Tiderfish

Ok so the title may be a bit over the top.

I was having a problems with my heater core steaming up my windshield, and creating a coolant smell in the cabin.

I replaced it with a brand new unit from Napa. Installed it and thought life was peachy since I didn't' have to pull the entire dash. I even replaced the hoses leading to it under the hood.

Fast forward 2 weeks, and I started using the heat, and noticed the heat is not that hot, but more importantly when I turn it on the windshield fogs up almost immediately.

I do hear a gurgle when I start the truck, so I know there is air in the core. I plan on bleeding out the air this weekend. I also pressure tested the core so I don't think it is leaking.

(1995 F150 351W E4OD 4x4 Short Bed Singe Cab)



What I don't get is the coolant comes into and out of the cabin via heater core. No mix or bypass valve at all. So if the heater core is not leaking, then where is this steam coming from?

unit505

I would think it's condensation and not actually steam. Temperature variance causing fog. As for removing the air from the coolant system, very easy $5 permanent fix. Get a cooling system flush kit and install the tee with the cap in line on one of the heater hoses. From that point on you can flush "burp" the air out of the system with the truck cold and do it in a matter of seconds.
Also....did you flush the system before installing the new heater core? If your old core was corroded and dumping pieces of rusty metal into the system, which sounds like the case if the old one was leaking, then you install a new core allowing it to become clogged. Also a possibility of some water from the leaking core being deposited into the air ducts via evaporation and standing somewhere. Check any low spots in the duct work that might allow a pool to form. I'd also check your condensation drain line. If it's clogged, you could have standing water in there. You can run a 10g solid core wire or coat hanger up the line to clear any clogs from under the passengers side of the truck.

Tiderfish

Thanks for the reply.

The old core wasn't leaking water, it was more weeping water. When I pulled it out there was no standing water anywhere. It was just a mist on the top of the core. I didn't see any standing water anywhere.

I replaced the engine with a brand new one in the last 6 months, and I put in brand new coolant. So I didn't replace the coolant. Just stopped it up, and replaced what was missing when I finished.

The water that was in the heater core stayed in there as I uninstalled it. When I poured it out, the water looked normal. No rust bits, no discoloration.

I will definitely install that flush kit. Sounds much easier then pulling the hose.

Chris_1

iTrader: (1)

You could just be getting steam from leftover residue in the air part of the system, which will eventually dry up if that's the problem. It would seem to be if the system holds pressure.
Maybe make sure your hose clamps are tight - that could cause a problem if they're not.

unit505

The hose clamps should be on the outside of the box in the engine bay. That rules that out if he sealed the core openings.

Tiderfish

Welp at lunch I bought a coolant flush kit. I has a T junction with a hose spigot at one end. it also has clamps and a cap for the garden hose side. Ill be installing it this weekend. Hopefully it will resolve this issue.

I also drove around and had the heat blasting for a while with the windows open. Then I rolled up the windows and left the heat on, and the windows didn't fog up. So perhaps there was some left over water somewhere in the system.

unit505

Sounds like a winner! Install tee in your longest hose and at the highest point that you can lift the hose. Remove the rad cap and insert the water hose in the radiator and barely turn on the water until all the air burps out of the tee. Put the cap on the tee and then the rad cap and you should be good to go.
You shouldn't even need to crank the truck as the motor is the lowest point and all of your air should be in the top of the rad and the heater core.

The good thing is that the tee cap can be slightly loosened while the truck is running and hot and seep out any remaining air. The cap is the same as a female water hose connection and has plenty of thread to allow it to be loosened without blowing off. Don't be dumb and do anything your not capable of as this is only an example of my own stupidity and I take no responsibility for your stupidity! Lol

dan2286

Do you have working a/c? Sometimes defrost can fog the windows up if a/c isn't working. The a/c actually removes moisture out of the air, and is the reason why the compressor runs while on defrost to speed up the process.

I know you probably found the issue, but just throwing this out there in case it comes up again.

Tiderfish

Thanks for all the replies guys! Happy Halloween!

The AC does work on the truck. It was the only way I could get the windows to stop fogging up. When they did fog up I wasn't using the defroster option. So the heat was coming out of the dash and floor vents. However the windshield would still steam up.

As for burping the air out of the heater core. If I install the T and just add water how is that going to get the air out? As I understand it, the heater core is always getting coolant circulating through it. So just adding water would be the same thing as letting it run normally.

I plan on installing the T and raising it as high as possible and venting that T to atmosphere to get the air out. I will probably hand pump the coolant by squeezing the main coolant lines.

The good news is that I ran the heat this morning and it didn't fog up the windows. Nor did I smell coolant in the cab. But the heat was warm at best. I believe once I get all the air out of the core, it will be normal heat.

The bad news is I still smell warm coolant when I get out of the truck. Especially when by the passenger side.

I do not know what this could be. When I did the engine swap, I replaced all the coolant hoses.... I may need to replace the radiator at some point. Does anyone know a good full aluminum radiator that is a drop in replacement?

unit505

As for adding water, your letting air out and need to replace it with water, so I always add water while I'm burping the system to completely fill the system. With that said, I have a t-stat gasket leak and have to top off the rad every couple of months. I burp and add. Some concept as drinking beer! Have you checked for gasket leaks, freeze plug leaks, etc? Also, need to check your t-stat. If some one has replaced it with a 165 or failed to replace it at all, then your not going to get much heat. I'd run a 185 or 195 and I'll bet that fixes it.