I have a 99 Civic LX (D16Y7) that has an overheating problem. The fan will not come on until it is almost at the red-line. Also.... the expansion tank gets full, but the excess coolant will not drain back into the system. I have completely flushed the cooling system. I've jumped the fan, so it does work. The relays work. I have changed the fan temp switch, thermostat and radiator cap. I've pulled the spark plugs, and they are normal. There is no black film in the expansion tank. There is no sweet smell coming from the exhaust. When I top off the coolant and burp the system, it will behave for about a week, but then it does the same thing. Is there a reason the coolant is not draining back into the system? I think this is how air gets back into the system. Any help is appreciated!

 

Sounds like a few problems. My good friend is a mechanic, I'll ask him and get back to you soon.

 

Same **** going on with my 99 hatch back

 

buy a coolant pressure testing kit and test it.. or bring it to a shop and have them diagnose it..
usually adding pressure will help find any leaks in the hoses radiator etc..

 

Thanks for the replys. Moolah is a little tight right now and was trying to stay away from the mechanic. How much would it cost to get the pressure test done?

 

i think autozones loaner tool program has a coolant pressure testing kit.. not too sure tho..
that would be the ideal way for you..
if not.. you can probably find a cheap kit for like $20..

 

coolant will not flow back, bad radiator cap, it is a two way valve, it also has to hold like 15 PSI or it will lower the boiling point of the coolant. Is the overflow bottle overflowing and making you loose coolant, that is a blown head gasket, do not fill it past the full mark. You dont need a sweet smell out the exhaust, coolant may not get into the exhaust but exhaust can get into the coolant, a CO test with a 5 gas analyser can determine that but you are short on funds. The Autozone pressure tester loaner may not have a fitting to check your Honda cap and radiator so ask for sure. If there is a leak at a hose or water pump, it may only leak at certain conditions, this may not be when fully pressurized at say 14 PSI, no leaks on the driveway??? Blown head gasket may be very minor now. ALSO there may be a fan timer on this car and it may be out of spec but not all Hondas use the timer, did you ever notice the fan on when the engine was off in the past, if not, then probably no timer.

 

Duane,
Thanks for the info. From what you have described, it sounds like I might have a small head gasket problem. There are no leaks in the driveway. The fan does not come on when the car is off. The rad cap is brand new. Is there another possible reason the coolant is not returning to the radiator? There are no cracks in the return hose or cap for the expansion tank. Thanks again for everybodys response!

 

Is it an OEM proper part number cap, if you suspect a head gasket, then get a CO2 test done at a shop that understands this with their 5 gas analyser. Most folk look at HC but antifreeze is HC (partially).

 

Yes, it is a OEM cap. I'm now suspecting the HC because NOW my heater does not blow heat at all. It still does not leave a leak anywhere that I can see. Not on the driveway, not on the floorboard.

 

It probably getting worse everyday, get it fixed NOW.

 

Thanks Duane, will do! Again thanks for everybodys input. Much appreciated.