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Trunk handle come out for no reason...'94 S500

7K views 20 replies 13 participants last post by  David Hanly 
#1 ·
Whenever I drive the car for more than a few minutes, the trunk handle is out when I park. If I open and close the lid, it goes in normally. When it's out, the trunk remains fully closed so I don't think it's a "pulldown issue.

I suspect it may have something to do with the trunk lock cylinder itself but I've even closed myself in the trunk so I could tap on the area around the lock to see if I could trigger the handle. No luck there. I've also checked the connections to the handle, electronic and vacuum. Strike two.

Is there something I should be looking at that I haven't thought of yet. I have a replacement handle from my parts car if it's the handle itself.....but somehow I doubt it is...but maybe I'm wrong.

Any assistance appreciated on this one, guys.
 
#7 ·
Sounds like your pump is dying under the seat. You can try to adjust the contact that pushes on the plunger when close the trunk lid. Open the trunk and directly under the trunk sill there is an access and you'll see the plunger and metal contact. Take a screw driver and slightly bend it so it makes contact when the trunk lid is closed and that may fix the handle but if not have your pump rebuilt.
 
#8 ·
Since I have repaired many of these(The pump under the seat is the one we are dealing with) pumps, and about handful of cars with these problems.. The best advice is:

A) how are your door locks working?

B) On the mid through late year cars.. If the vacuum fitting, rocks back and forth on the pump. You are toast!! The seal is broken. The tip of the nipple is broken on the pump.

C) Door locks work(they close and open in three seconds or so), and no broken nipples. Then the diaphragm of the trunk lid handle has a leak, but to find it you need a vacuum tester. I use my trusty one from Harbor Freight

Brake Bleeder and Vacuum Pump Kit

Or this one will work

Mityvac Vacuum Pump - Save on Mityvac Pumps at Harbor Freight!

The key is the device needs to hold 10" to 20" of vacuum

D) Disconnect the grey seat bladder line going to each front seat, and plug it up for testing. The coupes will have the aqua-blue line in addition to the grey line. Disconnect it, and plug that one up too for both seats.

All the best,

Martin
 
#9 ·
I turned off the seat lumbars and the handle still comes out. The door locks work fine.

Should I test the handle vacuum from the handle itself or from the pump end? Would a fault at the trunk handle cause the reverse markers to go screwy as well? Admittedly, they don't stay up as often as the handle comes out....which is every time I drive the car.
 
#11 ·
Why?... OH WHY? ... do people think that the trunk handle is held in place by vacuum all the time?


To the OP, you problem is just the contact switch (the one that turns on the trunk lights and operates the handle) at the trunk lock.


The trunk lock has a metal tab that contacts the switch when the trunk is closed, thus turning off the lights and retracting the handle.

Your tab needs to be bent a little, because with time it starts exerting marginal pressure on the switch when the trunk is closed. The slightest bump that you hit ... aaaaand you have a popped out handle, trunk lights turned on and the light on the dashboard switch also turned on.


This is a 0 euro/dollar/yen/whatever fix.


And every single time that someone gets to this forum with trunk handle problems, every single time people start throwing big theories with the vacuum pump or some other expensive item.

I may be wrong, but please... cheap things first!!
 
#12 · (Edited)
Why?... OH WHY? ... do people think that the trunk handle is held in place by vacuum all the time?
Because.....OH BECAUSE.....I'm not familiar with how the system works. Had I known, I wouldn't have asked for help. I don't have an interior trunk release switch so there is no dash light. If it's any consolation, I know that's not vacuum-operated. :grin

I'll check out the switch today. Thanks, Rallyus.
 
#13 ·
Testing of diaphragm actuators

MAVA, You mention the vacuum leakdown test method for the diaphragm actuators.

It is my understanding that there both vacuum & pressure actuators in the system.

Has your experience been that vacuum leakdown test method is a reliable indicator of fault in these diaphragm actuators?

I've got a '99 S500 with self-closing system making a fault requiring pump reset about every 3-4 trunk closings.

There does not seem to be a fault in any of the doors.

I see that there are 2 actuators in the trunk closing system. Is one to pop the handle out & the other to Open/Close the latch?

I see that these can both be purchased for about $40 each. I'm tempted to just order both of them and replace, but I realize that a leak can be anywhere and diligent diagnostics would probably be more prudent.

I've already been warned about these actuators having leaks only in certain position of stroke making diagnostics more troublesome.

Have you found vacuum leakdown fairly reliable for diagnostics?
 
#14 ·
MAVA, You mention the vacuum leakdown test method for the diaphragm actuators.

It is my understanding that there both vacuum & pressure actuators in the system.

Has your experience been that vacuum leakdown test method is a reliable indicator of fault in these diaphragm actuators?

I've got a '99 S500 with self-closing system making a fault requiring pump reset about every 3-4 trunk closings.

There does not seem to be a fault in any of the doors.

I see that there are 2 actuators in the trunk closing system. Is one to pop the handle out & the other to Open/Close the latch?

I see that these can both be purchased for about $40 each. I'm tempted to just order both of them and replace, but I realize that a leak can be anywhere and diligent diagnostics would probably be more prudent.

I've already been warned about these actuators having leaks only in certain position of stroke making diagnostics more troublesome.

Have you found vacuum leakdown fairly reliable for diagnostics?

Your problem is on the pump itself.


Just strip down your trunk lining and pull that pump out, on the left side of the fuel tank.

Open the pump and adjust the spring on the pressure switch so that it trips earlier.

The problem is that your pump is timing out, just that. Do nor order vacuum actuators. Jeezzz that's like having a steering wheel shake and the first thing you do is order new rims and tyres...
 
#17 ·
On my '99 S500 I had intermittent 'popping out' of trunk handle when vehicle had been parked.

The cause of mine DID turn out to be leaking seat air bladders. I confirmed these by listening for hiss when bladder valve was put all the way open.

Interestingly enough, I thought problem was only on passenger side as trunk handle seemed to stay in with that valve set to '0' and drivers set to '3' or '4'.

I bought a pair of bladders anyway. Once I replaced them I saw that both sides had leaks. Passenger side was just a bigger leak. Replacement of both of those fixed the trunk handle issue.

The seat bladder leaks at 15+ years age are to be expected but are not the only cause.
 
#18 ·
I Figured If I Waited Long Enough

I have this trunk handle issue. :crybaby2:

I knew this topic would pop up eventually. I'm reading two solutions to the problem. Bend a tab, and replace the lumbar bladders. I know my lumbar supports are inoperative, at least the dials don't seem to effect the lumbars.

I'm prepared to do two things. I'll adjust that tab, see if the issue goes away. I'll look into R&Ring those lumbar bladders this spring/summer.

The question that now comes to mind... am I damaging/stressing anything by not replacing those bladders tomorrow? :confused:
 
#20 ·
If you do have leaking air bladders. The leaking can eventually cause pump to burn out as it makes pump run pretty continuously. How long this takes; don't know.

If air bladders don't seem to 'puff up' very well or you can hear leak, you should turn control to '0' to help prevent the pump from running all the time. Some have reported leaking control valve also, but I didn't have this.

To hear leak, car must be running; doors closed, windows up & radio off to minimize noise. Listen close to seat back and scan around.

The pump that drives the air bladders is the expensive one under the rear seat.
 
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