aka the wallet diet

S14 disappearing coolant mystery

A few months ago I replaced my tired old original engine with a “better” used motor…or so I thought. Everything went well, she purred like a kitten. Fast forward a few weeks. I noticed my coolant level would always be lower than the last time checked. A faint smell of coolant upon startup also crept in. To be honest I turned a blind eye. I should mention that the car doesnt’ get driven much…3-4 times a month, max. About a month ago I pulled the dipstick for a level check. What do I see? Streaks of milky oil. Nooooooo. I researched relentlessly. Maybe it was condensation? Yea, thats it! Did I mention the car doesn’t get driven much? Short intermittent drives=condensation. So off to change the oil I go. The oil was dirty because of Sea Foam but no signs of moisture. For the heck of it, I checked the compression. 195, 205, 195, 200. Not too shabby. I start driving the M very optimistically long and hard.

I crack open the dipstick a week later. Streaky again. Allrighty, time to get to the bottom of this. I’m still thinking it’s condensation, but need to ease my mind. Look closely at the image below…faint milky streaks.

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Here’s my plan. If it’s the head gasket, it must be associated with the coolant loss. Cylinder pressure could be sneaking into the cooling system. At best, through a busted head gasket, at worst a warped or cracked head. I’ll unplug the coil and fuel pump relay and turn over the engine. If there’s a leak, I should hear a burble in the expansion tank.

The engine is stone cold. First, I’ll crank without the fuel relay and the coolant cap on. Done. To my surprise, there’s pressure release as the cap comes off. Strike one. Crank with the cap off – burble burble. Strike two. Maybe it’s just air in the system? Finally, with fuel relay in and cap on. Again, pressure release while removing cap, then…a quick whiff in the expansion tank. Gas odor. Steeeerike three! On to the head extraction.

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