Compression test question

Back in April I bought an 05 Civic sedan from a guy at work that he said his daughter overheated and his mechanic said needed a HG.  My son and I finally took the time to check it out last night and we did a compression test.  Here is what we got:  170 170 155 175.  I am going to guess that the cylinder with the 155 reading is the issue but we ran the car for 20 minutes with the AC on and the temp gauge never got higher than half way and the upper radiator hose was hot.  I am going to change the timing belt and water pump regardless so the HG isn't really that much more involved but the fact that the temp never went up intrigues me.  

What do you guys think? 

Doesn't really seem like a BHG to me.  Any chocolate milk? Any steam out the exhaust when it's hot?  Loss of water?  How about one of those combustion products in the coolant test kits?

Did #3 come up any with a squirt of oil down the hole?  Leakdown test?

Might be worth it to just pull the head and check for flatness and throw a new HG on it if that is a common failure point on that car.

Hmm what happens when you bleed the coolant? Does it just keep bubbling even with the no spill funnel or the front end high? 

I would watch the coolant levels over time and check the coolant temp, if it loses any over a period of time and/or the overflow gets full, I would look into replacing the headgasket.

It would have only overheated just once and not for a long time and you may be ok.

A compression test will only show a head gasket leak if its so bad you have to stand clear of the rad cap to avoid getting sprayed with coolant.

Does it miss first thing in the morning after being fully heated up the night before?  Is there a sweet smell to the exhaust at that time?

Compression test on a cold engine can be inconclusive.

These engines are ulev or something like that so they can be really hard to pick up a blown hg with a block test ( I don't know what it's actually called but it is when you pull air from the cooling system through a test fluid and look for color change), or at least that was the explanation I was given when one kept passing a block test but had a BHG.

I've also seen three of these that I'm an 100 percent sure had BHG and would run without overheating or other symptoms like 99% of the time then once every 2 or 3 weeks would get super hot then when cooled down drove perfectly fine. They where nightmares to diagnose.

If this is just a beater I'd do the TB and WP and check it over, then drive it around for a few weeks, If it doesn't act up is forget about it until something happens. 

If you think it has a BHG and want to do something about it, but don't want to pull a head, I have had excellent results from blue devil on beaters

Oil looks like it should, nothing out the tail pipe and no antifreeze smell.  Having not ever done a compression test before we did on a cold engine so I can redo it with the motor warmed up easy enough.  

I think I will do the TB and WP and see how it goes from there.

I got the car for my oldest to take his driving test and then sell.  He does not want an auto car but using an auto for his test to make it less stressful but after that I have no desire to hang on to it.

Thanks everyone.

In reply to Aaron_King :

Ignore if it doesn't overheat, or blue devil if it does and you think it's the HG.

If it's only temporary I wouldn't even do the TB WP on it.

It is possible that the only problem was mis-diagnosis. Amung my non car savvy friends, i have had many things reported to me as "I overheated my car". When infact they had steam or smoke coming from under the hood for some other reason or their temp guge did something out of the ordinary.

I ended up fixing a rad with a hole in it causing steam, a bad heater core, wiped up spilled oil and told one friend that because he just got it rust sprayed, there would be smoke coming from the engine compartment for awhile. All of those repairs were reported to me as a overheated car. 

His mechanic may have been playing along with the misdiagnosis to make some extra $.