What I Think Is A Heater Core Problem.

Garrett Street · October 11, 2011

Alright, I have a 99 Silverado. I noticed 3 days ago that the inside of my truck was starting to smell like anit freeze. I thought, crap heater core. But, I don't get any coolant in the floor boards. But, today when I got back from class, I noticed that under the engine bay on the passenger side right under the AC line that leads into the firewall, coolant was pouring out of a small tube behind the heat shield on the firewall. So, I now don't know if I have a heater core problem or something else? Any help would be great. I literally have no idea what is wrong this time.

ranger952 · October 11, 2011

Alright, I have a 99 Silverado. I noticed 3 days ago that the inside of my truck was starting to smell like anit freeze. I thought, crap heater core. But, I don't get any coolant in the floor boards. But, today when I got back from class, I noticed that under the engine bay on the passenger side right under the AC line that leads into the firewall, coolant was pouring out of a small tube behind the heat shield on the firewall. So, I now don't know if I have a heater core problem or something else? Any help would be great. I literally have no idea what is wrong this time.

Probably is. Start tearing the whole assemble apart to see. If that was my truck, I would be doing that very thing!

I did mine on my 1998 silverado. Not too hard, just takes a lot of time to wiggle everything in and out. :-)

Be prepared to replace insulation and other things like that if they got wet.

Good luck!

Garrett Street · October 12, 2011

Thanks for the reply! I already started taking stuff apart. But, the strange thing is, there's absolutely ZERO moisture inside the truck at all. None in the dash, carpet or floorboards. Could it be something else or am I just wishfully thinking?

wavery · October 12, 2011

Thanks for the reply! I already started taking stuff apart. But, the strange thing is, there's absolutely ZERO moisture inside the truck at all. None in the dash, carpet or floorboards. Could it be something else or am I just wishfully thinking?

Wishfull thinking if it's actually antifreeze that you are seeing......

You could do a temporary fix by taking off both heater hoses and put a pipe in between them (splicing them together). If the issue stops, heater core is bad and you can replace it when you have time. If the issue continues, the coolant is coming from the engine somewhere and spraying on the firewall (unlikely).

Could the water that you are seeing actually be just water? If it is, your AC evap core could be icing. As it thaws, it could be causing mold in the air ducts. That smells nasty too.

Garrett Street · October 12, 2011

No, it's definitely antifreeze because I just got the "Low Coolant" light. Gosh, I've been watching videos and reading up. This looks like a 10+ hour job. The part is like 100 dollars but the fix takes forever. Ugh. I'd rather pull the whole dang motor I think!

wavery · October 12, 2011

No, it's definitely antifreeze because I just got the "Low Coolant" light. Gosh, I've been watching videos and reading up. This looks like a 10+ hour job. The part is like 100 dollars but the fix takes forever. Ugh. I'd rather pull the whole dang motor I think!

You can certainly by-pass the heater core but it's coming up on winter. That is a b!tch of a job. I feel for you.

The other thing that you might try is getting a good radiator sealer. Put it in the radiator, turn the heater all the way on (High heat, low or no fan) and drive the truck for awhile.

Garrett Street · October 12, 2011

Is there any chance that might actually work? I'm willing to try anything, I'm really scared of this job. Lol

wavery · October 12, 2011

Is there any chance that might actually work? I'm willing to try anything, I'm really scared of this job. Lol

It may work...... try this one:

http://shop.advanceautoparts.com/webapp/wc..._T%7CGRP2053___

The key to using this type of sealer is to drive the truck or at least let it run at high idle for over an hour.

Just don't make the common mistake of thinking that if 1 can is good, 2 cans must be better. Make no mistake, if you overload the cooling system with this stuff, it can stop up the radiator.

I had an old truck that I put this stuff in years ago. I never had another leak in that truck.

Garrett Street · October 12, 2011

Thanks, Wavery! A small ray of hope in the horrible gloomy world of "heating core". I'll try that and let you know what happens. Although I do have another question. Why would I not be getting any moisture inside the cab? The only fluid comes out from inside the engine bay.

wavery · October 12, 2011

Thanks, Wavery! A small ray of hope in the horrible gloomy world of "heating core". I'll try that and let you know what happens. Although I do have another question. Why would I not be getting any moisture inside the cab? The only fluid comes out from inside the engine bay.

That does seem a bit odd and that's why I suggested to 1st try by-passing the heater core to be sure that is your problem. It could be one of the heater hose connectors is just cracked. They are just plastic.

I can't imagine where else coolant could be coming from unless it is spraying back from the engine, hitting the F/W and running down.

98 Z71 SLT · October 12, 2011

those plastic heater core connectors (at the firewall) are known to crack and split open over time...

i'd be checking that 1st...

ranger952 · October 12, 2011

Not trying to start any arguements here, but I strongly suggest you do NOT use any type of sealer to fix this. You might cause more problems that it fixes. Trust me, I have seen it.

Bite the bullett, and REPLACE the heater core. Also, replace the hoses that supply it while you are in there. Yes, it is a pain, but worth it.

Good luck.

ranger952 · October 12, 2011

Forgot to mention.....the bypass idea is a very good one to help diagnose.

Still, if it is the heater core, replace it!

wavery · October 12, 2011

Not trying to start any arguements here, but I strongly suggest you do NOT use any type of sealer to fix this. You might cause more problems that it fixes. Trust me, I have seen it.

Bite the bullett, and REPLACE the heater core. Also, replace the hoses that supply it while you are in there. Yes, it is a pain, but worth it.

Good luck.

We used to get a vehicle or 2 in that the radiator was plugged up with BarsLeak sealer too. I'm convinced that it was due to misuse of the stuff. Some people will put in a can to try to stop a leak. When it only slows the leak down, they put in another can. That's where the problems begin.

It's also important that the engine run as long as you can before shutting it off. It takes a long time for that stuff to find it's way through the cooling system.

If it were my vehicle and I planned on keeping it, I would simply by-pass the core until I could get to replacing the it (if that is indeed the problem). If the problem is a cracked hose connector, it's a fairly easy fix.

Garrett Street · October 12, 2011

I bypassed the core and that's definitely the problem. On the 20 minute drive home all the smell is gone, the windows didn't fog, and it didn't lose a drop of fluid. The reason none of the fluid ended up on the carpet was because it was draining out of the core, into the AC condensation catch, and out the hose at the bottom of the firewall. Looks like I'll need a weekend with nothing to do soon. Ugh, this is a HUGE job.