Coolant leak - Passenger AND Driver side footwells

[German-Whips]

Hi I'm wondering whether anyone can help me and shed some light on a coolant leak issue inside the car that I have.

Just recently I've noticed coolant leaking inside the car into BOTH the passenger and driver side footwells in exactly the same place and manner on each side.

I recently replaced the heater valve matrix after a major leak into the passenger side about 6 months ago. Checked that and that was all dry, so I don't think that's the issue.

What can cause a leak into both passenger and driver side footwells simultaneously like this? Heater matrix? Pipes?

Please can anyone help!

(Also just to add, my radiator cap has 140 written on the top, and has a yellow bottom with 140 on it, is this correct as per the recall?)

Thanks!

[Brianmoooore]

Matrix is the only thing I can think of that would leak coolant into both sides.
Your cap with the yellow base is one version of the replacement type.

[German-Whips]

Brianmooore, my car is a 1989 4 door M40 318i auto, is the yellow base cap rated 140 correct for my particular car? It hasn't got AC or any fancy kit like that.


Also, would it be the heater matrix itself, or connecting pipes and O-rings and seals which are causing a leak around the matrix at the points where they connect to the matrix?

Would this type of leak result in a sudden loss of pressure in the coolant system where the pipes blow and spew boiling and steaming coolant into the footwells in a matter of seconds?
When the valve blew it projected boiling water and steam a split second after I pushed my ex out and onto the floor of the open door. (Shouldn't have warned her thinking back at it, but that's another topic ;) )


Thanks

[johnono]

it sounds like the matrix could have split? but that would be weird cosidering you just changed it

[Brianmoooore]

Yellow based cap is correct for all M40 and M20 engined E30s. There was also another version allegedly issued as a replacement which still had a black base, but all that I've seen have been yellow.
All joins, O rings, etc. are on the passenger side, so if it's leaking out of both sides it's likely that the matrix is at fault, unless the leaking water is running along the pipe and finding its way into the heater box.

[German-Whips]

I removed all the plastic trim last night to see if I could find the source of the leak.

Theres a big puddle on the carpet thats on the transmission tunnel, just under a black box where the heater matrix is presumably.

Can anyone take a look at the pictures I've taken and please tell me what looks like is at fault? What's in that black box? Is it the Heater matrix?

How much is a heater matrix, and will a good second hand one from the zone do the job?

Thanks!

[Brianmoooore]

Heater matrix is inside the 'black box' and slides in from the LH side. They rarely fail, and I'd be perfectly happy with a second hand one.
Are you absolutely sure the puddle is coolant and not rain water?

[German-Whips]

Makes sense now looking at where its located. I'm not 100% sure if it's coolant or rain water actually now that you mention it.

I noticed the dribbling down to the footwells on saturday, and when I checked the passneger side it was there too, so I assumed a coolant leak as i noticed a similar style of leaking a few days before my heater valve blew.
It has been raining here recently though, so it may be water. Heaters are blowing hot. Temperature of the car stays bang on in the middle.

Where could water be getting in from?
Is there a way to check if its coolant or water?


Also, just wondering, can I prevent further leakage from occurring and halt coolant loss by keeping the temperature gauge knob on all the way to the COLD setting?
Will this stop water from entering the matrix and essentially keep the situation stable allowing me to drive the car until a new matrix is sourced IF the matrix is at fault?

Thanks

[bdx]

Coolant or water = Taste it or sniff it.

[Motorhole]

Coolant or water = Taste it or sniff it.

Definitely wouldn't recommend the former!

[German-Whips]

Can anyone confirm that I can prevent further leakage from occurring and halt coolant loss by keeping the temperature selection knob on the heating control panel all the way to the COLD setting?

Will this stop water from entering the matrix by closing the valve and essentially keep the situation stable allowing me to drive the car until a new matrix is sourced IF the matrix is at fault?

[pacerpete]

IIRC Turning the valve to cold will not stop the leak as the valve only works on the intake side .

Best bet if you need to drive the car to collect an excellent tested matrix off me is to loop the engine bay heater pipes / fit a joiner between the two in the engine bay.

[Brianmoooore]

Little point in changing the matrix if it's rainwater that leaking out of the box. TASTE it and see. (Taste a drop on the end of your finger - not drink half a glass full.)
If it's leaking any significant amount, the level in the coolant bottle will be dropping to match.
As said above, the way to bypass a leaking matrix is to pull both rubber hoses off at the bulkhead and join them together with a short piece of suitably sized pipe. Note which way they come off.