door locks in '87 300 TD - PeachParts Mercedes-Benz Forum

oso · #1 01-07-2009, 07:15 PM

Is the small vacuum pump under the rear seat the only source of vacuum or are the door locks connected to the supply out of the main vacuum pump?

JimFreeh · #2 01-07-2009, 07:45 PM

Quote:

Originally Posted by oso

Is the small vacuum pump under the rear seat the only source of vacuum or are the door locks connected to the supply out of the main vacuum pump?

Pump under rear seat is only source for the door locks.

Jim

oso · #3 01-09-2009, 10:50 AM

Quote:

Originally Posted by JimFreeh

Pump under rear seat is only source for the door locks.

Jim

Having a bit of difficulty trying to pull the seat cushion- the locking mechanism not budging. What now?

Bio300TDTdriver · #4 01-09-2009, 11:22 AM

Quote:

Originally Posted by oso

Having a bit of difficulty trying to pull the seat cushion- the locking mechanism not budging. What now?

Lift up on the black handle with one hand. With the other hand reach across the seat and pull up on the other side at the same time. Start on the passenger's side where you will only be lifting 1/3 instead of 2/3 on the driver's side.

oso · #5 01-09-2009, 01:27 PM

Quote:

Originally Posted by Bio300TDTdriver

Lift up on the black handle with one hand. With the other hand reach across the seat and pull up on the other side at the same time. Start on the passenger's side where you will only be lifting 1/3 instead of 2/3 on the driver's side.

The problem is that the latch does not release when the handle is pulled up. Works fine on the driver's side.

oso · #6 01-09-2009, 08:23 PM

Quote:

Originally Posted by oso

The problem is that the latch does not release when the handle is pulled up. Works fine on the driver's side.

It feels like the pin that holds the seat is not being pulled back by the handle. Any suggestions?

Jeremy5848 · #7 01-07-2009, 08:49 PM

An engine vacuum line runs to the rear seat (left side) but that is for rear seat headrest retraction only.

Bio300TDTdriver · #8 01-07-2009, 09:22 PM

Quote:

Originally Posted by Jeremy5848

An engine vacuum line runs to the rear seat (left side) but that is for rear seat headrest retraction only.

If he is using the TD correctly, then he doesn't have retractable headrests.

Yep his profile says TDT (easy Jimmy). So no negative air to the headrests.

babymog · #9 01-09-2009, 11:27 AM

Passenger side is where the pump is IIRC.

In '87 there were two different pumps (early - late). The early one has a black lid on a black box, the late one has a gray-white lid on a black box. They're not interchangeable.

babymog · #10 01-10-2009, 05:11 PM

It's in a foam block just under the sound-deadening blanket. I believe that the free side of the banket is the forward end, it pulls up without tearing/cutting. Lock/unlock the doors and you should hear the pump run.

oso · #11 01-10-2009, 05:45 PM

There must be more than one design - my car has the same carpet under the seats as the througout. Had no more time or patience so I cut out a flap of carpet right were I thought the pump would be and... there it was! Wrapped in foam and new looking. The one line coming out of it was tested and holds vacuum. When I tried to pull vacuum on the nipple of the pump itself, it would not hold. Am I wrong or the pump is no good?

Jeremy5848 · #12 01-10-2009, 08:16 PM

If I understand the operation, the pump is capable of producing pressure as well as vacuum. It locks and unlocks the various door locks in the car depending on whether it "sucks or blows." The two front doors and the tailgate key locks have electrical switches attached that turn on the pump. I suppose the pump runs forwards or backwards. My copy of the diagram for the 1987 300TD shows only one air line going to each lock actuator. So the pump is not just a "vacuum pump." It is a vacuum/pressure pump. Mercedes calls it a "supply pump."

So I don't know if your test ("pump won't hold vacuum") means anything. I'll see if I can find time to test my pump tomorrow or maybe someone has a spare on their shelf.

Jeremy

babymog · #13 01-10-2009, 08:21 PM

Lock and unlock the doors, see if it sucks and blows. If it doesn't even run, whether it holds vacuum/pressure is academic.

oso · #14 01-10-2009, 08:52 PM

Finally somebody talking the language I can follow! Yes- it sucks and yes it blows. Therefore I will not waste any more time on academic questions and get busy tracking the slow leak that causes the locks to "pop-up" few minutes after locking the car by key.

Bio300TDTdriver · #15 01-10-2009, 10:24 PM

Just thinkin' out loud: Why would a slow leak cause the locks to go up? If it takes vacuum (sucking) to pull them down and pressure (blowing) to push them up, then a leak would just cause them to stay where they are. Also if you have a leak, wouldn't they go down very slowly or not at all? How long does it take for your locks to go down after you turn the key and initiate the sucking?

An easy test would be to lock the car and then pull the vacuum line off and see if the locks all go up. If they do then a vacuum leak can cause them to go up. If they don't go up, then I suspect the pump is cycling on again and causing them to go up.

I'll have mine apart tomorrow to install keyless entry. So if you have questions about how the pump works let me know and I'll test mine and let you know.