So I am looking at this gauge for a compression tester

But I cant find a good leakdown tester, any recommendations on either?

Devin

 

bump

Devin

 

Otc are usually good tools just exspensive. The leak down test you use the compression pressure gauge. You just leave it under pressure and see how it leaks down for that.

 

Honestly, don't worry about it. If it starts without ether, it's got decent compression and not horrible leakdown. That is the worst possible case(parts are cold, engine is turning over much slower than it would be running).
If you check with a cyl pressure tester, leakdown factors into that reading - the piston has to compress air while it's leaking through the rings at whatever rate. Again, cranking speed is worst-case; with the engine running, the effect of leakdown will be a lot less.

If you're worried about your engine, throw a turbo on there. It'll take care of any power issues and make things feel a lot better. Even with worn rings, it'll still more than make up for it.

edit:
Remember that this engine has huge ring gaps, too. So a brand-new engine will have lots of blowby(which is also leakdown). This engine is just a very 'sloppy' design, which does make it less susceptible to failure.

 

i've had good luck with the harbor freight ones ..

i think they sell a diesel compression tester and generic leak down tester ..

you can just blow air into the cylinder also as mroth said .. there is usually a one way air check valve in a compression tester .. just remove this to allow it to flow and jack it straight from the air line to the cylinder ..

i haven't had to test one of these motors ..

the last few i did were sbc gas engines .. and i suppose much would carry over..

unhook the fuel fsv (gas engine unhooking ignition)

remove glow plugs and compression test each cylinder take readings for 5 second turn over ..

leave batt charger hooked up during testing .. the gauge will hold highest reading on each cylinder tested ..

record readings .. find the mean (middle reading psi and divide from there up and above % wise to get an idea how much each cylinder is compared to the others ..

last chevy customer (i don't usually do mechanic work but sometimes i do) complained his mechanic changed everything and still ran like crap .. smoked like a freight train ect.. so this was the procedure .. anyway .. yes it was a bad motor internally .. compression was off the top of my head something // like 67% 81% 110% 112% 61% 100% 71% 76%

so basically half the cylinders were worn out from the others ..

after dry compression testing add one or two teaspoons diesel oil/ clean atf into the hole one at a time .. add the oil .. crank for a second .. then put the tester back on .. re take the readings .. if the compression jumped dramatically .. then this points to ring blowby if it changes little .. this indicates loss occurs in the valve seat ..

after getting a general impression from the compression tester move onto leak down ..

you can (usually) use the compression tester as a leak down tester also .. they usually have a one way air check valve if i remember rite that requires removal to pull straight from the air chuck to the cylinder .. but a leakdown tester kit is preferable as it will also work as a mini flow meter indicating a percentage of air bypass .. ie say 10- 15 percent ..

but you can do without it .. if you want .. big thing is to get it into tdc .. i find what should be tdc on the crank .. (i think there are 2 revs per stroke so you need to double check it's the upstroke not the downstroke) i use a screwdriver to feel in the cylinder for the top of the piston .. (be careful) .. now the fun part .. you have to keep the engine from rotating as you apply 100 psi (or however much you want) of air to each cylinder ..

i get a big breaker bar with a deep socket and put it onto the crankshaft nut .. then tie the breaker bar down with twine (alot of it) like a web all over the steering appendages .. to hold the motor in place .. must do this for each cylinder ..

so .. now you got #1 locked down and a hot air line in your hand .. hook it up .. and listen for where the air is escaping .. some will always get through the rings .. just not alot .. you will figure out about the normal sound after you have gone through a couple .. open the oil fill cap and radiator .. listen .. where does the air come out ..

a little should always come out of the crankcase .. ie oil hole .. but alot on a cylinder .. indicates worn out rings or a cracked piston .. if air bubbles come out into the coolant this means you have a blown head gasket .. if air whooshes out of the exhaust this indicates a bent exhaust valve or burnt seat .. air whooshing from the intake indicates a bad intake valve ..

you can get a very clear picture of the inside of your motor through these tests if you are patient .. but i don't do it unless i think there maybe serious internal wear .. be sure to crank the motor a bit with the plugs out before putting it back together to clear out the oil from the compression test or you will lock up the motor / bend a rod ..

 

Wait so does a leak down test only need to get up to 100 psi compared to the compression test which would be like 400 psi? If so is that the reason I can't find a "Diesel Leakdown" tester, because any leakdown tester will work, diesel or gas?

Devin

 

Any leakdown tester will work as long as you have the adapters to screw it into your gp or injector hole.

 

Here is what I ordered:



I will probably read up some more on the process and write up how I did it after for anyone unsure in the future.

Devin

 

With a leak down tester, you pressurize the cylinder with shop air. 100psi in mostly because it makes it easy to calculate the loss.
The way the tester works is rather simple, the first guage shows input pressure, the second is after a small orafice and measures how much pressure the cylinder is holding. So 90 psi in the cylinder is 10% leakage.

About the only thing a leak down tester isn't going to catch is a bent rod.

 

Compression test is the best way for overall health indication. Leakdown is usually used to detirmine why you have low compression on one or more cylinders. A 6.9 should have over 400psi with not more than 10% variance between cylinders.

 

What about when the engine is running and you look for blow by out of the engine vents, I have a 7.3 that when you pull the oil filler off there is no huff or blow by like at all, the truck has 220,000 miles on it so I am assuming somebody must have put a new motor in it ? My other 7.3 that has 240,000 miles on it when you pull the oil filler when it's running there is some obvious huff but not to bad, the other engine runs better and smoother as well it seems.....


Just curious...

 

That has more to do with the CDR valve than anything. Block off the CDR(so you are seeing /all/ the blowby) and even a brand-new 7.3 will /pour/ smoke/gasses from the filler cap. It's why you can't run a RDT on one of these, without everyone around you thinking your truck is on fire.

 

btw .. what is the big deal with the cdr valve ..

i see alot of refrences to people cleaning this .. or they say u get oil consumption and smoke ..

but in 5 years driving this truck i have never ever even touched mine .. don't even really know much about it .. i think it's behind the air cleaner on the manifold .. that's all i know .. my truck doesn't consume oil or smoke at all .. am i being very bad by leaving this alone .. why does it mater to clean this .. and how often ... what is the cleaning procedure .. and will my engine explode if i never clean it ever

 

I haven't taken it off yet, I'm relying on the reputation these engine have for blow-by to account for my oil consumption, about a quart every 600 miles. Seems heavier than some suggest is reasonable but here it works out to about $6 so I'll do it next service and then it will be another little thing I know something about.

 

Ive never had an issue with mine either. Its the original with 276k and after 3k miles im sitting right on the bottom of the add mark. Ironically, seems the harder i run the engine, the less it uses. Towing to portland and back, about 1000 miles after running around, and i dont think it was even 1/2 a qt low.

Also, i bought a compression tester from harbor freight, the injector adapter doesnt work as it hits the valve cover before seating. The glow plug one i think is too long for the threads to start. I ground about 3/8" off, but circumstances prevented me from seeing if it would work. I dont see any reason why it wouldnt, its just that the adapter is as long as the glow plug, but the adapter is bigger, and i dont think it will go throught the port in the head / pre-cup so that it can seat. Either way, $30, its worth while to dump a little time into it. I do wish it had a 500psi gauge rather than 1000 though, something i could swap out if i want i reckon.