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Can someone please tell me what the ID size is on the nipple on the head where the heater hose inlet is connected to. Also, is this a restrictor to slow the pressure to heater core. 

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Intermission                                                               Please take 10 minutes and refresh your popcorn!   - John

First off, is this a 24V (99-02) or 12V(94-98)?      (in no particular order, try easiest first) 24V have electric control of the blend door, 12v have mechanical cable connection.

A centrifugal fan can not work in reverse, for the purpose of A/C anyway. Spin direction can change, flow cannot... in the middle and out perpendicular to the axis of rotation.    They hav

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Thank you^^^^^^^ The reason I ask is, when I measured mine it was only 3/8''. I have a  5/8'' barbed by 1/2'' mip I want to install for more flow. I have owned this truck since new & the heat has always been poor. I also removed my fan & counted 29 fins. I checked at a parts store for a new blower & it has 41 fins. Just looking for more heat. Do more fins mean more air movement? I removed my heater box last weekend & it is clean & all doors do what they are supposed to do. Core is only a little over a year old.

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My '02 blows a lot of heat but did not recently do so well even with the engine at operating temp.  I pulled fan and did what checks I could there which is not very much it seems.  Fan worked fine but sure didn't think to count fins.  Just made sure all were there.  I finally pulled heater hose and blew it out before trying something deeper and guess what??  Heat!!  Did seem to blow a plug out.  Maybe not quite as good as it was but it does get plenty warm now.  Radiator looks clean as a whistle inside so might just try blowing yours out unless it has never done good.  I think if everything is A OK you should have all the heat you could ever want.  I know both my '01 and this one sure did until this recent snafu.

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First off, is this a 24V (99-02) or 12V(94-98)? 

 

 

(in no particular order, try easiest first)

24V have electric control of the blend door, 12v have mechanical cable connection.

 

What is engine coolant temps?

 

Does the air flow change direction with the knob? feet/defrost/recirc/dash

 

If doesn't change or only changes on some settings, either vacuum lines or the bladder/s in the actuators have gone bad.

 

Recirc is as important for heat when the temp hits -47* as it is when the a/c is running and its 110*. Should be able to hit 140*+ vent temps. My chevy hits 190 for example.

 

Being in Oil'berta Canada, have you done anything to block some airflow to the radiator for the sub zero months? Even in the American south, I block about 2/3rds of it with no issue and we usually only see 20's as our lows. Otherwise, warms up to 180*, thermostat opens, back down to 140*.

 

If you removed the blower motor, does it spin free with little resistance? It will have a little, but not much. also, do you have all 4 speeds of the fan?

 

The evap core wasn't starting to plug up was it?

 

You say heater core is newish, it shouldn't need flushing unless coolant was garbage.

 

Thermostat stuck open not allowing to come up to temp?

 

Fan is only going to move so much air. Number of fins isn't as important as them all being there. Could be difference between two aftermarket venders or aftermarket vs oem.

 

 

After all of that, increasing the flow through the heater core isn't going to do much if any of the above are true. Nonetheless, the ID of the nipple is 3/8ths. You could drill it out a bit to maybe 1/2 inch at the most, which in THEORY, means 78% more flow, ASSUMING zero resistance elsewhere along the line, which simply isn't true. The return to the lower radiator hose (likely also 3/8), not even considering the heater core.

 

PXL_20201206_230621887.jpg.25c1d346fdc988e878db4e4c5cdb8ddb.jpg

 

My blocked evap as an example.

145837579_IMG_20200706_142319(1).jpg.53df2cfca37edb2550bf5d7965b7a467.jpg

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11 hours ago, jag said:

Thank you^^^^^^^ The reason I ask is, when I measured mine it was only 3/8''. I have a  5/8'' barbed by 1/2'' mip I want to install for more flow. I have owned this truck since new & the heat has always been poor. 

 

 

It is restricted for a reason, to protect the heater core from too much flow when the t-stat is shut. 

 

When I did my Cummins conversion on my '74 Ford I had to use the heater hose nipple from my gasser. When I did my first start I had a bunch of guys watching. When I revved it up  one of the guys shut me down, he said the heater hose was swelling up. The full flow nipple was too much.

 

Are you running a 190 t-stat?

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No mods done to my truck regarding the heater core. With a 190*F Thermostat I produce at least 160*F to 170*F temps from the center vents of the dash on a zero degree day. Never drilled out any fitting. Just clean the evaporator, double check your blend door, and just replace the heater core. If you want melt your face off hot jump from the 190*F to 200*F it will cook you out of the cab in less than 10 miles. 

 

No Cab Heat | Dodge Cummins Diesel Forum

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2000-24

Winter fronts on all 4 grill panels, hoses all good with no kinks, 1 hose is longer because of the singing sisters, 190 thermostat (Quad verifies that) & opens at 194 F, system flushed when I pulled hvac box out, new anti-freeze tested to -38 F, tested vacuum pots, 4 fan speeds, all zones work for switching air flow, motor spins free, all doors sealed when tested, no foam missing, evap clean like whistle. 

I haven't changed the nipple. Checked temp in vents like above & my thermometer crapped out at 112 F. Will get new one & try tomorrow & report back. 

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7 hours ago, LorenS said:

???

Compound turbos = singing sisters

143 F is as good as it gets.

Was there a reason for the blower motors to have changed to ccw rotation at the end off 2002 & so on instead of cw rotation?

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Been wat hing this one with interest. Mine is after market and suffers from the same problem. I can only get 130* on a good day. Thats with coolant  temp at 190*. Wonder if mine rotating the right way?

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All I'm using is a NAPA heater core nothing special. The aluminum style with the adjustable tubes. I'm only using a 190°F NAPA thermostat and no other mods to the cooling system. Like today I will remember to install my winter fronts. 160°F to 170°F out of the center vents. Running NAPA green anti-freeze mixed 50/50. 

 

https://www.napaonline.com/en/p/NRZNH9010015?partTypeName=Heater+Core

 

HVAC HEATER CORE Part Number : NRC NH9010015

NAPA ain't so bad when it cooking you out of the cab. :whistle:

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 I'll be watching this one as well. I recently changed my heater core and evap, cleaned up the HVAC box and checked seals. Once all back together I get about 120° at the floor vent, engine at temp driving down the road.

  Wondering if the T-stat needs replaced. If I stop at a red light the temp gauge drops pretty quickly to about 170-180° but comes back up once I start driving again. It sure don't hold the heat if I stop and idle long.

 @Mopar1973Man pointed out that when I did the heater core and evap that I did not flush the cooling system and possibly got some crud into the new heater core. Could be a possibility. 

 Here lately with the temps dropping some I've been running with a piece of cardboard between the intercooler and radiator. Seems to help a little.

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7 hours ago, jag said:

Compound turbos = singing sisters

143 F is as good as it gets.

Was there a reason for the blower motors to have changed to ccw rotation at the end off 2002 & so on instead of cw rotation?

 

Is your blowing spinning the wrong direction or maybe have the mismatched fan?

 

 

4 hours ago, Mopar1973Man said:

All I'm using is a NAPA heater core nothing special. The aluminum style with the adjustable tubes. I'm only using a 190°F NAPA thermostat and no other mods to the cooling system. Like today I will remember to install my winter fronts. 160°F to 170°F out of the center vents. Running NAPA green anti-freeze mixed 50/50. 

 

https://www.napaonline.com/en/p/NRZNH9010015?partTypeName=Heater+Core

 

HVAC HEATER CORE Part Number : NRC NH9010015

NAPA ain't so bad when it cooking you out of the cab. :whistle:

Have a new core just like that to go in. My factory copper one still seemed perfectly fine so I figured I would stick with it for the time being.

 

Aluminium only transfers about 60% of the heat that copper does but 160 seems perfectly fine, and alu is like 1/3 the cost.

Edited by That Guy
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Whatever "OEM" heater core I bought from Geno's a few years ago ($149 :stuned: ) does a fine job of cooking me out of the cab, too.  Did not have adjustable arms, so I just lopped them off with a tubing cutter to get it through the firewall.  Might they blow off if my engine gets too hot?  Maybe. They haven't in 50k miles.

 

I run a Stant Super-Stat, 190F ($8 at Rock Auto).  Part number 46289.  Watching the ECT on the Adrenaline (not the dashboard gauge), it holds temps very steady, slow swing of just a few degrees when cruising down the interstate, regardless of winter or summer.

Edited by LorenS
Added Stant part number.
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