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Brickers:
Alright, this is a long post but worth the read.
As some people may remember I hypothesized on the source of the sunroof sag issue a few months back. To summarize that post, I noted that the sunroof in my 1985 745t utilized a faulty design that placed too much tension/force on the metal braces that support the sunroof and control the venting action. I now have more information.
Using the two junkyards near my house as a testing ground, I closely examined the sunroof mechanisms from a variety of 700s across various years (noted by various design changes and front end modfication). What I discovered both frustrated and angered me.
Early 700s that I examined ALL (without fail) exhibited the defect mentioned above. What happens is this:
In 700 sunroofs there is a metal bracket on each side with two grooves in it. The front groove is long and closed at both ends. This groove allows a metal pin to slide back and forth, limiting and manipulating the sunroofs vent action. The second groove is closed at the top and open at the bottom, providing secondary (but pivotal) support for the venting mechanism.
When the sunroof is up ALL FORCE is applied to the small piece of metal (about 1/4" square) that closes the top of this second groove. This piece of metal is inadequate for the job, and over time the piece breaks from the combination of upward force applied via the levering and downward pull via springs and resistance.
The result is that the bracket snaps in two. Once it snaps in two, the back of the sunroof sags down in the resting position, and makes it IMPOSSIBLE to get it sitting right ever again. To diagnose your own, vent the roof, unlatch the springs, and look at the metal bracket that everything screws into between the car and teh sunroof panel. If it appears in two parts (going in two directions) it is split... it should be one long piece.
The interesting thing was what I noticed when I examined NEWER Volvos. (BTW, my years may be off since I don't have a very good way of telling the year of the vehicle being examined.) NONE of the newer volvos sunroof brackets were snapped, and all were in perfeect working order. One could posit that this is a factor of the car being newer, but 10 years is plenty of time for it to break if its going to malfunction at all.
Anyway, ALL newer volvos utilize a slightly modified design that redistributes the force applied to the metal bracket more evenly between the front and back of the metal bracket. It does this via one major change:
In the earlier models there is a metal arm approximately 2" long that reaches to a pin that sits in the aformentioned open ended groove. In the newer models this arm is replaced with a 5"-6" and reaches past the mechanism to th every back end of the bracket.
Additionally, there is a cross member arm extending from one side of the sunroof to the other that helps to push the brackets out slightly and keep the pieces oriented properly. This extender has springloaded ends that slip over silver arm extentions from the front groove. Instead of having the springs slip through holes in the little arms of teh front grooves (like the older models), the springs in the newer design have plastic O rings that slip sround the metal pins. Because of this and the enteder bar, the pull from teh springs is dissipated over the long surface of the enteder and arms. This furtehr lessens the strain on the metal brackets.
Basically, the extention of the control arms halves the force applied to the rear of the bracket by pushing some of it to the front, reducing the load on the weaker metal connection and all but insuring it won't break. FYI, the open ended groove is still there on the newer brackets, it just isn't used. I can only surmise that Volvo kept the old design for standardization and cost reasons; you could easily use the metal bracket in either design, fruthering my assesment of a cover-up at the highest levels of Volvo! ;P
So, what's an older 700 owner to do other than be pissed Volvo didn't replace the defective mechanism when they discovered it? I transplanted the main components into my 1985 745t's sunroof, and you may wish to do the same. You can't do the whole mechnaism without getting a whole sunroof (tracks and all) from a newer volvo, but you can get the main components.
Take all the components that hook the sunroof to the car at the rear, includin the levers, screws, cross members, etc. Even if you think you already have one, take the new one. Some parts have different groove sizes and connectors that you will need to finish the job. I found the easiest way to do this is to pull teh sunroof off (it only takes six screws to pop the top) for access and assemble the mechanisms off the car.
Sorry for the lack of photos, but I jumped into this one sunday when I had a free moment and didn't have time to get a camera.
Feel free to post with any questions, and goo dluck if you decide to fix it. Its not very difficult, just takes some time and logical analysis.
Regards,
Rick
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