I checked all the vacuum lines and they all work, I can hear the blend door closing all the way when I put it on heat, but i never get hot air coming from the vents. My first thought was that the heater core was bypassed for some reason, but both lines are connected to the firewall and engine, so that isn't it.

Does the coolant constantly flow to the heater core through the water pump, or does a relay open that path once the coolant is a certain temp?

I am pretty sure that is what happens with the radiator, and that is controlled with the radiator pressure cap. The one I have installed says it is a 16 psi cap. Is that the correct pressure?

Oh yeah it is a 1996 3.9l 2wd if that matters!
Zac

 

Yes the coolant is always flowing through the heater core at all times. Most likely it is clogged. Try flushing it out. Pull out the hoses from the core run you garden hose through do reverse flow first then switch. Do it until the water is clear or even longer. Be careful with the pressure to much and you may bust your heater core. If that doesn't work you may just need to replace the heater core.

 

I thought that was how it operated! I will try that and see what happens.

Do you happen to know what the correct pressure radiator cap is?

 

16psi I believe. If it looks old just replace it, they are cheep.

 

Ok....Never mind! Got any tips on how to remove the clamp from the return hose where it attached back tot he engine? That is without removing the alternator?

I released the clamp from the water pump on the pressure side, but the hose felt like it would break if I took it off, so I am going to hold off until I can get replacement hoses.

If it isn't one thing it surely is another

Zac

 

The cap looks aftermarket and new so I wanted to verify that it had the right pressure.

Thanks

 

You can use a penetrant or gently pry with a flat screwdriver/ spreading knife. I assume that the cold weather may affect the hardness of your lines as well. The copper will typically corrode and "melt" to the lines. They are not really melting, but the corrosion has a high adhesive value. FYI, your homes water pressure is 40-60 psi (typical) so you WILL bust your exchanger if it seals off from the pressure, so be sure to flush without giving total pressure initially. Using Red Devil Lye beads (Sodium hydroxide) mixed in water is very effective as well (as opposed to bleach). Understand that an alkaline is more aggressive than an acid when it comes to metals, however, acids are more easily made, and thus cheaper. Also, the "lye" when mixed with water is an exothermic reaction (produces heat) and WILL heat up to almost 170 degree's depending on the strength, so be patient when mixing. It will also burn you like paint remover does (since it almost the same thing), so no splashing. Youtube has a few video's, but I have yet to see one done correctly, through the entire process.

The cap pressure dictates the boiling point of the coolant/antifreeze while running. It should be around 14 to 16 psi. If your coolant temp is low you can lower the cap pressure and increase the heat to the system and vice versa.

 

When I do a heater flush I cut that line right above the nipple and flush. When done I cut the small bad piece from the nipple, clean the nipple up and reinstalled the hose. I learned this on a previous vehicle flush when the hose would not reseal correctly. I have never had a problem with the hose being too short to do this, and there was sufficent hose on our 3.9 to reconnect.

 

Now that is a simple idea, that I wouldn't have thought of! Thanks for the tip. That is a very smart suggestion. I actually have some 5/8" ID heater hose on hand now, so I can cut the old hose right at the nipple of the heater core, raise the old hoses so they do not leak everywhere. Then cut off the old hose from the heater core, clean the nipples, then install new hoses that are extra long, so they can be dropped to the ground and not spray all over the engine bay.

If using standard water from a hose (at a reduced pressure) does not produce any flow, is it even worth using a harsher method such as acids?

Some of you talk like you have flushed out your core many times...Why is that? Do these cores have a problem with clogging, or have you just owned that many cars that have needed that procedure done?

Thanks again for the help!
Zac

 

For me, it's a matter of yearly maintenance. Every fall I'll backflush my heater core, remove & clean the TB and install a new PCV valve. During the winter, I place the temp control about half way and that keeps it plenty warm inside. Anything higher than that and I have to start rolling down the windows. Just a little bit of faithful routine maintenance goes a long way.