: Heater Core Replacement: 
: Performed by yt nitram on a 1991 NA w/ driver airbag and auto climate control
: Special thanks to PerlZTT, clarkj, Whoa, and Steve91TT for help during the process : When: : Is coolant gushing at the feet of the passenger and/or driver? Do you smell a sweet smelling fluid and are your windows fogging up? Your heater core has most likely died a tragic death. : Alternative: : If you do not need the use of your heater, you can bypass the heater so that coolant flows only within the engine compartment. All you need is a U hose that you will use to replace the two hoses in the engine bay. This bypass is a safe, easy, and cheap alternative if you choose not to use your heater again. : Cost/Time: : The approximate cost for the actual heater core from Nissan is $80-120. The two hoses are approximately $8 each. Nissan dealerships like to charge $600-800 to do the heater core replacement. This is NOT a short little DIY, it is very involved and requires complete removal of the dash, guage pod, instrument cluster, partial dismantling of the a/c box, and complete removal of the heater box. Here are the basic steps and time it took me (inexperienced with no how-to): : 1. Remove dash (4 hours) : 2. Get to and remove heater core (3 hours) : 3. Transfer core and reassemble heater and a/c (3 hours) : 4. Reassemble dash (2 hours) : Keep in mind, those are hours of actual work. Often, I would end up working for 30 minutes and then running into a tough spot and I'd have to stop for the day to go inside and e-mail some guys who have done this before. Hopefully this writeup will help your replacement go swiftly. Be sure to organize the nuts/bolts/screws so you have an easier time choosing which ones to use when reassembling. I used masking tape and a black marker to organize screws from each panel or box. In some steps, it may be necessary to unscrew/remove a ventilation piece even though it is not mentioned in the step. Be sure to clean everything that was in contact with coolant, or the smell will linger for a long time. : Materials: : Socket wrench with 10mm and 12mm bits and a piece that extends the socket about 5 inches out : Tamper-resistant Torx bit, size T50 (only if you have airbags) : Penetrating oil (such as liquid wrench) : Philips screwdriver (preferably of 2 different lengths) : Flathead screwdriver (preferably w/ one very short and one very long) : Large pliars (for removal of shift knob and other small uses) : A system of organizing the nuts/bolts/screws : A 3 year old who can remove clips in extremely tight spaces, or at least extremely dexterious fingers : 1. Remove Dash : See the following document:
: Dashboard removal on twinturbo.net : That page doesn't go into much detail about removing the guage pod and instrument cluster. The hood over the guages comes off first (2 vertical screws). You must also remove both instrument clusters on either side of the wheel, and each have faces that are held by two vertical screws underneath them. After the instrument faces are removed and electrical connectors are untangled, the removal of the guage pod is fairly self-explanatory. : 2. Remove black metal brace spanning width of cabin : This step is very straightforward. There are 3 12mm bolts on the left, 2 above the steering, one tamper-resistant T50 Torx under the steering (if you have a driver airbag), 7 bolts holding two silver braces in front of shifter, 1 10mm connected to a ventilation piece, and two 12mm nuts on the far right. There may possibly be more steps if you have passenger airbag as well. Now you can remove the piece on the front of the heater box (one screw on top and I believe two on bottom). : 3. Push the ECU out of the way : Pull back the carpet of the passenger floor area, remove the wooden cover, and expose the ECU and alarm module. Unscrew the ECU from the body of the car and move it out of the way. It is not necessary to unhook the electrical connectors. : 4. Remove metal strip above the ECU : There are several nuts screwing the metal strip to the car and supporting the a/c and blower boxes above. Remove each of these, as well as disconnecting one hose that goes through a hole in the strip and into the a/c box - just wiggle it out of the hole where it goes into the a/c box. At this point, you can remove the 3 nuts that are holding the heater box in. There is one tucked deep on the bottom right of the box (near where you just removed the metal strip), there is another very visible right up top, and the third is very visible on the bottom left near the accelerator. : 5. Drop the bottom of the A/C box
:  : Some say the heater box can be removed without this step, or by just loosening the A/C box but not removing it. However, in my experience the bottom of the A/C box absolutely had to be removed from the car for the heater box to pull out. This is the most difficult part in my opinion. You must remove the clips on the front as well as reach behind the A/C and blower boxes and remove all of those clips. It is NOT easy and will require a lot of cursing and limber fingers. If you aren't too large, I actually found that the best position is to sit upside down in your passenger seat, meaning feet up beyond the headrest and head down on the carpet with your back where your ass normally sits. In that position, it is easier to get one's arms up behind the box. Use flathead screwdrivers of a few different lengths to try to pop off the clips in the back. You may think that if you get most of them then you can just use force, but in my experience all of the clips had to be removed. There are approximately 4 on the back of the a/c box and about the same behind the blower box, and there was an especially difficult to access one behind the a/c box just to the left of an opening where a few hoses come in. Drop the bottom half of the a/c box (including the styrofoam surround) and remove it from the car by gradually working it loose. The parts in the a/c box are very expensive and somewhat fragile. : 6. Remove the hoses in the engine bay
:   : There are two hoses going from the engine bay through the firewall and into the core (Fig3 shows these hoses with the engine removed). They are right next to each other and located behind the plenum (the green in Fig2 depicts the approximate area). Loosen the hose clamps on both sides of both hoses, then spray a lot of penetrating oil on the part of the hoses that overlap the tubes they are connected to. Let it soak for a few minutes, then pull like crazy. Some are able to cut the hoses lengthwise at the connections in order to pull them off, but I found limited room to cut unless you have a small sharp razorblade. Leave the grommet in the firewall. : 7. Remove the heater box from the car
:  : Yep, it's time. But wait, first check all around to make sure nothing is still connected to the heater box. There were some electrical connectors on the bottom of the heater box but after removing it I believe none of them were connected to the car, only other areas of the heater box. There is some type of computer module on the left side of the heater box, so disconnect those electrical connectors. Now just pull like crazy, slightly up, out, and to the left.
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07:52:06 03/18/02
