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.

[andrewwynn]

Sheer brilliance and I have the same power bleeder. Thanks for sharing so I don't have to invent that in my near future.

[Bmwe5320023.0]

2 questions.

1. Did you test cold or warm? If testing cold, I understand the thermostat will be closed, so only tests part of the system?

2. When you achieved the specified pressure, in your case 23 psi, how long did it hold this pressure?
How many minutes did you wait?
For example after 10 minutes, was it the same pressure, or did it drop and by how much?
This guide says it should not drop by more than 10% (2psi per minute). So does it mean 2 psi drop per minute is ok?
https://www.pelicanparts.com/techart..._Leak_Test.htm

[oldskewel]

Originally Posted by Bmwe5320023.0

2 questions.

1. Did you test cold or warm? If testing cold, I understand the thermostat will be closed, so only tests part of the system?

2. When you achieved the specified pressure, in your case 23 psi, how long did it hold this pressure?
How many minutes did you wait?
For example after 10 minutes, was it the same pressure, or did it drop and by how much?
This guide says it should not drop by more than 10% (2psi per minute). So does it mean 2 psi drop per minute is ok?
https://www.pelicanparts.com/techart..._Leak_Test.htm

Done cold or warm. Definitely not hot (cooling system not self-pressurized due to temperature).

The thermostat is not a perfect seal (it will stop a significant amount of coolant flow, but it will not seal - most thermostats have a jiggle pin to purposely allow minimal coolant flow through the thermostat), so the pressure I apply with the pressure bleeder does pressurize the whole cooling system (except that I'm not completely sure how good the sealing might be in the HVAC system - set that on hot to be sure).

In my case there was no leak other than the forcing of a very small amount of coolant into cylinders #2 and #3 (if I remember right). That was the reason for the test.

The motive pressure bleeder is pretty solid, and does not leak. Going in through that bleed screw was done carefully, with no leak there. And the whole cooling system itself regularly gets under pressure, with no leak in my case. So there was virtually no loss in pressure. I think I kept it on there for a couple of hours at least, with no noticeable pressure drop, and then checked for coolant in the cylinders. Sadly I did find some, leading to the head gasket job about 6 years ago.

From experience with other cooling system pressure testers, borrowed from auto parts stores for other cars of mine, they are not so good, and the tester itself can leak, especially at the gauge. So for those, leaking down at a faster rate like you cite may be the case, making the test not so good.

So in your case, if you're pressurizing through the bleed screw, you should be able to put soapy water around that to confirm no leak at the interface. And if you use a good pressurizing system (whatever you may be using instead of the Motive Pressure Bleeder I used; and that may be the weak spot in the system here) that holds pressure, the only leak should be from your cooling system.

[andrewwynn]

The last thermostat I took apart had a little hole about 2mm to let a water though. I suspect to balance temp and get the wax motor to get warm when starting from cold but world for sure allow pressure to equalize


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[80stech]

The pressure is in the entire system (both sides of everything) so thermostat and heater control valve have nothing to do with pressure test.

[Bmwe5320023.0]

Wow it held for two hours huh!
I purchased $50 kit off Amazon, will give it a shot to see how it compares to my self made solution.
How did you realize that your coolant was going into your cylinders?