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1300L Windshield Channel Drains?

2K views 17 replies 8 participants last post by  TRUKTOR 
#1 ·
Reportedly a design flaw of a 1300L is that water can get trapped in the windshield rubber channel at the corners of the windshield and can cause rusting in those areas. I have seen references to installing drains but not a lot of details. The seller, George Bull, mentioned that the best approach was to put a small dent in the sheet metal at each corner to drain any water out of that area. I managed to break a wind shield this past weekend so that repair has moved to the top of the list while the windshield is out. So is this the best option or are there other methods of dealing with this?
 
#2 · (Edited)
Yes, it is a weak spot, one that is not unique to UNIMOGS. As you no doubt know, the rubber gasket is basically an I-beam shape, with the inside
Of the channel in the gasket holding the glass, and the outside channel latching onto the weld / pinch seam which defines the opening.

Water then, actually has two places to collect - the inside and outside channels. The inside one is not much of a threat, since it is pooling where
It Is just glass and rubber - nothing to rust. It can lead to issues with the Glass, especially if laminated, and bubbling and fogging can happen.
The rain hits the glass, runs to the edge of the gasket, weeps In and tends to follow gravity , pooling at the bottom.

The other channel, the outside, does the same thing, and it is worse because it is trapped next to a painted surface, and worse yet, one that has an exposed, essentially unfinished edge. The paint bubbles, the raw steel is exposed, and the rust demons get to work. The 4 corners can be the worst hit, but really, the rot can happen all along the opening.

What to do ? Well, 'dents' at the lower corners could work, but they don't do a thing anywhere else. I have photos that show severe rust rot Along the the top and into the top corners, so gravity does not come close to getting all of the water to the bottom corners.

I think the number one thing to do is to invest in a new gasket. Before you even take your windshield out, you can check for problems with a Plastic putty knife or trim tool, opening up the lip of the gasket and looking underneath. If you have rust, you'll see something, and then you'll See more when the glass is removed.

Next, even with a new gasket, your local Auto Glass Pro (or pros) should be be consulted. The guys I know are of two schools : Goop, or no Goop.

Some will run a bead of glass sealer/caulk all the way Around after The installation, some think a 'Dry' installation is best.

Of course, salted winter roads make it all that much worse.

Instead of dents, I'd suggest thin nylon washers or shims that will create a drain or air gap, without dinging your paint. The gasket will hold them in place. Like a dent, they will actually open up a channel for more water to get between the gasket and the paint......but then they also open up a drain and some air flow to dry stuff out. With a dent, you are committed, but with shims, you can move them around or take them out if you want.

Honestly, I think a new gasket and a smooth mating surface ( good paint, not rust ridges) is the best, and then just
Monitor it.

More later, but I have some work to do..
 
#4 ·
I am having the glass tech remove the windshield tomorrow hopefully in one piece to make a pattern. I have a new Mercedes rubber gasket coming next week so I I will have some time to inspect and hopefully figure how and why it rusts. I do like the plastic shim concept in place of dents. George had 4 ambulances he imported and all four had various levels of rust showing predominately on the drivers side lower corner. He also had one that was reconned and painted by the German military for Ebola duty, that never got dispatched and went to surplus, it also doesn't have dents.
 
#5 · (Edited)
My green one had the problem -The lower passenger corner and just above the passenger side Wiper were the worst,I think. I pried up the gasket and slathered rust killer gel inside and out. I started checking it a little obsessively, and after driving in the wet, it was always wet. I was surprised to find the pooling on the glass side.....I eventually got one of those 'micro tip ' vacuum kits, the sort of thing that you clean
Your laptop keyboard with.....a little nuts, OK.
I'd wedge the gasket open and suck all of the water out with a necked-down shop vac with the micro tip.It worked, and I'd leave the wedges in until it was dry......just exactly the drill you want to impose on yourself after driving the world's premier off road truck in extremely severe conditions......
Like, uh , Rain.
It was my choice, I'll say that.
The Unimog was over 20 years old at that point, and I reckon that the gasket was original.
 
#6 ·
Also, when installing a new gasket - in my experience, the installers want to do so dry - a mistake in my opinion. The mog gasket appears to be a complex beast and it did not seat properly or willingly in my case. After the installation, I had to go around and lift the edges, squeeze some rubber friendly lube in there and went around with a rubber mallet several times to make it seat nicely (properly).
 
#7 ·
My 1986 U1300L experienced rust on the bottom two corners, a bit in the bottom centre, but the worst spot was at the top right hand corner. We ground it all out and lathered in the anti rust paint, anti rust goop and then filled the holes with a glass fibre impregnated filler. At least when the water lies there it's no longer lying on metal. We added a couple of drains. Can't say if they work or not, but it looks the part. You can just make out the drain in the attached photo.

The telltale is a rusty water mark at the corners of the window along the bottom edge of the window seal. Lift up the outer edge of the seal and if there is rust it should be easy to spot.
 

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#10 ·
I think that one thing that contributes to the problem is the particular contour of the Unimog sheetmetal . The 'pinch weld ' that the gasket grabs sits recessed a bit. This 'shelf' creates a void that can hold water, more so than if the pinch weld was not so deep, compared to the face of the A-pillar. The gasket is made to fill this void, but when it leaks, you have a relatively large area that Stays wet.

Also, you might as well check your two rear window gaskets for the same problem. It happens there as well, although probably not as often. It can be Pretty nasty , however.
 
#11 ·
The glass folks stopped by and pulled the windshield, plenty of blistered rust in the corners along the lower lip, not so bad up top or along the sides. No obvious holes but that might change once I do a good clean up as some of the blisters look ugly. It outdoors and we are in rainy spell so I it will take a few days before I can tear into it.
 
#12 ·
I hit the drivers side with a wire wheel and found far more rust than expected and several small holes. The factory paint system is quite robust, in many spots pinholes in the paint covered much large areas of rust underneath. The actual lip where the gasket is located is in good shape except the drivers side lower corner. It definitely is on the edge of needing a small piece welded in. Given that I plan to do a repaint in the future and will be pulling the windshield anyhow, I am going to hit it with rust converter, paint it up good and seal up the holes with epoxy and smooth any cracks and crevices on the lower lip. I also applied the dents in the sheetmetal as suggested by the seller since the paint had to be removed in this area to deal with the rust that had creeped under the paint. At the future point where the repaint happens I will plan on some weld repairs.
 
#14 ·
Thanks Scott, I did put in dents but far less aggressive. The windshield is in and with the new rubber gasket my dents appear to be sealed over. It going to come out at some point when the cab gets painted I expect I will revisit the dents and pound them in more.
 
#15 ·
For installing the windscreen, put a piece if string in it all the way around, bringing both ends past the other at the bottom. Spray everything with some soapy water, and set the lower channel on the cab flange. Hold the glass into the cab as you pull the string out.

Done.

You will be amazed how well the string works if you have not tried it before.

C.
 
#16 ·
I'm sure the larger, cupped drains in the lower corners will help in those areas, but the evidence shows that the moisture can be held in anywhere around the perimeter of the
gasket.
The center of the bottom chord, and the whole top chord, especially the upper corners tend to be problem areas,so I don't think the factory solution is necessarily the end-all and be-all solution.
 

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