Leak Down Test, Coolant Pressure Test

So, after my last post a month ago, with Torque and my OBD adapter, I've been monitoring the coolant temperature. I have not seen any coolant leak out of this car. What I have seen is a steady increase in temps as the car was driven after the initial fix. I knew something was up.

I bought a power bleeder to make life easier on me. Given this is the 4th time in a few months I've had to drain the coolant. What I found when I put vacuum on the coolant system was that it would slowly creep back down to 0 over the course of a few minutes. Something was wrong here. The tester is brand new and I don't have any other cars to test it on at this point.

My buddy Jeremy recommended that I get a leak down tester just to verify there are internal issues before I go digging the engine apart. This was a really good idea because it allows you to pressurize each cylinder and hear any leaks that may be present. It took a few efforts to figure out exactly what to listen for.


This Performance Tool leak down tester was about $70. It is self regulated at 15 psi regardless of the incoming pressure from the compressor. That is shown on the first gauge. The second gauge tells you how much of that is leaking from the cylinder. Whether by going around the rings, valves, or head gasket. These issues are manifested by hissing or gurgling from the exhaust, intake, coolant system, or dip stick orifice (he-he).

With my buddy Brandon's help, we began by spinning the engine and listening closely. You can tell when the valves are open or closed based on the noises made. When the piston is at top dead center and the valves are closed the gauge repeats at 20% loss. So that means that 20% (3 psi) of the 15 psi is escaping somewhere. Well with in tolerable limits. No cylinder seals 100%, there is always a little loss.

The intake valves were ope slightly with this picture. After we actually got her to TDC on this cylinder properly, we were at 20%. A-ok in my books. 
Air fitting, three brass fittings, an NPT pipe fitting, and a o-ring.


So that all looks proper. What's next? To factor out the coolant bleeder no telling the truth, I made a custom fitting to put in to the coolant bleeder screw hole. This allowed me to pressurize the coolant system with the overflow cap on. A full test of the entire system.

Reduce the pressure on the outlet using the regulator knob.
I used the regulator built in to the compressor to turn the pressure down to 20 psi. This is about what the normal 140 BMW cap will run on the coolant system. Unlike the vacuum created by the power bleeder, pressure is easy to hear escaping than vacuum, at least in my mind. After pressurizing things it held steady at 20 psi. I opened the heater diverter using the air con controls, fan low settings, heat max (90). There was no audible hissing that I could hear coming from anywhere.

My custom made fitting. I used a dozen brake line fittings but, it works like a champ. Just have to be careful with the plastic threads in the overflow tank. Don't want to strip those. 
That is super exciting because that means that not only is the head gasket in working order, so is the coolant system. After more than a month of down time. now all Helena needs is to be filled up with coolant and driven again, hopefully! 

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