[Marcusoweni8]

Bought a 2015 BMW i8 wrecked. Rebuilt it & drove it. Around 50 miles later a coolant leak started. It’s for sure in the mid engine, around the oil cooler.

Here’s the problem though, due to the mid engine, to run coolant through it it’s a long process of vacuum bleeding, but I can’t vacuum bleed with a coolant leak as it just keeps sucking air in infinitely, but I can’t find the leak without running coolant through it.

It makes it harder because with so many covers around the whole engine, all it did was soak all the covers which got coolant all over the engine, and on top of that the steam built up and covered everything else.

I attempted a leak down test(not with a professional tool) and couldn’t figure anything out with that.

The picture attached is where the coolant seems to be dripping the heaviest, but that still leaves me with multiple different places it can be leaking. But it at least narrows out thermostat, water pump, mid pipes, and turbo cooler, probably head gasket too

I would assume a seal as the car sat for 6 years, possibly only seems to leak after the thermostat opens(not 100%)

So all I’m left with to find this coolant leak is where water seems to have dripped the most a couple days ago. My question is how do I find this coolant leak if I can’t run coolant through it and already visually inspected for hours

[dickchow]

I just went through similar situation as you; there is a small leak around the oil/coolant heat exchanger; it seems to be a common weak point in the b38/b48 engine where the gasket or even the actual housing broke.

You can remove the exchanger and inspect first, but to take the exchanger off was quite a difficult task as space is limited.

you will need to drain coolant from the front-middle of the car first, remove the bottom engine mount (they called that a stabilizer link), remove the sound insulations (time consuming), remove the coolant pipe from the engine (4/5 difficulty), remove the 5 screws (the top and the top right screws are super hard to reach).

I ended up bought a new metal heat exchanger from ECS.

Eventually I also found a leak in the radiator and ended up replacing that too.


hope this helps.

[Marcusoweni8]

I’m in the middle of taking it off now, the top left screw has me ready to set the car on fire

[Marcusoweni8]

After removing the top hose the top left bolt wasn’t actually too bad. So anyway, I got the housing off and I don’t see any obvious damage, it could be a hairline crack or warping maybe? Did yours have obvious damage when you took it off?

[dickchow]

mine also looked fine but just change it regardless.

You took the whole housing out and not just the metal part? those screws were pain in the ass and only somewhat work in an angle.

[stressdoc]

Wow. I used to work on my 2002tii, but you guys are taking on some serious jobs!

[dickchow]

Originally Posted by stressdoc

Wow. I used to work on my 2002tii, but you guys are taking on some serious jobs!

hoesntly it wasn't bad, BMW is somewhat fun to work on in comparison to any Audi/VW/Porsche, they are absolutely a nightmare. Either an engine out or fully front disassemble to access to a belt.

[avdept]

There's way to see where it leaks, here's how I've done it.

Bleed the system. Find a way to produce smoke, cig, those electronic cigs also works and breath into one of coolant lines. After that try to pressure a bit with air compressor. With just a bit of pressure smoke will start to sneak through the places it leaks from