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Hi all.
I thought I had cured the water under the car after a run.I changed the cap on the rad tank and tightened up all the jubilee clips on the pipes running from it,I even loosely rigged up a bottle for the overflow tube to go into to see if the water was going down that.
However the bottle has been dry all week and there has been no water under the car at all....sorted?No!!I haven't used the heater all week until today and after my 45 mile trip today I parked at home and when I went out some 4 hours later the puddle(or at least wet area was there again)and the coolant level had gone down a little.
When I got to my destination and left 1 hour later there was no water under the car,it only seems to come out when the car is really cooling down at the end of the day,it is not seeping out during the journey.It only seems to drip for a while and then it stops.As todays puddle was a fair size I could see better where it is coming from-about 8" behind the front wheels in the middle of the underside of the car-so presumably at the back of the engine somewhere.I have no idea where it may be coming from.
Peter I know you said it can't be the heater matrix as the car would steam up,but the leak does seem to coincide with using the heater.
Any suggestions would be gratefully received.
Regards Rob
PS John I don't think is hamster P!!!

The only place I can think of at that point of the car which has coolant water in it are the two pipes running from the cylinder head across the bulkhead and through the bulkhead to the heater matrix. On the 2.5 the pipes running across the bulkhead are steel with rubber hoses connected at either end. The two pipes entering the matrix are also steel so there must be another rubber/steel joint just through the bulkhead from the matrix connections. In addition there's an air vent point at the highest point on the top tube only. On the 2.5 the tube is steel and therefore so is the vent point. Its an allen bolt in fact. Looking at the parts microfiche the 2.1 may have rubber hoses instead of steel tubes. Even if this is the case there's still a joint in both hoses half way along the bulkhead and there's also an air vent point, This time the air vent point is a knurled plastic cap. (the 2.5 has one of these on the outlet of the intercooler on the water side. I've never known it to leak but then you never know when it was removed last and whether it has been replaced properly.

The alternative to all this doesn't make for pretty reading. Options on the rear of the block are: core plugs (did the recent frost get it or have you plenty antifreeze in the engine?) and Cylinder head gasket.

Not sure how much of the tubes you can see. Its almost certainly a torch and mirror affair with asbestos gloves if you do it when its hot.

Let us know how it turns out.


noz cool.gif
I would second Noz on the heater pipes

On the 2.1 they are rubber pipes right up to the joint at the bulkhead.

The "vent" pipe has the silly slot headed toothed wheel type venting thingy. They leak! They also suffer if over tightened and will leak even more. Stupid ?~@k%^& things.

My sick 2.1 came off the raod due to one of these pipes bursting and pissing all down the back of the engine. I was convinced it was the head gasket.

Access easy as long as you back will stretch a bit



PS Looking for some cheap cheap replacement pipes. Boy racer type tubes seem the cheapest option at the moment
Thanks Noz for the post.
I will have a better look tomorrow as it was dark earlier.The thing I don't understand is why it doesn't do it all the time and only when the car is cooling down after a run.If it was the core lugs(in the cold snap it is parked on a sheltered drive and wouldn't have got cold enough to pop a plug) or head gasket,surely it would come out quicker when the engine is running,but it seems to leak for a short while when you would least expect it to-ie when it is cooling down and not under as much pressure.There is no oil in the water and vice versa-it doesn't use any oil at all.
To complicate matter further it didn't leak at all in the warmer months and appears to only do it now if I use the heater.
I can still drive the car,it has not got to the point of overheating or dropping a vast amount of water.
I'll keep you posted.
Thanks again
Regards Rob
Hi Bob,

OK one more possibility. The heater box is made standard for all models. The trim level depends how its fitted out. If you ahve aircon then there's a part of the box which is designed to take the evaporator. Since the evaporator is very cold and operates mostly in the summer, condensation forms on teh fins and falls to the bottom of the evaporator. At the bottom of the plastic casing there's a drain hole for the condensate to escape. It appears outside underneath the car just at the point you describe.

So how does the water get there? Well you might still have a pinhole leak in the heater matrix. During normal running the air flow is enough to evaporate the water or keep the steam from building up. However when the car and the airflow stops then the steam builds up and condenses inside the heater box especially in this cold weather. The condensate comes out of the heater box at the same point where it would if you had the aircon on.

OK a bit of a wild theory but I know you can get to the stage when any theory will do no matter how bizarre.

I could have explained it using particle physics but I didn't want to appear a show off !


noz cool.gif
Hi Rob

Just a couple of thoughts.
I cannot remember if your car had aircon or not. The source location for the water that you describe is very close to the aircon drain.
When do you see the puddle or patch of water? Do you have to start up and move the car to check? Or can you check it before you start up the car. I am trying to check that it is not pumping the water out on start up with a cold engine rather that leaking while cooling.


Hi all
It is definetly leaking whilst cooling.When I parked today the road underneath was dry and then when I move the car onto the drive later there was the damp patch underneath in the middle.(this is always the case).When I go to the car tomorrow the ground will be dry under the car again as it seems to only do it after a run so it could be what Noz described.It is not a permanent leak,ie it doesn't drip all the time.I will check the heater hoses where they go through the firewall tomorrow.I will also be doing a 120 miles trip in the morning and will have a look when I get back which is when it seems to do it.
I don't have aircon.Maybe I have imagined it but it seems to happen only after I use the heater(which is blowing out very hot air at the moment!)
Thanks to all-I really appreciate the help everyone gives and is indicative of this excellent site.
Regards Rob
Hi all
I drove on the motorway for 60 miles yesterday,parked for 90 minutes(no water under the car),drove for another 25 miles parked for an hour(no water under the car),drove for 10 miles parked for 45 minutes(no water),then drove 45 miles home.The heater was well used as it was -4!!Left outside the house for 5 hours before parking for the night(this is when it normally leaks)...but yes you have guessed it no water!!!!!There wasn't any on the drive either this morning.A quick coolant check confirmed that it hadn't leaked.
So I am just going to leave it!!!A quick check of the tubes mentioned revealed no obvious leaks.I think I have a fairly logical mind-if something leaks it should do it all the time?But then one of the things I have learnt with XM's is not to expect the expected and expect the unexpected!!!!
Thanks to all again.
I will keep you posted!
Regards Rob
PS.The light warning buzzer is still working biggrin.gif !!!!!!!!!!!!!!!!
"one of the things I have learnt with XM's is not to expect the expected and expect the unexpected!!!!"


With XMs you have the great game of trying and failing to identify, noises sounds, strange behaviour every time you use them.

Drop link rattles for newbies are a great thing to cut your teeth on, Oh an anything that involves leaks!!!!!!!!!!!!1
lol tongue.gif by the way this forum is a major part of my life for some reason hehe
Nothing has gone wrong with mine in the last 6 months/10k, I'm getting bored!

Hi Peter
You are a brave man to say that!!In my experience as we speak all 4 wheels have just dropped off your car and it has just been struck by lightning!!!Mind you if nothing has gone wrong you are easing yourself into BMW ownership nicely.
I had a 3 Series Estate for 30 months and did 67,000 miles in it,again to my eternal shame the only maintenance I ever did it in that time was to pump the tyres up,check the oil and water and change the spark plugs periodically!!!I didn't change the oil or any of the filters ever.It was definetly a case of if it starts,goes,stops and passes the MOT then that is good enough for me!! wacko.gif
Regards Rob
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