Source of Low Pitched Knock?

[appro Lurker Find all posts View Profile Close appro]

My 2005 Prado has had a low pitched knock coming out of it since I purchased it about a month ago. I wish I was the sort of person who can ignore these things, but they drive me nuts. I can hear it when going over rough surfaces around town and it gets worse as the surface gets worse. It's not a suspension type noise, but rather something bumping against something else.

From the driver's seat I can't really tell where it's coming from. I've been told that the front alloy bar can be the culprit. I'm also suspicious of the rear plastic bumper. The way it's secured to the rest of the vehicle doesn't strike me as the most sturdy piece of engineering that I've seen. If I bump the rear guard with the heel of my hand on the corners it makes a noise that could possibly be what I'm hearing, but I'm not sure. I've crawled around under the vehicle several times looking for anything obvious but can see nothing.

I thought I'd nailed it when the guys at Opposite Lock found a loose rear trailer plug relay floating around inside the back panel, but after securing it the noise is still there.

Is there anything common that might be causing this? I thought I'd ask the question here before I start taking radical steps like removing the rear plastic bumper to see if that makes the noise go away. My reasoning here is that if I remove the bumper and the noise disappears, then I'll know where it's coming from and hopefully be able to take steps to rectify it. Any suggestions are appreciated.

[Madkore Avid PP Poster! Find all posts View Profile Close Madkore]

Re: Source of Low Pitched Knock?

I hear ya appro - I have an undiagnosed noise which comes from around the steering wheel column and have spent many a waking hour looking for the culprit, but to no avail!

I wish I could help you but the best way is to try and nail down roughly where it is coming from, and try a few different scenarios to pinpoint its location.

From your description, you state it may be coming from the front alloy bar, or the rear bumper, which to me says you have absolutely not a clue whats causing it! :lol:

Unfortunately knocks or bumps may be caused by any number of issues (4wding, mechanic not putting something back correctly, damaged parts)...

I can only offer my empathy!

[dereki Member Find all posts View Profile Close dereki]

Re: Source of Low Pitched Knock?

I had a knocking that was driving me nuts... some small corrugations on bitumen would cause it.
It was hard to tell where it was coming from, I thought steering, suspension, side deck (was loose but not the one) etc. etc.

It turned out to be the alloy bar. The drivers side where the top tube wraps and joins to the main bar next to the
headlight. There is a bolt on the inside of the main part of the bar, visible from under the car... 1/2 a turn to
tighen... ahhhh noise gone.

D

[appro Lurker Find all posts View Profile Close appro]

Re: Source of Low Pitched Knock?

OK. I'm about 90% sure that I've nailed what's causing the knock. I'm fairly sure that it's the RHS front where the noise is originating. Since my last post I've had the missus take me for a drive down a corrugated dirt road while I sat in the dog box and I've decided the noise is definitely not coming from the rear. I also can't hear it as loudly when sitting in the front passenger's seat. It's loud and clear when I'm driving though.

On close inspection I've noticed that the Toyota alloy bar is sitting much closer to the body and headlight on the RHS of the vehicle. There are also a couple of small wear marks on the body that could only have been caused by the bar touching as it vibrates around. I loosened all the mounting bolts on both sides to try to drop the RHS a bit, but no luck. I guess the next step is to pay Toyota or ARB or someone else to adjust it for me. This is probably going to be a reasonable size job as the mounting holes will probably need to be elongated a bit so the bar can drop on the RHS.

It's a bit annoying that it looks like the bar has never been mounted correctly from the start. Has anyone else had a knock that they've traced to the alloy bar touching the body? Is this sort of thing common?

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Re: Source of Low Pitched Knock?

OK. I'm about 90% sure that I've nailed what's causing the knock. I'm fairly sure that it's the RHS front where the noise is originating. Since my last post I've had the missus take me for a drive down a corrugated dirt road while I sat in the dog box and I've decided the noise is definitely not coming from the rear. I also can't hear it as loudly when sitting in the front passenger's seat. It's loud and clear when I'm driving though.

On close inspection I've noticed that the Toyota alloy bar is sitting much closer to the body and headlight on the RHS of the vehicle. There are also a couple of small wear marks on the body that could only have been caused by the bar touching as it vibrates around. I loosened all the mounting bolts on both sides to try to drop the RHS a bit, but no luck. I guess the next step is to pay Toyota or ARB or someone else to adjust it for me. This is probably going to be a reasonable size job as the mounting holes will probably need to be elongated a bit so the bar can drop on the RHS.

It's a bit annoying that it looks like the bar has never been mounted correctly from the start. Has anyone else had a knock that they've traced to the alloy bar touching the body? Is this sort of thing common?

The alloy bar on my work Colorado dual cab 4x4 does exactly this. You pull it out and after a couple of weeks it creeps back onto the front left fender below the headlight and starts to knock. Put the car into Holden and they pull it out as I do and it just seems to keep coming back. Next thing I might try is to put a rope around the bar and tie it to a tree and reverse a little and see if I can reshape the bar to stop the knock.

I think a sand dune down south might have been the culprit with this problem as the front bash plate has a little bend in it as too the number plate!