1998 Clunk From Front Suspension When Going Over Speed Bumps

[rhkwon]

Whenever I drive over some speed bumps at a moderate speed (5-10mph) it feels as if the front suspension is knocking metal to metal. Or when I drive over a crack in the road it does the same thing. When I swerve sharply left or right it does'nt do this. Nor is there any sound or problem driving at all other speeds either in the city or on the highway. It almost feels like some kind of rubber bushing has gone out. The shocks seem fine.

Any suggestions as to what this may be?

[1990LS400]

A rubber bushing has gone out.

How many miles are on your car? Have any front suspension components been replaced yet?

I've got about 112,000 miles on my similar 2000 LS400 -- the first front end components to go were the strut rod/bar bushings at 70-80,000 miles. Based on my previous experience with a 1990 LS400 from new until 183,000 miles, I assume that eventually I'll be replacing all the ball joints -- don't remember at what mileage the ball joints were replaced on the 90 LS but I think it was between 125,000 and 150,000 miles.

[rhkwon]

It's got 90,000 miles. I guess that's what it is, a rubber bushing or both rubber bushings. Expensive to replace?

[1990LS400]

A Lexus dealer replaced my strut rods including bushings in May 2007 -- about $250 parts and $325 labor. The indie Lexus repair shop I normally use would have done it for a little less but they had a temporary equipment problem. New bushings can be pressed into the existing rods but the labor charge of doing that can be more than replacing the entire strut bar assemblies -- depends if you are going to do it yourself and have access to a press.

This article explains why the "semi-longitudinal tension rods and bushes" wear out quickly on the 98-00 LS400: http://www.autospeed.com/cms/A_3041/article.html

If you don't know what the strut bars (or whatever you want to call them) are, kneel down and look ahead of a front wheel -- you will see the strut bar running from the wheel suspension towards the front of the car.

[PureDrifter]

strut rod bushings for sure. tbh i have the carson polyurethane ones and they ride/feel fine and are much cheaper, but squeak/creak like hell, regardless of the lube used.

[rhkwon]

It's annoying as hell and aggravating to feel that clunk going over bumps and ruts. Thanks guys. That's why I love this board.

[Slvr99LS]

These guys are spot-on... it's the strut bar/rod bushings. I just did mine on a '99 and it made a world of difference in everything from steering to braking, not to mention finally being rid of that aggravating 'clunking'. It's a decidedly un-Lexus-like sound. '84 Chevy Cavalier... maybe. Anyhow, I opted for the less costly, though far more labor intensive method of replacing just the bushings rather than simply swapping out complete new bars. Hey, times are tough and those bucks add up.

Using a lift is highly recommended, if not mandatory for this job. Once the bars were removed from the car, (you'll need an impact gun or some good sized breaker bars for some of the bolts/nuts... and a torque wrench for reinstallation) cut a thin slot through the rubber and the outer metal shell of the old bushings with a Sawzall and they pretty much fall right out with a couple quick whacks with a hammer. Or a press would certainly do it, but I didn't have one handy at the time. It was clearly evident upon close inspection just how far the rubber had deteriorated after 10 years. These bushings are under a ridiculous amount of stress with this particular suspension design. Once you've studied the geometry, it's a wonder honestly that they last as long as they do.

After everything I'd read on the forums prior to undertaking the job, I figured a press would also be required to get the new ones driven home, but it fortunately wasn't the case. With a good friend laughing, shaking his head, and assuring me I was nuts to even try it (I take that as a challenge).... I had the new bushings chilling in the freezer for a few hours, plus made sure to carefully lightly sand clean both surfaces. Then, using a simple large bench vice and a suitable diameter pipe to carefully push against the outer shell of the new bushings.... and.... they're in. Not bad at all. The laughter ceased too. :) After working out the procedure for doing one side, the other side progressed far more quickly. The lower strut mount does have to be unbolted from the hub which was no problem with that corner of the car supported. A small scissor-jack worked like a charm and also allows for precise height adjustment while you're realigning all of the bolt holes - sometimes easier said than done. Assuming you want to do it yourself, I'd say a realistic figure would be 4 - 5 hours labor total including futzing around with removal of the old bushings. In retrospect, to do it all over again, I'd likely recommend just buying the complete new bars. That would make the job almost a cakewalk. Hope this helps.

[amcdonal86]

It could be strut rods, but don't overlook strut tower mounts.

[nc211]

It's your strut rods. If this is your first problem with the suspension on the car, then 99% sure it's those rods, as they're almost always the first to go. My advice? Avoid the dealership altogether on this one, and buy them online, then take them to an indi-mechanic. I would say you can do these yourself, but you need a few tools first, and probably not worth the extra $200 to mess with them.

You can buy them online for about $95 a piece "you need two of them, do this repair in pairs" from www.parts.com to avoid the stealership's prices.

You're looking for #12 in the attached photo "Strut Rods", in the "Front Suspension" section, under "Components".

The strut tower mounts "The rubber seat at the top of the shocks - you can see them under the hood" probably aren't ready yet. You'll know when they are, as they give a "pop" noise only when hitting harsh bumps at around 20 mph. You'll also beable to zero in on where you're hearing the noise from inside the cabin "high, or low and under the car". High = Strut mounts. Low & under the car = strut rods.