Tip & How-To about Honda Civic

How to inspect,diagnose and repair minor over heating problem for under 2 hours.

Copyright © by Mustgo on Dec 2009

How to inspect,diagnosis and repair minor over heating problem in under 2 hours.

Thanks for viewing my Fixya tip post.

My goal is to solve the most common over-heat,running hot on stop and go traffic and intermittent cabin heating problem (no heat)

The target audience is DIY'er who has a car that's just starting to over-heating and has about 2 hours to ran though my check list.


The first part is basic universal safety.

Follow by steps the required to fully diagnose the root cause of the problem.

Example:air pocket in coolant system VS worn water pump VS blown head gasket.


Follow by THE FIX.


If you are just getting the initial sign of over-heating then you will be able to replace the thermostat,gasket,black RTV,coolant mix and 50/50 mix coolant temperature sensor and get back on the road for under $80.

For those who has leaks on the radiator,water pump the repair cost will be much higher.

Losing coolant and having WHITE smoke coming out of the tailpipe after 15 minutes of warming up is a sign of blown head gasket.
This is an internal head gasket damage and the engine head(s) must be remove to do a head gasket job.


My tip is for folk what are encounter over-heating on the first week.
Hopefully under 3 times of over-heating.

Repeat over heat will warp the aluminum head(s),blow out radiator hose(s) and radiator.




MAKE SURE safety goggles are on at all time.


You will spill some coolant during this air pocket purge test.......BE KIND TO THE ENVIRONMENT and ANIMAL please clean up after the test!


When the car is completely cool,check the electric fan(s) for smooth rotation.

Make sure there is not wobble movement or touching surrounding plastic.

Clean/check/change the thermo/temp sensor,contacts and wires.

CRC Electrical Contact Cleaner is the ideal chemical to speed up the cleaning job.

Clean the metal contacts on fan relay,inside the relay socket and fan socket.

Follow the sensor all the way to the firewall to make use it's in perfect condition.

Inspect other wiring for cut,and exposed wiring.

Use 3M high temp. electrical tape to protect damaged portion of the wire.



THIS IS A 30+ minutes JOB.

The longer you can monitor the coolant system will give you a better idea of the condition of the coolant system.

Excavate air pocket in coolant system / check for head gasket leak

Air pocket can be trap inside the coolant system.

The water pump's turbine / fins is totally ineffective when there is not coolant surrounding the water pump.

This test will kill two birds with one stone.

Most radiator shop charge $75 just to excavate / air purge the coolant system.


Top of the coolant reserve tank to the COLD / COOL / LOW level.

Put the front end on a pair of ramp or park your car on a VERY STEEP HILL (radiator facing top of the hill) .

Keep the coolant reserve tank cap in a safe location.

The goal is to lift the vehicle higher to monitor the air pockets and let it escape.

The radiator should be 8-20" high from the stationary position to let the air pocket to escape.

Let the car ran and start monitor the temperature.

Monitor for air pockets escaping from coolant reserve tank.

Small amount of bubbles is OK at 1-5 minute mark

After the thermostat open up at 195-210 F,Electric fan should turn on automatically

If your vehicle has a secondary electrical fan then turn on the A/C and all lights,radio,and electrical items to ensure the fan is operation.

5-12 minute mark or after high idle you should see less bubbles.

If you DO NOT see any in rush of bubbles when thermostat opening between the 5-12 minutes mark then the maybe partially stuck or rusted badly inside the thermostat hosing.

Give the thermostat housing few gentle taps.
(follow the TOP large radiator hose to the top portion of the engine)

If you see larger bubbles surfacing after 15 minutes then should do a hydrocarbon (HC) dye test to test for potential head gasket leak.

A coolant pressure test is also a must to pressurize the coolant system to locate addition leaks.

Examples:radiator,head gasket,freeze plugs,or water pump

Let engine cold down,lower the car onto level server and top off coolant reserve tank to the TOP / FULL /HOT level.

Start monitor for coolant lost everyday.



If the radiator cap is over 5 years old or rusted badly then change it.
The spring can be weaken and will not hold pressure.

I recommend the thermostat that has a relief pop-let to reduce the change of burst radiator and coolant hoses.

Thermostat,gasket and black RTV is not expensive and it should be change every 4 years or 48,000 miles.

A coolant flush is require every 2 years or 24,000 miles.
Check your service log for the last coolant flush.

Low heat condition is cause by combination of stuck thermostat,low coolant level,dirty coolant system and worn turbine / fins on the water pump.

If the water pump has over 85,000 miles on it then water pump can SLOWLY leak into the time belt cover.

The turbine/fins on the water pump can erode badly after 96,000 miles.

Monitor coolant level and check for water pump,radiator,coolant hose leaks.

Place a larger cardboard under the radiator,water pump or timing belt cover. Monitor the coolant drip and inspect the problem area accordingly

Visual Inspect your coolant reserve tank for bubbles when the temp. is near 195F+. (after a long drive) If you see hydrocarbon leaks then you should stop driving the vehicle until a shop do a pressure test and dye tests.


If my post is helpful to you then please rate it!

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Make sure you click on View Details to get the link below.

Entering 24,000 miles brings up this maintenance schedule:

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