I need to replace the cap in my 88 745t. There are cracks around the top of the cap. I don't know if the one I have is the original, (correct rating) but it's grey in color. Groton's website offers the Black, White and Green. Which is correct?

Thanks,
--
Erwin in Memphis, '95 855t

Black cap it is. I'm getting an order ready today and will have one added.
--
Erwin in Memphis, '95 855t

Yes, go with the black cap. The ".75" measurement refers to kPa rating, or the pressure rating of the cap. I can't remember the exact conversions, but 75 kPa equals about 10-12 psi I think. Anyway, the black cap is the lowest available (grey is 100kPa, and green is 150kPa).

The reason to use the weakest one is that the higher pressure caps MAY rupture your existing cooling system. Over time the hoses, radiator, and connector undergo extreme stresses and wear in the engine compartment (engine heat, coolant heat, pressure, etc.). You may replace any one of these components with a new one capable of withstanding the green cap (all aftermarket radiators are generally able to withstand 150kPa). However, unless you replace ALL the components and hoses you still run a risk.

good luck,
rt

Switch to the black cap. It is the lowest pressure (easy on your hoses, radiator, cooling system) and least problem prone cap. I have switched to the black on my 765T and 944 and my Volvo mechanic agrees competely. Do search on this and you will find the same recommendations.