instantaneously equalized when you shut the engine off due to the IAC valve. The only place vacuum would be stored is in the brake booster. Perhaps it was leaking back into the upper intake and the hiss was more audible with the vacuum line removed that you saw. It's a stretch, I know. But a good thing to check, cheap maintenance item at the age of our vehicles.

I see what you're saying. I did the test you suggested earlier with the engine off and after 3 presses the brake pedal became hard to press, so everything seems normal there. But thanks for that bit of information, it's good to know for future reference!

 

[natenkiki2004]

Not a problem, sounds like you're good to go!