How do I replace the heater filters?

Discussion in '308/328' started by viper_driver, Apr 3, 2011.

  1. star4747

    star4747 Formula Junior

    Dec 28, 2010
    Midwest - USA
    Full Name:
    #51 star4747, Aug 27, 2011
    Last edited by a moderator: Sep 7, 2017
    Being a "new-be" with a 1983 308 QV the filter box cleaning looked like a Friday night project. Glad I did it... lots of crud. The filter material reminds me of the washable filter that goes in the front of a window air conditioner, should be easy to find at the local hardware store (just another excuse to go for a drive). Also fixed the seal around the battery cover.
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  2. 455Fosbery

    455Fosbery Karting

    Oct 3, 2013
    #52 455Fosbery, Mar 27, 2016
    Last edited by a moderator: Sep 7, 2017
    Having read this and other threads, I thought to add something that should bring additional value:

    - A 'cheap and cheerful' solution that would be easy to do without a lot of disassembly
    - Something that would provide effective filtration without constricting air flow
    - Something easy to replace periodically if needed

    OK, the various trails blazed before likely suffice but I wanted to share on the basis of "the more information the better".

    1. Disassembly: The goal was minimal effort.
    - Remove the cover to access the heater boxes.
    - Non-AC (driver's) side: Remove the securing bolt forward of the box and ease the box rearward as much as possible. Partially remove the plastic box front cover by popping the vertical inside edge of the cover open (the vertical edge on the other side does not necessarily need to come off totally).
    - AC (passenger's) side: Remove the plastic box front cover by opening it from the bottom horizontal edge. This will allow the entire cover to be removed as you move that edge forward (i.e., the top edge will drop such that it will clear the AC line)
    - Vacuum all of the accumulated debris being extremely careful not to touch the metal fins inside the box. You may also want to switch on the blower fans for a few minutes such that any debris between them and the box inlet will be blown out.

    2. Filter fabrication:
    - I measured and then cut a cardboard template (170mm x 128mm), fitting it into the opening in front of the box to verify dimensions and proper fit. I then reduced the size of this template by a few mm's on each side.
    - The reduced template was placed on some Aluminum screen wire which was then bent/trimmed such that it became a 'pocket'.
    - A piece of relatively thin cook top vent hood filter material was cut such that it was smaller than the pattern by about 10mm per edge. This was placed inside the Aluminum screen wire 'pocket' and I put the template on top, folding the Aluminum up (to get straight edges), removed it, and then folded it completely over.
    - I used the original template to press down and flatten the outer edges ensuring that they were as flat as possible. The reasoning here is that there is not a lot of room where the edges of the plastic cover engage the box (there is a lot more room further from the edges within the closed box).

    3. Fitting:
    - The result was exactly the right size (due to reduction of the template used) and very easy to slide in and fit without totally removing the plastic box covers. The side that has the Aluminum screen folded over faces forward such that the side against the fins does not have any bits that will keep it from being inserted smoothly.
    - I tested for air flow with and without these filters installed and there was zero perceptible difference.

    The only remaining question is any potential down-side to having Aluminum screen material in direct contact with the fins... I would have preferred copper, but could not find a good source (that my be my next revision!).


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  3. ragtop1

    ragtop1 Formula 3
    Silver Subscribed

    Nov 11, 2006
    Ontario, Canada
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    Larry Warren
    Thanks for reviving this thread. I just finished cleaning mine. Lots of bits in there. It seems the previous owner removed the filters and didn't replace them with anything. Will find some filters tomorrow
  4. 455Fosbery

    455Fosbery Karting

    Oct 3, 2013
    Hi Larry,

    Hope what I put together helps...

    With respect to the previous owner removing the filters, these actually have a habit of removing themselves without too much assistance! Mine had totally disintegrated and bits of filter material had been blowing through the vents off and on for the past 20-odd years. When I opened mine for the first time a couple of days ago, there was precious little left and what I removed crumbled in my hand.

    I am currently thinking of a way to vacuum out the system without damaging the vent-hose material. I can only imagine what lurks therein...


  5. qedqeq

    qedqeq Formula Junior

    Hey, thanks guys for this thread

    Didn't even know that those filters existed, so I just went out to the garage and checked mine. Sure enough, there was no filter to speak of, totally disintegrated.

    Got some filter element cut up from a furnace filter, and voila!

    Thanks again Guys,

  6. Harry-SZ

    Harry-SZ F1 Rookie

    Yes, thanks for the pictures!
    I will do this too.
  7. JohnnyTS

    JohnnyTS Formula Junior

    Jun 3, 2012
    just outside JHB, RSA
    Full Name:
    I've removed my VAC filters of post #45 on the diagram no.12 and cleaned them with a little washing powder, they came out like new and the left a clean scent on the car after putting them back.
  8. cheesypeas

    cheesypeas Karting

    May 28, 2008
    Finally got round to looking at this myself.
    Symptom: pieces of reticulated foam shot out of the heating/cooling vents.

    1) purchased reticulated foam filter suitable for computer fans.
    2) tested a piece in the oven to 100C. Result: no damage.
    3) removed fibreglass panel at the rear of the spare wheel well.
    4) removed bolt securing heater to allow space for heater front to be unclipped.
    5) found that the previous owner had already replaced them.
    6) checked the other side. That’s ok too.
    7) computer fan foam I had purchased was too dense.

    So looks like I have good official Ferrari foam.

    Measured the thickness at 4mm so 5mm replacement is probably ok. I guess this is 10ppi reticulated foam. I have no idea why there are square cutouts in the top.

    I know you love pictures....

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  9. 27811

    27811 Karting

    Jun 24, 2019
    Full Name:
    Found this thread yesterday, getting after this work today... Can't wait to see what treasures I find!

    This looks like the exact same type of foam Philips uses on their Transesophageal Echo machines for the computer cooling fans. If so, this foam can be soaked in soapy water, rinsed, air dried and reused if not deteriorated.

    So maybe if this work is done yearly you don't need to replace it.

    ZOOOOMZ Karting

    Aug 14, 2013
    Austin, Texas, USA
    Full Name:
    Tim Cronin
    Just to offer another alternative: When I did this a few years ago, I used spun polyester filter pad media that I bought from McMaster-Carr. It was sold in sheets, and I bought a 12"x12" sheet that was 1/4" thick, of white spun polyester material. Good for high temperature and coolant exposure. Also, doesn't block air flow significantly, so that was good. Cut it to size with shop scissors, and slipped it into place by removing the heater housing cover with the air duct attached.... It's been in there for maybe 4 years now, and is working fine. BTW, this is very similar to the filter material that's on the vent inlet fans on my 1988 328 GTS...
    Also, for folks who want to improve the performance of their Air Conditioning, this year, I added a new feature to my car's heater/ventilation system. I installed airflow dams in front of the heater filter pads, on both sides. I realize that this shouldn't be necessary, because the flow of the hot coolant to the heater cores is controlled by valves in the HVAC system, but in my car, I've always been able to feel warm air blowing into the passenger compartment anyway, even when the A/C is blowing full blast in the summer. I suspected that, even with the ventilation fans off, passive air was being warmed as it passed through the heater cores on the way to the passenger compartment, or, at worst, it was passing through at ambient temperature, which here in Austin, Texas, is often over 100 degrees!
    So, I fabricated air dams two ways, as you can see in the pictures below: on the passenger's side, I used an expandable pipe plug from Home Depot, and on the driver's side, I used a stainless steel plate I cut to the same size as the filter pad, which you can see peeking out from behind the plate, in the picture below.
    Both of these air dams work great, and they DEFINITELY improved my car's A/C performance, too! I'll just slip them into position in the beginning of the A/C season, then remove them in the fall, so I can use my heaters in the winter.

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  11. 27811

    27811 Karting

    Jun 24, 2019
    Full Name:
  12. thorn

    thorn Formula 3
    Silver Subscribed

    Aug 7, 2012
    Tallahassee, FL
    Not sure why one would even bother with foam instead of another material?
  13. 27811

    27811 Karting

    Jun 24, 2019
    Full Name:
    Was there something about temperature resistance somewhere? I haven’t tested this material yet and I’m not sure how hot the little radiator gets once the coolant starts flowing through these.

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