Heater core replacement 3100 94-96 Grand Prix WRITEUP w/ pics

[THe_DeTAiL3R]

 

Well I'm making a writeup on my successful heatercore swap. Was a pain in the ass but I've been more frustrated with other jobs....

 

Step 1:

 

Remove center console. If you don't have one, you're lucky. Mainly because it would have been easier working without the shifter on the floor.

 

Step 2: Remove the carpet stuff under the dash (oh hey look, there's my speaker crossover.. lol)

 

Step 3: Unscrew and remove duct to floor.

 

Step 4: Remove floor duct pan.

 

*note: Try to undo the clips that hold the big mess or wires, you'll be able to pull the parts though easier*

 

 

Step 5: Remove heatercore plastic cover.

 

Note: For the back screws, you will need to use a small wratchet, and deep socket.

 

 

 

Oh snap, coolant!

 

 

Step 6: You should have put a rag down to catch coolant, now it's on the carpet.

 

 

 

Pics of heatercore:

 

 

Pipes from heatercore going into firewall:

 

 

Small drip of coolant from corner:

 

 

 

Pic of pipes coming out of the firewall in the engine bay. (Top one is disconnected in pic)

 

 

Step 7: Remove NFG heatercore. Disconnect rubber hoses in firewall, remove the 2 screws from the inside.. it pops right out.

 

 

 

Pics of NEW heatercore. Note: unlike the factory one, this one has the metal tubes connected. I got this from GM dealership, unless they got it from NAPA or something.

 

 

 

Step 8: Install heatercore, installation is reverse of dissassemble.

 

 

 

Note: If you have good coolant, don't bother to drain it. When you disconnect the rubber hoses from the firewall, minimal coolant will come out. Have a couple rags handy and on the floor if you don't want to make a mess.

 

I had put Stop-leak in prior, which didn't work, so I flushed it well before installing the new heatercore.

 

Bars stop-leak. Most of this mess never made it to the heatercore, it just sat in the coolant reservoir. If you decide to ever use this crap, make sure you add it to a COLD radiator so it enters the system. Dumping this out it looked like sand in the bottem... YUCK.

 

This was a fairly easy job on a 3100 engine. I don't think I would recommend you do it yourself on a 3.4DOHC if you are a beginner, cause getting to those rubber hoses on the firewall would be a major PITA.

[slick]

For the 3.4, if you remove the upper plenum(15 minutes), you will have full access to the heater core lines. Everything else is the same.

[AWeb80]

Nice C-BAD.....that is an awesome write up....hope i never got to do it.....my consolis a PAIN to get in and out w/ that LCD DIC in there.....LOL

[Crazy K]

I have a loose HVAC unit, i will do a writeup on it. You have gotten an important part covered. good job.

 

Prevention!

Possible reason for failure? on my 95 CS, when i opened the HVAC case, the inside had been flooded about 2 inches deep. This was probably due to the drain outlet through the firewall being clogged. make sure that your drain is unobstructed. Additionally, bad coolant will corrode it out from the inside. so would electrolysis if that were to occur.

the heater core is made of nice shiney aluminum, heres the bad heater core; the area that looks dull is a thickening coat of rust!

 

Interchange?

All off the GEN 1 and GEN 1.5 model have the same heatercore. If you were to look for a used one, find a car with fresh looking coolant, and tear away. if the unit looks coroded once the cover is off, find a different one

Why a used? They are cheap, easy to remove, and are usually still good, and one other reason... If replacement and original heater cores have detachable pipes, you can replace the heater core without going under the hood. This ability to detach them may only be with the OEM in car ones, as C-bad found out the new one was permafixed together. Good to know for those who have too much of an obstruction to gain access.

I purchased a used heater core from a J/Y for like $10. since my car had the original, the swap was easy.

 

NO HEAT BUT NO LEAK???

If the heater core is not leaking, but is instead clogged, you can flush it in an attempt to fix it by reversing the flow, or even running water through the hose. some even recommend an acidic solution, like CLR to clear out the core.

read:

http://www.caddyinfo.com/heater.htm

http://www.vtr.org/maintain/cooling-flush.shtml

 

LAST BUT NOT LEAST... THE INFO IN THIS WRITE-UP COVERS EVERYTHING YOU NEED TO KNOW FOR ALL GEN 1 AND GEN 1.5 W-BODIES.

 

the only thing I would like to add that don't see c-bad say... is that I remove the accelorator pedal from the firewall fro clearance, and becareful on removeing the lower cover, as it is weak and could easliy crack.

[THe_DeTAiL3R]

Yeah it wouldn't be hard to get them from the junkyard.... just take a crowbar and hack the shit out of the interior until you get to the core.. LOL. Taking the core out is the easy part.

 

 

My old heater core doesn't look that bad, and it worked very well as far as heating the car. Is there any way to plug the leak? JB Weld?

[Crazy K]

For the cost of a J/Y unit I would not bother attempting to fix one. Mine appears to have a leak at the bottom of the left hand seam, where is may have had the seam stressed by expansion due to corrosion. I suppose if it were acid washed, it would come clean and could be fixed.

[ismellrealbad]

Mine is leaking. I went to AAP and the new one has detachable lines also. more to come and pics wed night/thurs.

[Crazy K]

Mine is leaking. I went to AAP and the new one has detachable lines also. more to come and pics wed night/thurs.

I have seen a 2nd type of heatercore with detachable lines, which uses a pair of snap rings and is thicker and blockier than the normal stock unit. it is it different, the job will be harder, as the fittings won't be the same... requiring complete line replacement.

[AWeb80]

a local friend just replaced his in his 95 GP in 30 mins he said.

[ismellrealbad]

Yup mine has snaprings. What specifically makes it harder? I was assuming I would have to remove the lines ayway. Although I was hoping once I got it apart I found that the lines interchanged.

[ismellrealbad]

false alarm. lower heater hose clamp either went bad or wasnt tight enuf. it was causing coolant to poor thru, run down the line and pool up in the HVAC box creating a nice size puddle on my floor and coolant to poor steady out the evap drain.

[GP1138]

Thank you for the writeup, C-Bad. I'm doing this tomorrow along with full carpet replacement.

[GP1138]

I got down to the heater core in both cars... The '95 doesn't appear to be leaking.. No liquid in the cover and there appeared to be a little mineral deposits on the metal but nothing too serious.. Is there some other reason my backseat carpet would be soaking wet?

 

 

 

[Night Fury]

Trunk leak?

[W30olds]

I just undertook this repair on my 95 Grand Prix. What a pain in the ass! It took me forever to get the stinking heater hoses off from the firewall. The factory spring clamps were a major PITA to get at. The upper hose wasn't that bad, but the lower hose was a bitch. The spring clamp was upside down against the firewall. I tried to spin it over, but the clamp wasn't having it. Time to back up and punt.....So long story short when I pulled out the original core I discovered it was the quick connect fittings. So the core was out, but the metal lines were still connected to the heater hoses. I couldn't pull it through the firewall due to the dang clamps. I eventually decided to rock the engine forward to gain more room to get at the clamps. It gave me enough room to finally get the lower clamp off against the firewall.

 

The whole process to remove the core wasn't to difficult. Its hard to get at the little bolts under the dash. Especially since I'm 6'3" and 240lbs. So it was a bear for my big ass. Overall it's done. I hope to never have to do this again. So now I've gotten the core done, and new heater hoses plus no more coolant loss. I'm happy with getting it taken care of. Just wanted to offer my advice on the motor idea if your struggling with clearance problems like I experienced.

 

Regards,

Andy