BMW 635 Fuel Tank Gasket page

BMW 635 Fuel Tank Gasket page

By Peter Siposs - April 12, 2002

My car had a persistant fuel smell everytime I filled up the fuel tank and for several miles afterward. Eventually I got tired of it and set out to cure it once and for all. The smell was clearly coming for the rear of the car so naturally I figured it was something to do with the fuel tank or connections to it.
I ordered gaskets from for about $7 plus shipping.
BMW part numbers are:
Main tank gasket: 16 12 1 116 966 ($4)
Sender O-ring: 16 12 1 150 391 ($3)

Before doing any work in this area be sure the tank is no more than about half full otherwise you'll have fuel spilling everywhere. Also only work in a well ventilated area preferably outside.

To access the top of the fuel tank just open the trunk and lift up the right side floor material. Then remove 3 screws holding down the round cover plate.

This is what you'll see under the cover plate. But before going any further, I strongly suggest cleaning the top of the tank. Since the area under the cover plate is exposed to road grime and weather its normally pretty dirty and you don't want dirt entering the hoses or the tank itself upon disassembly. I sprayed engine cleaner then rinsed with a hose being careful not to flood the trunk. The water and debris will just fall to the ground under the car so hopefully you've parked on a slight grade. Dry the area, then you can begin disassembly.

There are 2 fuel hoses, and 2 electrical connections. The large hose is the main fuel supply line, and the small hose is for excess fuel return.
The largest electrical connection is for the fuel level sender (for the fuel gauge), and the small electrical connection is for the in-tank fuel pump.

Disconnect the fuel hoses and the electrical connections. They are different sizes and keyed so don't worry about reconnection. Remove four 8mm nuts holding the level sender down and remove the sender. The sender must come out first in order to remove the pickup from the tank. It will have some fuel in it so go slow and let it drip back into the tank. Set is aside on a clean cloth (not in the trunk).

Remove six 8mm bolts holding the pickup assembly and lift straight up at first. You will see the in-tank fuel pump then the pickup filter. The assembly must be tilted once the filter is about to come out in order to clear the narrow opening of the tank. Be careful not to have any bolts, nuts, tools etc too close to the opening to prevent having anything fall in. Expect some fuel to drip from it while removing and set into a small bucket or pie tin. As you can see, I am wearing nitril gloves as it always seems that fuel smell stays on the skin a long time despite washing.

Here is the pickup assembly minus the level sender.

The pickup filter at the bottom is virtually certain to have some tiny debris particles on it (as shown in photo) so now is your chance to clean it. Remove the single screw holding it and remove. I just take it to the shop sink and backflush water through it while aggitating with a finger. Then dry with compressed air or let sit in the sun to dry.

Now you can finally address the gaskets. Using a small screwdriver, lever out the senders old gasket and replace with a new one making sure it is seated correctly in its groove.

The main large gasket is for the pickup assembly and simply slides over it from below.

Inspect the fuel hoses for cracks & splits. If they appear iffy, often just cutting off an inch or so is sufficient. While the assembly is out inspect the rubber hose connecting the pump with the assembly for cracks etc. With the tank open you can shine a flash light inside to check for rust etc. You can also test the in-tank pump for operation by simple applying 12 volt power to the leads. Reassemble in the reverse order and tighten the bolts/nuts carefully. Do not overtighten.
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Useful related links:

My BMW 635 page
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How to add a central locking switch
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How to fix the sunvisor mirror light
How to make a cup holder for your 635
Another BMW I currently own. An 81 320i.
633/635 (E24) Forum on the Web. Oustanding source of info from enthusiasts.
5-speed conversion process for 2002's.
Mesa Performance Parts - BMW/Porsche Parts

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