Odyssey ’96 - Coolant Vanishing

A few days ago engine overheated and blew loose the top radiator hose.
replaced the hose and engine is running fine but I have to keep addin
about 1 cup of coolant every day.

I cannot see any coolant leaks, either under the hood or under the vehicl
even after the engine has thorougly warmed up, or at the end of a trip.

I know that coolant can also leak into the engine combustion chambe
however:

The engine oil does not seem contaminated with coolant (ie. not milk
appearance).
No blue smoke from exhaust that I can tell (but keep in mind this i
summertime in dry California).
No engine light.

Any ideas on what may be happening?

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check for blown head gasket. look for bubbles in the coolant bottle
when the engine is running and at full temp. [on hondas, old "detroit"
symptoms of water in the oil or vice versa are /very/ rare.]

 

If your head gasket is blown, you'd actually see white-gray smoke
(even harder to see than blue). Blue is indicative of buring oil
(i.e., rings or valve seals).

Dan D
'07 Ody EX
Central NJ USA

 

Update:…

I an still not able to see any cooling system leaks…

I do not have a cooling system pressure testing pump, so, as a substitute
I created pressure in the system by letting the temperature rise.
disconnected the (2) radiator fans and let the engine idle until th
temperature indicator got to H (hot) but still no leaks. Soon after th
radiator cap valve opened (I guess this was when the pressure must have
reached 16psi) and then, of course, as expected, it started bubblin
inside the coolant overflow resevoir. But still no visible leaks fro
anywhere else in the system.

This is actually not my car, it is my neighbor’s 2nd car, I’m jus
helping out. However from his description seems like the last time h
noticed a coolant leak was after he had driven some distance on th
freeway (30 miles) and arrived to his destination. From his description
surmise that it must have been leaking/boiling over at the coolan
overflow reservoir. Also, from his description, seems like the boil ove
happened without the temparature gauge showing a temperature much abov
normal ?!

Does this info provide any more clues?.

Thanks again.

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there's no "as expected" about it - bubbles in the reservoir mean the
head gasket's gone. end of story.

it's going out the exhaust. see above.

head gasket on a honda is quite an involved process. if you decide to do
it yourself, google this group for a list of things to look out for. if
you pay someone else, don't do it before you do the math and consider
simply replacing the whole engine with a jdm import. labor for a many
hour job like this, that if not done right won't last long, is very
high. simply swapping out the whole deal is relatively quick and doesn't
take too long.

 

At least one of your head gaskets has gone south. You are blowing bubbles
in the coolant from a breach in one of the fire rings. This is a common
failure mode for Honda head/gasket designs.

Get a garage to confirm this with a pressure test and/or coolant test
strips.

The longer you monkey with the issue rather than fixing it, the greater the
probability that the engne will be economically unfixable.

 

Update:…

I an still not able to see any external cooling system leaks…

I do not have a cooling system pressure testing pump, so, as a substitute
I created pressure in the system by letting the temperature rise.
disconnected the (2) radiator fans and let the engine idle until th
temperature indicator got to H (hot) but still no leaks. Soon after th
radiator cap valve opened (I guess this was when the pressure must have
reached 16psi) and then, of course, as expected, it started bubblin
inside the coolant overflow resevoir. But still no visible leaks fro
anywhere else in the system.

This is actually not my car, it is my neighbor’s 2nd car, I’m jus
helping out. However from his description seems like the last time h
noticed a coolant leak was after he had driven some distance on th
freeway (30 miles) and arrived to his destination. From his description
surmise that it must have been leaking/boiling over at the coolan
overflow reservoir. Also, from his description, seems like the boil ove
happened without the temparature gauge showing a temperature much abov
normal ?!

Does this info provide any more clues?.

Thanks again.

-
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I pressure tested the cooling system this afternoon and it DID hold 20 lb
for 5 minutes.

I also did a compression test and obtained the following peak pressures:
Cylinder# - Pressure:
#1-173 lbs,
#2–167 lbs,
#3-170 lbs,
#4-160 lbs.

So now I’m confused!

P.S. Jim Beam: In my last post, when I described bubbles in the overflo
reservoir, I menat the entire coolant was actively boiling and tha
happened after the temperature reached H(ot) – remember I ha
disconnected the radiator fans to create both heat and pressure. Aren’
bubbles normal at that point? They are not gas bubbles from the combustio
it is the entire coolant boiling at that point.

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MEASURE COOLANT PRESSURE WITH ENGINE RUNNING?

Would it help to do a pressure test with the engine running? That is star
the engine and measure pressure. If pressure quickly rises with coolan
still hot then it must be gas leaking from the cylinders.

COMBUSTION GASSES VS. COOLANT VAPOR:

Sorry for the questions but I still do not understand the gas bubbles v
boiling coolant vapor issue. If you take a "healthy" cooling system an
disconnect the fan so that the engine overheats to boiling point then wha
happens? What would one observe? Wouldn't it be some boiling like actio
inside the overflow reservoir? Coolant vapor that forms inside the engin
and finds its way out into the overflow reservoir. Perhaps this coolan
vapor does not come in contact long enough with the cooler liquid in th
reservoir to re-liquefy and so comes out as coolant steam. Am I of
track?

PERHAPS STILL SMALL CHANCE THERE MAY BE AN INTERMITTENT EXTERNAL LEAK:

Perhaps, before I concede defeat, I'll have my neighbor drive the car on
more time on a longer trip on the freeway. He says that at some point h
had noticed some leak after running on the freeway and now that the cover
are off it may be possible to see where the leak is coming from and it ma
be, just may be, that it is not from the overflow reservoir.

COOLANT IS TRANSPARENT AND CLEAR:

One more thing, I took out some coolant from the radiator and put it in
clear glass bottle and it is completely clear. There's no sign o
contamination. Do they sell those strips for testing exhaust ga
contamination in the coolant at auto stores

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nope, that bubbling is head gasket. the cylinder pressure test doesn't
mean anything unless the leak is gross, possibly with head damage. and
the radiator pressure test doesn't mean much at low temperatures in early
stage gasket failure because the thermal and pressure distortion that
permits leakage hasn't happened.

and just so you know, the boiling point of antifreeze is >105'C, and
there's no way the coolant expansion bottle can reach that temp without a
direct heat source.

sorry to give you the bad news you're so keen to avoid, but there it is.
time to fix it asap before you cause permanent damage. in the future,
make sure the radiator/cap/hoses are in good condition. coolant loss,
even a little, can cause local overheating and the gasket will go.

again, examine the economics of engine replacement rather than repair.
many shops charge a fortune for a honda head gasket, don't do a good job,
and if they use abrasives, the motor won't last long, and it'll start
burning oil.

 

On Sun, 02 Nov 2008 21:43:26 -0600, ThomasE wrote:

<snip crap>

dude, you're in denial. change the freakin' gasket before you burn a
channel in the head metal, or worse, the block.

 

dude, you're in denial. change the freakin' gasket before you burn a

I still have not seen those head gasket failure telltale bubbles gurglin
up in the oerflow reservoir AT NORMAL OPERATING TEMPERATURES. The onl
time I noticed anything extraordinary in the overflow reservoir is when
artificially caused the engine to overheat (disabled fans). I have NO
ever seen bubbles coming up in the overflow reservoir at NORMAL or eve
HIGH-NORMAL operating temperatures (that is, above normal temp but no
quite at the H mark yet – that was during the disable fan test).

In retropect I think it may have been misleading for me to title this pos
“Coolant Vanishingâ€.

I’m not sure now whether it is vanishing or whether the coolant i
actually lost ONLY as a result of a boil over. It is not my car, it ha
not been me driving it, so I have to rely on my neighbor’s description
from when he last stopped driving the car 1 month ago and from my 3-
observations and tests while letting the car idle. I think, from what m
neighbor says, that there may have been instances of coolant loss withou
temperature rise, but he also talked about seeing coolant leaking unde
the car after certain trips.

More than denial, my primary motivator is trying to understand th
symptoms and evidence of this failure mode. I post mostly because I’
interested in cars, not because

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