ALH underbody plugs - why

[Gothmolly]

When crawling around under the car the other day I noticed that there are parts of the car with ~1.5" rubber grommets - and many places without grommets.

What do these plugs do, and why are they there in some places but not others?

 

[Mongler98]

they have fallen out due to rusting or just age. when the car was made, it eventually got dunked in a huge tub of paint to seal it up right after the metal work. this is for them to drain out all the paint.
the only purpose they have now is to collect dirt and make rust.
Clean it up as best you can, spray with rust converter and patch it up with some sheet metal and rivets and undercoating. If you feel frisky get the welder out and pull the carpets and fix it properly.

 

[Jetta_Pilot]

Another reason could be that that car had been towed on a flatbed. Then the tow truck driver might have hooked chains there to secure the car and did not replace the rubber plugs.

Happened to me a long time ago!

 

[Gothmolly]

So they're supposed to be plugged?

 

[williambill]

Yes, they are supposed to be plugged. ID Parts has the correct grommets to replace the missing ones. Before ordering, crawl under with a tape measure and count how many and which type (measuring the ID and shape of the hole). If I recall, there are a couple different types under there. This is how I replaced mine, then after installing the new ones, I sprayed them with a thick coat of automotive undercoating to seal everything up. Hope this helps!

 

[Gothmolly]

Thanks guys, definitely food for thought. Risk/reward math will definitely come into play.

 

[Fahrvegnugen]

Careful sealing them all up! there are four that are drains and if you seal them they will hold water. Two in front and two in back. Something else will rust out (the fenders) before The drain channels are a problem. I spray oil in those once or twice a year and hope for the best

 

[Mongler98]

Careful sealing them all up! there are four that are drains and if you seal them they will hold water. Two in front and two in back. Something else will rust out (the fenders) before The drain channels are a problem. I spray oil in those once or twice a year and hope for the best

what drains? i was unaware that any of these are supposed to be open. there are part numbers for all of these hols indicating that they are to be plugged. or so i thought. Water isn't supposed to get inside, a hole will let that happen. if your getting water in a place, fix it instead of letting it drain or its mold and rust town for you. The only drains i know of are the condensate, valance, and sun roof drains

 

[Wilkins]

Plugging those that should be plugged makes the car quieter.

 

[Gothmolly]

Plugging those that should be plugged makes the car quieter.

I wish - it's super loud, but that's because of the whistly/leaky door seals, the missing belly pan, the missing engine cover, and the bigger injectors.

 

[Fahrvegnugen]

what drains? i was unaware that any of these are supposed to be open. there are part numbers for all of these hols indicating that they are to be plugged. or so i thought. Water isn't supposed to get inside, a hole will let that happen. if your getting water in a place, fix it instead of letting it drain or its mold and rust town for you. The only drains i know of are the condensate, valance, and sun roof drains

I had all mine sealed up and the tow guy went to hook up and removed two caps in front and a lot of water flowed out. The two front oblong ones. I decided they’re drains. Two in back too. I keep the others sealed, and it’s like a drain channel. It held water with all plugs in (I could hear it slosh). If I parked on a steep decline I could get water dripping from under the front doors.

 

[Mongler98]

I had all mine sealed up and the tow guy went to hook up and removed two caps in front and a lot of water flowed out. The two front oblong ones. I decided they’re drains. Two in back too. I keep the others sealed, and it’s like a drain channel. It held water with all plugs in (I could hear it slosh). If I parked on a steep decline I could get water dripping from under the front doors.

sun roof? its leaking or drains are clogged or something is letting water in maybe rusted wheel well or whatever. pull the carpets up and find out! Could also be a condensate drain is clogged. that is NOT a drain, it is now but your in for a world of rust hurtin soon if it keeps up like this.

 

[Fahrvegnugen]

Unbelievable. I got the sunroof drain to work, then plugged holes in bottom. Then for no apparent reason sunroof drain separates. Thanks Mongler, hopefully I’ll be on track again soon with my holes sealed. The drivers side sunroof drain goes right into those oval frame holes when it’s nipple pops off. I think I’ll try pulling it’s nipple back on with some weed wacker string.

 

[Gothmolly]

Weird, my sunroof drains go down into the doors, or out under the back bumper. At least they're supposed to, but since the lines detached from the sunroof the water just drains into the headliner every time it rains. Very annoying.

 

[Mongler98]

Unbelievable.
Then for no apparent reason.

YEP, that's a VW for you especially one that's almost 20 years old!

 

[Fahrvegnugen]

This one is towards the center of the car on the front drivers side. Don’t think this one drains or why it’s missing. Maybe I didn’t have a plug that’d fit as it is a larger round hole.



This is the rear hole which is missing on both sides due to the tow guy.



Here are the front tow hook holes. He pushed the plugs up in there until I told him to stop doing that. These are the ones that drained the sunroof when it’s nipples detached. I took .105 weed wacker string and cleared the front sunroof drains (with nipples removed to avoid puncturing them) and tugged the nipples back on with knotted string so they’re draining again. I should’ve realized they weren’t working when my doors stopped squeaking. I sprayed some Wurth door hinge lube on the hinges to lubricate the squeak.