Check coolant level (sporadic)

[Bulk]

The other problem is that I could sit it up on jacks and run it for hours without the strengthening plate on and not leak a single drop. It's like a seal or gasket hits a critical point and then just fails. I have driven it regularly for 4 days now since my initial post and not lost any coolant

[SlickGT1]

Valley pan, usually leaks out the back.

Check that shit plastic Y coolant hose under the throttle body. Mine disintegrated and I was experiencing something similar.

You say you have a leak by the front left suspension. I suspect your expansion tank honestly. You should see white dried up residue as evidence of where the leak is coming from.

I also suggest you switch to an e30 expansion tank cap. It is 1.4 bar, instead of 2 bar our cars some with. I have a feeling the 2 bar cap is a cruel joke by BMW to force more parts on us.

[Bulk]

Awesome good tip Slick - Thanks

Originally Posted by SlickGT1

Valley pan, usually leaks out the back.

Check that shit plastic Y coolant hose under the throttle body. Mine disintegrated and I was experiencing something similar.

You say you have a leak by the front left suspension. I suspect your expansion tank honestly. You should see white dried up residue as evidence of where the leak is coming from.

I also suggest you switch to an e30 expansion tank cap. It is 1.4 bar, instead of 2 bar our cars some with. I have a feeling the 2 bar cap is a cruel joke by BMW to force more parts on us.

[David.X5]

I would also consider if your radiator cap is venting - I think it is in the location you describe and you would find no indication of a problem once it closed and resealed.

It could be working properly and the system is getting over-pressurized somehow,

OR, the cap could be bad and it is venting when it should remain sealed.

The pressure is known to rise slightly when you turn a hot car off as you stop shedding so much heat through air flow, so more engine heat goes into the coolant for a short period until it reaches some sort of steady state heat loss and then the temperature and pressure should slowly drop. You can buy/borrow a pressure tester to test the cap and measure the pressure if you want. Amazon has the Stant 12270 tester kit for $68. You would have to check if fits your car.

You can tape some small pieces of paper towel near the cap, and under the expansion tank as an indicator to help trace where the coolant was coming from. Avoid really hot areas like around the exhaust...

I ended up buying a UV dye kit and using that to trace my last leak - I couldn't find any sign of it visually. I used the recommended amount of dye, but it was way too strong - I wish I had started with a small amount of dye. Sadly, it turned the pretty BMW blue coolant green . My leak was coming out of the transmission thermostat housing clipped to the lower part of the radiator. People have had those blow out, so I was glad to have found it before a major failure.

[David.X5]

Just noticed that Amazon sells an Assenmacher Specialty Tools adapters to use the Stant tester on BMW cooling systems.

[Bulk]

Thanks David, I have ordered a new valley pan, URO collapsable pipe and intake gaskets. Hopefully that'll be the end of it. It actually hasn't leaked much since I first posted this.

[bcredliner]

Originally Posted by ants_oz

Mate, if it's leaking there will be trace evidence at the source. Shouldn't be rocket science to locate it before you start buying parts randomly.