LostMotion

Edit: problem solved.

Well I noticed my heater wasn't working tonight and now I'm looking for some answers. I did the HVAC DTC protocol and got no errors so I think the HVAC system is OK.

At this point I have completely ruled out a "badly" blown head gasket. I have no smoke coming out of the tailpipe and I can take the rad cap off and rev the motor without seeing any air bubbles. Also the oil appears clean form any milky residue. I have a CEL that I will check out tomorrow but it may have more to do with a new high flow cat. The CEL just appeared sometime today, but I have no idea when because I have an EMS and only noted the CEL when I unplugged the EMS to check. So with all that in mind I may have a "minorly" blown HG.

Would a "minorly" blown HG cause the heater to completely stop functioning? I really don't understand the connection completely between the HG and the heater but it seems weird that the heat would just turn completely cold given the circumstances.

The only risk factor for a blown HG would be my CAI. There was some heavy rain about 2 weeks ago which I drove about a mile in (car was not parked in rain) but I've driven my car many times (a short distance) since then with no CEL and I believe the heater was working.

The only thing I can think of is that some water got into the cylinder about 2 weeks ago and then today when I drove the car quite a bit (150 miles) for the first time today it blew the HG.

What code would I get from a blown HG?

I suppose at this point I should pull the plugs and inspect them and also check out the CEL.

LostMotion

I should mention that my vehicle seems to drive fine, no loss of power. I have not driven it hard (no WOT) because it is not fully tuned for a new header and high flow cat but up to 60-70% throttle it feels the same as always.

Edit: Also, my car does not appear to be overheating. I say appear because we all know the water temp gauge on the S is a bit sketchy. Also though after a long drive home tonight neither fan was on and the engine was very very cool. It's about 50F out though so that might be a factor.

Mrfixit687

Why do you think u have a "blown" head gasket? Your heater doesn't blow hot air, but everything else works? fans? You might have an air pocket in the coolant thats why it's not working, have u messed with the cooling system at all?

LostMotion

Only reason I think I may have blown the HG is that my heater is not working. To be clear though the entire HVAC system works fine as far as fans, A/C, everything except I get no heat.

I haven't messed with the coolant system.

Mrfixit687

is there any coolant in the resevoir? what mods have u done to the car

LostMotion

Well you got me thinking Mrfixit... I started digging through the service manual again and noticed a picture of "heater valve arm". It turns out this arm is what turns on the heat and guess what? The new Js heat shield I installed is obstructing its motion. So no blown HG. I was totally at a loss as to how I could have blown my HG but the CEL and the no heat (edit: and the rain + cai) made me a little worried, although I think they are both explained now.

Mrfixit687

good job i had a feeling a mod probably caused it

camuman

hehehe, when i installed my berk header i banged against that arm and bent it a bit. here in florida i never use the heat but maybe during a few weeks in dec. went to turn it on and was blown with cool air, not warm. looked in teh book, saw that arm, looked under the hood, bam... theres the problem. bent it back and heat worked again!

glad it was a simple thing.

ChefJ

Blowing a headgasket on a stock car is very very unlikely. If this were to happen I am sure the head would also be warped as it would probably have overheated extremely at one point.

LostMotion

Interestingly the CEL turned out to be VTEC rocker voltage low (or high), I can't recall. I reset and am running the stock ECU to see if comes back.