Porsche Enthusiasts Club Forum

Anyone know why the when new 'white' plastic tanks in our engine bays for coolant, brake and washer fluids all go off 'yellow'? Is it age, fluid contamination, UV, heat, all of these things?

Having bought all new in the last six months is there any way of limiting the degradation to yellow going forward? The clutch and brake reservoirs were fairly cheap, but the coolant tank was very painful.

I binned the oversized washer fluid tank for a very well priced 0.5l aluminium drinks bottle, does the job brilliantly well. I did consider similar or a custom ally coolant tank!

think you can cross UV off that list, but don't know what the culprit is

I would think heat god to be the issue

You've not seen how often I have my bonnet up at the minute!!

Not necessarily as we use lots of clear and white plastics in the microwave to heat food at near 100degs, none are yellow (OK tomato based foods stain some red over time). The coolant tank in the 924/944 is well away from the exhaust/turbo and water temps in the tank are sub 90deg. Some cars seem to suffer more than others. Is it the plastic or the environment they are exposed to?

I was once told by someone that was in to concours preparation that it is just age. He said that over time the oil or an impurity in the oil used in the plastic starts seperate and rise to the surface. He did tell me that you could chemically strip the surface to get it white again but I've never looked in to it.

Plastic does lose its oil, which is why it goes brittle.

You could try a regular clean with a good trim detailer as that is absorbed by the plastic.

Just an observation here...my washer bottle is original (1988) and that seems to have stayed nice and white, it only needed a bit of a clean on the outside to make it look pretty good. I noticed the header tank was very yellow and stained inside, so I went for a new one. However, it seems the new 'white' plastic tanks are different in a few ways including (and I might be wrong) a change in the material? They now seem to match the washer bottle - they didn't before.

Having had a 924 in the eighties when they were 'new' I seem to recall that the plastic in those was never as white as this new stuff. Perhaps the yellowing is really just down to age and the characteristic of that material?

The clutch tank and the brake tank will get stained from the fluid and anything that 'grows' in there!