Heater air flow leaks


Active Member
Hi All
Pulled my heater out today to try improve hot and cold air flows. Figured most of the air leaks are from foam seals on the flaps being shot, which they are, but what has caught me eye is the gaps in the duct to the face cold air vents.
If you inspect the photo looking into the top hole through the firewall you'll see what looks like factory made slots to behind the radio console. I'm thinking of blocking these to allow more air to get to the vents. Surely the radio doesn't get that hot it needs cooling:rolleyes:
Any comments please....
Cheers, Peter

(I haven't cleaned anything as yet, just pulled the heater box out and took the photos in case your wondering. No rust, just years of dust.)

20210826_190453.jpg 20210826_190503.jpg


Well-Known Member
The slots are there in order to plumb in the factory A/C system. Yes you should seal them. For the same reason there more slots taped up on the galleries that lead to the face vents. They are visible if you remove the gloveboxes and look up. Normally the tape is long gone now and you should have cooled gloveboxes.


Active Member
Brilliant.:thumb: Thanks Demetris. Always a logical reason for things in a P6. Have already pulled the glove box's out and the radio consul to get at the control linkages. That was the only way to disconnect them due to my large hands and small spaces. With all that cold air under the dash, it's no wonder the heater was struggling.


Active Member
Another question for you all.
After some to-ing and fro-ing with the garden hose I've improved the flow through the matrix after some blobby things found their way out.
However, on "heater Box Anyone" I read that good flow doesn't mean a good matrix due to an 'internal bypass' or is this just the US cars?
Can anyone shed some light on this please.


Well-Known Member
I believe the matrix are the same for all markets. You can try hooking the hose to the hit tap and running it through the matrix. Feel for cold spots in the mesh as that’ll indicate a blockage.
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Active Member
All back together again. Patched up the spaces on the cold air ducts. Heater matrix all great, tested with hot water. All flap seals rebuilt with 3mm neoprene foam and preloaded overnight to form a perfect seat. Any surface rust removed and complete anti-rust treatment. Fan motor dismantled and lubricated. Bottom main seal replaced with custom made seal. Repainted, installed and tested. We have heat and we have cold. (Just in time for summer) Thanks again for your help gentlemen.



Well-Known Member
I found that FamousFour list the bottom seal (369294) for gbp9.90......but to ship one to oz they want GBP35, so I passed on that.


Well-Known Member
While on the subject of heater airflow leaks
Ive had my P6 from new and always admired its heating output. Over its 50 odd years the output has diminished some what.
Ive been reluctant to look at the foam on the flaps as mine is an a/c integrated heater box.
You heater gurus on here may like to enlighten me as to pulling the heater out.
Is it a can'o warms?


Well-Known Member
With integrated AC i would guess you are up for an AC de-gas at the start, and a re-gas on reinstall at least.
Mine is an ordinary unit, but its output is very poor. i can hear the fan working, but feel almost no air movement, so I guess the fan blades are clogged, or there is debris in the ducts?