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MG MGB Technical - windscreen removal and reinstallation
|I'm polishing up the paintwork on my garage find and have got to the panel under the windscreen and am pondering removing it (the windscreen that is) to make access easier. I also have some rusty bits to deal with either side of the T section seam filler. The nearside side of the windscreen is also a bit high as the rubbers under that side are not compressed at all meaning it will leak. So I need to loosen up the bolt that side and lower the screen slightly. I have not done this before and am wondering if this could become complicated getting everything to line up again. Is this straightforward or are there any specific problems I'm likely to come up against?|
|If you can I would say don't touch it! It can be a real struggle getting it back. You risk possibly cracking the screen then you have the whole replacing the glass headache (you REALLY don't want to go there if you can help it). Once you remove the screen you might find the bottom seal needs replacing and that's a bugger of a job which then makes replacing the frame extra difficult. |
Also it's tricky to do anything with the screen with the dashboard in place and removing that can also open up a huge can of worms. Refitting the frame in the exact same palce might be tricky meaning you might then have to fiddle with the quarter light alignment.
To really fix the rust in the seams you probably want to remove the front wings. Otherwise all you can do is scratch the surface. The leaks under the rubbers you can fix with some black windscreen sealer goop. The stuff that never sets fully works well. I used that under the bottom rubber when I installed my screen.
My experience is fitting a new screen (then removing it after the glass cracked, replacing that and refitting it) so it might be different removing and replacing an existing one.
I've found anything to do with the windscreen is one of those jobs you need a healthy supply of swear words for!
|I removed and replaced my screen for repainting single-handed and had no problems at all. Can't say the same for when I had to have the glass and glazing seal replaced, and they chose to replace that bottom rubber seal as well, that was a right pain. Simply pressing the screen down is theoretically possibly by slackening the bolts, but depending on what is under the seals and why one side is high, could make that a non-starter if it has always been high since the last time the screen was fitted.|
As far as the filler strip goes there is only one way to derust that and the adjacent panels and that is to remove the wings, which entails removal of the roadster screen, and replace the filler strip.
Plenty of the old-fashioned non-setting screen sealer that Simon mentions should prevent any leaks, don't use the modern stuff as that is *adhesive* to glue the screen into the frame as that is part of structural strength.
What ever you do you must check the alignment to the quarter-lights before 'finishing' the car. The quarter-lights must only just touch the seal that is attached to the screen uprights. If this rubber seal is being compressed as the door is closed, then you run the risk of getting the 'Crack of Doom' in the door skins.
|I'm just doing some cosmetic work at the moment. Any major spray work I'll leave til next year but I have some rust 'fingers' making their way out from the seam. The point about the quarterlights is relevant for me at the moment. The gap between frame edge and quarterlight edge is not uniform and there is quite a bit of compression towards the bottom of the screen. The drivers side is especially bad, so much so that the PO had removed the sealing strip down the edge of the screen. I have put this back but it is stopping the door shutting properly. Looks like the bottom of the screen needs to be moved forward slightly and the windscreen raked back a bit more. It may be that I have to realign the screen to take care of this. Thanks Paul for pointing that out. I haven't investigated the 'crack of ddom' yet. It was a reshell with only 2 years use before layup so it may be ok. Not a good idea to tempt fate though!|
The main problem with refitting is if you use a new seal benath the windscreen - they take a lot of pressure to compress ! need an assistant pressing down and a lever bar in the fixing holes to pull them down - pushing the seal outwards is difficult as it rolls back underneath - use a smooth plastic 'pusher strip' or a length of cord underneath to pull it forward as you work across screen, before pulling cord out.
There is a bit of fore/aft movement in fixing - may need a bit of body fettling to get Q/L gaps to line, also check door gaps as door may need pulling back a bit. You can adjust incline with the two side fixing bolts.
Probably worth replacing the rubber pillar pads and use a bit of windscreen mastic to seal up (clean up with white spirit was OK for me) should be a lot easier if the old scuttle seal is reusable.
Make sure if there are packers between the ali screen fixing arms to the body that you put them back in the same place to avoid strssing / cracking the screen.
Done a few 'b's and midgets now all a pain !
Check the MGB Technical Archives for "MGB Windscreen Bracket Question" and also the article "Windshield Re-assembly Procedure" at www.mgexperience.net/article/windshield-reassembly.html
|I believe the windscreen to body seal is ok to reuse. Where is the 'play' in the fixing holes. In the screen pillar base or the body? I'm looking to move the base of the screen forward maybe 5mm. Is there this kind of movement available. I don't recon to be able to move the doors back at all. I presume the gap between Q/L and screen is supposed to be uniform? Mine tapers. I'll take a pic this morning.|
|There is a lot of *angle change* movement available with the bolts loose, don't know how much fore and aft but there is definitely some, probably would be 5mm. The bolt heads tighten down onto sheet metal of the body, go through as many thin spacers as are required to pack out the space, and the thick spacer, and screw into the screen leg. As well as just barely touching the pillar seal all the way up there should also be a uniform gap between the side of the 1/4-light frame and the thin lip on the inner edge of the pillar seal, maybe 3mm, have a look at http://www.mgb-stuff.org.uk/cod.htm. This allows the screen to 'wiggle' i.e. scuttle-shake without moving the 1/4-light, if you feel the gap at the top while driving over less then perfect surfaces you can feel the movement. The MGB has very low scuttle-shake, but it still happens.|
|I've had a re-assess this morning. I've decided not to remove the screen at the moment. If I did I would be led into lots of other things I don't want to do at the moment. I'll leave taking it off until next spring when the weather gets warmer. I've been able to rig up a device to keep the screen/body seal elevated around the area I'm working on. The issue of the slightly tight Q/L to screen gap I've temporarily resolved by splitting the rubber of that seal down it's length so it does not have so much spring and doesn't need as much force to compress it. The seal then becomes a flap hinged on the outside edge rather than a tube which is supported from both sides. This makes the seal significantly less stiff to compress but still has some spring. With a little silicone lubricant the quarter light slides over the seal such that there is little to no deflection at the top which means less force at the bottom of the Q/L. If the screen leaks I'll use plenty of black sealer under the rubbers. Any suggestions as to what to use?|
Moss sell a special automotive windscreen sealer - black mastic, that does not react with paint/rubbers etc and does not totally harden off/remains a bit flexible.
Cleans up with white spirit as I recall.
On the Midget I also use a lubricant on the door seal/Q.L rubber - a stick of stuff made for fire doors I think - will look when next in garage.
This thread was discussed between 11/11/2010 and 13/11/2010
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