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cowl vent produces hot air???

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On these hot summer days when I open the cowl vent on my 48 Windsor Chrysler, I get hot air coming out of the kick panel vents.  I have dual heaters on the car and they are both very warm to touch when I'm cruising along.  If I keep the cowl vent closed the hot air stops coming out the kick panel vents, and the heater motors don't heat up.  I took  a laser temp gauge reading on the heater motors and they are around 115 degrees and the temp at the kick panel opening is maybe a couple degrees cooler.  So I got up under the dash and had a look.  As some of you know there is a passage that dumps cold air straight down once the inner door is open.  Having a look inside between that door and the cowl vent I can see two screens on a bit of an angle with what looks like horse hair behind the screens, too keep the bugs out of the heater core and heater fans I suppose.  Then after that is ducting that runs to the heater core, heater, and then on down to the kick panels.  There is no way of closing off the flow of air going to the kick panels, and leaving the cowl vent open.  So I'm guessing air is suppose to not only come in from the cowl vent and straight down to the floor from above, as well as flow out the kick panels.  But why is it hot air at the kick panels?  That makes no sense.  

Thanks for any thoughts on this.

Cheers 

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Is this a problem you always had or did it just start happening?

If the dual heater control valve hoses are not routed correctly the valve will not work the way it should.

Or the heat(er) control valve on the engine block is either open or partially open allowing hot water to flow through the heater cores.

Sometimes these valves and the control cable get rusty/corroded inside and do not operate properly. You may have to remove the valve, take it apart and clean and lubricate it.

Sometimes the heat control and the defrost cables get hung up and won't allow you to change the air flow from the floor to the windshield for defrost.

Also, I looked in my parts book and only saw a screen but no horsehair for the cowl vent.

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25 minutes ago, joecoozie said:

Is this a problem you always had or did it just start happening?

If the dual heater control valve hoses are not routed correctly the valve will not work the way it should.

Or the heat(er) control valve on the engine block is either open or partially open allowing hot water to flow through the heater cores.

Sometimes these valves and the control cable get rusty/corroded inside and do not operate properly. You may have to remove the valve, take it apart and clean and lubricate it.

Sometimes the heat control and the defrost cables get hung up and won't allow you to change the air flow from the floor to the windshield for defrost.

Also, I looked in my parts book and only saw a screen but no horsehair for the cowl vent.

  I've only had the car for a year and the first issue I had was the coolant wasn't circulating.  The block was clogged up so bad no coolant would even come out of the block drain petcock.  Also the fitting that screws into the head that comes out at the back and where that control valve is was also clogged solid so I took it off and cleaned it out and inspected that valve and it was working fine.  I replaced the short length of heater hose as well as the formed 90 degree hoses that feed the heater.  Then the whole system was back flushed and it has been working fine pumping out awesome heat in the winter.  But it's always possible that the valve isn't closing completely.  However I did also take a laser temp reading on my heater hoses on the firewall and at the control valve and they are relately cool.  around 70 plus degrees.  I didn give some thought to installing a ball valve just past that valve and closing it suring the warm months if I have to.  But I'd prefer to keep things as original as possible under the hood.

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Where does the air come from that goes through the heater coils? Does the Chrysler have a duct to the radiator support or does it recirculate air within the car?  If you have air coming through the elements you can do two things, block the air flow and or stop the coolant flow.  My simple model 36 that fits up in the passenger door well has a manual shutoff valve on the rear of the head.  Closing it takes the heater core out of the coolant flow loop so any air going through the heater core isn't exposed to hot coolant flow.  But on 90 degree days you gonna get 90 degree air through the vent.

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My '53 has some type of air blend slider on the heat controls. Labeled "Summer-------Winter". I believe in winter mode it directs the air coming through the cowl, through the cab heater core. In summer it directs air straight from the  intake cowl to the cab, not through the heater core.  I can't be 100% sure if it works or not. I just shut off the water valve at the rear right corner of my cylinder head. It blocks any hot coolant from going to the cab heater core. Then I do have 100% confidence I am not blowing superheated hot summer air into my cab, when I want whatever cooling the ambient air temp can provide.

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12 hours ago, greg g said:

Where does the air come from that goes through the heater coils? Does the Chrysler have a duct to the radiator support or does it recirculate air within the car?  If you have air coming through the elements you can do two things, block the air flow and or stop the coolant flow.  My simple model 36 that fits up in the passenger door well has a manual shutoff valve on the rear of the head.  Closing it takes the heater core out of the coolant flow loop so any air going through the heater core isn't exposed to hot coolant flow.  But on 90 degree days you gonna get 90 degree air through the vent.

With the cowl vent open the air is coming in from outside the car through the cowl vent opening.  I have model 55 heaters and it's called All- Weather Aircontrol.  So it almost sounds like the air is supposed to come into the heater enclosure and as long as there is no engine coolant circulating in that part of the system, maybe if the heaters were turned on, the squirrel cage fan would force the outside air through the car by way of the kick panels and the heater opening perhaps ???  

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11 hours ago, keithb7 said:

My '53 has some type of air blend slider on the heat controls. Labeled "Summer-------Winter". I believe in winter mode it directs the air coming through the cowl, through the cab heater core. In summer it directs air straight from the  intake cowl to the cab, not through the heater core.  I can't be 100% sure if it works or not. I just shut off the water valve at the rear right corner of my cylinder head. It blocks any hot coolant from going to the cab heater core. Then I do have 100% confidence I am not blowing superheated hot summer air into my cab, when I want whatever cooling the ambient air temp can provide.

Yes I've seen that shut off valve on several pictures of the 251 flathead.  But I don't have that valve on mine.  I have a fitting that threads into the head and it has a 1/2" barb fitting on the exposed side.  From there I have a short 1/2" heater hose, and then that shut off flapper valve that's controlled by the Heat control knob.  Then 5/8" heater hose goes strait up to the 5/8" brass tube that feeds both heaters.  

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This image shows half of the wire screen that feeds one of the heaters.  Looking up from under the dash with the vent interior door open.  I even tried to stuff some clear poly vinyl up in there covering the screening.  The same material used for rear window convertable top windows, only a little thinner ( 30 gage)  It was a super difficult job using a long slot screw driver to spread it out so it covered all the screen.  However I still get the same amount of heat from the kick panel vents.  I can't really get up in there to seal it completely.  You would need the hand the size of a 3 year old child to get in there. It might be possible to get at it from outside by removing the cowl vent door.  

cowl vent passageway.jpg

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7 hours ago, harmony said:

Yes I've seen that shut off valve on several pictures of the 251 flathead.  But I don't have that valve on mine.  I have a fitting that threads into the head and it has a 1/2" barb fitting on the exposed side.  From there I have a short 1/2" heater hose, and then that shut off flapper valve that's controlled by the Heat control knob.  Then 5/8" heater hose goes strait up to the 5/8" brass tube that feeds both heaters.  

I think the factory valve screws right in the head.  This is probably one of the many universal type valves. A picture of it might help. Not sure how important it is but most are directional for some reason.  

 

They also are quite often bad.

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Looks like it might be getting hot air from the engine compartment.  Is there a seal between the engine compartment and the air intake?  Maybe I ought to ask, should there be one?  Looks like there might be one in the pic and it also looks cracked and hard as a rock.

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Well there is always the road side repair for a burst heater core.  Get a stick, whittle a plug, cut the feed hose,.  Insert and clamp plug, Motor on.  You can ask my wife about her scalded foot that signaled the need for the plug.

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Had a 48 Plymouth with the dual heaters. My understanding is that when the cowl vent is open the air flows through the heaters whether they are on or off. On my 47 Plymouth with a single heater the cowl vent has nothing to do with the heater.   

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5 minutes ago, YukonJack said:

Had a 48 Plymouth with the dual heaters. My understanding is that when the cowl vent is open the air flows through the heaters whether they are on or off. On my 47 Plymouth with a single heater the cowl vent has nothing to do with the heater.   

With that in mind, what's the point of the cowl vent in cars with dual heaters?  Why would Chrysler want hot air circulating in the car during the hot weather?  

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16 minutes ago, YukonJack said:

Had a 48 Plymouth with the dual heaters. My understanding is that when the cowl vent is open the air flows through the heaters whether they are on or off. On my 47 Plymouth with a single heater the cowl vent has nothing to do with the heater.   

 

3 minutes ago, harmony said:

With that in mind, what's the point of the cowl vent in cars with dual heaters?  Why would Chrysler want hot air circulating in the car during the hot weather?  

With the fresh air heater(with either single or dual cores) there are 2 levers for the venting. One opens the cowl vent with would force air into the car while moving. There is then a second lever that opens a lower door allowing the fresh air to blow straight in. If that lower door is closed the outside air is forced through the heater. With that lower door open nothing would stop some air going to the cores but most of it should flow straight through and out. 

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9 hours ago, Dodgeb4ya said:

Fresh Air and Dual Heater Instructions Pictures  (3).JPG

Fresh Air and Dual Heater Instructions Pictures  (7).JPG

Fresh Air and Dual Heater Instructions Pictures  (2).JPG

I'm a little confused when reading the first image.  Under "country driving"  it says if you open the cowl vent and keep the weather door closed you get heat in car without turning on the heater.  I'm curious how the the outside temperature would effect the heat provided inside the car during the fall and winter days?

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2 minutes ago, Young Ed said:

 

With the fresh air heater(with either single or dual cores) there are 2 levers for the venting. One opens the cowl vent with would force air into the car while moving. There is then a second lever that opens a lower door allowing the fresh air to blow straight in. If that lower door is closed the outside air is forced through the heater. With that lower door open nothing would stop some air going to the cores but most of it should flow straight through and out. 

Actually according to my lazer temp reader I get the same temp at the kick panel vent with the weather door open or closed ( cowl vent open, heater off)

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9 hours ago, Dodgeb4ya said:

Fresh Air and Dual Heater Instructions Pictures  (3).JPG

Fresh Air and Dual Heater Instructions Pictures  (7).JPG

Fresh Air and Dual Heater Instructions Pictures  (2).JPG

By the way, are these images taken from the factory owners manual? 

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I'm betting on the control valve being 

1. Aftermarket

2. Installed backwards

 

After checking into why they are directional I found they are a flap type valve. Pressure can open it slightly by just flexing the cable if it's backwards. It may only do so well above idle. With the cable springing it **** again when going back to idle.

 

When looking at valves with 1/2" and 5/8" connections the most common are made to flow towards the 1/2" side.

Edited by 50mech

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34 minutes ago, 50mech said:

I'm betting on the control valve being 

1. Aftermarket

2. Installed backwards

 

After checking into why they are directional I found they are a flap type valve. Pressure can open it slightly by just flexing the cable if it's backwards. It may only do so well above idle. With the cable springing it **** again when going back to idle.

 

When looking at valves with 1/2" and 5/8" connections the most common are made to flow towards the 1/2" side.

Well I have been wondering why that fitting would be 1/2" coming off the fitting that screws into the head, when all the heater hoses and steel lines are 5/8"   ???.  Perhaps I should take that valve off again and have another look at it.   I know that the lever on it is not at 90 degrees to the flow of direction, so to say.  But I was assuming that was designed that way because of the angle that the control cable was approaching the lever. I had a look inside when I had it off and the valve appeared closed at the time.  If it was at 90 degrees the cable wouldn't properly open or close it completely.  In the image you can see I added a new spring to insure it completely closed.  Behind the lever you can see an aluminium piece that is bolted to the valve and it's shape just doesn't look like anything factory and it's an odd shape.  Like a back yard butcher put it on there without even squaring it off.   However until now. I've gone with " if it ain't broke don't fix it".  The heater funtions work fine in the winter so I've never given that arrangement too much thought until now.   Out of the picture to the right end off that aluminium piece is where the locking clamp for the outer cable of the control cable is fastened.  

I don't see the  OEM valve anywhere in the parts catalog, or any mention of it in the service manual.   I've searched google for 251 engine pictures but I don't see the valve on any of the pictures.  

control valve.jpg

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I believe this pic is the factory valve. Good luck on one of those , the examples I've found have $600-900 price tags.

 

If that ones in with the flow backwards then whether that spring would hold it totally closed against the flow is ???

 

A four seasons 74662 or 74677 or maybe 74648 would make a decent replacement I think but there are a ton out there, you'd have to go through em.

 

677 goes 1/2 to 5/8 in the right direction.

The others use 5/8, not sure if the threads are correct on the screw in.

 

74685 has the cable bracket at a right angle to the hoses but it's all 5/8

 

Not that adapting would be difficult. Even cleanly if you search the parts store for a preformed hose that changes from 1/2 to 5/8 and cut out a portion of it.

Or a 5/8 barb adapter to screw in the block.

s-l400.jpg

Edited by 50mech

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5 hours ago, Young Ed said:

 

With the fresh air heater(with either single or dual cores) there are 2 levers for the venting. One opens the cowl vent with would force air into the car while moving. There is then a second lever that opens a lower door allowing the fresh air to blow straight in. If that lower door is closed the outside air is forced through the heater. With that lower door open nothing would stop some air going to the cores but most of it should flow straight through and out. 

Most cars from the mid 50's until now have outside air coming in when the heater is on. In my 47 Plymouth with the single heater the defroster vents are useless because without the admission of outside air you are just recirculating the same damp air that's in the car. Causing all the windows to fog up. I also experienced this in my dad's 52 Plymouth when I was about 7 yrs old and he'd hand me an old rag to wipe the inside of the windshield on my side.

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9 minutes ago, YukonJack said:

Most cars from the mid 50's until now have outside air coming in when the heater is on. In my 47 Plymouth with the single heater the defroster vents are useless because without the admission of outside air you are just recirculating the same damp air that's in the car. Causing all the windows to fog up. I also experienced this in my dad's 52 Plymouth when I was about 7 yrs old and he'd hand me an old rag to wipe the inside of the windshield on my side.

There are three levels. The recirculating heater and then either single or dual fresh air heater. Sounds like you have the cheapest model or an aftermarket heater.

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On my 51 Plymouth all the air from the heater comes from outside.  There is a control to close that off, but then you get no airflow because the fan is outside, right behind the grille. 

 

On my 51 the airflow goes like this

 

Grille - fan - heater box - duct to firewall - flap mentioned above- plenum to go to floor or defrost - then ducts to either the windshield if in defrost or the floor if not.  There is no inside air option, there is just a no outside air option.

 

Now I don't know what version I have, the ID tag is blank, there but blank.

 

Shot of my heater fan

 

QdsUA56ZlFOsaGsVAzpltIXnztM5YmHnBwpt2jOQ

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Sniper-

 

a pic of the top of heater radiator/ controls will give you a answer.

 

Not sure about others later years.

 

Most Mopars had the same factory installed/ dealer installed options, 3 differnet but close to same. Basic/ medium / top of line.

 

I have factory repair /parts manuals pics of all 3 available systems. But the latest in the mid/later 50's maybe not.

 

My manuals only cover thru 1950 Mopar. My 1950 Chrysler parts book is my best buy of all manuals...... Pics of all brands that other parts books/repair do Not have.  Has been of great help at times.

 

Trying to not get off topic here, from OP,  perhaps a PM to me with your pics? I will attempt to help.

DJ

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