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Discussion Starter #1
2010 528i with N52k and 55,000 miles.

I have a coolant leak, but all components on the engine are dry (except for the 2 spots where you see the white arrows in the picture below).

It leaks about 4 ounces every 2 months.

Today I put a pressure tester on the expansion tank and pumped it to 10 psi.

I got under the car and couldn't see anything dripping.

When you see the picture, the PentoFrost NF coolant was dripping from the power steering fitting. (note it was coolant not CHF).

Everything on the engine is dry and all the hoses are dry and I can't figure it out.

Ideas?


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The two gaskets associated with the oil filter / cooler / heat exchanger. Have they ever been replaced? I am just wondering if coolant is somehow finding its way into the engine oil.
 

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Discussion Starter #4
Here is the answer to your question.

The engine and transmission are spotless. When someone sees the engine in this car it blows their mind. The real joy is when you are working under the engine and its spotless. I've replaced a bunch of parts so there are no fluid leaks (except for this new coolant leak).

Next:

Yes, I have changed the oil cooler gasket and oil filter housing gasket 2 times.

Next:

The crazy part about this leak is when I'm under the car and I'm looking upwards I can see the two wet areas (where the white arrows are located in the picture), but nothing above it is wet. No other engine parts have Pentofrost on them. I'm looking at everything above the leak and towards the front of the car and nothing is wet.

I would have expected that pressurizing the expansion tank to 10 psi would have shown me where the leak is (but no dice).
 

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Try looking at your oil cap. If you open it and look on the inside do you see any sludge?
It could also be a very small hole in the radiator maybe from a stone hitting it.
Alternatively if nothing shows up then next time try using the universal coolant from Prestone. It has one wonderful side effect- the color is so fluorescent that it is super easy to spot a leak. Won’t kill your engine even if you are a die hard believer of only using original coolant. Can flush once you know where the leak is and have fixed it.
 

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Discussion Starter #6
You could be right that a small stone sprung a leak in the radiator. However, that would likely spray in a few areas and I would see wetness across a larger space.

Today I took the air box out. The airbox was directly above the wet spot where you see the white arrow on the power steering pump. That is the small area that was wet.

Unfortunately, the entire engine was dry. I reached my hand all over that space and my hand was dry.
 

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You might have to just resort to getting the engine good and warm to see if you can catch the leak in action. I once had recurring alternator failures in a MK1 VW GTI. I finally noticed a tiny little pinprick of a leak in the upper radiator hose that was directing a stream of antifreeze directly into the guts of the alternator (which wasn't really all that close, BTW).
 

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Discussion Starter #8
Good thinking.

When the car is hot I'll put it up on ramps and get underneath it with a trouble light.

Last year I replaced the big upper radiator octapus hose and big lower radiator hose (so its unlikely those hoses).

Next:

Sometimes I can smell coolant when I put my nose to the kidney grills.

Does that tell us the leak is likely to be the radiator (if I can smell it from the front of the vehicle)?
 

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Wife's N52 X5 went through three radiators. The factory one got a leak under warranty. Then, the replacement leaked, out of warranty, and I replaced it myself. It was very subtle. Didn't lose a lot of coolant and there was a small stain on the bottom right side. I finally caught some steam coming off it after one drive. As I recall, the car had some coolant dye still in it from the BMW warranty repair.
 

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when working on a car, dont disregard the last work done...replacing parts with new can bring up an issue with them, or the installation of.
there are reasons we insist on warranties on these new parts of ours.
 

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Discussion Starter #11
when working on a car, dont disregard the last work done...replacing parts with new can bring up an issue with them, or the installation of.
there are reasons we insist on warranties on these new parts of ours.

I would be happy to know the new upper radiator hose I just replaced is leaking or I didn't install the hose correctly. However, when I use my bare hands to feel the radiator hose from end to end, its perfectly dry.
 

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Discussion Starter #13
As mentioned you need to have a strong dye in your coolant so you can see where it comes from.
You mentioned, Try looking at your oil cap. If you open it and look on the inside do you see any sludge?

I took a peek at the oil cap and there is no sludge.

I just replaced the valve cover last year and I didn't see any sludge on the top end.

Let's say there was sludge. How is the sludge related to the coolant leak?
 

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Wingnut
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the BMW coolant leaves behind a white residue area around any leak..its very easy to see.
 

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Discussion Starter #15
I can't see any white residue on any engine part. However, I can see it on the black, plastic belly cover that covers the engine. The leak is on the drivers side directly below the power steering pump.

What is frustrating is I pressure tested the expansion tank to 10psi and there were no drips.

I'm going to have to put the car on ramps, start it up and let it run until I can see a drip.
 

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Wingnut
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the cooling system is pressure rated to handle 2 bar..
 

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The cap probably has a number on the top. It will be the millibar for that cap. If it has a "200" on it, then that cap open at 2.0 bar.

Having said that, the cooling system should not get to 2.0 bar. If it does the cap will open and blow off excess coolant. So, it should be operating at something below that level.
 

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Wingnut
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yes, but operating and testing are 2 different things
 

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Discussion Starter #20
Here's a new development in the coolant leak saga from 4 minutes ago.

I just got back from a 5 mile trip.

I smelled coolant coming out of the kidney grill so I popped the hood to look around again.

I didn't see any coolant wetness anywhere but I did take 2 pictures of the crank pulley (see below).

The crank pulley looks like it has white stains characteristic of coolant and also rust stains from water.

Does it look like the radiator sprung a leak and is shooting a stream of coolant directly into the center of the crank pulley?

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