Jacking a 450SL with hard top off - PeachParts Mercedes-Benz Forum

78 450sled · #1 03-12-2007, 07:01 PM

Hello...I have had my 78 450Sl for about a month and it's time for new tires. I have heard that on some cars it is NOT good to jack it up with the hard top off. I have a Porsche 928 and they say not to jack it up with the doors open or it will break the windshield. I'm going to keep the doors closed but I was wondering if anyone has heard anything bad about jacking 450SL's up with the hard top off. It was 80 here today so I don't want to put it back on unless I have to.

Strife · #2 03-12-2007, 08:36 PM

I find NO mention in any manual that the hardtop should be on (only) for jacking up a 107. This is a really strong, ridgid car, and I don't think there would be any problem at all. However, I would NOT do this in ANY convertible with the door or doors open.

TRUE: In high school, some classmates made a convertible for themselves by cutting the roof off of a Buick and tarring the back and cowl, and removing the carpets (it already had drain holes in the floorboards from rust). From 10 feet away, it actually looked pretty good. Fun ended after they got a flat, and jacked up the car. They couldn't open the doors after that!

page62 · #3 03-12-2007, 09:34 PM

There's a reason the designers of this car called it "der Panzerwagen" (the tank). Go take a closer look at the frame rails along the door sills. Of all the convertibles ever made, chassis flex is probably less of an issue with this car than any other! Even doors open or shut aren't gonna make a difference...

If you do experience ANY flex while jacking...you've got serious issues. Just be sure to use the "approved" jacking points as shown in your manual or repair book.

PS: I wouldn't know what it's like to jack my car with the hard top on...it hasn't been on the car since the day I bought it! (And that was the first time in 10 years it had been on the car!)

Furndog · #4 03-13-2007, 03:44 PM

So if I have my car on jack stands, and they are at the approved points by the manual, and I have some sagging in the back end. What could be the cause of that?

page62 · #5 03-13-2007, 05:45 PM

Quote:

Originally Posted by Furndog

So if I have my car on jack stands, and they are at the approved points by the manual, and I have some sagging in the back end. What could be the cause of that?

What exactly do you mean by "sagging"?

Furndog · #6 03-14-2007, 09:11 AM

When I jack the backend of the car up to put on the stands I use the differential to lift the car up, and then put the stands on the hinge points where the rear suspension attaches at the end of the frame rails. When I release the floor jack, the rear section of the car settles down a couple of inches. I noticed it when the space between the the hard top and the rear deck was wider than usual. I know that most cars have some flex built in, but is this unusual, or do I need to set the jack stands in a different place?

Thanks for any insight on this situation.

Roncallo · #7 03-14-2007, 12:52 PM

One of the things I have found with the 560SL is that the frame is extreamly stiff. The concreat floor in my garage is level enough that you can not tell by walking on it that there are any low spots. But every time I put my car on stands that are set to equal height I usually find that one stand is loose.

Essentially if the stands are located forward of the rear wheels and aft of front wheels you should at least be flexing the frame less than if the car is on the ground with weight on wheels.

Now if you put the stands in a dumb location like under the floor boards you will cause local damadge to the vehical in that area but the structural part of the frame should not flex.

If you have excessive flexing, you really need to take a look at why.

John Roncallo

Furndog · #8 03-14-2007, 02:41 PM

Thanks John. My 450 never does seem to sit exactly even on all four stands either.

I guess my question to this topic is that if I feel that there is excessive flex in the car, and considering the weight of the suspension and the fact that the wheels are not on the pavement when on jack stands, what do I look for that may indicate a problem? The frame and the bottom parts of the car all look solid from what I can see laying under the car, is there other areas that I need to check?

page62 · #9 03-14-2007, 03:26 PM

Here's some wild speculation...

It may not be your frame. It's possible the body mounts are worn out or loose, and what you're seeing is excessive body movement in relation to the frame when you change the jack points from the diff to the suspension mounting points.

Well, at least it sounds convincing...

Furndog · #10 03-14-2007, 04:04 PM

I am fairly sure that the body mounts are both worn out and loose. More likely dried out, from the looks of the other rubber things underneath the car. I actually have the subframe bushings on the short list to be replaced. All that I have read on these posts states that new bushings will greatly improve the road feel, and perhaps reduce some of the flexing.