I am Greek, but i'm living in New York City which does mean leaving your car parked in the sun all the time. on a side note my brother found a aluminum tank for a good price for an s13 that we are going to modify to fit.
I meant hood off so the plastic is exposed..UV light is hard on most plastics..
And Mmmmmm Iduno about how wise the S13 idea is.
See, the japonaise tend to have a little 8mm line in and then an overflow..pissing coolant onto the ground.
The stock way Volvo does the tank is really
THE RIGHT WAY. They way it works is how serious race/rally cars do and it's really properly called a "de-gas" tank..
See..coolant cools...but a frothy mixture full of air doesn't cool in the same way (air being a nice insulator..So if you're making some heat and the coolant in direct contact with say the head around the exhaust port and it is boiling the coolant right at the surface --you get bubbles in the coolant..
The stock set up pisses that coolant into the tank and the frothy aerated coolant sits on top, and the all liquid coolant drawn off the bottom goes back to the rad either directly like stock Volvo or in some of the cars I have done, via a T in heater return pipe.
It is a VERY GOOD way to plumb the car...In my V4 powered Saab I had cooling problems and bleeding (got to bleed out the air or I would have severe cooling problems--Saab being nice, gave you a bleed screw on the back of the heater element to do this) and just replumbing the car to use the Volvo 240 tank solved all the problems..It was a "single change" experiment so the change was clearly result of the re-plumbing..This allowed me to run 1 step hotter heat range for the spark plug...and solved a tenancy to wet the plug on cold starts on cold days. I did this in 1987 and it was interesting to see that with the Saab 900 they routed the coolant the very same way as Volvo---and that was different than how they circulate the coolant in the Saab 99 with the same engine..and 900 had vastly fewer problems with localised overheating..
I believe the problem is called "nucleate boiling"..and it is a problem.
IF you decide to use the S13 tank because it's shiny mod it so it functions exactly like the OEM tank.