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The hatch glass separation debate: is it really the struts?
My 1984 is showing signs of delamination, i.e. the black adhesive along the top of the glass is at least 50% separated, mostly on the left side:
Luckily, the glass has not started to detach from the frame, and I want to keep it that way. However, I also want to have hatch struts that work year round. Mine only work in warm weather, and even then they are weak. I really want the hatch to open on its own when I press the footwell button, as it was meant to do.
The common explanation among online communities has long been that when the struts are replaced with OEM ones that are much stronger, the increased pressure they put on the hatch causes the glass to separate. Many people have attested to this happening, sometimes within a week or less of replacing the struts. This really points to strong struts as the culprit.
However, there are compelling arguments for the contrary, i.e. that the struts have nothing to do with delamination/separation, and the latter is caused by not closing the hatch gently with both hands, one on each side of the spoiler. Closing with one hand causes the hatch to twist, and slamming the hatch causes vibration, both of which eventually wear down the adhesive and cause separation of the glass. Clark's Garage states this, and this post from 2016 offers the most concrete case of all, with the word coming directly from Porsche about the issue.
Having read this, I thought, perhaps what happens when people replace their struts is that the way they have been closing the hatch all along (slamming and/or with one hand) is now much more catastrophic and can cause accelerated separation. Unfortunately, the person who responded right after the above post refuted it by saying that he had always closed the hatch in the prescribed manner and yet it separated after replacing the struts. It's possible his case is an outlier, or that someone else closed the hatch improperly after the new struts, but it's impossible to know.
I can live with the hatch not staying open, but it sucks. It won't open with the button at all, which means if the car is running when I want to open it, I have to shut off the car to use the key to open it, and then have it fall on my head. I really really want to install new OEM struts (not the weak Jeep Wrangler ones that people have used, which don't pop up the hatch on their own and don't have the electrical connectors), but I really really don't want to regret doing so.
Let's try to get to the bottom of this once and for all?
. I really want the hatch to open on its own when I press the footwell button, as it was meant to do.
Good luck. My car went back to the dealer 7 times when new to try to get it to do that, Including changing from the single leaf to the double leaf latch that Porsche switched to shortly after it was built. The dealer gave up.
As for the cause of the delamination, the root cause is clearly not too strong of struts, otherwise they all would have failed when new. The cause is the weakening over time of the adhesive bond. Putting weaker struts on may allow the weakened adhesive to hold longer, but does not address the root cause, and likely the bond will fail eventually.
So why does the adhesive fail? There are two prime suspects, oxidation and UV exposure. I lean toward discounting oxidation, as we all live in the same atmosphere, and many cars do not show delamination. My car shows none, even though it has strong struts that will lift the hatch purposfully, even when cold. (Yeah, once I crack it open. ) So that leaves UV exposure. Given that the glass in our cars is not UV absorbing, this is a distinct possibility. My car has been garaged since new, and is relatively low mileage, in other words, low UV exposure over it's lifetime. I'm open to other theories, like the twisting by one-handed closing, but I think that just puts additional stress on already weakened adhesive causing failure earlier.
You can see on your car that the left side has mostly failed, but there may be a portion that is still bonded below the trim, where less UV will penetrate. You will want to do what you can to try to preserve it.
Even though my car has no delamination (at this point,) and based on my belief that it is UV breaking down the adhesive, I put pinstriping tape over the exposed portion at the top of the glass. The details are in this post:
I’m on the same page as @orig944 . My car shows no delamination, and while I don’t know it’s full history, it has been in Ireland it’s whole life, which would limit its uv expose (us being at 54N latitude and all).
Hmmm... I agree that UV exposure would be a big contributor to the adhesive breaking down. Since taking that photo I had 90% UV film installed in all the glass and the tint guy put pinstriping tape over the delaminated part. It looks good and I want to keep it, but it also prevents me from seeing if it's getting worse.
Interesting that @orig944 says no hatch struts are strong enough to pop the hatch open. Did you try adjusting the latch pins? I've read lots of accounts from people who said their hatch starting popping up after replacing the struts with new OEM ones. But you and @jeyjey are both helping me lean more towards "it's not the struts." I look forward to hearing what more people say.
I have come to accept that there are two types of hatches, those that have delaminated and those that will delaminate. I'm also at peace with how and why the delamination occurs so rarely discuss that anymore.
I do have some work around solutions to offer for the problems you've stated.
The simplest would be a spare key to unlock the hatch (with the car running) and a stick to prop it open.
A better but more involved remedy is to replace the hatch seal, this will add enough upward force with the hatch closed, and if the latches are adjusted correctly, will cause the hatch to open beyond the latching point when the switch is actuated from the cabin. The hatch can then be lifted by hand from outside and the stick or lower compression strut assemblies can hold it up. Good luck.
A better but more involved remedy is to replace the hatch seal, this will add enough upward force with the hatch closed, and if the latches are adjusted correctly, will cause the hatch to open beyond the latching point when the switch is actuated from the cabin. The hatch can then be lifted by hand from outside and the stick or lower compression strut assemblies can hold it up. Good luck.
The hatch seal is a good idea, I hadn't thought of that. It's not my ideal scenario but at least the footwell button would open it. I wonder if something less involved than replacing the whole seal would work? My seal is in working condition so I wonder if there is something I could add that would provide enough boost to allow it to pop open.
The hatch seal is a good idea, I hadn't thought of that. It's not my ideal scenario but at least the footwell button would open it. I wonder if something less involved than replacing the whole seal would work? My seal is in working condition so I wonder if there is something I could add that would provide enough boost to allow it to pop open.
As you have stated, once the glass starts separating from the adhesive, then the seal is eventually going to fail and separate.
Replacing the struts with OEM is not the direct cause of the accelerated glass separation but an enabler.
There are two locations/index pins with locking closures. Those have to release the hatch frame simultaneously or otherwise the frame twists. Focus on making sure the maintenance is performed to prevent it from happening.
On closure, the hatch frame should be closed with 2 hands simultaneously containing the closure rate and uniform movement with left and right hand. Once reaching the locating or index pins, gently close.
BTW. With the glass removed from its hatch frame, the frame can be easily distorted. So as the hatch top seal fails, the hatch frame distorts inducing a shear force between the glass and frame.
Last edited by T&T Racing; 12-09-2023 at 09:15 AM.
Hmmm.
Interesting that @orig944 says no hatch struts are strong enough to pop the hatch open. Did you try adjusting the latch pins?
I have actually machined fixtures to very precisely center the latch pins in the latch catches, and adjusted them so. I now believe the actual issue is friction between the latch pin mounts, and the hatch seal. I've lubricated with dry lube, light oil, and greases, but once the seal conforms to the pin mount, it takes a bit of upward pressure to release it. The hatch will release and rise by itself at the push of the button (or the remote control release I have equipped the car with) if the hatch has been previously released within the last hour or so, or if it is hot out. I have purchased off ebay what the PET calls a water drip pan, the plastic part at the bottom of the latch assembly that diverts any water to the drain tube, in order to 3-d model it. It is my intention to design an aluminum replacement with an upward spring assist to the pin that overcomes the initial friction to the hatch opening. Unfortunately, this is about number 20 on my list of things to do right now. But I will, however, eventually overcome this 38+ year old annoyance.
A better but more involved remedy is to replace the hatch seal, this will add enough upward force with the hatch closed, and if the latches are adjusted correctly, will cause the hatch to open beyond the latching point when the switch is actuated from the cabin..
I wish you luck with this. Again, with a brand new 944, with a brand new hatch seal, this was not achievable, even with seven trips to the dealer.
OK, a little different twist to this. When I had my car (only 50-60K) the sunroof would lift slightly whenever I closed the hatch quickly. I feel that you are compressing the air in the cabin when closing quickly, and this lifting is to release the pressure. This excess pressure is trying to push the class off the frame a little with every closure. As sail by others, close it slowly. Try it.
To add to the hatch strut theory, the hatch in my 944 is terribly delaminated. To the point where at idle, with my bad engine mounts, the glass will rapidly vibrate against the metal frame and cause a terrible vibration induce resonance from the friction between the two. With that said, my hatch struts have been bad since I bought the car 10 years ago and the delamination has only gotten worse. The car has sat outside and inside, in the sun, rain, hot, and cold. All with bad hatch struts, and the delamination getting progressively worse. I haven't replaced the hatch struts because I wasn't sure if it would further the separation.
I have another hatch, however it's from a later car with the third brake light. I'm debating installing it and swapping my spoiler to the later hatch, as my spoiler is in much better shape. But then I will have to live with the look of the later hatch with no third brake light, just the trim on the hatch. Decisions I suppose.
. When I had my car (only 50-60K) the sunroof would lift slightly whenever I closed the hatch quickly. I feel that you are compressing the air in the cabin when closing quickly, and this lifting is to release the pressure
The sunroof lifting is not to release pressure, it is caused by the sunroof latches not being in the locked position. They are in the remove the sunroof position. My car had this issue for a while until I fixed the switches on the mechanism.
the adhesive dries out and de lamination is accelerated by the pressure put on by the struts, but the struts themselves do not cause it. We have fixed, over the years, hundreds of the delaminate 924 and 944 rear hatch glasses with great success
I have another hatch, however it's from a later car with the third brake light. I'm debating installing it and swapping my spoiler to the later hatch, as my spoiler is in much better shape. But then I will have to live with the look of the later hatch with no third brake light, just the trim on the hatch. Decisions I suppose.
If you do decide to replace the hatch, maybe before doing so you could “take one for the team” and try putting in new struts to see if they push out the glass?
12-08-2023, 02:59 PM
The hatch glass separation debate: is it really the struts?
) So that leaves UV exposure. Given that the glass in our cars is not UV absorbing, this is a distinct possibility. My car has been garaged since new, and is relatively low mileage, in other words, low UV exposure over it's lifetime. I'm open to other theories, like the twisting by one-handed closing, but I think that just puts additional stress on already weakened adhesive causing failure earlier.
I'm also at peace with how and why the delamination occurs so rarely discuss that anymore. 
