BJ74 Mystery Noise - Need Help (1 Viewer)

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Hello all

I took my BJ74 (1988 BJ74, 13BT, RHD, Japanese import, FRP top, all stock as far as I know, other than the radio) on a three-day, easy desert trip recently - nothing difficult, mostly sandy washes - and came back with a strange noise coming from somewhere under the hood. I'm not trying to be vague, but I can't figure out where it is coming from. It started very sporadically on day 2 while driving in a flat wash, and was almost constant by the end of day 3.

Disclaimer: I'm much less mechanically knowledgeable than most on this forum, so I won't be surprised if it's a simple answer. I did take the car to my Toyota mechanic but they weren't able to identify anything from the video.

I tried to link it to the suspension, acceleration, braking, steering, air conditioning, but nothing I did could force the sound, so I couldn't tie it to any specific component. To me it sounds like something spinning making contact somewhere under the hood, but I have no idea. And of course, it stopped after 10 minutes on the highway so I had nothing to show a mechanic. That it would start off-road and stop on the highway makes me think I didn't permanently dislodge anything, but that confuses me even more...

Here are links to the videos I got right before getting back on the highway. It's hard to hear over all the rattle of the car over washboards, but you can hear it clearly when the camera is outside the window. Unfortunately I couldn't tell what I was recording while driving at the same time so the part of the video with the sound is really short.

VIDEO 1 (sound happens once right at the end)

VIDEO 2 (sound most obvious when the camera is outside the window)

Any help GREATLY appreciated.
 
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Joined
Jan 21, 2018
Messages
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Southern California
You better tell more abut your vehicle.
Removeable FRP top?
Correct - 1988 BJ74, 13BT, RHD, Japanese import, FRP top, all stock as far as I know, other than the radio. I'm sure some of that is repetitive but I can't keep track of all the variations between models.

If any other relevant information is needed please let me know.
 

FJBen

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Sounds like something just getting loose and rattling on the dirt road. It doesn't sound mechanical, but honestly it's really hard to tell from that video.

I know everytime I wheel or go on rough roads I can always hear some new noises after awhile. Stuff just gets moved around and loosened. Could be a skidplate loose and flexxing over bumps?
 

woody

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I've had some odd tapping noises under the hood of my BJ74. Air in the fuel lines was my diagnosis....mostly since I had issues with the fuel filter getting air in it and running poorly...discovered the soft fuel lines were 1986 original and cracked, and pulling air into the lines. Replaced "most" of those and the issue has largely gone away. (need to finish)

Worth checking, and a mostly easy process.
 
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This sounds a lot like the noise I was getting when my fan was occasionally contacting the shroud on big bumps. The radiator mounting bushings were kind of collapsed and there was maybe half a cm between the blades and top of the shroud, it should be fairly centered. I would check motor mounts and radiator mounts if that clearance looks off.

Edit: I'm guessing you're talking about those little screeches you can hear when you hang the camera out
 
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Joined
Jan 21, 2018
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Southern California
Sounds like something just getting loose and rattling on the dirt road. It doesn't sound mechanical, but honestly it's really hard to tell from that video.

I know everytime I wheel or go on rough roads I can always hear some new noises after awhile. Stuff just gets moved around and loosened. Could be a skidplate loose and flexxing over bumps?
The interior is rattling around for sure, the windows are particularly loud over the washboards. But when the camera is outside the window you can hear the sound more distinctly. I did initially think it was something flexing and chirping under pressure, but I tried driving over some bumps slowly and at an angle to get things flexing, but nothing would happen. I also tried jolting over some speed bump type bumps but again, no luck. I hope it's not something rattling around because that sounds like a pain to track down! Thanks for the tip.
 
Joined
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Messages
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I've had some odd tapping noises under the hood of my BJ74. Air in the fuel lines was my diagnosis....mostly since I had issues with the fuel filter getting air in it and running poorly...discovered the soft fuel lines were 1986 original and cracked, and pulling air into the lines. Replaced "most" of those and the issue has largely gone away. (need to finish)

Worth checking, and a mostly easy process.
I wouldn't quite describe it as tapping, it was a pretty aggressive chirp - between a buzz and a chirp. I never realized how hard it is to describe a sound with a keyboard... but it is worth checking out. Thanks for the advice.
 
Joined
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Messages
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This sounds a lot like the noise I was getting when my fan was occasionally contacting the shroud on big bumps. The radiator mounting bushings were kind of collapsed and there was maybe half a cm between the blades and top of the shroud, it should be fairly centered. I would check motor mounts and radiator mounts if that clearance looks off.

Edit: I'm guessing you're talking about those little screeches you can hear when you hang the camera out
Correct - the very end of both videos with the bouncing chirp.

I'd imagine the sound you're describing would sound very similar to what I was hearing. I had my head out my window for like 2 days while camping, trying to figure it out, and It did sound a lot like something spinning was involved. The fan would make a lot of sense!
 
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Okay, then yes, from what I can tell that sound is pretty much identical to what I heard. It would also happen just like you're describing. Stumped me for a while and I could only really recreate it by driving fast enough on bumpy trails.
 
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I actually didn't because I was right about to swap the engine when I figured it out so it didn't matter. I'm sure there's a part number for the rubber bushings for the radiator, or an adequate replacement from a hardware supplier. More helpful though, to confirm this actually was the problem I put some colored tape inside the brim of the shroud, drove really fast on a crappy road by my house to recreate the sound, then checked for scuff marks.
 

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