Help me find an access trapdoor

Sat Mar 24, 2018 7:09 pm

1989 320i convertible rhd. Heater matrix emptied coolant all over the inside, and having dismantled the glovebox and all the other stuff I have managed to remove it and clean out the mess inside the heater box. In the ceiling of the matrix ”˜home’ I wiped clean(ish) what feels and looks like a micro filter which was filthy black. I have looked around both foot wells and although I have lots of bits removed I still can’t see an obvious trapdoor so I consulted OEM, and there is a micro filter listed but there’s almost zero info on my problem. I have spent a little time this a.m. opening up the fan panel in the firewall with nothing apparent.
I’m keen to find it before I re-fit the matrix so I can replace the filter afterwards. Help please.

Sun Mar 25, 2018 10:06 am

The temperature blender flap inside the heater box is covered in a thin layer of black foam rubber. I think you may have found this.
Turn the temp. knob, and see if your 'filter' moves.
In the unlikely event that you do have one, I think it's accessed from the RH side of the heater box, behind a cover which should have a red or orange label on it.
Does your temp. dial have numbers around it (degrees), or just blue/red?
Re, the exploding matrix; check that your coolant pressure cap has been replaced by the post '97 version, and is not the original.

Sun Mar 25, 2018 10:15 pm

Hello, thanks for the prompt response. The ”˜ceiling’ is quite ”˜fabricky’ and shades of light-to-dirty grey. Didn’t think of waggling the levers ! Car is ”˜89, my wife bought it a year later, and I’m sure it was recalled and a different pressure cap was installed, or.......did they just send us one???? I think maybe they did, wife can’t remember. We’ve done almost 200,000 miles, and everything is original except the radiator and thermostat, new 50/50 BMW coolant(flushed first) I did 2 years ago, and timing belts, shield gaskets, one exhaust, tyres. Amazing really, still got the remains of the protective yellow colouring on mechanical parts. The temp control is red/blue, no numbers. While your there, Is there a vent pipe to empty water from the heater box which goes through the floor onto the gearbox space? If so, mine is blocked, needs a clean out. According to OEM there’s a part no. for a filter, (non a/c) which is available anywhere? Dark outside, quest resumes tomorrow. Best etc, Trevor

Wed Mar 28, 2018 8:23 pm

Hey Brianmoooore, moved forward a lot, many thanks. Feeling a bit stoopid I just turned the temp dial and all was revealed.....coolant saturated black mud on a mid-green fabricky textured flap. Thought I might look into the heater box from above took out the fan, easier to clean out the mud, wipe round etc. job done. I know that you know .... no filter. Confusing that the exploded view OEM shows my car as having a filter, although the drawing of the filter is on its own, not part of the whole heater unit. Thanks, Trevormoooore.

Wed Mar 28, 2018 8:33 pm

Just so happened that I was playing around with a spare E30 heater box, a couple of weeks ago, watching what happened inside when the various knobs and levers were moved, trying to figure out an answer to another member's heater problem.
The OEM diagrams show all sorts of parts that may not be fitted to your car. You need to key in your VIN, and look at the list of parts below the diagram. Only the parts listed should be on your car.