So the other day I noticed I was losing washer fluid (it wouldn't stay filled to the brim). Found that the plastic "lid" that holds the heater element inside the tank (PN 203-869-02-08, looks like there's no updated part) had split in half. Another German plastic fail. Ordered a new lid (which comes with the associated gasket) and 2 new grommets that seal around the 2 heater tubes from the dealership.

Everything went well (including popping the new grommets into the 2 holes in the lid and feeding the new lid/grommets through the heating element tubes) until the final bit. For the life of me I cannot get this new lid to pop back onto the tank - it requires a ridiculous amount of downward force. There's a lip that runs along the inner part of the outer edge of the lid that I assume needs to "click" into place against a corresponding outward facing lip on the tank. Yes I lined up the notch in the photos.

I tried pushing. I tried wobbling. I tried hammering with a piece of wood. I tried pliers. I tried putting my knee on it. Basically I was pushing so hard I was afraid I was going to damage the tank. With that said, I'm guessing that's why the original lid split along the lip - the diameter of the lid where the lip is located is slightly too small.

After 2h of cursing, I managed to get it 90% of it on. However, I don't think the lips are completely hooked. As a result, I'm stuck with a slow weep. I can now only fill to the top of the tank instead of the top of the neck (estimated 85% of original capacity). While I can live with this, it would be nice to complete the job properly.

Is there some special magic or tool required for popping this thing back on?


Old lid


Old lid split


New lid and gasket

 

Can you get it one if you remove the grommet?
My guess is that you can.
Try the old grommet, it has already been compressed.

There is a chance that the new grommets are too wide.
For GM fuel-gauge/fuel-pump, I'm convinced the spec is: -0mm / +what_ever_you_******ing_feel_like. Buy 4 different fuel-pumps, get 4 slightly different grommet - all thicker than the one that came with the car.

The tank can likely take a lot of force, much more than your body weight, as long as it's "properly supported". "Properly supported" may mean a form-fitting support. Although, it more likely means well-supported bottom. This of course assumes that the tank is out of the car, and under a press. :-)

You can try two things, I suggest doing them both.
1) Throw the top unit, with the grommet, in the freezer overnight. Remove from freezer, and have everything ready so that you can install as fast as possible.

2) Use a propane torch, using constantly moving and fast motions, heat up the area the unit goes into.
Note: The correct way is to remove the unit, and put it in a oven at temperature-X, or put it on a good part-heating hot-plate with that temperature.

The above is actually how many items are press fit, like the wrist-pins for pistons. There, the pistons are on ax x-temperature hot plate for x-mins. Then the wrist-pin is pushed in.
Some machinists/mechanics will just press in the wrist pins using a ********-load of force. Sigh...
Note, it depends on the piston/wrist-pin spec, if the wrist-pins can be properly pressed-in without heating the pistons.

Good Luck!

 

Thanks for the information/tips.

For the thermal method to work, the lid has to be heated while the tank would have to be frozen. Reading up online, it looks like the lid (which is made of polyethylene) can be softened by heat. I think I could've softened the lid by baking it in a toaster oven, but didn't want to risk warping it, especially with the bit involving feeding the part back through the heater element. Also wasn't too sure if baking the lid with the heater element attached would've been a good idea. Not to mention the lid would then resting on its side. A couple of small pieces of wood to lift up the assembly may have worked.

The grommets sealing the heating tubes to the lid actually fit quite nicely. Snug and waterproof but not excessively tight. Sliding the heater tubes through them was quite effortless. It was only the ring gasket between the lid and tank that was causing the problem.

Since the the problem was the lid in its original form being too "small" to fit over the lip of the tank, I decided make some cuts in the lip of the lid to allow for some flex. I used a Dremel, but a hacksaw blade would've worked too. Marked an X pattern (ie 4 notches) with a marker and tape measure, then cut the notches. I then used a mini file to get rid of all the excess plastic bits and to deburr the edges. This is required especially at the location of the lip.


New lid modified with 4 notches

With the extra flex, the lid was successfully reinstalled when forced on. The tank did not need to be removed. It was still a very tight fit though. I used my fingers for the job.


Notched lid installed

The next day I could still feel wetness around the tank lid. Turned out there was still a slight weep (~20mL/day) between the lid and the gasket. Opened up the lid again, drained the tank maybe 2cm below the bottom of the lid hole, dried off the area, and added a ring of RTV gasket maker between the gasket and lid. I didn't add any between the gasket and tank because I didn't want to mess up the sealing surface in case it didn't work.

Popped the lid back on and waited 24h with the reduced fluid level, then filled up again to the brim to test. Leak is sealed and gone. Mission success.


Washer fluid full

 

Good idea!
I'm glad that you got it fixed.