Head Gasket problem?

I flushed coolant of my 98 Accord a week ago. Some very small liquid
drops sprayed out from exhaust pipe while the car was left idling
there to get the fan turn twice (required for coolant flush). A palm
sized of ground behind the exhaust pipe got wet after 5 mins. It
smells and looks like coolant. I didn't see that problem again after
that day. Coolant level didn't have any obvious change in the
following week. The coolant temperature is always normal too.

Yesterday, the Check Engine Lamp is on while I was driving on a
freeway. The DTC is P0420 - "catalyst system efficiency below
threshold".

I wonder if this means the head gasket is blown that the coolant
leaked into engine and then into catalytic converter? Or they're
irrelevant? If this is true, how come I didn't get high coolant
temparature?

Thanks.
-H

 

So, no coolant loss?

If so, I'd say either one of the O2 sensors isn't working correctly, or
the cat is clogged or damaged.

If you can get a hold of a Haynes service manual for that model Accord,
it will explain troubleshooting steps.

 

I would guess it is just simply water - another product of burning gasoline
in a combustion chamber. Has smell - sure, so many gases are added to it, so
yeah it will smell.
However, if you think that your gasket is blown, then look at your oil
dipstick - does it have whitish, yellowish foamy type drops. If you want -
do an extra oil change - look at your oil.
I wouldnt think it is so easy to blow a gasket - you have to do something to
your engine, like overheating, extra stress, etc.

 

Thanks for all the replies.

I checked the liquid out from the exhaust pipe this morning. It
seems it's just water. The MIL is never on again after I reset it.

To make sure everything is really working fine, I checked the
radiator coolant and engine oil, and didn't see trace of them in
each other.

Thanks again for you guys' help!