87 4kq coolant reservoir cap bad?

[Brett Dikeman]

At 11:16 PM -0700 4/18/03, auditude at cox.net wrote:

>Once the cap pops, it has to be replaced.  It's like a fuse that way.

Yeah- for some reason, they never seem to seal right after they've gone.

>   You should be able to get a new one anywhere, but especially at an
>import parts place.

Why?  The dealer charges barely $10.


>I don't know if there are different pressures, but if you spec one
>for the car you should be fine.

The cap on my car(blue, like the old one) is from the VW parts
department, and I matched part numbers- they're all the same AFAIK.

>I'm wondering if you had a different problem that caused it to boil over


Nah.  Overfilling the tank would cause it to pop...you've -got- to
have some air to provide room for the coolant to expand.  If there
isn't enough air, that doesn't change the volume the water needs to
expand when it gets hot, and you will overpressurize the tank.  When
the cap releases, you'll get a surge from hoses etc contracting, and
then a boilover from the coolant's boiling point dropping suddenly
due to no pressure :-)

B
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