Odd suspension squeak

[itsdancarl]

I have a 1994 Ls400 with an odd suspension squeak. The squeak only happens when braking. Definitely not a brake squeak. The squeak sounds more like a chatter and gets louder depending on how fast I'm braking. But this squeak does not happen when in reverse. I've replaced the UCA on the driver's side because the ball joint boot was torn. Both front struts are brand new, and just today I took the sway bar bushings off and greased them. Sway bar endlinks don't have play, and the rest of the ball joints don't have play. Still the same noise. Any suggestions on what it could be?

[fsuguy]

Hi itsdancarl,

This is a bit of a long shot, since "chatter" is not clear to me.  However, if you have a "clunk" when you go over a slight bump, bumpy roads, or when you are moving fairly slowly and hit the brake, soft or hard, it is possible that your front strut rod bushings are either worn out or have reached the end of their usable life. 

For the first generation LS400s, this bushing is a pretty thick rubber bushing (about 1") and around 3" in diameter sandwiched between two steel plates with 3 bolt holes around the perimeter, and a single one in the middle.  Do not confuse this SRB with a lot of info on this forum with the other, later model SRBs, which will get very confusing in a hurry, since the later models have a different design.  To replace the Gen 1 SRB, from the front of the car, at ground level, looking below the bumper, look for a large nut with a threaded bolt end facing forward near each wheel; these are on the two strut control rods which face forward and at a slight angle to the front of the car, and pass through the center of the SRB; the SRB is mounted to the frame with three smaller bolts.  The strut rods are designed to help maintain the strut geometry and  alignment.

To change the SRB on the Gen 1 car, it would help you to first get a good idea of what you are working on, so first loosen up one front wheel, jack up the car and safely support it, then  take off the front wheel and identify the steel rod, and its general direction. 

Once you have the wheel off, look for a steel rod about 3/4" in diameter, roughly but not quite parallel to the ground and angled slightly toward the  front center of the car - this is the rod which goes through the bushing.  Once you know this, you will have a pretty good idea of where the nut is and can easily locate it from the front of the car. 

Next, using a properly fitting socket and large ratchet (3/4") drive and a breaker bar (you will need the torque and leverage), loosen this nut.  Note that there is another large nut on the other side of the bushing, and that one should not be loosened - doing that will alter your alignment characteristics, so DO NOT tinker with that second large nut.  Once the front large nut is loosened, remove the three smaller (12mm or 13mm) bolts securing the SRB to the frame, and the SRB can now be removed. To get the 3 smaller bolts loose you may need to use a smaller socket drive and/or wrenches , since if I remember correctly, one of them is slightly harder to get at than the others, but not extremely so.  After these 3 bolts and the front nut are taken off, you should be able to work off the bushing - the whole sandwich assembly should come off as a single unit. 

Installing the new SRB is simply the reverse of the removal procedure, and you may have to work a bit at getting all the holes aligned to get all the bolts re-installed.  Whatever you do, don't get tempted to loosen the large nut at the back of the rod; also, do not tighten the large nut on the strut rod before the 3 bolts are installed and tightened. You should be sure to get the torque specs and use them.  Finally, once the 3 bolts are torqued correctly, with the car on the stands, tighten the large nut fairly tight , but not to final torque specs - you will want to do that when the car is on the ground and the bushing is under load.  This will prevent the SRB from early failure.  Total time to do this (both sides) should take you an hour at the most, if you have the correct tools on hand, and you don't foul things up!  

Finally, I apologize for not providing the correct tool sizes and more exact instructions, since I did this a few years ago, and exact processes have been forgotten.  Will try and clean this info up and post it as a how-to with pictures soon. Good Luck!!

 

Edited January 11, 2018 by fsuguy
terminology correction - bearing for bushing

[M.Yasir]

If the squeak is coming while you are breaking i would check the life of my break pads or the health of the rotor which would need turning