88mjblue Posted March 19, 2015 Share Posted March 19, 2015 I’ve had this sound since I got it (a few months ago). I brought it in to a mechanic when I first picked up the jeep, he said it was the cat rattling. I banged around there and the cat is indeed bad, however, the sound doesn’t come from there. I have since replaced the cat (which was completely shot) and the video was recorded after the replacement, with the same sound still present. It sounds like it’s coming from the driver’s side of the engine bay. Maybe a loose bolt? It has a rhythmic quality to it… Video shows this sound from inside the cab and also at the engine bay trying to pinpoint this noise. https://youtu.be/jE9FMPCRtMg Link to comment Share on other sites More sharing options...
Fernando87mj Posted March 19, 2015 Share Posted March 19, 2015 Have you checked the pulleys or harmonic balencer for play in it ? Hopefully this might help and (off topic) but your jeep looks really clean and nice and awesome ! original amc/jeep keys Link to comment Share on other sites More sharing options...
88mjblue Posted March 20, 2015 Author Share Posted March 20, 2015 Thanks! I looked up some videos of the harmonic balancer sounds, I always thought a bad balancer was more of a squeaking sound, but this could be it, I will do some more reading on harmonic balancers... Link to comment Share on other sites More sharing options...
mfpdm Posted March 20, 2015 Share Posted March 20, 2015 Might be the clutch on the fan. My TJ had one go bad and it sounded close to that. Link to comment Share on other sites More sharing options...
88mjblue Posted March 20, 2015 Author Share Posted March 20, 2015 Nope, not the fan clutch. I replaced that and sound was the same before and after. Link to comment Share on other sites More sharing options...
gogmorgo Posted March 21, 2015 Share Posted March 21, 2015 It sounds a bit like some of the knocks my MJ was making with loose/missing bellhousing bolts and/or cracked flex plate. Of course you've got a manual... I don't know if a cracked flywheel would behave the same as a cracked flexplate, but you can always check the bellhousing bolts. Also check to make sure the exhaust isn't sitting against something and rattling.Does the sound change with throttle or load, clutch in/out? Link to comment Share on other sites More sharing options...
88mjblue Posted March 22, 2015 Author Share Posted March 22, 2015 The sound doesn't change in terms of quality when the clutch is depressed or when driving/under load, but it does get rhythmically faster with increasing rpm. Does that change anything, or give anybody a clue to what it could be? Link to comment Share on other sites More sharing options...
mfpdm Posted March 22, 2015 Share Posted March 22, 2015 Since it is tied to rpm that would narrow it down a little. You've already replaced the fan clutch so I guess a process of elimination is next. You could pull the belt off and see if the noise is still there. That would eliminate the tension pulley, steering pump, ac compressor, and water pump. Then I guess it would leave the harmonic balancer and maybe the oil pump. If is goes away with the belt off, I would suggest checking fluid level in power steering, may even think of flushing it. If still there then I guess it would be a process of swapping components. :dunno: Just listen to it again in a loop. Is it louder towards the back of the engine? Have you put a long wrench/screw driver to parts of the engine and to your ear to see if you could hear it stronger at different positions? Almost sounds like something metallic rubbing on something. Have you pulled the valve cover and inspected for any lose components? Link to comment Share on other sites More sharing options...
88mjblue Posted March 22, 2015 Author Share Posted March 22, 2015 Since it is tied to rpm that would narrow it down a little. You've already replaced the fan clutch so I guess a process of elimination is next. You could pull the belt off and see if the noise is still there. That would eliminate the tension pulley, steering pump, ac compressor, and water pump. Then I guess it would leave the harmonic balancer and maybe the oil pump. If is goes away with the belt off, I would suggest checking fluid level in power steering, may even think of flushing it. If still there then I guess it would be a process of swapping components. :dunno: Just listen to it again in a loop. Is it louder towards the back of the engine? Have you put a long wrench/screw driver to parts of the engine and to your ear to see if you could hear it stronger at different positions? Almost sounds like something metallic rubbing on something. Have you pulled the valve cover and inspected for any lose components? Thanks for this reply, really good stuff. I will try the belt removal and see if the sound goes away then. What should I check for when removing the valve cover? Link to comment Share on other sites More sharing options...
glundblad Posted March 22, 2015 Share Posted March 22, 2015 This is probably not it but I will offer it anyway. At times, mine rattles like that but usually it's only at takeoff and it is somewhat infrequent. I crawled underneath and kicked at the bottom of the tranny a bit and found the rubber gasket that the tranny sites on is worn. I bought a replacement but haven't gotten around to changing it. Link to comment Share on other sites More sharing options...
88mjblue Posted April 30, 2015 Author Share Posted April 30, 2015 Update: I had some time tonight to work on the mj, here is the result: Belt off = sound gone Belt on = sound present I don't think it's the PS pump - fluid is topped off and is clean, steering seems fine. I did try to pinpoint the sound a bit better, and it sounds like it's coming from the alternator - is that possible for an alternator to sound like that??? I don't have any charging issues, my battery reads 14 V when engine is on. (but then again, I don't have any high powered accessories, all stock here) I tried the screwdriver method, but was afraid I might get electrocuted touching the alternator to my ear, is that safe to do? Any tips? -Thanks. Link to comment Share on other sites More sharing options...
88mjblue Posted April 30, 2015 Author Share Posted April 30, 2015 So here's what's been done: - x2 new idler pulleys (no a/c) - new water pump - PS fluid - new fan clutch - new serpentine belt So this leaves:- harmonic balancer - alternator Did I miss something? Btw, the repairs made above did not affect the sound, stayed the same before and after those new parts were put on. Link to comment Share on other sites More sharing options...
Megadan Posted April 30, 2015 Share Posted April 30, 2015 You can also use a piece of wood in place of a screw driver. Same effect. Especially if you are afraid of being shocked, or other such injuries that may result. Link to comment Share on other sites More sharing options...
88mjblue Posted April 30, 2015 Author Share Posted April 30, 2015 What about the harmonic balancer? Can I rule out the balancer or not? Spinning with the belt off doesn't make the noise, but maybe the load of accessories would make it sound? Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 30, 2015 Share Posted April 30, 2015 from the sound it sound like something needs lubed. have you tried to lube of the barring's. on both alternator and the balancer. remember grease can dry out and make things sounds weird. Link to comment Share on other sites More sharing options...
88mjblue Posted April 30, 2015 Author Share Posted April 30, 2015 from the sound it sound like something needs lubed. have you tried to lube of the barring's. on both alternator and the balancer. remember grease can dry out and make things sounds weird. I think that could be it. I got the belt off again, and used some wood to listen up to the alternator best I could, sounds like it was coming from there, but couldn't rule out the harmonic balancer, hard to tell - I put the pole to the oil pan near the balancer, but not as clear as up to the alternator. Take a look at this vid I took of the alternator spinning freely. Is this a normal sound for alternator? All other pulleys sounded fine. (Except balancer, I could not spin it, obviously) From the maintenance records I have (which are pretty detailed) it seems (and looks) like the original alternator - it works fine, just might need to be lubed? https://youtu.be/yPi22M04xaE Link to comment Share on other sites More sharing options...
Marine1Texas Posted May 1, 2015 Share Posted May 1, 2015 yea just spinning may not hear it. you have to take in account the pressure your getting from belt tension. if it is alternator is could also be on the back side where the tension opposite of front barring. I know those barring last about 60k or so. Check if there is any slop play in the shaft as well. I have had a alternator make funky noises however work for the longest time. It almost always from the front barring I have found. Link to comment Share on other sites More sharing options...
88mjblue Posted May 1, 2015 Author Share Posted May 1, 2015 I was just looking up alternator bearings, they're only ~$10, so maybe I'll give it a shot if it's not too difficult. I am almost 100% certain it has the original alternator, and it has 110k+ on it. Link to comment Share on other sites More sharing options...
Co-MAAAN-cheee Posted May 6, 2015 Share Posted May 6, 2015 Google steelman chassis ear. I bought ste6600. It has 6 alligator clips with microphones you can attach all around your vehicle and listen to them while driving. I have 4 cars and have accurately located several noises. Awesome tool. Link to comment Share on other sites More sharing options...
88mjblue Posted May 14, 2015 Author Share Posted May 14, 2015 Google steelman chassis ear. I bought ste6600. It has 6 alligator clips with microphones you can attach all around your vehicle and listen to them while driving. I have 4 cars and have accurately located several noises. Awesome tool. The wood stick worked for me, but I will keep this in mind for other softer sounds, and for sounds that occur when driving. Update: the rattling noise is gone! Noriyori_Kudo^ was correct, it was in fact the front alternator bearing. Rather than taking the alternator case apart and replacing the bearings, I decided it was time to upgrade, and put in a new Bosch 100A alternator I got for cheap. Link to comment Share on other sites More sharing options...
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