Well, I've had my C4 baptism. I replaced the heater core in my '89 over the last week and it was about what I figured it'd be-a beech. At least you don't have to pull the front case half off the firewall. I think GOD made that core, then GM built the car around it!

One thing I'd like to broadcast is the trouble finding a replacement core. I started by checking the local parts houses; AutoZone ($41), Advance ($43), NAPA ($53) and Charles Auto (independent, $71). I got the Advance unit 'cause it was quickest by a day. Problem was, the rear cover wouldn't seat to the front cover because the return tube (smaller) was off the centerline spacing of the original by about 1/2" and wouldn't fit into the groove in the rear cover.

Also, the small tube spacing from the face of the core was about 3/8" inch greater than the original. Either of these abnormalities will prevent the cover from seating fully.

To make a long story shorter, every one of the above cores I checked were exactly the same manufacturer, same tags, numbers, boxes and packing but different "brand" names and they all had the same problem. Some guy in Mexico is making them all wrong. I also queried Ecklers ($78+ship) and it had the same manufacturers PN as the problem cores. A semi-local hi-volume-'vette Chevy dealer found one thru his dealer network in GA for $147+ship. It may have been GM NOS but that's a long way to go from OH and way too expensive for a heater core so I didn't bother to ask. Local Chevy dealer said NoLongerAvailable.

I finally went to a local old-time radiator shop hoping he could re-core mine with the original tanks & tubes. That's $60-70 if he had the correct 2"x7" core stock which he didn't. It's way too expensive to buy a standard (big) section of core stock just for one little heater core. He ordered a core from his usual supplier ($57) and it was identical to all the other cores, PN & verse. Luckily, this was a radiator tech, so he just repositioned the small tube to match the original, took him about 5 min, and it fit perfectly. He didn't charge me for the mod since his book said it was supposed to fit.

By the way, he uses a small tip oxy-acetylene, torch but uses air-acetylene to get a lower temp, hits the joint quickly to reduce heat spread and cools it just after freezing with copious amounts of brush applied liquid flux. I'll have to setup an air-acet system the next time I do any copper radiator repair. Also, GM cores have the tubes silver soldered into the tank which is stronger than plain "soft" solder used for all the rest but aftermarket cores are all soft soldered.

The core that's made incorrectly carries numbers 0398202, 6552893 & H90E on an aprox 1"x3/4" round-cornered grey tag. The 0398202 is the manufacturers PN. I don't know what the 655xxxx number is and I think the H90E is the date code. Hope this helps anyone in the same fix. Now all I have to do is finish getting all that stuff put back where it came from.

 

Daggone! Sorry to hear you had so much trouble, but thank you for sharing detailed info with the rest of us.
I can't begin to tell you how much time and trouble posts like this have saved me.

The board's Search function is a terrible thing to waste!

 

thanks for the info! ive been havin heater core issues lately, and its been on my mind to fix/or get fixed.