We have a 95 Civic (125K miles; very clean and in pretty good shape)
which we use occasionally. About 1.5 years back the temp indicator
rose to almost 75% (had never happened before). I opened the hood and
the coolant reservoir was empty. I topped it and took it to the local
Pep Boys for a check. They said that the radiator was leaking and
replaced it.

Now, 6 months back I got a high temperature indicator and once again
the reservoir was empty so I filled it but then every few weeks the
tank would go empty. I examined closely and it seemed like the top
hose connecting the radiator to the engine might have been loose (had
some leak around it) so I fixed it.

About 2 weeks back when I took the car for an oil change I asked the
mechanic to see if there was any evidence of a leak around/beneath the
engine but he didnt find anything.

Now 4 days back once again the temperature rose to almost 90% (just
below the red line) on a hot day as I was nearing home. But this time
reservoir was full, however I opened the radiator cap and directly
filled it with coolant (took almost 0.25 liters in which was puzzling)
and the car has been running fine since then.

However I still took it to a local mechanic (he's pretty good) who did
a compression check on the radiator and it seemed like it was slowly
leaking. He also did a combustion leak test (http://
www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm) and
found that there are exhaust gases in the cooling system (the blue
liquid instantaneously changed to yellow). He thinks its the head
gasket and quoted me $900 for the job (including machining the head).
Now before I shell out $900 I want to make sure that it indeed is the
head gasket. Some questions which I have are:

(i) Could it also be a leaking water pump (hasnt been changed in a
while even when the timing belt was)?

(ii) Is the combustion leak test perfectly accurate (this morning I
ran the engine for about 10 mins and didnt observe any bubbles at all
in the radiator).

Any advice from you talented folks on rec.autos.makes.honda is much
appreciated.

Update:

I took the car to the local Honda dealer who diagnosed the problem to
a leaky water pump. Now I am really confused as my mechanic thinks its
the head gasket (based on the compression leak test; see my original
post) but Honda dealer says otherwise.

My mechanic can do the head gasket as well as the water pump timing
belt for ~$900 (I live in the mid west) so I am thinking of replacing
both. Does changing the head gasket has any adverse effect on the
engine performance because t works really well right now (just as
new) ?

| www.arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm) and
This liquid costs US$50 ! 1 can use ordinary pH indicator
strips ( has 4 colours ) to detect a rise in acidity ( caused
by CO2 dissolved in coolant ).