Pressure testing cooling system on E53

[oldskewel]

I just wanted to share my method for doing a cooling system pressure test on the E53 (specifically mine is the M54, but I bet it works on all). I rigged this up chasing down problems in my engine (probably head gasket - we'll see: https://xoutpost.com/bmw-sav-forums/...s-coolant.html ).

Usually when I do a pressure test on my water cooled cars, I rent the tester tool at my local store, rent a special adapter if needed (e.g., for my Lexus), and test it. None of the local-store-available adapters work with my X5, so I rigged up the following two options. Both work great.

Both options use my Motive Products Power Bleeder brake fluid bleeding tool as the pressure source. Unlike most cooling system pressure sources, this one has a pretty big (a few liters) volume of compressed air, so it works well for longer duration testing.

I use soft, clear vinyl tubing for all this stuff. The thinner diameter the better, since the resulting force will be proportional to the pressurized AREA, so keeping that small helps keep things together. I use 1/4" OD stuff, with bigger stuff as adapters - as shown in the photos.

Option 1 - I used an old expansion tank cap, removed the innards that provide the pressure release functionality, plugged internal holes related to that pressure release, and drilled 15/64 holes through the whole thing, routing a 1/4" tube straight through. Sealing and plugging of internal holes was done using Permatex Black, just because that was readily available. Shoe Goo would probably work great too.

Option 2 - To allow testing of the release function on the actual cap, you want to pressurize the system somewhere else. Also, Option 1 seems just a little more sketchy than this second one, due to its simplicity. So for higher pressures (I've taken it to 23 psi while standing safely to the side and pumping - another benefit to the brake bleeder pressure source), I do it through the coolant bleed screw port in the upper radiator hose.

I think the threads there are M10-1.0 - that is what I cut into the plastic adapter that screws into the brass fitting (which I think is just a straight through extender - male and female threads). I just used what I had available in my garage - and figured the brass piece in between would make it less likely to mar the threads on the radiator hose.

I think the pics do most of the explanation required.