Heater Core WTF?!?!?!?

94 Shadow (GF car)
2.5 TBI
Auto

The original heater core failed at about 160k, and now I have put 3 different cores in over the last year and a half. ( I have this job down to about 4 hours now :mad:) They last about 3 months and then one day you start the car and get a whiff of antifreeze and within a few weeks, the car will start loosing enough coolant to get close to overheating. The 1st replacement core was from Autozone, I went to Rock Auto after that and the one in the car is from NAPA and just started leaking last week. I cant for the life of me figure out why these are failing. They are plumbed with stock hose routing, I eliminated the intake heating loop after the last one in case that might have caused an issue. I have put a pressure tester on the radiator and have no indications of leakdown, and I ran the car up to temperature with the gauge installed and the pressure peaked below 20 psi (if I remember right). Nothing to indicate a pressure spike or abnormal conditions, the car runs cool even with the A/C on and 113 OAT.

Anyone else have a problem similar to this or got any suggestions on where to start?

find in your area a radiator manufacturer .. not a rad shop but someplace that makes radiator cores

auto , industrial .. whatever
you want them to put it on the "flux" table" where they wash the core down with flux before baking it in the oven (this is how they solder the tubes and fins when making a rad)

bake it along with their other rad cores , then dunk the whole thing in the dip tank (full of molten solder) , and blown out through the fins

doubt that one will ever leak

they might not want to do it with a used one for good reason but a new in the box heater core shouldn't be an issue to run through the system again

one with (any) water in it would possiably explode when dunked in the molten solder

someone's trying to save a little to much money making the ones you've been buying

if you wash a new heater core with soap and water it helps take away some of the hot metal smell too

wow dbbl post bug followed by edit post bug ..

Could try using liquid glass or something to seal it from the inside.

they are failing simply because someone is using pizz poor manufacturing .
no other reason for the failure , it's either soldered together properly or it's not though the quality of their solder might be in question too
thus my solution , I've worked for a couple of places as I described above and done every job in the shop from cutting tubes and stacking cores to packing & shipping them out the door

some cores look like little radiators , like the o-e mopar fwd ones without the all over solder coating others look like a block of fins with a complete coating of solder everywhere

a harrison core for something mid 70's GM would look like the later

are these cores you have been getting a brand name or are they some unnamed generic brand in a napa / rockauto box ?
if not a brand name they are probably an offshore cheepest price part the part chains are pushing

there should be a tag soldered on or a part number stamped somewhere an H or M would possiably indicate a harrison or modine part number

A bad motor mount might cause the heater core to fail. Since the engine would rock forward a bunch it would pull on the heater hose, especially with a TBI model where it connects to the top rear of the engine. I've never seen it happen before but there is always a first time for anything.

The one I bought for my Daytona a couple years back from Rock Auto was an aluminum unit. Knock on wood, it's still working, and no leaks. Although, I don't think it puts out the heat it should. It works, but in the middle of a cold Indiana winter, it never really gets the interior real warm.. It defrosts the windows fine, and makes it somewhat comfortable, but I usually have it on full heat all the time. I never have to turn the temp down in the middle of winter... I thought maybe it was a thermostat issue, but I installed a new one when I bought the car, and I never get a code 17. The temp gauge reads the same warmed up cold weather or hot, so I doubt that's it...

But to address the OP's question, have you thoroughly flushed the system when you changed the heater core?

I remember years ago, I was friends with a Chrysler service manager, and I remember him telling me about having coductivity issues in the coolant in these motors. It can quickly destroy a temp sensor, like the ones used to cycle the fan, and can do a number on a heater core... I had an issue with a temp sensor in the Scamp, and he told me to flush the system & use new coolant and distilled water. As I remember, it cured the issue...

May not be your problem, but thought I would throw it out there...

Dig around on ebay, you can find old style copper ones from time to time.

As mentioned above, coolant conductivity issues could be a problem, and that is a good point to bring up. Electrolysis can be caused from poor condition of coolant, and/or poor engine grounds. Easily tested with a DMM.

http://www.aa1car.com/library/coolin..._corrosion.htm

Great link, RattFink.

Several grounds on my Sprit R/T were bad. Often a loose self tapping screw into sheet metal.

I've learned that aftermarket parts are JUNK.

Definitely look at the electrolysis issue and flush it out very well.

You can also try putting a restrictor in the intake side of the heater core. Ford did this to keep cars from popping their heater cores. A washer of the appropriate size would create enough of a restriction

Thanks for all the input. I don't think I have an electrolysis issue. I did double check the grounds to be sure. I only use distilled water with an antifreeze chaser in my cars as the water here in AZ is thick enough to chew, not good for cooling systems.

Spectra seems to be the single supplier for these, I figured NAPA would have better QC and their rejects probably go to AZ and Rock Auto. That is probably not the case, I think they are all the same and just poorly manufactured.

All motor mounts are good, they have been replaced as needed and there is plenty of slack in the hoses. I bypassed the intake manifold routing so that isn't an issue.

The liquid glass seems interesting, I did some additional research, I might just hook up a hose and pump to the heater core and flow some liquid glass (sodium silicate) through just the heater core to try to seal it up. Fortunately heat is a secondary requirement here, but still needed for the GF and defrost purposes.

The restrictor idea is interesting, I was thinking of this now anyways. since I just looped the heater core hoses, the car seems to run a bit hotter. I think it might be bypassing too much coolant without the heater core restriction in place. No matter how good your cooling system is, when ambient is 118 there isn't much room for heat transfer. My temp gauge is off the first mark before I even start the car!

On the heat quality topic: I tend to believe these Turbo dodges never had great heat. I've owned three, 87 daytona, 89 turbo van, 86 daytona. I replaced the heater core in all three, thermostat, etc... Either they were weak from day one, OR I've often wondered if whatever seals off the blend door (cold/hot) if those seals have gone bad, it would allow more cold air in, therefore giving off lukewarm air rather than the temperature these cars might have put out 30 years ago....

Strange issue with the heater core itself though. I did my 86 like 5-7 years ago, and its still fine....

dodge heaters were always one of the best
my old turismo had heat , good heat in 1 1/2 mile every winter morning

if the car runs hotter with the heater core out of the loop it's most likely because you've reduced the total cooling surface of your system not the lack of restriction at the core

one of the things that can help an overheating car is turning the heat on ..so the reverse applies

like I said in my earlier post , find a local company that manufactures radiator cores .. heavy industry won't be using boxed rads so there has to be something around you
they will have a dip tank full of 30/70 rad solder
dipping the new core won't be difficult

How about an over pressurized cooling system causing the heater core to blow? Blown head gasket maybe? Could combustion gasses be filling the cooling system and perhaps the radiator cap isn't popping off to the overflow at the specified pressure as it's supposed to?

Maybe the radiator cap is bad and not allowing it to vent to the surge tank when needed?

Radiator caps are cheap, it can't hurt to replace it.