Wet passenger floor in my 05 Tahoe

[mijohnst]

This morning when I went outside the entire windshield was fogged up from the inside. Guess I know my issue. lol

Fogged windows are very much a sign of a heater core problem, especially if it is actually wet to the touch. It will smell and taste like anti freeze as well.

 

[OR VietVet]

Have fun and replace surrounding parts as needed and recommended.

 

[MikeW]

Please let us know how it goes as my 02 I fear needs a core replacement as well. Really interested who is going to do it and cost …. THANKS!

 

[mijohnst]

I've spent the last 2 days pulling out my dash to get to the heater core. Not a fun job but I've gone cautious and slow as recommended. I've packaged, labeled and documented everything. I pulled the canister out and I'm surprised to see the compartment where the core lives and it's dry. No antifreeze residue that I could see. Even the old core didn't show anything any signs of leaks as I would have thought.

Now I'm second-guessing myself. I *thought* it's antifreeze because I can smell it and it fogs up my windshield in the morning. Would freon do that too? Is it possibly the AC evaporator leaking? The only thing that was wet was the compartment around the electric fan in the picture. It had standing water in it. That's not normal, is it? Water could have gotten in from the cover over it I guess, but how did it get there?

My second issue is I can't find an easy way to get the enclosure open to look at the evaporator. I guess in later models they used plastic rivets to put the halves together. Some YouTubes I've watched show it just coming right apart but mine won't because of those. I guess I'll need to drill them out. Has anyone else had to do that? What the crap was GM thinking?

Frustrating to say the least...

 

[OR VietVet]

There is only one way moisture/water gets in there and that is from a backed up evap drain or the heater core. I have seen also where the hose connections, on the firewall side leaking under pressure and the coolant would actually spit out and follow the core tube into the box from the outside but that is a very rare thing to happen. Refrigerant is a gas, not a liquid. The a/c system is under pressure at all times, even when engine is off and and sitting. When the defrost is on, in order for the compressor to cycle to help with the removal of moisture in the air inside the cab, the refrigerant pressure must be high enough for the pressure switches to cycle the compressor. If you have an evap leak it just releases pressure till it equalizes and then it will be almost static till it does in fact leak all out. Coolant does not build pressure till the engine runs and starts to build very slight pressure just from the water pump moving it in the system but it needs to build heat to really get the pressure up there. There is always moisture in the air as well, so depending an the atmosphere in that box and the ambient temp, I guess there could be some "sweat" in there. But, that sweat is not going to leave a foggy film on the inside of your windshield. You may have mold in there though. Those a/c drains can cause problems and still look like they are dripping it all out on the ground. You say you can't see signs of the heater core leaking. The leak does not have to necessarily be at the outer edge for you to be able to see it. It can be inner core area and hard to see and also, be aware that the core is hot when coolant goes in and out of it and when you shut the engine down and flow stops, the wet that may be there then may not show by the time you get it apart because the hot core evaporates the moisture of the coolant and then looks dry. The smallest leak may never show till only when under enough pressure. Replace that core. Double check the housing for the evap access but IMO I would leave that alone if you can't get it open. Why look? Just for peace of mind? I get it but I would leave it alone for fear of damaging the case. Any you tube videos show how to just open the case for evap replacement? Look for numerous videos and then make the decision.

 

[mijohnst]

PNW, thank you for the quick and very detailed response. I really appreciate it. I feel better understanding more. I just got done crying into my pillow so this really helps me feel better. I'm with you on leaving the evaporator alone if can. I just wonder what the dealer would do... replace the entire unit and instead of just an evaporator if it were bad?

Before I go through all the trouble of put it back in, I dropped a scope into an opening to have a look around. It pretty damp in there with some debris near the bottom. I can stick my finger in there and it feels kind of dirty kind of grease and it's all at the bottom. I used my scope to look at the other side form the opening I'm looking in. Is that normal? Sorry for the poor picture of my scope. Looks like the back wall is still a little wet in there too.

 

[OR VietVet]

That looks like mold to me. Best to get case open, do not break it, and clean that all out. Was the a/c compressor cycling on defrost before you tore this down? When the evap leaks it will leak refrigerant oil too and you may well have an evap leak if the refrigerant is all gone. Get it open and inspect. Glad you went further and found this.

Plus, when it does leak the oil the dirt or mold will gravitate to that and gather and that may be what we are seeing there.

 

[mijohnst]

That looks like mold to me. Best to get case open, do not break it, and clean that all out. Was the a/c compressor cycling on defrost before you tore this down? When the evap leaks it will leak refrigerant oil too and you may well have an evap leak if the refrigerant is all gone. Get it open and inspect. Glad you went further and found this.

Plus, when it does leak the oil the dirt or mold will gravitate to that and gather and that may be what we are seeing there.

Thanks again PNW. I'll go ahead and drill through all those plastic rivets tomorrow. I'd rather be safe than sorry with this amount of work. Luckily, I have already purchased a new OEM evaporator because I thought if I had to replace the core I might as well go ahead and replace that too. I can go back through and put new aluminum rivets back through when I'm done. It sucks so much that GM would seal it up like this. If I screw it up I know of another same year Tahoe at the PYP junkyard nearby that I've already stripped parts off of. It still has this same unit inside of it and I'll just spend a few hours pulling it out of this fails. Again, thank you for your guidance. I'm looking forward to this being done. lol

 

[OR VietVet]

"I'm looking forward to this being done. lol"

By now so am I.

 

[mijohnst]

I was able to get it apart today and install the new evaporator and wanted to share a few notes. I drilled down the top of each of those plastic rivets just a little with a large bit and then used a putty knife to gently pry them apart. It actually came apart pretty easy. Be gentle when pulling one end off because there are separate compartment pieces and blender doors that will fall out if you're not careful. Also, it helped me to take a picture of the END blender because it controls two doors inside and needs to go back exactly the way it came off. See below

For anyone that does this in the years that used the plastic rivets (mine is an '05), I realized they put an unused screw hole right next to almost all of them so I didn't have to worry about redoing the rivets with the aluminum ones like I was expecting. Instead, I went down to Ace and bought sheet metal screws exactly the same size and length as the 5.5mm screws used one it and put on in every screw hole around the lip. Sealed up solid as before. They use the plastic rivet when building these because it's faster automating it instead of using screws is my guess. Here is a re-shared picture of what I'm talking about.

PNW, thank you very much for your help!