Guide rods? - PeachParts Mercedes-Benz Forum

VW1300 · #1 01-19-2008, 11:41 AM

All this talk about ball joints and guide rods reminded me that when I bought my car a year ago, the mechanic who inspected it told me that my guide rods are "just starting to get loose".

Now a stupid question - is a guide rod the same as a tie rod? If so, is this the source of a "klunk" when I turn the wheel all the way to the left or right when I pull into a parking space? During normal driving, the suspension is quiet.

thanks,

rkohut · #2 01-19-2008, 12:10 PM

Quote:

Originally Posted by VW1300

All this talk about ball joints and guide rods reminded me that when I bought my car a year ago, the mechanic who inspected it told me that my guide rods are "just starting to get loose".

Now a stupid question - is a guide rod the same as a tie rod? If so, is this the source of a "klunk" when I turn the wheel all the way to the left or right when I pull into a parking space? During normal driving, the suspension is quiet.

thanks,

He probably meant guide rod mount. The guide rod is a non-adjustable solid metal rod that connects the front control arm to the guide rod mount which is mounted to the inner wheel well body.

The tie rod is a separate adjustable metal rod which connects the front-end steering system together.

Guide Rod Mount
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=28X1CH0HL2A30NWFX9&year=1983&make=MB&model=300-DT-001&category=L&part=Guide+Rod+Mount

Guide Rod
http://catalog.worldpac.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=28X1CH0HL2A30NWFX9&year=1983&make=MB&model=300-DT-001&category=L&part=Guide+Rod

Shawn D. · #3 01-19-2008, 02:46 PM

Quote:

Originally Posted by rkohut

The guide rod is a non-adjustable solid metal rod that connects the front control arm to the guide rod mount which is mounted to the inner wheel well body.

Sure, the guide rod itself is non-adjustable, but that's like saying that a tie rod sleeve is non-adjustable. The guide rod assembly (the guide rod and guide rod mount together) is indeed adjustable and that's how the caster is set. The guide rod mount has a threaded stud which goes into the guide rod, and that threaded stud is turned to adjust the caster.

sixto · #4 01-19-2008, 04:06 PM

The guide rod has that ball joint in the rear and also some rubber biscuit bushings in front which require the spring to come off for replacement.

The typical symptom of worn guide rod bushings is a clunk as you come to a stop, as the weight of the car shifts forward on the guide rod.

Sixto
87 300D

VW1300 · #5 01-19-2008, 10:40 PM

Well I don't hear a clunk when I stop, but I do when I crank the wheel all the way left or right. Is that a tie rod end? It is very possible that my memory does not serve correctly and the mechanic said "tie rod"...

If so, does one replace just the outer tie rod ends, or do the whole thing and not worry about it for another 100,000 miles?

d.delano · #6 01-20-2008, 03:15 AM

I have the same symptoms and just replaced the guide rod mounts and bushings. I vote for lower ball joints.

Shawn D. · #7 01-20-2008, 11:49 AM

Quote:

Originally Posted by VW1300

Well I don't hear a clunk when I stop, but I do when I crank the wheel all the way left or right. Is that a tie rod end? It is very possible that my memory does not serve correctly and the mechanic said "tie rod"...

If so, does one replace just the outer tie rod ends, or do the whole thing and not worry about it for another 100,000 miles?

I've never heard a tie rod make a "clunk" -- I've always heard a groan. In any case, the outer tie rods see much more wear than the inner, so if they are a problem, you could probably get away with just doing the outer ones, which is what I did on my 300td. On my BMWs, though, a whole tie rod assembly (inner and outer tie rods w/ sleeve) is just about the same price as one tie rod end, so I usually just change the whole thing.

That having been said, I'd look at the sway bar end bushings and sway bar mount bushings. The way W123s are set up, these perform a fore-aft locating function and see forces when braking and turning the wheels.

hey_allen · #8 01-20-2008, 12:38 PM

Mine seems to be clunking from the guide rods, but I saw it RUSTING in the guide rod bushing when I was down there doing a starter change.

No points for guessing what the next suspension replacement is going to be!

VW1300 · #9 01-20-2008, 02:32 PM

Quote:

Originally Posted by Shawn D.

I've never heard a tie rod make a "clunk" -- I've always heard a groan. In any case, the outer tie rods see much more wear than the inner, so if they are a problem, you could probably get away with just doing the outer ones, which is what I did on my 300td. On my BMWs, though, a whole tie rod assembly (inner and outer tie rods w/ sleeve) is just about the same price as one tie rod end, so I usually just change the whole thing.

That having been said, I'd look at the sway bar end bushings and sway bar mount bushings. The way W123s are set up, these perform a fore-aft locating function and see forces when braking and turning the wheels.

Well it's a groany sort of clunk. I'm thinking I'll change the tie rods, because it's easy, not expensive, and the car could probably use it anyway. Besides, the car needs a front end alignment as it is - it pulls a little to the right. While I'm in there I'll look at the sway bar mount bushings - by the way, what am I looking for in terms of signs of wear - general loose feeling, cracked bushings, the usual, etc?

If the tie rods don't solve the clunk/groan problem, I'll look into the ball joints. For the record, is this something that any good mechanic can diagnose and handle? I have a very competent, trusted regular mechanic near my house I'd rather use than my local Mercedes specialist, who is also good but tends to try to fix everything whether or not it is necessary at the moment. I've read up on the ball joint procedure and it's something I don't really have the time or patience for right now.

thanks,

hey_allen · #10 01-20-2008, 05:15 PM

If the 123 ball joints are anything like the 126 one, you'll need a mechanic with the special ball joint press to install the lower ball joint. I tried working out a way without it, but no joy.

I ended up finding out that none of the local MB dealers had the tool anymore, and neither did the first indy that I was referred to.
I finally found an indy that did, and it almost tipped over the bench that the vise was installed on, when trying to put enough torque on the installer to drive the ball joint into the spindle!