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2002 Honda Accord 4 cylinder cooling system

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Apr 22, 2019, 7:08 AM

Post #1 of 2 (180 views)
2002 Honda Accord 4 cylinder cooling system Sign In

My 2002 Honda Accord 4 cylinder (213000 miles) has been giving me fits with cooling system issues. Last summer, I replaced the coolant temperature sensor and thought I had licked the problem. I neglected the obvious radiator cap replacement at the time. I've just replaced the radiator cap but in the process of messing around with this latest cooling system problem, I've noticed that the radiator fan does not come on when the engine comes up to temp. I unplugged and shorted the barrel connector to the temperature sensor with the system energized and found that both the radiator and condenser fans come on. Could my new temp sensor have gone bad this quickly? I'm considering ways to test the new temp sensor but trying to maneuver a cup of boiling water into the engine compartment so that I can plunge the temp sensor into it seems like it will be a little tricky. Is there something I can do to test the temp sensor? Could a combustion gas leak from a head gasket issue cause a lowered temp and therefore prevent the fan from coming on? I hope not because I can't even test the system pressure because the kit that the parts store rents out does not have an adaptor that fits despite the manufacturer's claim that it does. Should I just throw up my hands and walk back into the parts store and tell them that they sold me a temp sensor less than a year ago and now it doesn't work?

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Apr 22, 2019, 8:59 AM

Post #2 of 2 (169 views)
Re: 2002 Honda Accord 4 cylinder cooling system Sign In

Have you pressure tested this cooling system? Same tester should also test the cap. If not you can still know something start with a cold engine. Now squeeze an upper or lower hose, feel the pressure should be zero now how much it takes to just pinch it on a long stretch. Now start the engine and before it has time feel the same spot. Should take some times (several minutes) before you feel much change or a change in temp - careful of heat and moving parts of course.
If it never builds pressure it's losing it somewhere leak or not. Coolant would boil and fool sensor(s) and be super late or stay confused so doesn't know to send signal to run fan.

Why? Any cooling system leak AFTER the pressure cap even if remote to a tank that little hose counts. If this used cap on radiator you'll find it low should always be full to spilling or close only check while stone cold.

So whether boiling (vapor) or an exhaust leak into system either are vapor doesn't exchange heat so it just get's worse. The later would build pressure quickly fooling the test above with pressure before it had time for plain expansion by temperature to make the pressure - follow me? You can do that without tools.

From there get it tested or buy or rent a cooling system tester. Beware it could push coolant backwards and lock engine if leaking from engine gaskets. Harder to do is take plugs out and turn engine by crank bolt, not much room and don't thing you can get at it thru a wheel well? Check that anyway. It wouldn't turn by hand or if coolant in cylinder lock or plug out there it is - coolant comes out is a diagnosis.

Sorry for the long read but that's where I'd start with that complaint. Damage unknown fully until apart to fix depending on even more testing,


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