Cooling System Understanding

Have a 98 Civic EX; 162,000 miles; Last November at 150,000 did a flush and fill after acquiring the car..At that time made sure that antifreeze in overflow bottle was at MAX mark and radaitor was completely topped
off; watched it for a couple weeks; no change in fluid levels...no symptons of overheating
1 week ago I had to add approx 1 quart of antifreeze (using dexcool) to the radiator; antifreeze in overflow bottol was at MAX level..Temp gauge stayed at 9 O' clock position all week after adding antifreeze..
Today watched the temp needle go from 9 O'clock position to close to the red mark ..A/C was on at the time; and was idleing in traffic..At highway speeds the temp needle is at a 9 O'clock position rock solid.. Radiator fan is on; condensor fan was cycling off and on every 18 seconds.. No visible signs of leakage and do not see evidence of antifreeze in the oil..Added another quart of antifreeze..Might have headgasket going bad..
Both times the fluid in the overflow bottle was still at MAX level..even though I needed to add 1 quart to the radiator..
Question's, isn't the radiator supppose to draw coolant from the overflow bottle should the antifreeze level in the radiator drop??
Does this sound most probably like headgasket going bad ??
Thanks,
Rich
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On 7/19/07 5:42 PM, in article 5DRni.29008$ snipped-for-privacy@newssvr23.news.prodigy.net, "Big Brother"

You'll get some comments about using dexcool in a Honda. Anything other than Honda coolant makes them eat water pumps.

You have a leak. Probably the water pump, but also check hoses, heater core, radiator itself.
As soon as the radiator gets air in it, it is no longer able to draw anything back in from the overflow tank, so nothing will happen there unless & until there is absolutely no air in the rest of the system.

Not really. Headgasket going bad usually involves the radiator boiling over. You'ld see it bubbling up in the overflow tank. Check the coolant for an oil slick and check the oil for milkyness (coolant in the oil). Either or both are subtler symptoms of a headgasket failure.
It sounds more likely from your description that its just a leak.

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E Meyer wrote:

well, technically, it's simply bubbling exhaust gas, not boiling as such.

with an open deck honda, [what the op has] coolant in the oil extremely rare. pressure leakage is straight into the coolant and that just bubbles out of the expansion bottle.

for a honda like this, coolant loss, bubbles in the expansion bottle and sweet exhaust small on morning startup are the most likely symptoms. but if they're uncertain, use a chemical test.

leaks warrant serious investigation. leaks from the coolant pump can precede disaster if the pump bearing seizes. likewise, coolant loss to the extent the motor overheats are highly likely to cause head gasket failure. gasket won't leak fast at first, but it /will/ start to leak, and get progressively worse as the miles roll by. fix leaks asap!

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Big Brother wrote:

It can't do this if the radiator cap is not sealing correctly. Pressure test the cooling system for leaks and pressure test the cap to check its seal. The cap should hold about 13-14 psi or whatever is marked on the cap.
Eric
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I would have thought of that if I had enough time <8^P
Yes, the radiator cap should be the first thing. I recommend replacing it with a genuine Honda cap on suspicion if it is more than a few years old or is an aftermarket cap. The top seal is vital to recovery of coolant from the reservoir; the tiniest leak there will replace coolant in the radiator with air as the engine cools.
Mike
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