I feel like I’ve been posting a lot, and I do apologize as I don’t mean to spam the forum. However, I find this site a bit more difficult to navigate than other forums I’ve been a part of. Nevertheless, I’m thankful for the wealth of information available here and everyone so willing to give their sound advice.

I posted previously about a potentially failing check valve that controls the HVAC unit under my dash. Under load, my AC begins to blow air out the defrost vents. You all have lead me to believe I indeed have a failing check valve (or 2) within my system on my 2001 ram.

What I didn’t mention though, is some strange behavior regarding my heater. The AC blows ice cold, and the heater CAN be hot - but only under certain conditions. When the heater is blowing out of the front vents in the dash (towards the driver and passenger) the air is pretty hot. However, this is only when I’m driving / the truck is moving. At a stoplight, the air will become lukewarm. Not cold, just lukewarm. The heat will resume whenever I take off from a stop.

I am also experiencing no heat when I set the system to defrost mode. The air is not cold, again - it’s lukewarm. What I’m curious, is could this be a sign of a failing blend door and something the Heater Treater would fix? I know it’s not a hard job to do, but rather tedious. Before I pull the trigger, I’m wondering if anyone else has some input / advice on where to look. I don’t believe there are any issues with my heater core. Both the main and return lines going into the firewall are hot, as well as my upper and lower rad hoses.

or, I just need to replace the check valves plus the heater treater?

 

My father was probably the most UNmechanical person you could ever meet. However, he always told me to check the cheap and easy fixes first. If they work, great. If not, then you dig in deep. What I would do would be in this order;

Make sure the cooling system is full and all the air bubbles have been farted out. (Not the most technical way to put it but I have an ....odd....sense of humor. )

Make sure the heater core is flowing well. Both hoses shold be hot when the engine is wrmed up. If one is hot and the other is cold, try flushing the core.

Make sure the water pump is flowing good. I had a Town Car that got cold sitting at lights. The aluminum impellers were eroded from age and wear plus the coolant not being changed every 5 years or so. That's what I think is the issue, but check the cheap and easy first. Water pumps are a bit labor intensive so check the rest first.

Now, the vacuum units are under the hood that cause wild vents. Youtube has good videos on "wild vents".

 

Never thought about the water pump! Normally the truck doesn’t sit long enough at idle to build heat. It’s got a 180 T-Stat in it and I know it should be replaced with a 195. But today while sitting in a drive through for nearly half an hour, the temp did get pretty warm. Warm enough for the fan clutch to lock up. It took me by surprise at first, as it sounded like an airplane taking off when I accelerated! Okay, maybe an exaggeration, but I’ve never heard the clutch actually engage on it. My 68 Chrysler has the same type of fan so I knew exactly what it was. But I’m wondering if it was building heat due to an aging water pump.

Both the lines for my heater core are hot when the truck is up to temp. It will blow hot air when you drive. Which makes sense, as the WP will be flowing those juices through the heater core at a more quick pace.

It could be air bubbles too, but I’m not sure, will try my hand at burping the system. Coolant is a bright green color and looks to be pretty healthy. I believe the radiator hoses were recently changed - so that could be my issue right there as well!!

but what about the defrost blowing only lukewarm air and not hot air? Could that be a blend door issue?

 

The vacuum actuators are in the hvac unit under the dash. Check valves are in the engine compartment. Check valves only keep vac in the system to work the actuators. The blend door regulates the temp. Remove the motor and look at the coupler. If it's worn it will allow the door to move and not keep air from flowing past the core. The coupler is plastic and it fails a lot that's why heater treater made it out of metal. I believe their are pics of both on their site.

Asking questions is not spam and what the forums are for. I got my coffee and sit down to check out the forum and only two posts(yours being one of them)! More posts the better, Gives me something to check out.

 

It does sound like your water pump is heading south. Try grabbing the edges of the fan and see if you can wiggle the water pump shaft. It shouldn't move laterally. If it does, the shaft bearings are worn. If so, it's time for a new water pump. The same if you see any green stains or wetness at the weep hole under the shaft. Either one is a sign of a failing water pump. There's a lot of stuff to get out of the way to replace the water pump so make sure it's bad first.

That is also the time to replace the bypass hose. When I did a major tune up on my '96, all the hoses looked pretty good, until I pulled the mount holding the a/c compressor and alternator to the side. It was swollen and about to pop. Usually on a cold nasty day. If you think your timing chain is over 120K, I'd go ahead and go a little farther and replace it too. I had 150 to 165K on my chain and it wasn't about to break but definitely needed replacement. My engine now runs smoother than ever and has more grunt. Mileage didn't go up much, but performance is much better.

 

That could explain the annoying squeaking I’m experiencing within the engine bay too! At first I suspected it might’ve been a worn pulley or tensioner or even the AC clutch going bad but eventually noticed it made the same little squeak with or without the AC on. It’s intermittent, and not terribly loud - but just enough for me to notice it. Or, it actually is a tensioner issue and I have more stuff to add to my list. Granted, for a 23 year old truck - I’m always impressed at how well it’s held up.

I’ve got a great shop I go to in town. If I can supply my own parts, they will only charge me labor. Great family friends of ours.


I’ve heard the best course of action for our magnums is to upgrade the timing chain to a double roller and call it a day. I see good results with the Mopar Performance chain. May pull the trigger and buy that one. As for the WP, maybe one of the nicer ones on RockAuto.

 

Yes, a good double roller timing chain and gear set is a great replacement for a stock worn chain. I also use a timing chain tensioner as well. It has kept my timing rock solid since replacement several years ago. All chains tend to stretch a bit over time, even double roller chains..

https://www.manciniracing.com/maratichte.html

 

The HT is only for a broken blend door drive. You can take it apart and see if it's cracked. It's not that hard but a small, right angle ratcheting screwdriver is reco'd

Your symptoms don't sound like a blend door issue because even a failed blend door tends to just stay in one position (unless vac controlled which, of course, your '01 is NOT).

 

Don't buy "Heater Treater" get "Blend Door USA" instead much better quality.
Here is a video comparing the 2 of them.

 

I actually Have Blend door USA's "blend door fix" for my truck much better quality than Heater treater.
Its a nice CNC piece.