cooling system pressure and expansion tank cap - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

• cooling system pressure and expansion tank cap by overdrivegear on 07 Jun, 2010 21:21
• 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.
  
  
• #1 by GEE-BEE on 07 Jun, 2010 22:29
• I installed the later round type tank....
  
   non sensor
  
  GB
• #2 by the caveman on 07 Jun, 2010 22:36
• 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.
• #3 by overdrivegear on 07 Jun, 2010 22:45
• Quote from: the caveman on 07 Jun, 2010 22:36

  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.
• #4 by Baron VonZeppelin on 08 Jun, 2010 00:20
• 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.
• #5 by one_tinted_tail on 08 Jun, 2010 01:39
• 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.