93 civic temp gauge is rising - please help

I have been having a problem with my Honda Civic DX for the past few
months, since the spring weather got warm. My usual commute was about
40 miles highway (65 to 70 mph), then about 5 miles of stop-and-go
traffic in town. Once I got into town, and sat at a stop light, my
temp gauge will start to climb either while I was stopped or when I
accelerated. Turning the heat on full-blast would cause the temp gauge
to fall back to its "normal" position. I have also found that if I
leave the heat vents in the open position while driving, the temp gauge
will stay at its "normal" position (but this is not fun in the summer).
As I stated, I first noticed this problem in the spring, and I am
guessing it is because I had turned the heat down lower than it was set
in the winter months (I live in Pennsylvania).

Outside ambient temprature also seems to have an effect on the
situation; the only time the temp gauge has risen when I was not doing
long distance driving (I was just running down to the conveinence store
2 mi from my place) was thus: I had the heat vents closed, and was
stopped at a stop light (one with a particularly long cycle). I
accelerated when it went green, making a left turn going up hill. The
temp gauge shot up. I turned the heat on full-blast, and it wen back
to its "normal" position. This was on a rather hot July day.

My car is currently spending the night at the local dealership. They
had it all day today, and could not even duplicate the inital problem:
they can't get the temp gauge to rise past its "normal" position. They
are going to keep it another day to try to solve the mystery. They
reported to me 3 things: 1) the fans are coming on, 2) the pressure
for the cooling system checks out ok and 3) the coolant was low
(whether this was in the resivor or radiator I am not certain, but will
ask tomorrow when I call them).

Let me give a bit more background about the car. She is a 93 Civic DX
automatic. I bought her in 2003 when she had 100k miles on her. The
timing belt was new, and the water pump was replaced shortly after I
purchased her (someone had installed it incorrectly, leading to a
coolant leak). I have had the car in for services 2x since then, both
times with a trusted mechanic/dealership: the first service was at
105k, and the second at 120k (last October). The car currently has
about 132k on her. The oil was last changed (and fluids checked and
topped off) in May. Since the middle of May, my commute has been
severely cut (I teach, so I am off in the summer), so I am not putting
many miles on the car right now, just short trips around town; this
past schoolyear, I was putting between 80 and 100 miles per day on her.

I have done some reading up about similar problems others have
experienced with their Hondas, and came up with a few possibilities: a
plugged rad, a blown head gasket, a bad thermostat, and a timing belt
and water pump that need replaced. I am hoping maybe someone will read
this post, and have other ideas about what is going on with my car, or
maybe someone who has experienced the same problem can post something
helpful. The mechanic at the dealership seemed to think replacing the
thermostat would help, as he has seen a similar problem in another
Honda before, and that seemed to cure it; but I don't think that
explains why the coolant would be low.

 

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Ummmmm, why would you take the car to the dealer without checking and
seeing that the coolant was low? That's your job. Why would you not
check the coolant 'for the past few months'.

Forget the Internet for now, just move the owner's manual to the
bathroom. It's not doing any good in the glove box, presently. Read the
recommendations about when you've "had work done on the cooling system".
It says fill reservoir to MAX and check it (from time to time). I'd
suggest three days in a row, when engine is COLD, and top up to MAX
again until it stops 'sipping' coolant overnight.

'Curly'

 

Give them a tad more credit: Thermostats do fail, and your
car is old enough for it to do so. Failure most certainly
does typically cause overheating. Replacing it is
inexpensive and also preventative.

Right, that may be just normal consumption of coolant. A
little is lost from the cooling system over time and between
coolant changes.

Do not let the temperature gage climb into the red zone.
Pull over if you must and let the car cool down. Overheating
the engine can cause more expensive damage.

That the system passed a pressure test is a good sign. You
might also inquire about the dealer testing the coolant
chemistry for combustion gases. This too is a tipoff that a
head gasket etc. has failed.

You've done good research. I know there are many sites that
discuss head gasket breaches. Read them carefully and look
for the symptoms, since it's about the worst case scenario
here.

Hopefully it is just the thermostat. In the alternative, the
radiator may indeed be partly clogged or require a good
cleaning.

Updates are welcome, to help others.

 

Let me make something very clear - I am almost neurotic about checking
the coolant in the car. When I was doing my school commute, I was
getting the oil changed about every 6 weeks, which meant a fluid check
as well by the mechanic; they reported to me they never had to put more
than a "splash" into the resivor; yesterday, the coolant was much lower
than a "splash"; IIRC, he said it was about 1/4 low. I also would pop
the hood at least once a week to check the resivor. But, apparantly,
the resivor isnt a good indicator, as I am learning now, I have to
check the radiator itself. I also check for spots under the car every
time I pull out of a parking spot, and especially after parking her
overnight.

 

Thank you so much, this helps to clarify why the coolant would be low
and the thermostat not working. I will definately update over the next
few days.

 

Just a quick update - I called the mechanic to confirm that the TB/WP
were replaced at 100K 3 yrs ago. I asked him if it could be a plugged
rad or blown head gasket. He said if it was either condition, the car
would be overheating while I was driving (which it has never done). I
asked him about the coolant, and he said it was about a quart low
yesterday when I brought it in, and confirmed that I should
periodically check the coolant levels from the radiator rather than the
resivor (which I learned yesterday).

I also wanted to re-post a very useful link I found on this forum last
night: https://techinfo.honda.com/rjanisis/logon.asp From "Owners
Manuals" on the left-hand column you can access PDF manuals; I've found
this to be especially useful, since my manual is in the glovebox at the
moment.