Freeze/core/drain plug location - coolant leak

[steven65msp]

My 1990 535i has a coolant leak and I'm wondering if it might be a bad freeze plug or drain plug, but I'm not sure where they are on my engine.

Coolant leak symptoms:
Temperature gauge reads normal. No discoloration or build-up in oil. Engine runs well.

Location of leak seems to be on the passenger side (right side) about 12 or 18 inches back from the center of the front wheel.

Some days it seems not to leak at all, other days it leaks while driving, and still other days it leaks while parked. Leaked enough while parked today to run across the ground to the car in the next parking space. I check the level each day and top up the surge tank to the cold mark when needed. I cracked open the bleeder screw and fluid immediately runs out clean with no bubbles.

Leak does not seem to be from any hose, water pump, radiator, radiator cap (on surge tank), or the surge tank.

If it leaks while driving, wisps of steam occasionally rises up from the rear passenger side of the engine. Leak is down low where I can not see what is happening. When I see the steam, I also smell the coolant. When the car is in motion I assume the steam is sweep away under the car and I neither see nor smell it.

Thanks,
Steven65msp
Saint Paul, MN

1990 BMW 535i
E34 - M30 engine, 165k miles

[Kalevera]

I would first run a cooling system pressure test. If there's coolant on the ground, you'll quickly find the source of it if it's external. I would try to do this with the engine warm/coolant leaking.

One thing to remember is that there's a lot of plastic that can develop hairline cracks in the system that can expand and contract. Cracks in the head or block can act the same way.

There are freeze plugs on both left and right sides of the block, below the head, obviously. The drain plug is on the rear passenger's side, midway down the block. The plug should be a M12 19mm with a crush washer. The plug can leak if, after a coolant flush, the washer isn't reinstalled.



best, whit

[Jeff N.]

One item to check is the reservour tank. I had a hairline split between the upper and lower plastic seams. Water would dip down the tank support onto the tranny housing where it would evaporate.

Insidious to find as it basically left no trace whatsoever and would only occasionally leak.