Coolant Vanishing: '95 Civic EX 1.6 - Attn Tegger and Techs

my idle question is, how much negative pressure is required to suck
the coolant in. obviously, the spring keeps the in valve shut at zero
pressure, but when the coolant cools off, there's negative pressure in
the block which sucks the coolant from the reservoir. we assume the
pressure of the spring on the valve leading from the block to the
reservoir is what it's labeled as, but i just wonder how much residual
vacuum remains in the block when the spring shuts the input valve. for
no reason other than idle curiosity.

 

Actually, the thermostat on most cars is below 212 F. And the boiling
point is above 212 with the antifreeze.

It's actually going to be about 4% from O to 80 c (about 180 F).

http://www.simetric.co.uk/si_water.htm

Coolant will expand by a different amount, because it has antifreeze and
other additives in it.

Solids don't increase by 40% in volume from -40 F to 212 F. Why would
you think water would?

Jeff

 

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Yep. That's exactly what I said in the first place:

'Curly'

 

try driving up grapevine [california i5], in summer, at 95. i guarantee
you'll see more than that. unless there's something wrong, it won't
overheat, but fluid level will be right at the top of the bottle.

 

almost zero. there are two springs - one for high pressure exit, the
other is practically zero return. unscrew the radiator cap when cold
and see how much vacuum there is when you release.

 

There are no springs on the inlet valve.

If you study the bottom of the rad cap, you'll discover either:
1) a round, thin rubber flap smaller than a dime, or
2) a wiggly post with a plastic disc on the end of it.

These are the inlet valves. It takes /next to/ zero negative pressure for
the rubber flap type to allow coolant back into the rad, and /definitely/
zero for the wiggly post type, which is always open until pressure shuts
it.

This assumes, of course, that both types are CLEAN. Goop and crud will plug
up the inlet and prevent free flow of coolant back to the rad.

This futher assumes you're using the correct OEM ND caps. If you've got
aftermarket crap, all bets are off as to how they work.

 

wow. i stand corrected. my "estimate" obviously didn't include the
zero temp term,
i.e. if volume = A +B(absolutetemp) I was estimating that A = 0, which
obviously it doesn't.