• Advertisement

underbody knocking noise

For all suspension modifications

underbody knocking noise

Postby sirprosper280d » Tue Oct 25, 2011 2:22 am

Got a 2002 Isuzu KB 280 DT LX. Happy with the performance, power and comfort. However, of late am hearing an underbody knock sound on my driver side footwall. the noise is as if something is knocking hard just under the footwall and is audible. the noise occurs when i make turns even at low speed. at high speed it occurs on sharp curves. the same noise occurs on bumpy roads. checked all suspension bolts and side excalliper bar all tight. what could this be?
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby Yarno » Tue Oct 25, 2011 6:29 am

Check the U-bolts on the RHS of the rear diff, these sometimes come loose or move from their original position resulting in a knock sound through the car.
User avatar
Yarno
FAQ Team
 
Posts: 291
Joined: Sat May 09, 2009 8:11 am
Location: Aspley
Age: 36
Country: Australia
City: Brisbane
Vehicle: Isuzu MU 93 V8 monster, Toyota Landcruiser 200 sahara. MU 1996 3.1.

Re: underbody knocking noise

Postby geeves » Tue Oct 25, 2011 2:26 pm

I have a similar knock due to bent exhaust. If its this it might be easier to put up with it till the exhaust rusts out. Front sections take a long time to rust though
Sanding your knuckles before starting work can help. That way you cant skin them
User avatar
geeves
Site Admin
 
Posts: 8193
Joined: Sun May 10, 2009 1:36 pm
Location: wellington
Age: 55
Country: NZ
City: Wellington
Vehicle: 94 bighorn
96 wizard

Re: underbody knocking noise

Postby turnturn » Tue Oct 25, 2011 2:49 pm

Top or bottom suspension arm bushes?
Sway bar bushes?
My money is on it being something rubber failed or failing.
User avatar
turnturn
Global Moderator
 
Posts: 887
Joined: Wed May 13, 2009 4:26 pm
Age: 51
Country: New Zealand
City: Dunedin
Vehicle: 1992 Isuzu Mu 2.8 Manual (UCS55)
Snorkle, Intercooled
1993 Isuzu Mu 2.8 Manual (UCS55)
Spare Parts/Donor
1994 Isuzu Mu 3.1 Manual (UCS69)
Snorkle, Intercooled
1996 Isuzu Mu 3.1 Manual (UCS69)
Completely Standard

Re: underbody knocking noise

Postby sirprosper280d » Tue Oct 25, 2011 8:27 pm

Thanks guys i will check all the areas highlighted; U-bolts, exhaust lines and front suspension bushes. i will keep you posted on the findings. is it safe to continue drivining the car behaving this way?
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby geeves » Wed Oct 26, 2011 2:46 pm

That would depend a lot on the cause
loose diff no
loose bushes maybe
loose exhaust yes
Sanding your knuckles before starting work can help. That way you cant skin them
User avatar
geeves
Site Admin
 
Posts: 8193
Joined: Sun May 10, 2009 1:36 pm
Location: wellington
Age: 55
Country: NZ
City: Wellington
Vehicle: 94 bighorn
96 wizard

Re: underbody knocking noise

Postby sirprosper280d » Wed Oct 26, 2011 3:35 pm

managed to check diff U-bolts yesterday night. they were loose offcourse though tightening them didn't solve the problem. i will check bushes and exhaust line.
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby sirprosper280d » Mon Nov 07, 2011 6:46 pm

Checked front suspection arm bushes, sway bar all intact. Exhuast line looks okay all bolts in place and tight. next step is to completely take out the exhaust line and drive the car to verify if the knock is coming from the exhaust. will keep you posted on frinding.
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby sirprosper280d » Mon Dec 05, 2011 10:20 pm

On what side of the torsion bar is the Bump Stop located?
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby jellis » Tue Dec 06, 2011 11:11 am

check that your body mount bolt is tight.
cheers, Josh
jellis
Isuzu Guru
 
Posts: 414
Joined: Sun May 10, 2009 10:23 am
Age: 26
Country: australia
City: sydney
Vehicle: 1992 isuzu mu 2" lift all round
33"x 12.5 federal's

Re: underbody knocking noise

Postby sirprosper280d » Thu Dec 15, 2011 10:43 pm

To my surprise the underbody knock sound disappeared yesterday. i drove the car as hard as i can to shake it out and see if the noise is still present. had planned to check torsion bar bump stop and underbody mounts this weekend, so i will just go ahead with the inspections. thanks guys
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.

Re: underbody knocking noise

Postby sirprosper280d » Thu Aug 30, 2012 7:54 pm

the underbody noise resurfaced, and a closer examination revealed scratch marks on both exhuast pipe and torsion bar. am confident to conclude this to be the root cause of knocking sound. the exhaust line from the engine pass just on top of the right torsion bar and leaves a clearance of roughly 20mm. obviosly this causes the torsion bar to hit the exhuast pipe on bumps or sharp turns. checking on another KB280DT the exhaust line does not pass over the torsion. am planning to have that position of exhaust line (between engine exhaust manifold flange and silencer flange) removed and rerouted properly to avoid interefence with the torsion bar. will update you on the outcome. thank guys for your invaluable contributions.
ISUZU DIESEL
sirprosper280d
Isuzu Baby
 
Posts: 39
Joined: Sat Apr 23, 2011 3:12 am
Location: Zimbabwe, Zvishavane
Age: 33
Country: zimbabwe
City: zvishavane
Vehicle: 1997 ISUZU KB280DTLE, 2002 ISUZU KB280DTLX, 2001 KB280DTLX, 2002 KB300TDILX, 2006 KB300LX DMAX.


Return to Suspension

Who is online

Users browsing this forum: No registered users and 1 guest