Why does my e36 hate coolant so much?

Clarkey · 23 Nov 2012 at 16:32

Found a leak. Actually more of a torrent, coming out under the car directly under the heater core. Presumably the leaking core is draining down the evaporator drain pipe (lowest point in the HVAC box) and coming out underneath hence not having damp carpets. The carpet directly under the core is damp actually, I took the console out to look.
I can't feel any wetness on the piped going through the bulkhead from the engine bay side so I guess it isn't simply leaking from there.

Matt82 · 23 Nov 2012 at 18:18

bypass the heater core as a temp fix??

shoes · 23 Nov 2012 at 18:25

I also have a spare one of those which I think he's having if it turns out to be the heater core.

Clarkey · 23 Nov 2012 at 18:30

It's definitely the core yes, I unhooked the drain pipe and water was flooding out.

Berger · 24 Nov 2012 at 00:05

So how did you not notice the drive being completely soaked in sticky coolant or water?

tenwierdufos · 24 Nov 2012 at 10:16

Sounds like a right PITA, unlucky you didnt find it before other damage was done.

im going to have to check mine now as it uses about a litre a week at the moment, has AC and cant find where its going!

Any idea where the drain pipe comes out?

Clarkey · 24 Nov 2012 at 10:28

Berger said:
So how did you not notice the drive being completely soaked in sticky coolant or water?

It wasn't there before, leak has become considerably worse quite quickly though. The drain comes out on top of the gearbox so I guess when it was only a slow leak it all evaporated from the gearbox before reaching the ground.

tenwierdufos, you can see the drain pipe if you simply pull out the OBC and cubby hole. I assume you would certainly have the accompanying window misting though.

tenwierdufos · 24 Nov 2012 at 12:25

I shall have a look, i was thinking maybe if it was temporarily redirected into a container i could find out if there is any antifreeze draining out there! Its full of bright red stuff. You are probably right thinking if it went on top of the box it wouldn't be dripping down, gets rather hot back there.

No window misting at the moment mind but if its not there the only other place i haven't checked is probably into the cylinders!

Cheers for the info.

Simon · 24 Nov 2012 at 19:06

Sounds like you found the clause of the problem at least. That's a good thing !

andy_mk3 · 24 Nov 2012 at 19:13

At least you've found the cause! On a side note, I've found most BMW's are usually a nightmare to bleed, and usually vac the system and fill it from the vacuum, always works a treat

shoes · 24 Nov 2012 at 22:40

At shoes right now, we replaced the heater matrix, the car still has no heat and it overheated on the test drive. At my wits end with it, maybe it is head gasket or cracked head?
The old matrix was leaking like a sieve though.

BigToe · 25 Nov 2012 at 11:05

As crazy as it sounds, it could still be an issue with a big airlock. The E36 can be a real bitch to bleed properly. The trick I learnt from one of the BMW forums was to park the car level (it doesn't need to be pointing upwards), take the bleed screw out, unfasten the upper hose from the radiator, hold it as high up as possible and use it to pour coolant straight through the stat slowly. Any air still in the system should bubble its way up through the hose. Once water starts pouring from the radiator, connect the hose again and refit the bleed screw.

I did this after probably five separate attempts to bleed the system in a conventional manner and it finally sorted my overheating issues. That was on the M44 engine, I've since done this with my M52 and it worked flawlessly.

Clarkey · 25 Nov 2012 at 12:45

I will bear that in mind for next time. Managed to drive it home without any drama last night though, even with working heating at any rpm range. The one last thing I did before leaving was replace the radiator cap, I think that may have helped somehow.
The heater matrix is still having a good old leak though. Only explanation that I can think of is that the used one that we fitted (which was fine before) had become damaged. I've ordered a brand new one anyway, so will put that in and hope for the best.

Clarkey · 29 Nov 2012 at 18:20

Ugh, finally got this thing back in one piece. It was still leaking water out of the heater box with the replacement (used) matrix in. Despite the fact it didn't seem to be losing coolant level, I replaced it with a brand new one, then it sprung a massive leak from the hose connections.

It's working ok now though, only issue is that when idling the heat is quite a bit hotter from the passenger side than drivers. Both feed pipes into the matrix are scalding hot though so it's a bit strange to me. The only thing left is the heater valve unit, apparently they can become blocked so I'll get another one and clean it.

Two things I learned..

Changing heater matrix in an e36 is ****ing awkward.

Trying to bleed out the cooling system is a waste of your time.
My method...
Remove bleed screw and tank cap. Fill it up to the brim, keep adding more until no more bubbles come out of the bleed hole.
Bleed screw back in. Squeeze rad hoses repeatedly, you want to see a nice stream of water going into the expansion tank every time, with no air. If the level falls, add more.
Cap back on, drive the car for a good few miles, wait for it to fully cool down (I mean overnight) then repeat the procedure.
It will 'bleed' itself during normal driving, I found idling and/or revving just doesn't work.

If you have a leak then it will royally **** everything up and you will NEVER get it bled properly.