I hooked up my coolant funnel to the radiator hole and noticed little bubbles at idle. I did this after I noticed air keeps coming back into the system after each bleed. When I rev the engine larger bubbles come out. I thought the head gasket may be leaking, but my block tester is not detecting anything. Where else could air be coming in from?

 

Not a real good sign, and something you want to resolve asap.

If it were me, I'd pull the plugs and look for 1 or 2 different from the rest.(write down which plug came out of which cyl.)

Then do a warm compression check (wide open throttle)

See if there's any cyl. lower than the rest, do they correspond to a plug that looked a little different? (hopefully you don't have new plugs in it)

The next would be a leakdown test on rad and each cyl (during cyl. test, listen to muffler and intake thru throttle body, you may get insight to any int/exh valves leaking.
(or oil dipstick tube to see if rings are bad)

For the cyl test they/you will screw a hose with a sparkplug type tip into sparkplug hole and apply compressed air (naturally, the valves will be closed on that cyl - TDC compression stroke)

luck,greg

 

Wouldn't the block tester detect exhaust gases leaking if it were a leaking head gasket? No coolant in oil, and it does not appear to be losing coolant

 

Did you recently change the coolant or do any other work on the cooling system?

 

Yes, I have replaced all the hoses and bled the system properly per the sticky several times. Nothing seems to get rid of the air coming into the system. I even removed the t-stat to make sure it was not sticking. This helped keep the temps down for a while, but it will overheat when idling for 10 mins. Reving the engine in park will lower the temp, but I still hear the air in the heater core. I am wondering if air is coming into the system at another location since my block test kit did not detect anything. I tested the napa block tester solution by breathing into the tube and it changed color so I know it is working. I also recently changed the plugs and they looked all the same. I bought a coolant pressure tester which I am going to pump to 12psi and see if I can see any external leaks but don't think any will show as no coolant is leaking.

 

In your second response you say you're not losing coolant, reread what you said first time.

Your detect tester is just not picking it up.

DI's are very forgiving in regards to purging out air, if you have air in it, you'll only end up with a low resevoir. (after you button it up and drive around the block) - (I wouldn't drive it around w/o the tstat, unless it was stuck shut)

You state in your second post, it overheats when idling, how's your fan clutch? - Fan shroud intact?

And I believe our systems run with 15psi, normally

luck,greg

 

It does not appear to be losing coolant. I replaced the fan clutch and the shroud is fine. Pressure testing appears to be dropping slowly. There is a leak somewhere. I am going to wait till it is stone cold to make sure and re-run pressure test

 

OK,

the pressure test should hold 15psi for at least 5min, IMO, unless tester says otherwise.

Remember, the pressure may drop if everything is not sealed perfectly (including the tester connections)

Here's how I sucessfully do mine every 2 years (probably the same as you)

Drain it thru' bottom hose to rad - re-attach hose

Fill rad thru' top plug, wait, do it again, start 'er up

Fill thru' plug as necessary, (heater fan on, to detect when core is hot)

Keep filling thru' plug, slowly, 'cuz it's starting to puke a little-

Once it won't take any more thru' plug, I re-install plug & check the resevoir tank (usually has some in it by now)

Drive around block, let 'er cool down, re-check resevoir, fill to halfway, check after another drive cyle & cooldown

I checked mine today after April flush, (I don't trust it) and it was still half full tank.

I've had (2) 220deg. occasions in traffic this year and no apparent problems

luck,greg

 

I found a leak on the bottom of the coolant tank. A hose appeared to be not tight enough. I will check the pressure again when stone cold as this may have an effect when the coolant cools.

 

It will suck air in that leak while it cools.