cooling system pressure and expansion tank cap

[overdrivegear]

It was recently brought to my attention that I should not use a black expansion tank with my diesel.  I did a 1.6 NA swap into a cabriolet (videos here):

1987 VW Cabriolet 1.6 Diesel engine running pt. 1

1987 VW Cabriolet 1.6 diesel running pt. 2

and I just kept the gasser expansion tank and cap.  Someone told me that if I keep that black cap, I will run the risk of blowing a head gasket
So my questions are, does the color of the expansion cap make a difference and if so what cap should I use?  Do these coolant caps actually vent pressure according to their color?  I was under the impression that these caps didn't vent pressure at all.

[GEE-BEE]

I installed the later round type tank....

 non sensor

GB

[the caveman]

The caps will vent , although only at higher pressures than normal-i.e. when you're overheating, so no, not in a normal fashion. In that case, i don't  see why a different cap pressure would make a difference, but i would try to find a definite answer if you're having issues.

[overdrivegear]

The caps will vent , although only at higher pressures than normal-i.e. when you're overheating, so no, not in a normal fashion. In that case, i don't  see why a different cap pressure would make a difference, but i would try to find a definite answer if you're having issues.

I'm not having issues.  I just wanted to avoid a noob mistake with the wrong 'cap pressure'.  Kinda sounds silly, but then again there is a fair amount of silly business with these Volkswagens and I wouldn't put it past them.

[Baron VonZeppelin]

I'm gonna say .... ol wives tale. 
[but reserve the right to be wrong]

Maybe should send this in to MythBusters.

I believe they will vent in the high teens-20'ish, but never seen black or blue listed as gas or diesel specific - or even listed with a psi rating. So figured they were the same other than color of the plastic.

I have both color caps amongst my a1/a2 diesels.
I think the score is 3 black and 2 blue, on my fleet.

[one_tinted_tail]

sounds like bumper fluid talk as well, and I like the reservation of right to be wrong, HA!

they pop at extremes, yes, but not aware of color/pressure differences.