I have something of a mystery with my 1993 Dodge Dakota V6 3.9 liter. The air coming out of the vents is luke warm at best. I am not a mechanic by any stretch of the imagination, I have asked several people for thoughts and ideas, then I Google and compare symptoms. Thermostat and heater coil are the two most common answers, although I have also heard collapsed hose. I am not losing any coolant in either the radiator or the reserve, there has been a couple of times since I noticed that I am not getting hot air that I have driven 60-90 minutes straight and it is not overheating. I am going to get it pressure tested, then maybe have the thermostat replaced. However I am perplexed, nothing seems to fit the problem that I am having.

In March I lost a hose, 4AM heading out of Albuquerque, New Mexico, it had been blowing hot air and then went ice cold, I hit the side of the road and check it was blowing steam. A couple of hours to get a tow truck I got it the the shop, had the hoses replaced, new fluid and was back on the road. Used the heater several times without any problems, was as hot as normal. Since I have been in the Central valley of CA and it has been 85+ for several months I have not had to use it. Any thoughts on what I should check next? Flush the cooling system? That was suggested when the hose blew by the shop, but I was talking to my dad and he said that was not needed.

Thank you or any thoughts and ideas.

 

You probably have air trapped, most likely in the heater core. If you lose coolant from a blown hose you should always refill the system as if you had drained it to make sure you get all the air out.
To check if your thermostat is working start it and feel the top hose once it warms up. If the thermostat is opening it will be warm to hot. You could get a point & shoot temp gauge to see what temp the thermostat opens. Stock is 195 degrees. I have a 180 degree thermostat and mine has 145ish miles. It used to get a bit warm in summer using the AC so I went with lower temp thermostat.
Look online for the correct methods for filling coolant, Eric the Car Guy has videos of it. You have to have the heater set all the way to hot and the fan on motor running after the initial fill with the rad cap off to let water flow through the heater core and drive the air out.

 

i just had this problem with my 93 and like stated above, flushing the heater core worked.

 

So I went out and ran it with the radiator cap off for 20-25 minutes. Fluid level rose to the top of the cap area, but did not over flow. The hose was warm and felt firmer than when I started it, something I was told is a sign water is circulating. The air seemed a tad bit warmer, but that could be that I was in shorts and at-shirt in 32 degrees.

My dad is suggesting have the thermostat replaced. I think that it was last replaced 2012-2013 when I lived in Florida. Actually all the hoses and radiator was replaced then.

If I go with having the thermostat replaced should I have the system flushed at the same time? Anything else I should think about having done?

 

Did they flush just the heater core or the entire radiator system?

 

Having it flushed certainly won't hurt. (well, except for maybe your wallet....) You could likely fix it yourself, simply by backflushing the heater core. When you go to put the hoses back on, try and keep as much fluid as possible in them.....

 

i just backflushed the heater core. Took 5 minutes and now heater blows hot

 

Just found the instructions to back flush the system and it seems to be in my skill set. What size hoses did you use when you did it? Also one or two barbed adapters? I have to order from Amazon.

 

regular old garden hose with hot water. Worked like a charm but made a mess of water everywhere.

 

A quick update. The heater is blowing way more hot air. But I would not suggest doing what I did.

After watching some more videos on YouTube, I realized that when I took the cap off yesterday and ran it that I did not take of the reservoir cap also. So this morning repeated the process and noticed that it was warmer. I have a thermostat and gasket on order and planned to install it today. Ran to the store for some more anti-freeze after check my bucket of fluids in the back and realizing that after the problem in New Mexico in March that I had new replaced it. When I came out of the store noticed a big puddle, open the hood and I had not tightened the cap properly. So about a quarter of my new anti-freeze went in the reservoir. Luckily the store is only about 2 miles away. Noticed on the way home that the air coming out was about 50% warmer than it was earlier.

Still plan to back flush the heater core when I change out the thermostat, which will be in couple of hours, letting it cool down now.