2003 Civic- intermittant overheating

About a month ago my daughters 2003 Civic reached 100K miles and we had
pur family's long trusted mechanic do the 100K timing belt, spark plugs
and water pump replacement.

A couple of weeks later the car's temp gage rapidly soared up during
city driving. Not wishing to take any chances, daughter called AAA and
had her Civic towed back to the mechanic who'd done the 100K maintenance.

Our mechanic test drove it and told me that he couldn't get it to
overheat. There was plenty of coolent in the system and while we
discussed it on the phone I suggested that maybe the thermostat was
flakey and asked him to replace it. He did that.

The car didn't overheat again for about 8 days, but while on a road trip
the temp gage soared up while on the highway. She limped the car to a
repair shop where the mechanic there diagnosed it as a failed cooling
fan temperature sensor and replaced the sensor.

The car is still intermittantly rapidly overheating as indicated by the
temp gage. I showed her how to stop the car, open the hood, and see if
the cooling fan was running. She reports that it is.

I suppose that it could be nothing more than a defect in the temp gage
system, and the engine isn't really overheating, but the fact that the
gage sweeps up over a period of a minute or so and doesn't snap to a new
reading has me doubting that.

At this point my best guess is that something is causing the coolant
circulation to quit. My limited experience with Civics has me
remembering that the water pump is driven off the smooth side of the
timing belt, so perhaps there isn't enough tension in the belt to drive
the water pump properly and when the belt slips the pump stalls?

Thanks for any leads guys,

Jeff

 

no, that's the tensioner. the coolant pump is toothed so slippage is
not a problem.

much more likely it's the head gasket. open deck blocks like this car
just leak exhaust gas straight into the coolant with no other side
effects. the subsequent foaming doesn't carry heat away efficiently so
it overheats. it's a frequent occurrence with this model and most
people don't notice until it gets bad enough to start to overheat.

 

Now that makes more sense than my suppositions.

Is there a simple way to confirm that as the source of the problem like
being able to spot the foaming somewhere, or maybe by air pressurizing
each cylinder through its spark plug opening with the
crankshaftpositioned so that cylinder's valves are closed, and looking
for bubbles in the coolant?

Thanks,

Jeff

 

you might be able to get it with a conventional pressure test, but your
problem is that it tends to be one-way, and only when hot so
pressurizing the coolant and waiting to see if it drops doesn't always
show.

another [usually successful] method is to run a chemical test on the
coolant. but the kit is massively over-priced given that the chemicals
cost only a few cents.

yet another, if you have the gear, is to put a pressure gauge on the
cooling system, and run compressed air into the cylinders, and see if
you can get a pressure increase on the coolant side. it's usually the
middle two cylinders that leak.

i have strong opinions on repair of honda head gaskets that are not
shared by the majority of the repair industry. basically do NOT let the
head get skimmed unless it's actually warped. and do NOT allow
abrasives to be used in the clean-up process. google this group for
details.

last thing - if you're not repairing yourself, consider simply replacing
the engine with jdm. it's frequently much quicker and therefore cheaper
than paying for the extensive labor necessary for strip-down and re-build.

 

If you've got a head-gasket leak sufficient to cause overheating, you'd
find lots of air in the rad and a reservoir level way higher than normal.
Head gasket problems generally result in overheating at idle, not at speed.

Next time this happens, turn the heater and interior vent fan on, full-
blast. If this helps, then you have an intermittent circulation problem.

Was the new thermostat OEM or aftermarket?

 

later stages, not early. this might be later stage if it's overheating,
but then again, the coolant's been changed with both the coolant pump
and the thermostat work, so level is not a reliable indicator.

not a reliable indicator. late stage maybe, but some will overheat on a
long hill at full throttle, and be fine the rest of the time.

turning the heater on is "limp home" - it cures nothing. and
"intermittent circulation" problems on a honda? i've never seen one.

wouldn't have caused the initial overheats.

 

At ANY stage, if the head gasket is blowing.

If coolant is blown into the reservoir and the level in the engine is
low, the coolant will only circulate sufficiently when the water pump is
spinning fast.

If the problem is poor circulation due to low coolant, turning on the
heater will NOT help, which is which is why I suggested that.

I have. Aftermarket thermostat was sticky.

 

sorry dude, that's not accurate. if you drain and fill the rad, there's
air in the system. it doesn't blow the fluid out of the expansion
bottle, it just burps out through the expansion pipe and away.

same with head gasket - if the gas is not leaking fast, it burps. only
when it's leaking bad does it start to foam to the point where liquid
starts to fill the bottle.

see above.

when it's running hard, there's more gas getting into the coolant. if
it overwhelms the system, the motor will overheat. if it's not running
hard, it can usually cope much better. you need a system to be half
empty for the situation you're describing, and after a coolant and
thermostat change, that's most unlikely unless it's been really boiled.

if the coolant is that low, then yes, you will not notice any heat, but
it's not apparent that's what you meant.

i would avoid "intermittent circulation". low coolant is low coolant,
not "intermittent circulation".

that's "defective thermostat".

"intermittent circulation" is something like a collapsing hose - honda
have a steel pipe on the intake side of the pump so you'll never see one.

 

Well, I just picked daughter up at our trusted mechanic's shop where she
brought her Civic back in. He found the coolant about 3/4 gallon low,
which says to me it's losing coolant at a pretty good clip. There's been
no white "smoke" out the tailpipe and no "sweet smell" there either.

Daughter told me that when she had the fan sensor changed "on the road
trip" about ten days ago the fellow who did the work had to put about a
gallon of coolant in. She said she drove over 300 miles before the
overheating started showing up again.

My mammary just reminded me that maybe 20 years ago I located the source
of a similar mystery coolant loss. It was a hole in the expansion tank
which was causing a loss of coolant, but naturally that wouldn't show up
in a coolant system pressurization test.

Wouldn't it be a pleasant hoot if all that went wrong was that they did
something to disconnect the coolant expansion hose when they did the
100K maintenance, and then forgot to reconnect it?

I just pinged our mechanic and asked him to look for that.

Jeff

 

I'd never use an aftermarket thermostat on a Honda,except for an
emergency,and then only until I could get a real Honda TS.
The aftermarket one listed for my Integra GS-R was the wrong temp,too;180
degF instead of the specified (IIRC)195 degF proper temp rating.

A real Honda TS is not that much more expensive,and it could save your
motor.

And watch out for reversed installation of the TS. that's not good.

--
Jim Yanik
jyanik
at
localnet
dot com

 

Sounds like a case of a bad water pump.