Wondering if anyone used this unit and had good results?

http://www.harborfreight.com/cpi/cta...emnumber=93039

I have a knocking noise and I am not sure if it's normal diesel knock or something else. I haven't been around other 24v for a long time to compare. Figured a compression test would get me pointed in the right direction.

Was looking for a boroscope, but they are spendy!

 

No one owns a compression tester?? I have one for gas engines, just not one for diesels.

I'm just wondering if it's worth my time and money to mess with the Habor Freight one or pay $200 for a 'real" one.

 

haven't really heard of that many people using a compression tested on a diesel.

 

I dont know about the tester but I broke a ring in #3cyl and it caused a ticking / knocking noise and had I ran a compression test it would have saved me a dropped valve still would have had a rebuild but may of saved a sleeved cylinder

 

for a 24v, that set will not work. You need a special adaptor to fit in the injector hole with a special hold down. Snap-On sells just that peice for $113.

Rick

 

As far as I know Cummins doesn't use a compression test for 6B's (12v &24v). They use a blow by test. If it fails the test then you have worn or broken rings, or scored cylinders. If the blow by test passes, then compression should be good at least as to the condition of ring sealing. Valve sealing, and the head gasket are the two other most likely compression leaks. Loss of coolant, white smoke in the exaust, making milky oil are all signs of a failed head gasket. I haven't heard of many guys having valve issues, but I haven't looked in DTR for that either.

As for the blow by tester. Cummins must have either got the tester design from a clever field tech, or an inhouse DIY plummer. All it is, is two short pieces of 1/2" PVC glued into a tee with a bushing(reducer) in the 90º hole, and brass hose barb threaded into the bushing to accept a hose from a PSI gauge. The trick thing is there is washer glued inside the pipe that is after the gauge port to create a restriction. The restriction makes backpressure which is readable useing a gauge.

To use it take the hose off the crank case breather and attach it with a short piece of hose with the washer restiction away from the engine. Hook up a psi gauge with a hose long enough to locate the gauge in the cab of the truck to take readings while driving(under load).

Clever and simple. I don't have the specs, by all you would need to do is use a known good engine as a base line. Take psi readings from that engine at various rpm's under load including high. Then test the suspect engine in the exact same way and compare. How much of a differance is tolerated I'm not sure. I can get the specs from work for the Cummins tester.

Doing that test is far easier than pulling injectors for a comp test, and it makes sense. I can get pics of the tester and specs if any one would like.

 

Post up some pics Tbone

 

here is snap-ons....

http://buy1.snapon.com/catalog/item....re&dir=catalog

 

I'm pretty sure it will work.

http://www.harborfreight.com/cpi/cta...emnumber=93039

Designed to measure cylinder compression on most Cummins diesel engines. Includes adapters for Cummins 5.9 liter with 24 mm ports, V-185, 210, 225, 555, VT-255, VT-555, V-6/V-8/V-12, 903 V-8, 2.9 liter, 3.9 liter and 5.9 liter.

Are the 24v injectors 24mm??


Yes I know about a blowby test, but that is worthless to compare the cylinders to each other. You mike have ok blowby, but ~300psi in all cylinders but one with only 225psi. I am pulling the injectors out anyhow.

 

Because it's a pain in the *** to do it compared to doing in on a gasser.

 

When we tore down a Deutz diesel, we did compression checks on it. Easier on those than an ISB since the injectors are outside of the valve cover, but nonetheless.

 

If you are already pulling the injectors, why not do a comp test?

Comp tests are only an idicator of compression psi. If one is low as stated in your example, it doesn't tell you if its a valve, head gasket, or a worn cylinder.

In the marine industry (in which I work) the blowby test is a basic tell all on cylinder health, gas or diesel. If you have excessive blowby, the engine is getting worn out. If your 5.9 Cummins passes the blowby test, I would do a leak down test before a comp test if you suspect issues with the engine. It will identify the bad cyl. and will help pin point the comp leaks. That way your not shooting in the dark as to what is wrong and will tell you where you are headed for repairs. You may only need to do a vavle lash adjustment to fix the leaks. If a cylinder fails the comp test, you are going to have to pull the head one way our another. So the comp test is no better than the blowby test in that respect, next step is to pull the head. One exception the blowby test already told you that one or more of the cylinders is worn and leaking. A comp test just identifies the bad cylinder not what causes it.

Imagine telling a customer that they have bad compression on 2 cyl's and you tell them that they need a rebuild. After pulling the head and finding ok looking cyl walls and loose (not stuck) rings, what should you do then? Many shops go ahead with the rebuild and send the head with for rebuild as well. Not good trouble shooting when only a valve lash adjustment was needed, or at least checked. A blowby test would have let you know the general health of the cylinders. Valve lash adjustments are common maintenace for a 6B in the marine business. Of course marine engines are run much harder than in automotive applications.

So to sum it up, a blowby test is quicker, easier, and really more accuate than a comp test for cyl health. Both have limitations as a diagnostic tool. The blowby test is testing only one thing, ring sealing, not three varibles.

I will take pics Monday of the blowby tester, and send them on as well as specs that I can find in our manuals.

 

Uh.... .....

I said I wanted to do a compression test since I had the injectors out. I don't understand why you say "If you are already pulling the injectors, why not do a comp test?"


Are for the rest of the info...

Do a compression test and if a cylinder is weak, then sure a leakdown test will help figure what is wrong, but either way the head is going to have to come off.
Before you do a compression test on a solid lifter engine, it's SOP (standard operating procedure) to adjust the valves first.

A blowby test is great if you don't want to do a compression test. BUT, like I said before, it groups all 6 cylinders at once, so you can't tell if you might have a week cylinder.
It's entirely possible 5 cylinders have no blowby, but that 6th one does and that's what shows on the blowby test. Only it's under the limit so you write it off that it's good to go.

Post up the info on that blowby test. Would be useful I'm sure.

 

Wouldn't something like a vacuum leak cause a false fail on the blow by test, since the vacuum pump dumps the air into the crank case?