Black Coolant
 

I replaced my water pump this weekend due to it seizing up and breaking off all the belts. When I drained out the coolant from the radiator, it was black. That bothered me so I drained the whole system from the engine block and yet again the coolant was still black. I know it is supposed to be blue if you use BMW coolant, which I do, but I had just changed the coolant this summer.

Could the black coolant possibly be from the water pump going out?
Just sorta worried about going on an upcoming 700 mile adventure.

did a google search and found a few links:

http://www.mustangforums.com/m_4119600/tm.htm
(this one is talking about diesel engines so don't know that it applies):
www.penray.com/images/99.014.pdf

http://www.mini2.com/forum/faults-fi...ant-color.html

I found this, but it is from 2002.

I'm going to stop by Baron BMW tomorrow and ask around. Could it be from old coolant lines?

Black like it was dirty black, or black like it had oil in it. If you let the coolant sit for awhile could you see oil pockets form in the coolant?

Usually black coolant means you have oil getting into the coolant, but you can tell it is oily.

^^Exactly. Let the "fluid" sit and see if it separates into black and green.

If it does and you can identify the black as oil and green as freeze, you have a problem.

Oil in coolant = game over.

Check your oil and see if it has a milky color.

To mohaughn and campaiar; there were was no oil pockets or separation of the coolant. It looked more as if it was just dirty.

To jimmyloose; the oil is still mobil 1 caramel brown.

When I stopped by BMW today I had the parts guy go and ask a technician or two about it. He asked the head tech and got the oil answer from him AND that it could be from old falling apart pipes. He also asked the mini head tech about the coolant dye decomposing and he had never heard of that. After I purchased a few things I asked my friend who works there as a service manager and he said it was probably a bad batch of coolant. He also said that if I had a bad head gasket, then oil could get in that way, but I replaced that three years ago (I'm sure its fine).

So I a couple answers. I'm going to change the coolant next week and see if the colour has changed at all. Plus I'll thoroughly inspect it for oil or anything of that matter.

Input is still welcome.

EDIT: I totally forgot to bring up something. Does the water pump happen to have any grease or anything in it. Because if it does, then that would explain why the coolant was black?!

A little update on the black coolant. I'm in the process of replacing almost all of the cooling system, so once again I had to drain the coolant. There was absolutely no sign of oil or any separation between the coolant and other aqueous solutions. I'm either guessing the black colour was from bad dye or from the water pump having grease in and around the bearings, and when it went out the grease got into the coolant. <- Just a complete guess, but it seems that oil is not the culprit in the black coolant mystery.

The waterpump bearing is a sealed unit. If its lube was leaking, the pump would fail immediately.

That is pretty much what happened, while cruising on the highway. Water pump quit spinning and burnt/broke off the belts

The PenRay coolant article mentioned fluid turning black from high concentrations of metal... maybe the water pump/bearings was wearing out and breaking down with metal particles contaminating the coolant. + how old was the coolant?
Usually when a head gasket fails you get the cloud of white steam (coolant) out the exhaust. Not sure about only oil leaking into the coolant without the higher coolant pressure pushing out the other direction into the engine (just guessing, no SME on that theory)

If you have around 100K miles, you should probably change the coolant hoses and the two coolant manifold blocks.

I'm almost positive that the water pump was to blame for the colour of the coolant. The coolant was barely 6 months old. I have almost 200k and I've almost replaced the whole cooling system. :)

Your theory about the water pump grease getting into the coolant sounds probable.

How long have you owned the car? It sounds like prior owner put some of that miracle-in-a-bottle radiator stop leak in the rad. Some brands are known for turning the coolant black and also not good stuff for the water pump to be chewing on.