Is 75% Leakdown bad???

diesel_importer

diesel_importer

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Oct 21, 2007
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Yep, finally got a leak down tester from a friend yesterday. Cylinders 2-6 are in great shape; from 5-15% leakdown. Cylinder 1 was showing about 75%. I shot some Aerokroil in it and leakdown went to around 2%.

Here's what I want to know. If I pull the head to check things out, and the head, valves, gasket, and cylinder wall look good. Can I do a ring job on that cylinder and keep on truckin?
 
side note: This is the 12v I've been troubleshooting for a while. Changed injector pumps and the miss went from cyls 2 & 3, to only cylinder 1. It never ran bad til the barrels on 2 & 3 cracked. I still don't know what caused the issue I have with #1.
 
are you going to pull the motor, or try to do it in the truck?

is the truck a 4x4?
 
I've never tried a 12v, but I know a 4x4 CR can be done in the truck. Drop the piston out, hone it, and slap it back together.
 
yes 4x4. I'm guessing I'll have to remove motor mounts to get engine high enough to take off oil pan?

Should i get a T bore gauge to check cylinder measurements?
 
Loosen the motor mount bolts, then you can raise the engine high enough
 
I would be curious how much scoring is on the cylinder, and if new rings would even fix it.
 
i ran one .020 over in the truck with the lisle micrometer hone. on the #1 cylinder and used atf with diesel as cutting oil. worked great, still trucking with 30k on the repair
 
Before you go pulling the cylinder head switch the dv's and holders around to see if the misfire moves.
 
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Yes, I'm curious on the cylinder condition as well. I will know by this weekend what the verdict is.

Rivierra- was the cylinder in bad shape, so you just honed and went with bigger piston and rings?

LReiff - I've went thru everything on the fuel system. Nothing helped.
 
Top ring let go and gouged the wall pretty bad on the #1, so like you said we went 20 over and put bigger piston and rings in, this is a stock 1999 truck tho, no power added.
Also w took the old poison and a ring set weighed those and made the new piston the same weight to keep balance relative
 
I tore the head off yesterday to inspect. Everything looks pretty good. Head and gasket look ok. The cylinder walls still have alot of crosshatch. There are some spots on the cyl wall, but I'm not sure how deep or what they are from. I guess I'm going to pull oil pan and piston this week. Hopefully I'll find a bad ring.
 
Here are a few pics. I'm really not sure where my problem is. No broken rings. I don't have a dial bore gauge to check cylinder, but after looking at these pics some more, it looks like the upper part of the cylinder may be worn. There's still alot of cross hatching, but there are some marks about 1 1/2" down in the cylinder.

Anyone see anything (I know the pics are the greatest- from an Iphone)

IMG_0349.jpg

IMG_0348.jpg

IMG_0347.jpg

IMG_0346.jpg
 
I wonder if you just had a stuck ring?

Sent from my DROID X2 using Tapatalk
 
Looks like it just needed a week with a 16 year old kid behind the wheel to burn out all the carbon and free up the rings!


By the way, what injectors were you running?
 
Believe me, this thing has had a miss for a while. I've hammered on it a time or ten. I'm gonna take head to get checked out and valve job done. I want to get a dial bore gauge and definately hone and replace rings.
 
If you just shot lube in it and it knocked out all the blow by, then logic serves it was something the lube touched.

If it was a stock to mild build, I'd run a light hone pass, clean it up, new rings, and go.
 
The only thing is I could hear lots of air coming from crankcase, and when I sprayed oil in the cylinder, leakdown was almost nonexistent.
 
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