rear hatch clunks over bumps
01-13-2017, 07:20 PM
#2
Registered User
Join Date: Aug 2013
Posts: 1,103
Do you drive a Ford? Everything clunks on a Ford. From day one.
If it's a Nissan, it should not clunk. I installed a rear sun-shade on my first Z31 ('86NA) and that clunked almost from day one. It was dealer-sponsored and sold ($200) but was not Nissan OEM. So Nissan would take no blame. I finally stopped the clunks by compressing additional foam gasket material between the frame of the shade and the glass it was designed to sit on.
If you have a full rear hatch like an '86na or turbo without a shade, you are right to check the weather strips (I call them gaskets) and see that they do push the hatch back upward against the hatch mechanism. After years, those gaskets lose their spring and just flatten under the weight of the hatch. But they should still eliminate any clunk when you are driving over speed bumps and holes because the hatch would be held in place by the gaskets working constantly against the latch mechanism.
If when you close the hatch slowly you do not have to push down on the hatch to compress the gaskets and get the latch to grab - you have flattened gaskets and need to replace them. Or any arrangement that keeps the upward pressure working against the hatch mechanism. There are one or more 'fixes' that add more foam rubber depth to the gaskets and maintains the upward counter-pressure you need to stop the hatch from bouncing around on rough terrain. You can figure those out - if in fact your gaskets aren't doing their job any more. You can tell if the hatch latches itself under its own weight and doesn't need a push.
If it's a Nissan, it should not clunk. I installed a rear sun-shade on my first Z31 ('86NA) and that clunked almost from day one. It was dealer-sponsored and sold ($200) but was not Nissan OEM. So Nissan would take no blame. I finally stopped the clunks by compressing additional foam gasket material between the frame of the shade and the glass it was designed to sit on.
If you have a full rear hatch like an '86na or turbo without a shade, you are right to check the weather strips (I call them gaskets) and see that they do push the hatch back upward against the hatch mechanism. After years, those gaskets lose their spring and just flatten under the weight of the hatch. But they should still eliminate any clunk when you are driving over speed bumps and holes because the hatch would be held in place by the gaskets working constantly against the latch mechanism.
If when you close the hatch slowly you do not have to push down on the hatch to compress the gaskets and get the latch to grab - you have flattened gaskets and need to replace them. Or any arrangement that keeps the upward pressure working against the hatch mechanism. There are one or more 'fixes' that add more foam rubber depth to the gaskets and maintains the upward counter-pressure you need to stop the hatch from bouncing around on rough terrain. You can figure those out - if in fact your gaskets aren't doing their job any more. You can tell if the hatch latches itself under its own weight and doesn't need a push.
01-14-2017, 08:10 PM
#4
Registered User
Join Date: Aug 2013
Posts: 1,103
Right! Welcome to Zdriver, BTW! 
I remember that my original new '86 had gaskets so new that if the hatch release was pulled, the hatch would unlatch and sit there, held down by its own weight but not latched. It would bounce over bumps so I had to get out, go back and press it down to latch it. No clunking at all. My turbo had tired gaskets the day I bought it and I think I removed and reinstalled the rear gaskets reversed so there was more upward pressure on the hatch. I also looked at adjusting the latch position so that it pulled the hatch down tight and there was no 'play' distance for the hatch to bounce and 'clunk.'
Also check your rear mounts, visible up inside the rear wheel well. They wear out (your Z is getting up there in years. It's 30!) and can cause a 'clunk' in the rear at every bump. They are replaceable and new aftermarket mounts work fine. They are just hard rubber cylinders with a bolt cast through the center, fairly easy to install. That 'clunk' will drive you crazy because it never misses a bump, even the small ones. Cheers!
Your two rear struts are replaceable with new and aftermarket but they are not likely to help much in eliminating clunks because they tend to relax after use and will not exert enough, if any, 'pull' pressure to hold the hatch in place. Gaskets are your likely culprit and you may have to improvise replacements or 'renovation' there. 30 years is a long time to ask foamy rubber to stay resilient like new.
Struts are replaceable and you will want to do that when the old ones do not help to slow the slam of the hatch or hold it up when opened. That hatch is heavy and needs to be damped at close time 
unless you like slamming stuff. The struts are the only help you get in holding the hatch up. Without them, you need a stick of just the right length. Replacement struts need to be checked to accommodate the weird ball/socket Nissan design for installation. Improvise, improvise! 
I remember that my original new '86 had gaskets so new that if the hatch release was pulled, the hatch would unlatch and sit there, held down by its own weight but not latched. It would bounce over bumps so I had to get out, go back and press it down to latch it. No clunking at all. My turbo had tired gaskets the day I bought it and I think I removed and reinstalled the rear gaskets reversed so there was more upward pressure on the hatch. I also looked at adjusting the latch position so that it pulled the hatch down tight and there was no 'play' distance for the hatch to bounce and 'clunk.'
Also check your rear mounts, visible up inside the rear wheel well. They wear out (your Z is getting up there in years. It's 30!) and can cause a 'clunk' in the rear at every bump. They are replaceable and new aftermarket mounts work fine. They are just hard rubber cylinders with a bolt cast through the center, fairly easy to install. That 'clunk' will drive you crazy because it never misses a bump, even the small ones. Cheers!
Your two rear struts are replaceable with new and aftermarket but they are not likely to help much in eliminating clunks because they tend to relax after use and will not exert enough, if any, 'pull' pressure to hold the hatch in place. Gaskets are your likely culprit and you may have to improvise replacements or 'renovation' there. 30 years is a long time to ask foamy rubber to stay resilient like new.
Struts are replaceable and you will want to do that when the old ones do not help to slow the slam of the hatch or hold it up when opened. That hatch is heavy and needs to be damped at close time unless you like slamming stuff. The struts are the only help you get in holding the hatch up. Without them, you need a stick of just the right length. Replacement struts need to be checked to accommodate the weird ball/socket Nissan design for installation. Improvise, improvise!
Last edited by zxguy1986; 01-14-2017 at 08:26 PM.
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