Fred H

On my 1984 944, I have developed a water leak at the rear hatch glass. Once the appearance moulding was removed, I found the glass had separated from the metal frame it was glued to, and that the metal frame was slightly bent where the left hinge is mounted. Water was entering where the urethane seal had separated.

Is it possible to separate the glass from the frame, straighten the frame, and reglue (urethane)the glass or does the hatch have to be replaced. I can find no separate PETs part number for the frame or the glass, only the appearance moulding.

Thanks in advance for any guidance you can provide.

Michael Stephenson

This is a very common problem. I have never seen a 944 with a perfect seal. <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

Many have tried, few have succeeded. <img src="graemlins/crying.gif" border="0" alt="[crying]" />

Here are a few "instructions" I saved from the 924/944 E-mail list.

I have seen several people use carefully applied electrical tape or duct tape, but this is only a temporary fix.

Best of luck.

[quote]Author: Jim Demas &lt;JDemas@earthlink.net&gt;

1 -Rear Hatch Reseal
The rear hatch seal of the thin aluminum frame to the heavy glass, a design used on all of the 924/944/968 series, has one major flaw. Very strong struts are used to lift the heavy (est. 80 lbs) piece of glass with it's corresponding frame. These exert a lot of force when fully compressed, with the hatch closed. Due to the design of the hatch, with the aluminum frame representing only a small portion of the hatch structure and weight, the entire extent of that force is transferred to the bond between the glass and the aluminum frame. Over time, this bond will deteriorate and separate, resulting in a leaking, rattling hatch. The only option is to reseal the hatch with 3M's windsheild adhesive, either by following the procedure outlined below or by taking the vehicle to a glass shop that will perform the work. The hatch can be removed as per the instructions in the Haynes manual; open the hatch, disconnect the struts, and remove the four socket head screws at the hinges, under plastic caps in the rear of the roof lining. What follows is an article from Jim Demas describing the process:



Hatch Reseal Procedure
I have seen posts regarding help on subjects such as rebonding the rear hatch frame to the glass. I will outline here what I have used in many concours restorations.

The procedure is almost the same as for setting bonded windshields... and uses the same material... a super strong isocyanate urethane bonding caulk from 3M. 3M claims that it "Exceeds OEM strength requirements." They are truly not kidding. I have used this stuff for precisely these two uses... and a word of caution is on order at this point... it is the strongest pliable sealant around. Unbelievable stuff... as you cannot tear a dried 3 inch long piece from the cartridge nozzle later.

Make sure that you put it where you want it before it dries... it is tremendously tough stuff... and very hard to remove from improper areas once cured!

What is it? 3M "Window-Weld Primerless Super Fast Urethane Auto Glass Sealant." It is part #08609... and comes in a cartridge gun tube of 10 fl. oz. (295.7ml). It is made by their Automotive Trades Division... and is sold by companies who supply body shops and auto glass shops (almost all auto paint wholesalers carry it). One tube is sufficient for one hatch, with a little left over.


Directions...


1. The bonding surface on the frame (or in the case of windshield, the pinchweld) should be clean and dry (remove dirt and as much of the old sealant as possible). A heat gun may ease removal of the old sealant.

2. Prime any bare metal with 3M Super Fast Urethane Primer, Part #08608

3. Clean glass with 3M Glass Cleaner, part #08968. Windshields (or rear windows) that do not have a black ceramic band on the perimeter (to hide the sealant) will require priming with 3M Super Fast Urethane Primer, part #08608, for UV protection of the bond (this is one reason why the bond fails in many of the hatch frame separations).

4. With sealant cartridge in a cartridge gun, and the nozzle cut to the desired bead size you wish (1/4" is preferable)... apply the sealant to the frame (if a windshield)... or to the glass(if a hatch... you can apply it to the frame if you wish... whatever is easier for you).

5. Position the glass or the frame onto the surface which has had the sealant put on it... place in final location... and gently press for proper fitting. You may paddle the sealant around the edges if desired.

6. Clean up using 3M General Purpose Adhesive Cleaner (great for removing old decal and pinstriping glue residue, too)... part #08984 or 08986.

7. Let cure. Higher temperature and humidity makes the sealant cure faster... lower cures slower. Though it firms up in a few hours and sooner than this... 24 hours is a good timeframe for proper curing. If you can... give a hatch 48 hours before using to give it the extra strength of a very full cure. The hatch is a very stressed unit... much more than a windshield (remember: a windshield sits on the glue... the hatch does just the opposite). Avoid reconnecting the hatch struts for as long as you can bear.

8. You are now done! And you have fixed the windshield or hatch as good as new or better. This stuff is amazingly strong and tough. - Jim Demas <hr></blockquote>

[quote]Subject: Resealing rear hatch glass

"Russ Bullock" &lt;bro@hpcc.epa.gov&gt;


The following is Part I of "mein kampf" with the
hatch on my 1980 931. I'm not sure how things might
differ on other derivations of the 924-to-968 lineage.

Stage 1 - removal of the hatch

Remove the defogger connections from the lifting
struts and release them with a flat-blade screwdriver,
upon which you are left holding a rather heavy hatch.
Let it down, and work from inside the car to remove
the two socket-head bolts holding each hatch frame
hinge to the body shell. These hinge bolts are behind
two pop-out panels at the back of the interior
ceiling. If you have the rear hatch wiper, getting
the hatch off involves an additional step that even my
factory manual doesn't mention. The power and control
wires for the wiper must be disconnected from the
wiring harness. This connection is not anywhere near
where the wires feed into the rear body pillar. It is
accessible through the side panel. Then these wires
must be withdrawn thru the hole in the rear pillar
near the top of the hatch. I nearly yanked them out
in a bad sort of way when I first tried to lift the
hatch out. If you have the wiper, it must be removed
from the hatch.

Removing the spoiler trim is a royal PITA! The top
trim was easy. The side trim is attached with what I
would call knurled-**** nuts which have nearly useless
flat-blade slots in the top of them. The factory must
use a special tool to fit over the stud and engage
these slots on each side of the nut. A flat-blade
screwdriver with a gap filed out in the middle helped
a little, but I still had to use a pair of vise-grips
on most of them. The rear spoiler is attached with
phillips head machine screws with a hardness rating
similar to that of butter. I actually got most of
them off with a screw driver after a liberal overnight
soaking with penetrating oil, but two of them had to
be drilled out.

Stage 2 - separation of glass and frame

The sealant had completely let go from the glass at
the left hinge, which was the motivating factor behind
this project, but the remainder of the seal was still
very much intact. Separating the glass from the frame
was the toughest part of the job. I started with a
1.5" wide flexible putty knife, slipping it between
the glass and the seal. The metal blade and that
amazingly tough urethane sealant did not want to slip
past each other without considerable force and a
variety of four-letter words. WD-40 applied to the
working surfaces helped a lot. I also sharpened the
end of the blade by grinding on only one side (like
scissors) and used the unground side on the glass side
of the bond.

In addition to this putty knife work, draw your
attention to the top side of the hatch and use a sharp
utility knife to cut the outer edge of the glass from
the sealant. WD-40 comes in handy here too. Cutting
this edge bond first allows the putty knife operation
on the other side of the glass to go a little more
smoothly. I kept a thin block of wood wedged between
the glass and frame where I had already achieved
separation. This helped to force open the gap so that
the putty knife could do its job. Take care with the
wedge block so that the aluminum frame is flexed, but
not permanently bent. Also, take care not to have the
razor-sharp putty knife slip all the way through and
jab your other hand holding the frame. Yes, I did it.
In the words of Monty Python, "This but a scratch!"

It took me about four hours to separate the glass from
the frame. The bond at the rear of the hatch was
definitely easier to separate, and there were two
small rubber spacer blocks in the gap between the
glass and the back wall of the frame recess. These
blocks are used to push the glass forward on the frame
and adjust the gap at the front hinged side to a
minimum. Keep these rubber blocks if you find them on
your hatch. You will need them for re-assembly. I
almost didn't notice them since they blend in with the
black rubbery sealant.

Stage 3 - Cleaning the frame and glass

Once separated, I cleaned the glass of remaining
sealant with a razor blade scraper followed by 4X
steel wool. I tried using a Scrub-Brit pad, but found
that it left visible scratches in the glass surface.
I used some fine polishing compound and a cotton cloth
to remove any of these scratches that were more than
an inch or so from the edge, since they might be
visible after the glass was re-bonded. I was not at
all concerned about scratches where the sealant would
be applied. I even thought about sanding the glass
along the edge to provide a better bonding surface,
but I figured that if the factory didn't do it, it
wasn't necessary.

Concerning the use of solvents to soften the old
sealant: GOOD LUCK! I even went so far as to try
GumOut carb cleaner, the stuff with Xylene and other
possibly carcinogenic (and definitely flammable)
solvents. That sealant took everything I could throw
at it. Apparently, it takes 20 years of UV solar
radiation from North Carolina sun to make this stuff
turn loose.

Cleaning the remaining sealant from the frame was not
too difficult. I used a sharpened flat-blade screw
driver to get the major part of the stuff out of the
frame recess, and a wire brush on an air grinder for
final clean-up down to bare metal. Little, if any, of
the frame shows when the glass and trim are all
together, so I didn't bother with any cosmetic re-
painting of the frame where I got a little wild with
the wire brush. The black sealant primer can be used
for that later anyway.

Stage 4 - Straightening the hatch frame

If you catch the hatch sealant disease at an early
stage, you might not need to worry about this. Put
the bare frame back on the car, snap down the rear
pins, and bolt the hinges down lightly to put the
frame in proper position on the body. Then test fit
the glass in the frame, using those rubber blocks I
mentioned at the end of Stage 2. The hinge area seems
to be the focus of stress on the bond between the
glass and the frame. If the gap between the edge of
the glass and the wall of the frame recess widens at
the hinges, you may need to straighten the frame to
provide an adequate width to the bonding surface near
the hinges. Otherwise, you may be doing all of this
again soon.

If you were careful to not permanently bend the frame
during Stage 2, you should not have to worry about
this gap anywhere else around the frame. I, being the
worrying type, noted almost no gap at the "elbow" on
each side of the frame and I debated with myself
(you'll do it too before this job is done) whether or
not to correct the situation. I opted to leave it
alone, which I now believe was the correct action. I
used a make-shift wooden jig and a wood block with a
2-pound hammer behind it to straighten the frame near
the left hinge as best I could, and left the rest of
the frame alone. This hammering was done with the
frame removed from the car of course.

The following is Part II of "mein kampf" with the
hatch on my 1980 931. I'm not sure how things might
differ on other derivations of the 924-to-968 lineage.

when last we left our hero..................

Stage 5 - Re-bonding the glass to the frame

Once I had everything cleaned and straightened, I re-
installed the frame and fastened the rear hold down
pins before bonding. Before tightening the hinge
bolts, I made sure the hold-down pins were locked down
in final position, insuring that the frame would be in
proper geometric alignment with the rest of the car
after the sealant cured and the frame was as rigid as
the glass.

In a posting by Jim Cooper some time ago, he had
recommended a primer be used on the bonding surfaces,
specifically, 3M Super Fast Urethane Primer, Part
#08608. My local parts shop ordered #08608 and the
supplier said this part number had been superceded by
#08684, which is now called 3M Black Urethane Primer.
When I went to pick it up, I found a tiny 30 ml bottle
waiting for me. At $8 per bottle, I thought this
priming operation could get expensive. However, this
stuff is very fluid and it goes a long way. The 30 ml
bottle was enough to cover the frame recess and a one
inch margin around the bottom surface of the glass,
and still leave me enough to cover where I got wild
with the wire brush in Stage 3. Before priming the
glass, I cleaned it with 3M Glass Cleaner, part
#08968. Both bonded surfaces must be primed with a
single coat. It was near the recommended maximum
temperature of 90 F (32 C) when I did this, and the
primer set very quickly, making it difficult to paint
a smooth continuous stripe on the glass. Pick a
cooler time or place if possible. You will need your
own paint brush. That tiny $8 bottle of primer
doesn't come with an applicator. The primer must be
allowed to dry for a minimum of 15 minutes. I had to
let mine sit overnight. I was worried that dust might
have settled on the bonding surfaces overnight, so
just before applying the sealer, I brushed the cured
primer with a clean dry brush.

The sealant I used was 3M Window-Weld Super
Fast Urethane Auto Glass Sealant, part #08609. It
comes in a cartridge gun tube of 10 fl. oz. I first
tried to use a light-dUty caulk gun to squeeze the
stuff out, but the gun was twisted mass of sheet metal
before any of the viscous sealant could make it to the
end of the tip. By the way, the tube does have a seal
that must be punctured at the tip end, and the back
end of the tube has a rupture disk that must be struck
with a hammer before any gun will work. The following
day, I obtained a new "professional-grade" caulk gun
for about the same price as one tube of sealant ($12),
which seemed like a reasonable expenditure. After
dusting off the cured primed surfaces once again, I
used the new gun to apply the sealant and it worked
fine. I applied a 1/4" bead of sealant to the middle
of the frame recess on the front and sides of the
hatch, and just in front of the rubber blocks on the
rear of the hatch. I was left with so much sealant
still in the tube that I decided to add another bead
to the rear surface, just in front of the first one.
The channel for the glass is much wider at the rear of
the hatch, thus the need for those two rubber blocks.

I positioned the glass on the frame by first centering
it as best I could and lowering the rear part of the
glass onto the frame with the edge of the glass
against the front of the rubber blocks. I then
pivoted the glass down onto the frame. Pressing down
lightly on the center of the glass centered it side-
to-side pretty well, but I did have to adjust the
centering slightly to achieve an even "squish" of the
sealant on each side. I then made sure the gap at the
front edge of the frame was no more than about 1/8"
all the way across. The glass kept sliding back on
the left side, and it was at the left hinge where the
original bond had failed. Deductive reasoning
suggested that I not allow this condition to persist,
so I added a small shim behind the rubber block on the
left side to keep the glass forward on that side.

Once I had the glass positioned where I thought it
should be, I pressed down firmly on the glass to see
if it had seated firmly in the frame. No additional
sealant squished from behind the glass, so I felt
assured that the glass was seated properly. There was
still some sealant in the tube, so I used that to fill
the gap between the glass and the frame in those
places not already filled by the "squish", most
notably the rear area where the rubber blocks created
about a 1/2" gap. I paddled the sealant around here
and there, mostly just to make myself proud. It turns
out you can't see any of it once the trim is in place.
Just make sure the sealant is not built up beyond the
glass and the frame, or it might interfere with the
installation of the spoiler and trim parts.

You have about 10 minutes to work this sealant before
it starts to harden. Even after it start to stiffen,
it can be molded slightly. However, once it really
starts to get stiff, you don't want to play with it
too much or the strength of the final bond may be
reduced. Don't worry about clean up of small drips or
smears. This stuff comes off of un-primed glass quite
easily once cured. I didn't see any need to add
weights on top of the glass to seat it during curing.
I was more concerned about the front gap and keeping a
large bonding area near the hinges.

The sealant cured for three days before I had the time
(and the courage) to lift the hatch and check the
results of my labor, which appeared to be good. I re-
installed the spoiler and trim hardware, which
required drilling through the extra sealant in a
couple of places. I did not re-install the lift
struts until just this past weekend, months after the
glass was sealed in. I have been trying to determine
if I these new struts (with 944 part number decals)
might be too stiff for my 924 hatch design. From what
I could tell, the hatch design changed very little
from the 924 to the 944, and even the 968 looks the
same, other than spoiler trim. The new struts are in,
and the glass and frame are still happily joined as
one.

Now, what's the deal with that smoke from the new
lift struts?

Russ Bullock - 1980 931 - Efland, North Carolina
6 September 2000 <hr></blockquote>