For you coupe owners with vacuum operted seat back locks.

Twice I've experienced the same basic problem. Car starts to take a little longer to shut down, transmission shifts a little harder, and trunk lock seems to loose vacuum quicker. These are indicators of vacuum leaks in seat lock mechanisms (at least in my car). Leaks in other areas may have same effect....I don't know about that.

Both times I traced the problem to a loose connection under the front seats. One time the driver's side, another time the passenger side.

As best I can figure, the "primary" vacuum line (all these are solid blue) comes to the seats on the passenger side right in front of the bottom of the seat front near the door jam. Pull the carpet up and you will see where a rubber junction sends one line accross to the driver's side and another line under the passenger seat.

Disconnect that line and see if it is getting vacuum with engine on.....remember that the doors have to be closed for the vacuum to get there. If you have vacuum at that point (easily felt by placing finger over opening) then the problem is under one or the other of the seats and you can plug that particular line and "fix" the vacuum leak's impact on other operating systems. In my most recent case I plugged the passenger seat line and now my driver's seat locks work fine.

Probably will have to take seat out to get at the leak.

Nic
'85 300CD

I have never had any problems with my seats, even though the lock doesn't work. I think the previous owner plugged the lines under the seat because of a leak. I have been thinking about getting the locks fixed in the seats someday, but I am still unsure that is something that I want to do because I am sure it will fail again.

I don't know whether its a good idea to drive without them locked. One person wrote that he knew of a driver who had been badly injured when the seat back flew forward in a wreck.

If you take the seats out (not a terribly hard task), you can get at the fittings and vacuum valves. It could just be one has come loose. They aren't real complicated, just impossible to get at with seats in car.

Do the trouble shooting to see if its both seats or just one that needs your attention.

Nic

I might give that a try when I get my car back from the transmisson shop in a few weeks. I am wondering, if that will fix my door locks and it losing the vacuum, or if the leak is somewhere else.

Excellent! Just what I need, I'll check it out! Thanks a lot!

I've been looking at all the vacuum junctions around the seats and they are all good.

Now... here's my story.
When the car is running, door closed the seatbacks don't lock.

However if I manually 'push' the locking latch on the right side of the driver's seat, both seatbacks would lock...

I still can't quite figure out why it does that...

My engine shuts off fine, it doesn't shut off at the same instant but it does shut off firmly.

The transmission shifts fine..

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2008 BMW 335i Coupe

Thats strange Holston, but these vacuum bugs are weird. I mean why on earth does my car shift harder when there is a leak in the seat lock system? But it definately does. I can better understand the slower engine shut down as the system was leaking vacuum, leaving less vacuum to operate the shut down dohicky.

On the seats, I think the vacuum just goes to each latch and when applied, the lock does its thing. Maybe when you manually lock that one, it "seals" the vacuum line in there and then the others have sufficient vacuum to work. Could be that in the mechanism you are manually locking, there is a leak that weakens the overall available vacuum, at least until you lock it by hand. Make sense?

I'd definately check that one out for problems.

Nic

update

I started by seeing if there was vacuum from the main line (solid blue) and there was enuf.
So I decided to plug the line going to the 'T' for the driver's side seatback locks.

Instantly the passenger side locks work!!
Then I thought maybe I should disable only one of the driver's side locks. I disabled the one that I could move by hand...
and voila! it now works beautifully!

I guess I just gotta find a seatback vacuum element and replace it...
I'll see if it's just the rubber tubing connecting the element to the hard plastics.. but I think it's not that simple as I checked the rubbers already.

Thanks a lot NIC! Very helpful!

The door locks now work faster and the engine shuts off instantly.

The transmission is more consistent now.

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2008 BMW 335i Coupe