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MG MGB Technical - a windshield - top gap

I just replaced the bad top seal on my "new" B, and there is a gap. The holddown clamps are tight, and the leak seems to start about 6 inches inboard of each clamp(I can even see a little daylight near the center) was there before, but I thought that was the bad seal, and not a gap...anyway it leaks! I wonder if after the car was painted by the PO, the windshield was tightened down too tight via the center rod, and pulled down. Is that possible? Recommendations on a fix...aside from "don't drive it if it rains...." I've already heard that.

Joe Walck

"don't drive it if it rains...."
So, what's wrong with that, there in the rain forest?!

I expect you also have the window/gutter issue; send pics from both sides with windows up.

This problem is related to general distortion of the frame, which needs to be fixed methodically.
There may be a remaining issue if the top was replaced with everything bent, but that's to deal with (or suffer with) after the frame fixing.

It is not a matter of the WS being "too tight".

There have been extensive discussions about this in the past, both here and on MGExp. People seem to have a lot of trouble, but I can get a top to fit correctly, though it is fiddly.

FR Millmore

A couple of points from experience which may be worthy of note. At either end of the header-rail there should be a small plastic buffer secured by a couple of small screws. These should contact the top of the screen and stop the header from tipping backwards when clamped and thus opening a gap in the centre. Its worth checking they are fitted. Secondly some time ago I purchased another 'B' that had a brand new hood and header-rail. It had never been fitted. When I attempted to fit the assembly I soon found out why. The header was completely the wrong profile compared with that of the screen. Investigation via a couple of contacts in the trade suggested that a quantity of poorly manufactured rails(presumably another example of cheap engineering)had recently found their way into the market place. On checking mine, the poor quality was evident, poor pressing, misaligned holes and below par paint finish. It was never going to fit properly. I certainly needed to replace the rail but how to ensure I didn't get another bad one? I was advised to find an original and restore it. This I did and the final rail to screen fit was perfect. So Joe, it might be worth taking a look at the surface of the header rail (as seen from inside the car) if its full of ripples it's almost certainly a poor one. As a foot note, to ensure that another unsuspecting person did not suffer the same fate, the poor one went to the recyclers and not e-bay.
Chris Woodfield

I can't speak for anyone else but the plastic blocks on mine are about 1/4" clear of the top of the screen frame so are not playing any part in aligning the header rail, and I'd have thought they were a bit flimsy for that anyway. The pivot between frame and header rail is at such an orientation that unless the pivot was very loose the header rail can't tilt back and fore in any case, however it may have been bent back by the top being too tight perhaps. The flanges on my pivots are horizontal across the car, and only angled very slightly downwards from front to back, so that is the area I'd be looking at.

I'd also be looking at the tension in the centre rod. It only needs to be nipped up to stop pressure from the top lifting it up, although given how close the clips are to the outer edges of the screen I've never been able to imagine it being able to do that anyway.

What type of seal did you fit? It should be a closed-cell sponge which is highly compressible to take better account of mismatches in the curvature of the header rail and frame top rail, denser seals won't be able to do that.
PaulH Solihull

I also believe that your problem lies in the shape of the header rail. It seems apparent, from your photos, that the center of the header rail is way too far from the windshield. I would try to locate a used header rail and fit it to your top. RAY
rjm RAY

I suppose it "could" be the header rail, but I've had plenty of tops fit like that which I fixed so they fit fine. I have no experience with non OE rails.

Paul is correct that the plastic blocks never seem to touch the WS, even though you might expect them to act as fulcrum points like Chris suggests. They seem to act as a sort of theoretical anti-rattle limit if the seal is really gone.

The bolt-on pivot anchors Paul refers to are extremely difficult to bend, accidentally or deliberately, so that is not likely to be the cause. Not uncommon for the side rails that anchor at the pivots to be bent, anywhere from the pivot back to the support points on the side of the car. Also the fixing screws there are frequently loose or bent, which throws the entire frame alignment out.

FR Millmore

Paul is right about the gap between the plastic blocks and the screen. I purchased a second set of blocks,cut them approximately in half and double stacked them so that there was contact between them and the screen. My car is a MK1 and the hood frame is the early grey, double scissor, folding type and possibly due to age, does have movement in the final pivot point where it fixes to the header. I found that by ensuring the blocks made contact, the small amount of header pivoting movement disappeared. Having said all that I have seen many roadsters with gaps between the blocks and the screen and the header-rails seem to fit OK. So not too conclusive. I'm still leaning towards a misshapen header.
Chris Woodfield

Just went out and had a look at mine. This is a pack-away top on a 69 - evidently a top replaced on the original header rail because I have the sliding rivet pieces inside the header.
Some observations:

1 the blocks on both sides of mine do contact the top rears of the side rails in such a way as to act as Chris suggests above - whether that is the design intention I do not know,

2 the ends of my fitted header/top overhang the outer line of the side rails - perhaps 1/4 inch, on both sides

In the attached photo I notice the LHS header end has a slight overhang, but the RHS appears to be flush with that side rail line. I wonder (picking up on Chris's experience with the poor quality header replacement - particularly with regard to screw hole misplacement) is it possible that the clamp positions on this header were just a little too far apart (or just outboard on the RHS) and that the header was deformed upward to enable the securing clamps to home on the screen rail receivers?

Roger T

If we consider the quite complex shape of the header and the rail, there are a number of radii that need to be spot on, in order for the two parts to marry up. If Joe's header is a replacement, it may well be of the quality found in many re-manufactured parts (the type that all of us no doubt have experienced), they just don't fit! Looking at the image, the gap at the centre point is clearly too large and in my opinion probably unlikely to have been caused by over tightening the centre screen rod. I thinks its worth Joe releasing any hood tension, undoing the header clamps and trying to roll the header forward until it looks to be in the correct position to seal properly. If the outer points of the header are now raised to a point where they won't seal, then my money is on an incorrect shaped header. This is precisely the situation I experienced.
Chris Woodfield

Well, I found a fix, good old 3/4 x 3/8 inch weather stripping, stick one side, smooth foam the other. First I applied it to the top of the windshield frame channel (which is 3/4 in. wide), but it didn't look good there with the top down. So I took it off, then stuck a new piece to the rubber seal on the top header. It's completly flattened near the outside, and seals the gap fine. It stuck fine, and seals great, and with top down, it's hidden in the back. NOW I feel I can put the car on the market and feel good that it only leaks as much as any other MG....FYI, here she is FOR SALE:

Joe Walck

FYI Sold to first man to look at her, $8,500, now the wife is happy again.....she can get to her TD

Joe Walck

This thread was discussed between 16/11/2011 and 07/12/2011

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