odd compression test results
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Cross-Country
Joined: May 2011
Posts: 63
Likes: 3
From: Boston, city of champions
odd compression test results
Just pulled my engine due to a front timing cover leak under the hpop and head gaskets, coolant blowing out the Degas bottle on occasion and soot in the coolant. So I decided to do a compression test while the cab was in the air before I pulled the engine. Engine is 2.5 year old Ford reman with about 30k on it. Using a brand new Mityvac Digital guage and lang adapter. being that my big Ashcroft and nice OTC adapter grew legs.
Cylinder 1 367 (trans was in gear, cab hit the stub when I was lifting it realized it on cylinder 3)
Cylinder 1 383 wet
Cylinder 3 434
Cylinder 5 426
Cylinder 7 443
Cylinder 2 425
Cylinder 4 426
Cylinder 6 425
Cylinder 8 319
Cylinder 8 538 wet (maybe too much oil)
Back to Cylinder 1 455 wet
Back to Cylinder 8 437 (Dryish after after several rotations retesting cylinder 1)
Back to Cylinder 1 438 (Dryish after after several rotations retesting cylinder 8)
Any of you guys have any thoughts on these results?
Cylinder 1 367 (trans was in gear, cab hit the stub when I was lifting it realized it on cylinder 3)
Cylinder 1 383 wet
Cylinder 3 434
Cylinder 5 426
Cylinder 7 443
Cylinder 2 425
Cylinder 4 426
Cylinder 6 425
Cylinder 8 319
Cylinder 8 538 wet (maybe too much oil)
Back to Cylinder 1 455 wet
Back to Cylinder 8 437 (Dryish after after several rotations retesting cylinder 1)
Back to Cylinder 1 438 (Dryish after after several rotations retesting cylinder 8)
Any of you guys have any thoughts on these results?
Cargo Master
Joined: Nov 2010
Posts: 3,244
Likes: 40
Do you have an o-ring on the lang adapter? It doesn't include one.
I suspect cylinder 1 and 8 you also didn't have the compression tester in all the way. Are all the glow plugs out? Are you cranking by hand or with a bar?
I suspect cylinder 1 and 8 you also didn't have the compression tester in all the way. Are all the glow plugs out? Are you cranking by hand or with a bar?
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Cross-Country
Joined: May 2011
Posts: 63
Likes: 3
From: Boston, city of champions
Yes mine did include an o-ring and I even got extras just in case (Last time I did a compression test on a 7.3 I had my OTC adapter and the o-ring only lasted a few cylinders). I spun the motor using the starter while the motor was still in the chassis with all the glow plugs out. And it was threaded all the way in til the o-ring was tight against the cylinder head.
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Cross-Country
Joined: May 2011
Posts: 63
Likes: 3
From: Boston, city of champions
I think I figured out the odd results, the truck was sitting for about 4 months so it took a bunch of rotations to get oil back around the all the rings set in the cylinders is what my best guess is.
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