Leakdown Test

August 10, 2005
 I now had my leakdown tester from Eastwood, so I decided it was time to find out what shape this AMC 304 engine is really in. I got out the air compressor, set the #1 cylinder to TDC and tried to attach the hose from the leakdown tester. But every time I tried, it would get about 1/4 of a turn on and stop. I didn't want to cross-thread the block, but no matter what I did, I couldn't get it to thread on there. The spark plugs and my TDC whistle both thread on with no problem. I also tried cylinder #3 with the same result. The leakdown tester hose would not thread onto the engine block. I inspected and re-inspected the threads on the hose and they looked fine. They appeared to be the right size (14mm) and thread (1.25 pitch).

I went over to the hardware store to find a nut that would fit on the spark plug so that I could run it over the the threads of the hose fitting. So I brought my spark plug over and of course they didn't have one. The only thing I could find was a threaded insert that cost $5. I got home and tried it on the hose fitting. It threaded on with no problems. I compared the leakdown tester threads to the TDC whistle's threads. The TDC whistle threads had a bevel on the end, so I tried filing a bevel onto the end of my leakdown tester hose. That didn't help. Then I tried filing down the threads. That didn't help either. So I gave up for the day. This is what the hoses looked like at that point. The blue one came with the leakdown tester. The black one came with the TDC whistle. The black one has two thread's on it so it fits both 14mm and 18mm holes. The 14mm is black from being used:

August 11, 2005
 I've seen a bunch of online instructions for making your own leakdown tester that made it sound like finding a replacement hose would be easy. So I went to 3 auto part stores looking for a hose or even just the 14mm threaded fitting and I couldn't find one. So I decided to sacrafice my TDC whistle by cutting it in half and putting quick connect fittings on it. This actually makes thing easier because I can plug 1 hose into the engine and use it both for the TDC whistle and to do the leak down test.

August 13, 2005
 I finally got everything setup and hooked up to do my first cylinder test. But as I set the pressure to 100psi, I noticed that even with just a capped hose connected, the output side of the leak down tester manifold only read 80 psi (it should be 100):

I went ahead and hooked it up to cylinder #1 and took reading. I got 58 psi on the engine side with the input set at 100 psi. That means a 42% leakage. I know the engine is in bad shape, but it can't be that bad.

August 21, 2005
 I went to the hardware store to look for another pressure gauge to replace the one on the engine side of the leakdown tester. The only gauge they had came on a manifold with a trigger on it for filling up tires. I got it and put it on the leakdown tester. It read even LOWER pressure then the leakdown tester.

At this point I decided to go ahead and test all the cylinders with this setup. The values might not be accurate, but the relative data may be usefull (which cylnders are worse then others). All of the testing was done with the input pressure set to 100 psi. Here is what I got:

CylinderPressure% LeakageNotes
15842 %Plug had some carbon buildup
25842 %Plug was fairly clean
36337 %Leaking out exhaust
45842 %Plug was very clean
52783 %Lots of carbon, top of plug was covered with oil; seems to leak out exhaust
64852 %Clean plug
75347 %Some carbon buildup
82278 %Some carbon buildup