Building a leakdown tester

From VanagonWiki

I built my own leakdown tester using commonly available parts from a harware store and parts from my compression tester.  I think that the pictures are pretty self explanitory of the parts needed and how to assemble the tool.  The part that I used were:

(2) 100 psi gauges

(1)  male

quick disconnect fitting to connect the tester to your compressor hose.

(1) reducer to conect the 

quick disconnect fitting to the brass "T"

(1) 1 1/2" brass nipple

(1) 2" brass nipple

2) 1/4" brass "T" joints

E

poxy glue

Teflon tape

Fittings from a

compression tester to connect the leakdown teste to the spark plug hole.

The hardest part of this project was building the restrictor that goes between the two guages (see the black arrow in the last picture).  To build it you will need a  0.04" (#60) or 1mm drill bit (I found one at a model/hobby/craft store) and a small piece of aluminium flashing or other suitable material that you can drill easilly and precisely with that tiny drill bit.  To build the restrictor you will need to put some epoxy in the brass nipple to create a small plug about 1/4" or 5 mm thick.  Let it dry and then drill a small hole it it.  THis plug is there to hold the small piece of aluminium flashing in place so the hole size in the plug should be large enought so that it does not block the small 0.04" hole in the piece of flashing.  Next drill the 0.04" hole in the flashing and cut a piece with the hole so that it will fit inside the brass nipple and epoxy it in place, making sure it is sealed so the only place the air can get by it is throught the 0.04" hole.  That is it!  You now have everything to assemble the Leakdown tester as pictured.

To use the testor you need to put the cylinder you will be testing at TDC compression and then block the motor from turning.  Hook up the testor to the cylinder you will be testing using the fitting and hose from a compresion testor and then connect the leakdown tester to your compressor.  Turn on the coompressor and try to get the gauge closest to the compressor to read 100psi. If you cannot get any pressure build up then you may have to turn the engine a little by hand to make sure the valves are well closed (they have to be exactly at TDC) but be very carefull as the compressed air on the cylinder may cause the motor to turn abruptly.  Once you get presure built up in the cylinder read the difference in the two guages and it will tell you how much air is leaking by you rings, valves, ansd possibly the metal sealing gasket between the cylinder and teh head.  If you have a big enough compressor to get 100 psi on the first gauge (the one closese to the compressor) then the second gauge will give you the percentage leak down if you substract tha gauge value fromm 100 ( eg. if the gauge reads 91psi you will have a 100-91= 9% leakage). If yo cannot get the first gauge to read 100psi you then have to do a little more math, but you can still get a leakdown value. The formula is : (first gauge reading- second gauge reading )/ first gauge reading x 100 .