Heater core replacement


on Saturday 17 November 2007
in A-Z Index - Everthing is listed in here > Heater

How to remove the heater core without removing the dash

Can you remove the heater core without removing the dash? Yes, the process is listed below, however also read the comments by John and Paul at the bottom before you decide to take the leap.

Removal

First remove the 2 heater hoses from the heater core pipes on the firewall side under the bonnet ..they are located on the drivers side at the rear of the engine.

Remove the rubber grommet situated between the pipes at the firewall

(One thing that will help a lot is a by-pass hose to connect from the engine outlet to the inlet. This will allow you to drive while working on the heater core. This one I picked up at the local auto shop and cut the ends off for length. No reason you couldn't use some flexible hose.)

Remove the panel under the steering column and remove the 2 plastic heater/aircon tubes..remember to disconnect the plugs for the temp sensors etc from the tubes.

(This is not absolutely necessary. It just gives you a little more room to work. I've done mine with it in place.)

You will see a black plastic box that I think controls the heater flaps...remove the plugs and screws (approx 5 chrome looking ones) holding the box in place (including 2 tiny philips head screws on the bracket) and remove box. Some screws are difficult to get to and you need a small screwdriver or a quarter drive socket and I think they are 6 or 8mm heads.

You will now see a black plastic cover over the heater core pipes held on by the same chrome looking screws...remove this.

(The top pic is what you will see when you climb under the dash on the driver's side. There are 4 screws on the controller box, and 4 plugs. The lower pic shows the top screws in the controller bracket. The top screw in the plastic cover in unfortunately in the shadow. Most of these screws you will have to do by feel, 'cause you can't see them from below.)

Now for the tricky bit...from under the bonnet you must get a quarter drive ratchet and appropriate sized extension (approx 1" to 2") with an 8mm socket and place it through the hole and try and locate the small hex headed screw that holds the heater core pipes to the rear of the heater box...this is the hardest thing to do on the whole job!! See tech-tip, bottom of page.

(I agree. This is a PITA. Here's a couple of pictures to give you an idea where the screw is. Itls located above and toward the left of the lower pipe. It also has a phillips head so you can use a small screwdriver. I've even used a small blade screwdriver. The screw I've used for the picture is not the same sort that is fitted.

To make it more interesting, there's a foam rubber piece that may cover the screw. You'll need to push it down and out of the way.

Once removed, go back under the dash and unscrew the 2 heater pipes from the heater core (4 screws for each pipe).

There is also a spring and a cable attached to the brackets that controls the on/off valve and that must be removed....make sure you remember where it goes back as it is quitedifficult to put back on.

9. Look now at the side of heater box itself and you will see a little bracket that holds in the heater core. It is held in place by one screw that swings out of the way when it is loosened and voila!... the heater core will slide out of the heater box.

(This bit is pretty straight forward. The cable clamp clips over the top of the bracket. Pull on the top and it will pop off easily. The bottom of the clamp fits through a hole in the bracket.

IMPORTANT. Do not remove the pipes! The top pipe will lift above the heater core as it slides out and the lower pipe will push forward enough to get it past. Leaving the pipes in will avoid the temptation to disconnect the cable from the tap. Refitting the cable is extremely difficult+++.)

Re-fitting

Re-fitting is the opposite of the above except for a few minor points....you must slide the heater core back in WITHOUT THE PIPES ATTACHED. However before doing so read the next section...

The next part is very difficult.... before attaching the pipes you must re-attach the cable through the little hole on the pipe bracket.

(Not necessary if you have left the pipes where they are)

I found this difficult to do as you have turn the pipes and bracket upside down and round and round the get it through the hole and there isn't a lot of room to work in. Also don't forget to re-attach the little spring that helps operate the on/off valve. Remember, you must slide the heater core back in WITHOUT THE PIPES ATTACHED, then apply some good sealer (ultra grey for example) to the faces of the heater core and the pipes and then screw each of the pipes back on with the 4 screws.

Now the hard bit...you must then replace the screw that holds the pipes to the back of the heater box. This can only be done from under the bonnet and is much easier if you have 2 people...one placing the screw through the firewall on the end of a socket and the other under the dash guiding the screw into place. This is not easy (I did it by myself but wish I had help) and it is tempting to not replace it but the heater core will probably move around and vibrate and cause other problems so I recommend that it be done.

(Recommended. But I left mine out cause it just didn't seem like it was worth the effort. No rattles or vibration so far. Actually, by the time you refit the boot in the firewall and connect the hoses, the pipes can't move very much anyway. If you do put it in, I found blue-tack is great for holding the screw onto the end of the screwdriver/socket.)

Once the heater pipes are bolted on it is a simple matter of refitting all the other bits. Make sure you remember to replace the plastic cover that goes over the heater pipes before replacing the control box and make sure to plug in all plugs that were removed.

I couldn't get the rubber firewall grommet back into place without destroying it so I sealed the firewall hole with silicone (bit rough but no choice).

(Use a light oil or grease to help it slip over the pipes and into the firewall.)

Some points...

It was approx 3 months since I did this job and I did remove the dash, as I didn't realise until I had done it that I didn't have to!! There are some minor things that I have probably forgotten so if you find something I haven't mentioned please let me know. A suggestion is to remove the drivers seat for more room to work under the dash.

Good luck!

Regards

Paul Hewitt


Some additional points by John Penlington, from Unique Autosports:

We have done it both ways removing and not removing the dash. We believe removing dash is the surest way with less hassle as the pipes though the firewall can be trouble and more room to get to it, plus you can fix the top of the dash were they lift as it also is much easier to do than in the car as we do.

Paul's reply:

You don't have to pull the dash but it certainly is easier to get to if you do and yes it is the only way to fix the lifting dash problem so maybe its a good time to kill 2 birds with one stone. Also you don't have to disconnect the aircon either way so make sure that whoever does it doesn't disconnect the a/c as that can cause all sorts of other problems due to idiot a/c regassers (as I have learnt).

Garry's comment:

There is no way I would consider pulling out the dash. Using this method, you can still drive around when the work is half done and it takes much less time. It took about a day and a half to remove the dash and replace the core. It took about 4 hours to do it this way. Depending on how you go with the screw in the front of the heater box, it shouldn't take you much longer.


Tech-tip by Richard Scullion 2/10/06

Thanks for your tech article on removing the heater matrix without taking out the dash - saved me a load of hassle. I wanted to suggest an addition as regards the bolt you have to reach through the bulkhead. The article suggests you should be able to get a socket on it, but I couldn't get a socket square on at the angle I had to go through the bulkhead at. After several hours of trying different ways I went to Halfords and bought an 8 mm spanner with a 180 degree swiveling joint on the end (picture attached). This can be pushed through the bulkhead straight and then bends to sit square on the bolt. I also discovered you can reach it with one of these from inside the car but I think it's still easier to go through the bulk head.
 


 

 


 

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. It may help to have somebody try to push the tubes inside the firewall from the engine bay. Fig4 sh

- Ty Martin

Thou shalt not place rear wheel on backwards