348/355 heater core removal how to

So yesterday I ended up doing something I had not planned on while working on my 348. I don’t see any threads on how to remove the heater core from a 348 or 355 and even though it turned out to be very simple and straight forward I thought I’d do a quick write up with some pictures.

I decided to go ahead and completely restore my 91 348TB. I am taking plenty on pictures and will organize a thread for the restoration in the future when I’m a little farther along.

Anyway the first order of business I decided to tackle is the interior including a dash swap. When I removed the dash I found that the air ducting was completely destroyed and in several brittle pieces. I got suspicious when I removed the center console and the downward piece of the duct fell on the floor, I thought I’d just glue it back on until I pulled the dash and found everything destroyed. Luckily I sourced a much newer (355) one from Russ at Ferrparts that is complete and not insanely brittle.

The fun began when I realized that because the defrost vent sticks up through the dash the heater core must be pulled out of the way to be able to remove or install the piece. It gave me a chance to start on some deep cleaning on the car that was planned anyway, but here’s the way it goes. Starting with a picture of the offending vent that cause the removal. Obviously, old on the left and new on the right. Of course to remove the heater core nothing in the cabin needs to be pulled out, it is all accessed from under your front bonnet.
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First up is to remove all the under hood carpets, there are plenty of threads covering that so I won’t go into that much. Remove it all including the floor carpet so that you don’t get antifreeze on it. Your tool kit straps are riveted through the carpet so you will need to drill the rivets and replace them later. There are two oblong rubber plugs in the steel floor. I was not sure how much antifreeze I would loose so I popped them out and set a bucket under each to catch any that came out.




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Because the heater core sits on a shelf in front of the firewall there is very little needed to keep it in place. There are only 3 13mm bolts and the 4 lines that need to be unhooked. If you look straight down over the core you will see an oval rubber plug on the side closest to the right/passengers side of the car. Remove that and you will see the bolt. You will need a long extension for removal of all the bolts. The next is in through the air inlet, your recirculating flap must be open to see the next oval rubber plug, again remove it and the bolt below. The last bolt is on the edge of the heater core towards the center of the car. That one is not under a plug and is visible.






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Next unhook the two antifreeze/ heater lines and the two A/C lines.
You must prepare for unhooking the AC lines by having the system sucked out by a professional. The 348, if not converted, uses R12 as a coolant which is environmentally harmful and UNDER PRESSURE. Have the system properly drained. Luckily mine was already done in preparation for the upcoming major service planned for the car so it didn’t slow me down at all. The two lines are a 24mm and a 17mm. Using line wrenches is preferable when working on lines like AC and brakes etc.

Next unhook the two hoses for the heater. You just need to unhook the two lines the come up from underneath and not the other little hoses that hook to the helper pump etc. I wrapped rags around each hose and made sure I wouldn’t make a mess on the shelf part of the firewall. I was not sure how much was going to come out and it turned out to be only about a cup of fluid that drained out. Image Unavailable, Please Login Image Unavailable, Please Login




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So with the three bolts out and four lines unhooked your heater housing is almost free. There is foam gasket around the firewall and on the curved part that sticks through to contact the vent I was replacing. The case can be well stuck by this gasket. Gently push left and right and up and down until the unit starts to come loose. Once it does pull it back a 1/2 inch or so and reach up to edge where the gasket is a carefully peal it one way or the other. Either leave it stuck to the firewall or stuck to the case. Work all the way around and get it loose without ripping the foam gasket if you can. If you have a new one obviously you can just rip it out and clean it up later. You can get a roll of the foam gasket sold for windows and doors in exactly the same size and density at your local hardware store for $5 or you can buy a gasket from Ferrari for $500. Your choice. j/k I was able to get my gasket out in good shape and did not actually check price or availability of the gaskets from Ferrari. That was just an assumption.

If you are completely removing the unit you would want to unhook the electrical connectors and you could remove it to perform whatever work on it you need to. I just needed to pull it out far enough to change the inner vent out so that’s what I did. When I let the unit tip down about another quart of antifreeze ran out while I was working and moving it around. If you kept it level I’m sure you could avoid that.



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Once I had my inner vent swapped I did some deep cleaning of the core and surrounding area while it was easier to access. I then reversed to steps and reinstalled the unit. Next up I under the hood is to fix my recirculating flap and replace my hidden fuse with a glass fuse holder. The cleaning is nowhere close to done and I will be doing more of that before the carpet gets it’s own cleaning and reinstalled. My pedal box, master cylinders, wiper motor etc is looking pretty good now though.



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The screws hold the piece to the firewall. Once you pull out the heater core you will see the screws. They are partially under the gasket. It’s not connected to the core at all, but held to the firewall with those screws. I’ll see if I can get a picture in the morning and add it.

 

I found one picture I took from the inside when the vent was out. You can see the 6 squares in the firewall. The screws come through from the trunk side to hold the vent on. The heater core curved horseshoe parts just slide into the screwed on vent and have foam gasket between them. They are not connected by any screws/ glue etc.


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Yeah, the sticky foam gasket takes a bit a wiggling to get it to start to come loose, then I reached up and worked around the whole thing to get it all to come loose without ripping the foam up too much so I could reuse.
Here’s a picture up the upper three screws from the trunk side. The lower screws are not accessible until the core is pulled forward.



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