worf928

Short Story: I think the filler necks and reservoirs turn yellow because the steel insert rusts (though probably for other reasons as well.) Replace it with a stainless or aluminum insert before you install your new washer filler neck and/or reservoir. This may slow down the turning-yellow process.

FI 928s that use the washer fluid system for the intercooler will feature the color change about 5 to 10 times (IMO) faster than NA 928s. Also, getting rid of the rusty steel insert is a good way to keep the rust bits from circulating through your intercooler plumbing.


Longer Story with picture:

The new washer filler neck I put in a year and a few thousand miles ago - just before the TS install - has turned yellow. But, the new coolant reservoir I installed at the same time is still nice and pearly white. WTF? Crappy Porsche part? Maybe but...

... I cracked my filler neck when I was doing the SC install. So, today, I pulled it to replace it with another new one. The stock steel insert in the neck, used to add a little strength for the hose clamp, was rusted as badly as, if not worse than, the 17-year old one I pulled out last year. The insert in the new washer fluid reservoir was also starting to rust but wasn't nearly as bad.

After thinking about it for a while and then trading some thoughts with Wally, we came to the tentative conclusion that the hot washer fluid straight from the intercooler, that's always being nicely agitated by the intercooler pump, is accelerating the rust of the insert. Add in the fact that the insert in the filler neck is in air, but open to the hot vapor of the washer fluid, while the fluid reservoir insert is immersed in the fluid and we have a good explanation for why the two inserts of the same age show markedly different rusting. (After all, rust needs oxygen.)

So, I used the nifty flappy bearing blind-hole bearing puller to remove the insert from my new filler neck and the insert from the almost-new reservoir and measured them. They're a shade under 1" OD (25mm actually). My local hardware store doesn't stock surgical stainless tubing (imagine that!) but they did have 1" OD aluminum tubing. Following Wally's suggestion I cut two lengths of the tubing to fit and then cut them lengthwise to allow them to squish a little bit upon insertion (don't want to bust the plastic necks) and presto - new, non-rusting inserts.

In the picture below, from left to right, you see:

1) My new filler neck with the new aluminum insert.
2) The aluminum insert that will go into the fluid reservoir.
3) The steel insert removed from my new filler neck.
4) The 1-year old filler neck, yellow, with its super-rusty insert.
5) The not-so rusty insert removed from the 1-year old fluid reservoir.

The proof in this pudding will be the color of my filler neck a year from now.

AO

Yeah, but that thing is a PITA to replace...

worf928

Which? The filler neck? Not so much.

The washer fluid reservoir? A bit.

The coolant reservoir? I'll let the one in there turn yellow before I do it again.

Marine Blue

Thanks for posting this Dave.

I think I will add this to my list of parts to replace next year along with the coolant reservoir.

Bill Ball

Good work, Dave. When I was installing my intercooler, I removed that rusty metal section and just left it out. I don't see a need for it. The hose clamps do not need to be very tight as this is not under pressure. No leaks and the intercooler seems to be working well using that bottle as a reservoir.

Mrmerlin

If you have a new filler nack simply dip it in hot water and remove it, I suggest to also remove the collar from the washer tank, all it does is rust and as Bill said there isnt a need for metal to be in there anyway, I have removed many of these collars and never had any problems.
If your fitting a SS collar thats nice but its not really needed

worf928

Yup. They don't have to be tight-tight, just tight enough to seal. So, removing them without replacement is an option. I just like being ****-retentive. And the inserts will prevent an accident if you tighten the clamp just a tad too much. ("Just a litttle mo... CRACK!") My old-old neck was pretty brittle.

BTW, Andrew, the washer fluid reservoir does not have to come out to remove the insert. It just needs to be loose. The slide hammer just fits up in the wheel well.

Last, I checked PH of the out-of-the-bottle washer fluid. It's 6.5 - slightly acidic. The old rusty fishy-smelling washer fluid was 7.0. New fluid with a bit of Water Wetter is 7.0. I'm thinking of adding a little WW to the mix.

Anyone done that? Run Water Wetter with the intercooler/washer fluid?

worf928

This thread isn't so much about the intercooler or whether or not the inserts are good or superfluous.

The main point was: if you go to the trouble and expense of replacing the neck or reservoirs, or if you are removing them for an SC install, remove the inserts (and replace with aluminum if you want to) before you put them in. It may extend the useful life - or at least the useful-looking life - of the neck and reservoirs.

I'll report back in a year with results of running new washer bits with the AL inserts while leaving the coolant reservoir steel insert in place.

Mrmerlin

your best bet is to remove the metal collar it will rust and it will eventually plug the pump for the WWasher.
if your running a bigger pump for coolant i would still remove it. It serves no real purpose other than acting as a contaminant. Just snug the clamps for the hose and you will be good to go.
The washer tank collar usually corrodes and falls into the bottom of the tank this will in time plug the WWasher lines and pump . Tanks removal is a good idea to remove any small pieces that have fallen into the tank.
A few hand fulls of stones and some simple green and some vigorous shaking will scrub the tank prior to installation.

Mitch Johnson

+1

6mil928

I gotta change mine hope it's not as bad as you guys say.

Tom in Austin

Guess this explains all the rusty crud in the coolant exp tank when I first got my car. Hopefully the new one it will stay clear for a good long time before I have to think about taking it out again.

If I ever have to go down this road again, good to know these inserts are the answer ...

worf928

I wrote in the thread title "+fix, maybe" Just don't blame me if they still turn yellow even without the inserts. Heat-cycling also probably has a lot to do with the plastic getting yellow.

I took a look this morning at some engine pics of my '91 when she was a little girl (24k miles and 6-years old) and both the neck and coolant tank were pretty yellow. A single data point is almost useless, but perhaps the yellowing occurs pretty quickly with the as-shipped part. Problem is that it'll take a couple of years for my experiment to run its course.

ew928

Do other cars have engine bay tanks that yellow/ripen as quickly as the 928 tanks or is everyone a victim of German Plastics Excellence.

Are there more modern plastics that handle engine bay environments more gracefully.


My coolant reservoirs all hate me. (leak, neck crack in less than 2 years)
And damn that Stuttgart engineer jockey that designed the coolant reservoir and it's impossible mounting system.

FlyingDog

I would blame UV and heat more for changing the plastic yellow. My clear/white fuel jugs stayed that way event with gas in them for months. They got left in the sun one day and they were suddenly yellow. All clear plastics will degrade from heat and light. Most turn yellow as they degrade.