Heater Core Bypass

R

racingmason23

New member
Ever since I purchased this car the heat has done some weird things. If I start the car and let it idle for and hour the air coming out is still cold. This week I went to Lms 4 plus and 170 thermostat and it's worse. Driving down the interstate with cruise on I have no heat just cold air but as soon as I go wot I instantly have 90 plus degree heat. The blend door is on recirculation as well. In a parking lot or stop sign I have to rev it up for a few seconds and then it gets hot but cools back of quickly. I know I got all the air out of the system too.
 
Yep I have this issue too, drove to the gym this morning with lots of heat. Backed the car into a nice spot far away from the other gym rats and before I could it into park the vents started blowing cold air. If I rev it up, it comes back on  :wall:
 
Try this:
TSB 12-4-2

04/05/12
REDUCED HEATER DUCT DISCHARGE
TEMPERATURE AT IDLE IN COLD AMBIENT
TEMPERATURES BELOW -9 DEGREES CELSIUS (15
FAHRENHEIT)
 
Check your coolant levels. I had this same problem and had the dealer check it out. When sitting at a red light, cold air would be coming out of the vents by the time it turned green (it would heat back up once I got going). The dealer said that literally all they did was top the coolant off. I still don't understand how that helped, but I haven't had a problem with it since then. That might not fix your problem but it's an easy place to start.

Sent from my SCH-I535 using Tapatalk

 
I have 51000 km on mine...so 30000 miles maybe

This does feel like a coolant flow issue....I've checked the coolant bottle and it appears to have enough extra coolant when cold....so I doubt that's it
 
JoeB said:
Check your coolant levels. I had this same problem and had the dealer check it out. When sitting at a red light, cold air would be coming out of the vents by the time it turned green (it would heat back up once I got going). The dealer said that literally all they did was top the coolant off. I still don't understand how that helped, but I haven't had a problem with it since then. That might not fix your problem but it's an easy place to start.
Click to expand...

This may actually be the issue, I went out to work on the car this morning and added maybe a cup and a half of coolant to the overflow bottle cause it was visibly down maybe half an inch from full cold line. I ran the car with the bottle cap off til it came up to full temp, I squeezed all the rad hoses and watched the coolant bottle for bubbles....which I am 90% sure I saw some come up.  I went out for a drive to my parents house, left the running with heater and fan on high for half an hour and when I came out it was blowing all kinds of heat.

Gonna watch it for a few days and see if more coolant drains out of the overflow bottle....but for now it seems fine.  :ok:
 
So further testing this morning confirms it, at idle the temps coming out of the vents is 130* F with ambient air temps just above freezing here. I let it idle for 10 minutes at least. Driving temps were off the scale...somewhere above 155*

According to that TSB it should hold 136* F when ambient temps are minimum 61* F....so I'm happy with my results
 
To the original poster I would get this looked into soon, it concerns me that you may not have enough coolant in the top of your motor at cruise rpms
 
I burped the system after the thermostat install, and did it again after 4DR posted the TSB.  I'am taking it to the dealer since its still under my 90 day warranty.
 
My '10 SHO did this last night in the drive through, not only zero heat but it was pretty cold air coming out. As soon as I took off it was HOT. Ill try topping off the coolant today, should  I just pour some in the overflow?
 
If you top off the coolant and the problem happens again...... and again the coolant needs a top off --> You might check for the seal leaking from the T-stat install.  Aniother member found this to be a problem.
 
BiGMaC said:
If you top off the coolant and the problem happens again...... and again the coolant needs a top off --> You might check for the seal leaking from the T-stat install.  Aniother member found this to be a problem.
Click to expand...

Yes but it was right after a 170F thermostat install on my 2013.

jimmyducati said:
My '10 SHO did this last night in the drive through, not only zero heat but it was pretty cold air coming out. As soon as I took off it was HOT. Ill try topping off the coolant today, should  I just pour some in the overflow?
Click to expand...

Don't forget to put 50/50 water with concentrated coolant, yes the overflow tank.
 
Just in case, check for a small leak right here in the picture.  I had a drip there.  The dealer put a clamp on it for me.
1_zps91ac3995.jpg
 
I also have this issue with my 2011 but I also have 2 questions -
1) My 11 has the green coolant. Am I correct in that the good ol' Prestone 50/50 is fine (or is it a special FoMoCo blend as I found out with the orange stuff in my 07 Expy)?
2) Am I correct in that if I just add it to the recovery tank it won't "burp" the system?
 
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