LEAKDOWN TEST

[normde2001]

Has anyone ever tried a "leakdown test" on diesel engines the way they do on small gas engines? It should work if you can inject air into the combustion chamber.

 

[RoyJackson]

A buddy of mine does it on Mercedes Benz diesels. Biggest difference is the fittings you use and you've got to pulll the injectors (that's where the cylinder is pressurized).

 

[polecat]

extrulate on this one guys???why and how???know my engines firly well but are u tryin to figure out if u have bad rings????or leaking valves??/..we used to always take comrression tester..test dry and then add a little oil in one cylinder at a tme and then do another compression test and figure out the differences...u r looking for an average ...or a particularly bad cyl...???/ /forums/images/graemlins/grin.gif

 

[normde2001]

Assuming the compression test is low, you crank the engine to TDC, valves closed, and pump 30-40# of air into cylinder via sparkplug hole or fuel injector. listen through air intake for intake valve leakage, exhaust for exhaust valve leak, crankcase vent for ring blowby leakage, (some expected at end gaps), check for bubbles in radiator or spray soap and watch for bubbles around head gasket. Never tried it but I would used a piece of tubing as a stethoscope. You can buy fittings for sparkplug holes, and I guess, get creative for diesels.

 

[polecat]

learn something everyday /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[SnowRidge]

</font><font color="blue" class="small">( extrulate on this one guys???why and how???know my engines firly well but are u tryin to figure out if u have bad rings????or leaking valves??/..we used to always take comrression tester..test dry and then add a little oil in one cylinder at a tme and then do another compression test and figure out the differences...u r looking for an average ...or a particularly bad cyl...???/ )</font>

Some of the small engines have automatic compression releases to aid in starting. This renders compression testers useless for qualitative purposes. A leakdown test is used instead.

SnowRidge

 

[Inspector507]

SnowRidge,
Look at the attached........looks close

 

[SnowRidge]

</font><font color="blue" class="small">( Look at the attached........looks close )</font>

Hmmm, Bubba's lookin' kinda glassy eyed. Too much catnip?

SnowRidge

 

[Inspector507]

He does well with catnip, but the female cat of the house, Bitsy, gets mean. We don't allow catnip anywhere her /forums/images/graemlins/grin.gif
Little Miss Priss who won't drink normally (see attached)

 

[SnowRidge]

</font><font color="blue" class="small">( Little Miss Priss who won't drink normally )</font>

Quite a coincidence, our female feline drinks the same way sometimes.

SnowRidge

 

[larso1]

Norm, I did a leak down test on my Iseki 2-cyl. diesel. I used a leak down test kit which was composed of gages, tubing and fittings. I borrowed it from a friend who owns a automotive and small diesel repair shop. As I remember, the gages gave inlet pressure from the compressor and the other gave leak down in %. Instead of finding a fitting for the big threaded injector hole, I had a smaller fitting made up that connects to the threaded glow plug hole. My front cylinder was reading at 22% and the rear was at 38% (kind of high leakage past the rings). After I did the test he told me I should have done the test with the piston at BDC, middle of the cylinder, and TDC. I let the air push the piston down and took my readings only at BDC. I have since replaced the rings and rod bearings with the block in place on the tractor. Worked very well and didn't have to deal with the high pressures of a compression test (450psi+), which he said was not nearly as conclusive.

Bill in CO

 

[normde2001]

"After I did the test he told me I should have done the test with the piston at BDC, middle of the cylinder,"

I would guess any time both valves are closed would be a good time.

 

[larso1]

Valves were not an issue. I had backed off the lifter adjusters so there was no way they would open. The issue was the cylinder bores do not wear the same at the top as they do the bottom. I'm sure you know that.

Bill in CO

 

[normde2001]

"The issue was the cylinder bores do not wear the same at the top as they do the bottom."

Good point. Gotta admit, I had not thought of it.