Heater core replaced 3 times in a year

[noel]

Hello.
This my sound odd, but, I have a 91 chevy stepside pickup. A year ago I had to have the heater core and the intake manifold gaskets replaced at a dealership. These two things seem to be common problems on 90's model chevys. In July, I had to replace the core again, this time I did it. I flushed the system and putting coolant/water. I now have to replace the heater core again. I've read about others having the same problem, but haven't read much about how to fix it. These are aluminum cores. I talked to a guy at a radiator shop today and he said I had some kind of electrolysis going on, and that he suggested flushing again. Tonight, I read a post on a usenet group where a guy stated that it could be a bad ground and that current could be passing in the antifreeze to the core which would cause the aluminum corrosion. Does this sound possible? Any toughts?
Thanks

[mdshunk]

Many heater cores are suspended in rubber mounts, so your electrolytic corrosion thought might be right on. This could be making the heater core into a big semiconductor. Could you take the inside plenum back off and alligator clip a wire onto the core (fins?) somewhere and run that to a chassis ground like a nearby trim screw or something? Do the heater core inlet and outlet pipes stick out through the firewall enough to clamp a little wire on there to ground? I'm just taking your electrolytic corrosion idea here and running with it. I actully have no idea why you're experiencing high this failure rate. I'd be hopping mad if I went through 3 heater cores in a year.

[Wgoodrich]

While you have the core out tell us where the leak is located. Is is corroded like acid hit it, shiny like it is rubbing a hole in it, at a solder joint such as caused by vibration? Many causes can be your problem.

Also be aware antifreeze is not just antifreeze. Some antifreeze is approved to be used in aluminum systems. The wrong antifreeze can eat a hole in your system quickly just like acid. Be sure your antifreeze states recommended for aluminum systems. Also be aware antifreeze becomes harmful to your system if not mixed at least 50% water. Pure antifreeze is a no no in auto cooling.

Tell us more.

Wg

[k6ekb]

I can imagine your frustration. My 1998 Chevy Pickup is currently in the shop for its fifth heater-core replacement. A grounding strap installed between the heater core and the chassis didn't help any. A voltmeter reading of .2 to .3 volts DC is consistent between the radiator coolant and vehicle ground even after the grounding strap was added and the coolant was flushed and replaced with new coolant. Any ideas about where the current is coming from would be greatly appreciated...

[cboggess]

When you are mixing your antifreeze with water be sure to use distilled water.

[noel]

I know this is a long time to reply, but I thought I would do so to maybe help someone else out. My last heater core has lasted since when ever it was, Dec 03? Anyway. I had a freeze plug to start leaking and thankfully, it was one I could get to without lifting the engine out. I replaced the freeze plug with a rubber stopper one. It was a pain to get in. But It worked. While I was putting in the new rubber plug, I stuck my finger inside the block and pulled out a wad of rust. I flushed out the block with the plug out and big globs of rust was coming out in the water. I did flsuh out the cooling system with two part system flush, but this just didn't get the job done. The block is so full of gunky rust that as nothing short of dipping the block and a rebuild would take care of it. And without doing so, the rust (iron oxide) just keeps on polluting the coolant and this is what causes the electrical path, even after flushing it. I also think that GM knew this and started to make the soldering a little better. They have eating two of my cores while I only paid for one. Hope this core holds out until next spring! Heck, I hope the truck holds out to next spring.

[wbesaw]

I heard of this problem before. I understand that the problems is that the cores can't take the pressure and blow. If you kink the end of the intake hose connection a little (reduce it the same size as the return, just on the end, because you still have to connect the larger hose to it) it will reduce the flow and make it equal to the out flow. Make any since?

[joed]

5 year old post. I think the problem has been resolved by now or he has a new car.