Will, when your financial aid comes in, may I suggest that you buy a white, 100kPa cap? These are also known as 1.00 Bar caps, because 1.0 bar = 100 kPa. I use one on my 1991 745 SE Turbo. The very high pressure of the green, 150 kPa caps scared me for cooling systems this old and with the known weaknesses that they have (heater control valve, etc). But I thought that the very low pressure of the 75 kPa caps would not prevent localized boiling in the hottest parts of the engine, the parts that need constant cooling the most. Localized boiling disrupts cooling by breaking the coolant-to-metal contact at the site of the boiling. I was able to find the 100kPa caps at FCP Groton. When you input your car's make, model, and year from the drop-down menus, just tell the site that you have a Volvo, 240/260 diesel, 1981. The caps are just $4.99 + shipping. It seems that a Volvo screw-on cap will fit nearly any Volvo coolant tank: mine is on a new, genuine Volvo 960 tank in a 740, and it is identical to the old green and black caps that I have, and will fit the original 740 tank too. So, compatibility is not a problem.

If you do install a 100kPa cap, make sure that your hoses are in good enough shape to handle the slightly increased pressure. And, of course, make sure your heater control valve is in good shape. I have had new ones, of the all plastic design, begin to fail on me in just a couple of months.

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Scott Cook - 1991 745T, 1985 RX-7 GSL-SE, 1986 Toyota Tercel (Don't laugh, it is reliable, faithful AND gets 41 mpg!)