Coolant Disappearing, where is the leak?!?

[ME30W]

I'm putting about a quart of coolant into the reservoir every other day, but I can not seem to figure out where it is going.

I put the car on a lift and could not seem to find any leaks. Paid special attention to the radiator and heater core, but everything seemed normal.

The oil and coolant are clean, and I'm not blowing any white smoke.

Anyone have an idea of where this coolant is going?

[jlevie]

The first thing to do would be to pressure test the cooling system. If there is a leak you'll find it.

The only other possibility is a head gasket leak that is pumping air into the cooling system. A some point the pressure rise will cause the cap to lift, which will dump coolant. That may only happen when the car is being driven and leave no evidence. A simple check for that is to route the overflow hose into a container.

[DaveNorCal]

How about the water pump having a worn shaft/bearing and continually losing a mist of coolant?

[ME30W]

How about the water pump having a worn shaft/bearing and continually losing a mist of coolant?

The water pump was replaced about a month ago, and this problem only became present last week.

[coldweatherblue]

check the hose going from the thermostat to the water pump. it's an e30 thing, during braking the engine moves forwards on old mounts, causing the hose to strike the cooling fan. over time it can cause a leak unless you replace the mounts or zip-tie the hose to the timing belt cover.

[dannyyisntt]

Have you seen the price of coolant these days? I'd check to see if your neighbor is stealing it at night

[CorvallisBMW]

I had the same problem once, and the leak would only appear when the car got really hot and the pressure was above the normal operating level.

Remove your fan clutch and let the car idle. Make sure to keep an eye out of the temp gauge, but let it climb to 3/4 or so and check for leaks. It won't hurt anything but will build up enough pressure in the system to make spotting the leak much easier.

[dnguyen1963]

Does your exhaust put out white smoke? If yes, you have a leak in your HG and the engine is slowly burning the coolant.

[ME30W]

Does your exhaust put out white smoke? If yes, you have a leak in your HG and the engine is slowly burning the coolant.

no white smoke, no over heating, no milky oil or oily coolant

[OrganicMechanic]

pressure test the coolant system at 19 lbs--it should hold steady, if not you are losing from some where.

[Dirtsquirt]

Check the hose that connects to the rear o the cylinder head. My car has a slow leak there (that only happens when hot). The only reason I found it was that the tranny was cleaner than normal.

[Vivek]

This may only be an m42 thing: but the screw on top of your radiator (I use it for bleeding it, but I think there's also one on the bottom that I've never touched) may be leaking. On my car it was plastic and mostly stripped, and hard to tighten properly. It would lose basically all the coolant without a trace and overheat. I replaced the radiator and it has been perfect since.

[ME30W]

it was a minor crack in the head causing the problems.

had to get a new head put on