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

I told them to look for signs of a leak. If they find none, they
will call me. How much should a dye test cost, and is it better or worse
than a cylinder pressure test? The car already had a system pressure
test, and passed.

 

you don't usually do a separate dye test for antifreeze since it's
already dyed. dye is more commonly used for differentiating different
types of oil leak [engine oil and mtf are similarly colored and hard to
tell apart sometimes] or for a/c systems.

the best thing at this time is to take the vehicle to someone that has
an interest in fixing the problem, not trying to tell you the vehicle is
too old to be worth bothering with. there are plenty of independent
honda specialists out there. find one and check to see if they have a
good reputation.

 

The two tests are meant to check for different problems. They are NOT
equivalent.

I'm assuming the "system test" means they checked the cooling system by
pressurizing it. If that test did not use dye, then the test was
incomplete. A dye test also will not pick up leaks that come from the water
pump, since those leaks take lots of time fo be seen from under the timing
belt cover.

If there is suspicion on a head gasket leak, you must do the cylinder
pressure check.

 

Only if they can confirm a leak into the cooling system from the
combustion chambers. And this is not difficult.

A head gasket is not something you just go and replace on a whim.

No. They need to remove the crank pulley and lots of other parts when
replacing the timing belt.

That's a good idea, but does add to the labor cosrt.

I'm not working from home for the time being (BIG adjustment after
working from home for 5 years) and putting in lots of hours at the
office. My replies will therefore not be as timely as they used to be.

 

I appreciate the replies. I'll have them do the pressure test if
there is no sign of a leak. If it's the kind of leak a dye test would
show, it should be visible by now anyway, I hope.

 

-----------------------------

I should have said "Coolant that is _boiling-hot_ isn't supposed to take
up much more room than cold coolant, as long as the rad cap is keeping
the pressure up".
The word 'boiling' was used as an adjective, not a verb the first time.
If you (disable the cooling fan so as to) boil it, you'll certainly fill
the reservoir to the top, but in a healthy Honda cooling system, the
level in the reservoir isn't supposed to go up and down 4 - 5 inches
every time you drive it.

'Curly'

 

What did the dealer say he thought the problem was?

If the reservoir is empty, but the radiator is full (I'm still not clear if
that's what you are saying), have you checked that the reservoir itself, or
the hose to it is not damaged and is actually letting the coolant leak out?

 

but that's not true. as the liquid warms up, it expands substantially.
that's why the "max" mark on the bottle is only half way down, not
near the top. and that's why old fashioned thermometers work - as the
volume of liquid in the bulb expands, it rises through the tube.

http://www.forestry-suppliers.com/product_pages/View_Catalog_Page.asp?mi=8225#

 

but that's not true. as the liquid warms up, it expands substantially.
that's why the "max" mark on the bottle is only half way down, not
near the top. and that's why old fashioned thermometers work - as the
volume of liquid in the bulb expands, it rises through the tube.

http://www.coolstuffcheap.com/verther.html

 

----------------------------

Apples to oranges. The thermometer has a capillary tube that amplifies
the amount the mercury or spirit is expanding, and it's expanding toward
the air bubble at the top. That's exactly like the Volvo or Dodge system
with the pressure cap on top of a reservoir half-full of air.

The Honda coolant expands a bit and builds pressure, but it's the hoses
that probably absorb most of the expansion, not the reservoir. If you
were talking about gasoline expanding, that's very different. Water
doesn't compress, and until it boils it doesn't expand much at all.
That's why the water pipes in your house hammer when you shut off a tap
suddenly. For that reason I've installed an air trap in the water line
to my bathroom shower as a shock absorber. All is now quiet on the
Western Front.



'Curly'

 

motsco_ wrote:

Water will expand by about 4.3% from freezing to boiling:

http://www.newton.dep.anl.gov/askasci/chem03/chem03335.htm

So if a cooling system contains 8 liters of water (about 2 gallons), it
will expand by about .3 liter, which is about 11 onces, or nearly the
volume in one can of soda.

The coolant will expand by a different amount, because it is not pure water.

Jeff

 

I think the key here is; "Liquids cannot be compressed."

If a given liquid (at normal ambient temperatures) is heated, it will
expand but remain in a liquid state hence, it has to go somewhere to
accommodate the resultant expansion.

In modern cars, this is the coolant reservoir while in the older tin of
the past, it was simply the space at the top of the radiator.

JT

 

Liquid expansion indeed would be accommodated by hoses until the psi
equals and surpasses that of the radiator cap setting at which point,
coolant will flow into the reservoir.

As I stated earlier, a liquid cannot be compressed (volume-wise) but it
certainly can react to pressure, (boiling point etc.), so accommodation
must be provided for such expansion from temperature increases.

BTW, at around 39°F, water is at it's most compact physical volume.
Temperature increases/decreases will cause it to expand.

JT

 

no, they're fiber reinforced so this /doesn't/ happen. or at least, not
to a significant extent at 13psi. otoh, you can argue that the metal
tubes in the radiator expand if you really want to get fixated on this
stuff.

but what we're discussing here simple thermal expansion, not boiling.
"expansion" when boiling is due to phase change - a whole different ball
of wax.

water is one of the few substances out there with weird anomalies in its
thermal expansion coefficient.

 

apples to apples - it's exactly the same principle.

and how many liters of fluid are in the bulb? it's /exactly/ the same
principle having a 3 liter coolant system and a 500cc expansion bottle.

it's not an air bubble.

it really doesn't matter whether the expansion bottle is pressurized or
not - the expansion is the same because the volume of the liquid is not
affected by pressure.

untrue - the fiber reinforcing of the hoses is there to specifically
prevent that. it would be impossible to maintain the 13psi pressure to
prevent boiling if the hoses could simply expand.

dude, did you read the wiki cite? thermal expansion coefficient of
water is /huge/ compared to something like steel.

indeed, but it's got nothing to do with thermal expansion.

 

It turned out to be a leaking water pump. I believe the Grand Prize
goes to Tegger (or maybe Ray) for guessing that. I'm relieved. The pump
also had one frozen bolt, so I'm wondering if the pump really *was*
replaced 5.5 years ago and 50k miles ago, like th printout from the West
coast dealer said. It shouldn't have been in such bad shape - the
replacement interval is 6 years and soemthing like 80k miles...

 

Er, the entire structure expands as temperature rises... Engine,
radiator etc.

Um, I said "boiling point" as a yardstick that is subject to change
depending on how much pressure the liquid is subject to at the time.

 

But it does. ALL materials expand with heat.

The reservoir level naturally rises and falls as the coolant heats and
cools. This is the purpose of the various seals in the rad cap, and for the
very presence of the (unpressurized) reservoir in the first place.

You don't have to take my word for it. Check your own reservoir's level at
dead-cold. Drive the car to full-hot, then have another look at the level.
It will be at least a half-inch higher.

Coolant is constantly traveling in and out of the reservoir with every
heat-cool cycle. It's a normal and necessary feature of a modern sealed
cooling system's operation.

 

?? the average honda owner, meaning me, can see a rise of maybe an
inch or so in the reservoir after the engine is hot.

 

of course, the coolant at operating temp is quite a bit above the
"boiling point" of 212 degrees, that's why it's pressurized.
in other words, you've gone from about 500 fahrenheit degrees above
absolute zero, to about 700 degrees. as a first approximation, that's
gonna see a 40% expansion. i hope your hoses don't expand that much.