Blowing cold with the heat on...

WhiteMamba · October 16th, 2010, 12:10 AM

My car is blowing cold air with the heat on and the car fully warmed. My heater core is brand new, my radiator is full and has brand new fluid.

My car does have underdrive pulleys....

Any thoughts? What would cause this issue with the above in consideration?

WhiteMamba · October 16th, 2010, 01:15 AM

t-stat is brand new as well.

HMERacing · October 16th, 2010, 01:19 AM

is it switching over to heat? have you checked for a loose vac line?

HMERacing · October 16th, 2010, 01:21 AM

I'll make ya a steal, I mean deal! I should be in Mo tommorow to pick up some parts. I will just swing by and pick up the car to diagnose it for you...

For Free!!!

ryanw · October 16th, 2010, 01:36 AM

Once the coolant is verified to be full, feel the heater hoses that go to the firewall. With the engine at normal operating temperature, BOTH of the heater hoses should be hot to the touch. If only one is hot, this indicates there is a blockage in the heater core or there is air trapped in the heater core preventing proper flow. If the coolant is really brown, has been neglected, or if stop leak has been used at some time in the car’s service history, the heater core could be stopped up. The blockage can sometimes be cleared by removing the heater hoses and using a garden hose with a sprayer to flush the heater core out. If neither of the hoses are hot to the touch, there could also be a malfunctioning heater control valve, if used on the model you’re working on. Check for presence of a heater control valve by following the heater hoses back to the engine. Sometimes, a vacuum line could have a break causing there to be no vacuum to operate the valve.

ryanw · October 16th, 2010, 02:07 AM

Hey check this link out. Heater control valve location on 1991 mustang - Ford Mustang Forums

86er · October 16th, 2010, 02:32 AM

prob just the blend door not moving from the evaporator to the heater core

WhiteMamba · October 16th, 2010, 09:07 AM

Originally Posted by 86er

prob just the blend door not moving from the evaporator to the heater core

If it is this how do I fix...

WhiteMamba · October 16th, 2010, 01:41 PM

Ok...so I think my BRAND new heater core is clogged...Which makes sense since the old one was leaking and I had put some shit in to stop the leak BUT thought we got all out when we did the turbo and drained the radiator and such.

One heater hose is hot and the other is cold...which side do I put the garden hose on to clear the clog?

ryanw · October 16th, 2010, 01:59 PM

I think the hot one. that should be supply side. You may need the heater to be on to open the blend door when your flushing it out. But if the blend door is open then im thinking is shouldnt make a difference aslong theres not a one way valve in the system and both heater hoses are disconected

WhiteMamba · October 16th, 2010, 02:41 PM

Originally Posted by ryanw

I think the hot one. that should be supply side. You may need the heater to be on to open the blend door when your flushing it out. But if the blend door is open then im thinking is shouldnt make a difference aslong theres not a one way valve in the system and both heater hoses are disconected

Mission accomplished! I now have heat even at idle. I flushed it with the garden hose and it starting gushing out the other side after a minute.

Thanks gang!

ryanw · October 16th, 2010, 02:51 PM

Originally Posted by WhiteMamba

Mission accomplished! I now have heat even at idle. I flushed it with the garden hose and it starting gushing out the other side after a minute.

Thanks gang!

Your welcome.... did you see alot of crap come out

WhiteMamba · October 16th, 2010, 02:53 PM

Originally Posted by ryanw

Your welcome.... did you see alot of crap come out

not really but once it came out it was really gushing out so if there was something in there it musta been some small stuff.

I think it was only partially clogged as I would get heat on occasion and sometimes not but never at idle.

i will drive more later and make sure it's all good.

ryanw · October 16th, 2010, 03:06 PM

Maybe you had some air traped in there to

WhiteMamba · October 16th, 2010, 07:32 PM

burned my hands feeling the heat today!!! lol...it's nice to have it back!

DJG · March 6th, 2011, 10:47 PM

Originally Posted by WhiteMamba

burned my hands feeling the heat today!!! lol...it's nice to have it back!

Trying to bring this thread back from the dead, I know... However, due to forum rules, I can't send PMs yet.

I'm having the exact same problem with blower functioning and no heat. Going to check the coolant line temps tomorrow and, if I find that one's hot, one's not; should I just run a garden hose through the core, or use a pressurized nozzle?

Any assistance would be greatly appreciated.

Thanks, in advance!

Danny

FastStang91Lx · March 6th, 2011, 10:54 PM

No real pressure will do you any good. It's basically like your radiator, only smaller. High pressure won't work any better really. Just make sure you flush the lines back and forth. And be careful with the lines too, they can break easy. Kinking the garden hose shut a few times while the heater core is full of water and then rapidly releasing it is all the pressure that you'll need to open the plugged cores back up.

DJG · March 6th, 2011, 11:02 PM

Perfect - Thank you. Hopefully this does the trick!

October 16th, 2010, 12:10 AM	#1
WhiteMamba Regular 88 Notch Join Date: Aug 2010 Location: Saint Charles IL Posts: 431 iTrader: 0 reviews	Blowing cold with the heat on... My car is blowing cold air with the heat on and the car fully warmed. My heater core is brand new, my radiator is full and has brand new fluid. My car does have underdrive pulleys.... Any thoughts? What would cause this issue with the above in consideration? __________________ 88 Notchy 306 with 70mm Turbo 510 RWHP on 10lbs K thnx Can we chat?

October 16th, 2010, 01:15 AM	#2
WhiteMamba Regular 88 Notch Join Date: Aug 2010 Location: Saint Charles IL Posts: 431 iTrader: 0 reviews	t-stat is brand new as well. __________________ 88 Notchy 306 with 70mm Turbo 510 RWHP on 10lbs K thnx Can we chat?

October 16th, 2010, 01:36 AM	#5
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	Once the coolant is verified to be full, feel the heater hoses that go to the firewall. With the engine at normal operating temperature, BOTH of the heater hoses should be hot to the touch. If only one is hot, this indicates there is a blockage in the heater core or there is air trapped in the heater core preventing proper flow. If the coolant is really brown, has been neglected, or if stop leak has been used at some time in the car’s service history, the heater core could be stopped up. The blockage can sometimes be cleared by removing the heater hoses and using a garden hose with a sprayer to flush the heater core out. If neither of the hoses are hot to the touch, there could also be a malfunctioning heater control valve, if used on the model you’re working on. Check for presence of a heater control valve by following the heater hoses back to the engine. Sometimes, a vacuum line could have a break causing there to be no vacuum to operate the valve. __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

October 16th, 2010, 02:07 AM	#6
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	Hey check this link out. Heater control valve location on 1991 mustang - Ford Mustang Forums __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

October 16th, 2010, 02:32 AM	#7
86er I Post Entirely Way Too Much Join Date: Nov 2006 Location: Memphis, TN Posts: 7,626 iTrader: 0 reviews	prob just the blend door not moving from the evaporator to the heater core __________________ Just a truck 5.4 3v: 264hp 317ft lbs rock stock The "search" button, its not just for porn piecing together the next project faster than your first sexual experience

October 16th, 2010, 01:41 PM	#9
WhiteMamba Regular 88 Notch Join Date: Aug 2010 Location: Saint Charles IL Posts: 431 iTrader: 0 reviews	Ok...so I think my BRAND new heater core is clogged...Which makes sense since the old one was leaking and I had put some shit in to stop the leak BUT thought we got all out when we did the turbo and drained the radiator and such. One heater hose is hot and the other is cold...which side do I put the garden hose on to clear the clog? __________________ 88 Notchy 306 with 70mm Turbo 510 RWHP on 10lbs K thnx Can we chat?

October 16th, 2010, 01:59 PM	#10
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	I think the hot one. that should be supply side. You may need the heater to be on to open the blend door when your flushing it out. But if the blend door is open then im thinking is shouldnt make a difference aslong theres not a one way valve in the system and both heater hoses are disconected __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears Last edited by ryanw; October 16th, 2010 at 02:04 PM.

October 16th, 2010, 03:06 PM	#14
ryanw I Post Entirely Way Too Much 1991 Ford Mustang GT Join Date: May 2007 Location: San Diego, California Posts: 6,063 iTrader: 0 reviews	Maybe you had some air traped in there to __________________ DART 331ci stroker, AFR 185 heads, Trick Flow R intake, Accufab 70mm tb, 75mm pro m Maf, 30lb injectors, jba headers, 2 1/2" x pipe flowmaster super 10 mufflers, 255 fuel pump, 3:27 gears

October 16th, 2010, 07:32 PM	#15
WhiteMamba Regular 88 Notch Join Date: Aug 2010 Location: Saint Charles IL Posts: 431 iTrader: 0 reviews	burned my hands feeling the heat today!!! lol...it's nice to have it back! __________________ 88 Notchy 306 with 70mm Turbo 510 RWHP on 10lbs K thnx Can we chat?

March 6th, 2011, 10:54 PM	#17
FastStang91Lx I Post Entirely Way Too Much 1991 Mustang LX 5.0 Join Date: Jan 2010 Location: Minnesota Posts: 5,572 iTrader: 2 reviews	No real pressure will do you any good. It's basically like your radiator, only smaller. High pressure won't work any better really. Just make sure you flush the lines back and forth. And be careful with the lines too, they can break easy. Kinking the garden hose shut a few times while the heater core is full of water and then rapidly releasing it is all the pressure that you'll need to open the plugged cores back up. __________________ Point made in less than a few hours with minimal response. http://www.moddedmustangs.com/forums...ml#post4465184

March 6th, 2011, 11:02 PM	#18
DJG Newbie Join Date: Mar 2011 Location: Seattle Posts: 11 iTrader: 0 reviews	Perfect - Thank you. Hopefully this does the trick! __________________ Black '88 Notch Vortech S-Trim V-1 @ 13psi - 466rwhp/446rwtq

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