Ok, one of the 7.3 IDI's I just bought has a supposed 180,000 on it, and the guy said it was burning 1-2 quarts in a 30-40 mile trip, he didn't say it was low on power or anything, I've heard that the valve seals can do this and I'm thinking with this much oil usage he would have broken rings , any thoughts or comments on what it might be?

 

The CDR can let these engines use oil, but I have never heard of one using that much threw the CDR. The CDR is probably one of the most neglected parts on these old girls. They should be cleaned every other oil change at least. I would lean towards the valve seals. If the rings were broken, the compression would be low, I would think, resulting in hard starts and low power.

 

If the valve seals were that bad, it would really smoke. James bond style.

Chet

 

I should have a chance to pull the valve covers this weekend and look at the valve seals, anything specific i should be looking for as far as wear goes?

 

Idk that it would smoke that much to be honest... but using that much it wouldnt want to idle down i would guess. Likely a combination of things, for instance: Bad exaust valve seals, leaking oil and pressurizing the crankcase spewing massive oil via CDR. Check the radiator as well, it could be pumping the oil into the antifreeze, but seems to me that would be kinda obvious.

Step 1: check for oil free radiator
Step 2: check for obvious leaks
step 3: remove and clean CDR
step 4: test drive and hope it stopped

 

THis engine isn't in a truck, its one of the ones I bought, supposedly has 180,000 on it from a 1992 truck, I'm replacing the engine in my dually, going from a 460 to a 7.3, and I know it was a runner so I'm hoping I could use it but the guy said it was using 1-2 quarts in about a 40 mile trip, never said it was low on power or hard to start though, and I've heard it could be valve seals so I was gonna take a look before I go pulling parts off multiple engine to build a runner for my dually

 

A compression test would tell you if the rings are shot. I can't think of a good way to test the valve seals. If there is no oil in the cooling passages, chances are it is either a front or rear seal or valve seals. If he is sure nothing was leaking out and sure it was being burned, then I say valve seals. While you have it out of the truck, it isn't a bad idea to pull the heads and replace the head gasket, valve seals and inspect the rest of the valve system. If you do run the engine before that, don't expect to see a lot of smoke because Diesels will consume the oil as fuel. You will notice a change in the exhaust smell, though.

I ran almost 50/50 filtered used motor oil in my 1983 Mercedes 300SD and it didn't smoke any more than before but I could smell a change in the exhaust. It smelled like free fuel to me, so I was all giddy about it.

 

I can't test the compression because I have no way of running the engine

 

the engine doesn't have a fly wheel on it?

 

one of them does, but i don't have a starter and i don't trust an engine stand to hold a running 7.3, last thing i wanna do is drop one of these things, I may end up trying to run it though, but i only get to work on them every few weekend because my shop is in bethel and i'm going to college in lima, i finally get to take them home this weekend, i may end up running them on a stand to check compression, i'm just afraid of one of them pulling itself off a stand

 

Well, you don't want to test compression with the engine running because you will likely blow up your gauge. Get a flywheel/flexplate on the engine, install the starter, hook up a huge battery and crank it over to test compression. You just don't want to ignite fuel with a compression tester attached.

 

wow i feel dumb for overlooking that at first lol, I could do that, I run a semi battery in my truck so i got plenty of battery, anyone ever use one of the harbor freight compression testers? are they any good at all for a short time use? and what would be considered good compression?

 

You need a Diesel compression tester with a glow plug adapter. Gasser testers don't go high enough for Diesel compression. 450PSI is good but you also want consistency across all cylinders.

 

12 Piece Diesel Engine Compression Tester

this should work right?

 

Yeah, that should do it. I see GP adapters and injector hole adapters. It is easier to use the GP adapters, FYI. At least that way you don't have to pull the injectors and replace the crush washers which are hard to find by themselves.