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So in the past two weeks it has been freezing cold in Los Angeles, California and I've been busting the heater up quite a bit. I've been filling at least the size of an Arrowhead eco-shaped half liter water bottle every two days or so and the car does not over heat or show any signs of overflowing from the tank, I couldn't check whether it's leaking or not due to the heavy rain. Could the heater result in coolant loss or does it have to do with the heater core?
 

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You have a leak somewhere. The cooling system is a closed system, i can understand a bit of coolant loss over a 1 year period but adding water on a regular day basis is not right. I would definately get underneath and check for any signs of leak, if you cannot see any visable leaks, it is possible the leak is internal which is never a good sign. I would also cehck the underplenum oil cooler for leaks.
 
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Hmm I will take that in consideration and the car is a 540i no ///M5. I'm supposed to be getting Bilstein sport shocks and Eibach lowering springs fitted within this month the guy that is going to do the job is a BMW mechanic he himself has a few toys (e30 ///M3, e34 ///M5, Lotus Espirit, and so on) and I'm sure he will find whatever it is but I'm worried of something happening before it gets to him so I'll just refill her and get along with it until I take it there.
 

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Have then do the routine hose checks and sniff for antifreeze. Also have them pressurized the expansion tanks to force pressure into the system to see where the leak might be coming from. The only other place if not from the expansion tank is the water pump. It might be giving out and leaking very slowly.

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You should never have to top up the coolant really.

I suspect a leak at the heater matrix perhaps, within the dashboard....or water pump/t-stat locations.

Are you getting any vibrations, rough running ?
 

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Finding coolant leaks can sometimes be quite tricky. But with a loss at this rate hopefully that'll make it easier. It's possible that your leak is in the engine bay somewhere but only happens under pressure and also drips onto a very hot part of the engine, resulting in it being boiled off and not spotting anywhere noticable. I had this problem on my old E36. The coolant hose that failed sat over a very hot part of the block and as a consequence there was virtually no trace of a leak until it got a lot worse and it eventually leaked when not under any pressure.

A start is to make sure the dampening under the bonnet (hood) is clean. That way you should be able to see if steam is getting up to it and causing some staining or crusting on the material. This might at least give you an indication as to location. This was a clue that helped me at least locate the vicinity of the leak. Check that material for any signs of a leak, it could be something as simple as a poor cap, is there staining near that area on under the hood?
 

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Alright, first off, I would visually look for any leaks, if its a slow leak, you wont be wet when you find it, but you will see this weird green-ish white residue on the engine block. If that is the case pressurizing the cooling system and checking for any sort of leak is about all you can do. If you have recently noticed a streak of condensation that builds up on the inside of the windshield that would be an indicator of a leaking heater core/lines inside.

Check the easiest stuff first, check all visable coolant lines for leaks where the clamps would be, check the top of the rad for any leaks, engine drain plugs, heater lines, (oil cooler, I dont think the 540 has one but i know the m5 does). Last thing would be an internal leak, i dont recall the M62 having common headgasket issues BUT i have personally assisted in 1 headgasket rebuild on a X5 4.4
 
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Discussion Starter #8
the engine runs solid as usual I'm thinking it's the pump or something with the heater cause there are no leaks in the engine bay
 

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Thank you guys for the help I'm just busy to take the car to the shop and plus we don't have another spare car to drive while she's in the shop my mom is driving an e36 M3 and I'm driving this until her X5 is back from the body shop so let's hope for the best.
 

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Finding coolant leaks can sometimes be quite tricky. But with a loss at this rate hopefully that'll make it easier. It's possible that your leak is in the engine bay somewhere but only happens under pressure and also drips onto a very hot part of the engine, resulting in it being boiled off and not spotting anywhere noticable. I had this problem on my old E36. The coolant hose that failed sat over a very hot part of the block and as a consequence there was virtually no trace of a leak until it got a lot worse and it eventually leaked when not under any pressure.

A start is to make sure the dampening under the bonnet (hood) is clean. That way you should be able to see if steam is getting up to it and causing some staining or crusting on the material. This might at least give you an indication as to location. This was a clue that helped me at least locate the vicinity of the leak. Check that material for any signs of a leak, it could be something as simple as a poor cap, is there staining near that area on under the hood?
Good advice that regarding the underbonnet insulation, like it. A loss of seal on the cap is one of the last things someone might look for, but good to check, and, of course, an easy fix. :)

I might check it by wrapping some kitchen towels round it (paper towels) and tie wrap them on securely. Then after a decent drive, check them for moisture.
 
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