pvfjr
1/2 ton status
One more pic for fun. I found the source of the "knock".
CK5
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5.3 Knocking--Update, found the problem
- Thread starter pvfjr
- Start date
Pretty amazing that a forged steel connecting rod will bend,before a cast aluminum piston will break,isn't it??..
I've seen a few engines that developed a bad skip that nothing could cure,the mechanics changed the plugs,wires,coils,and adjusted valves,yet one cylinder still refused to fire properly--one engine even had what appeared to be a bad head gasket replaced and it still skipped!....a compression test revealed low compression on that cylinder ,only 75 lbs instead of 150 like the others had...it wasn't until the head came off for the second time that the guy noticed one piston stopped about 1" short of TDC before it started back down again!..guess that will lower the compression ratio a lot!...the rods in both engines looked like banannas...
..Hydrolock was the suspected cause...one engine was a Nissan 4 cyl,the other a 3 cylinder briggs and stratton inline diesel in a tractor..the Nissan had a bad head gasket and it filled the cylinder with coolant ,and when it was started the next day it bent the rod...the tractor engine has a factory "defect" that allows oil to get directly into one cylinder when adding fresh oil,and will hydrolock easily if your not careful when adding oil..
I've seen a few engines that developed a bad skip that nothing could cure,the mechanics changed the plugs,wires,coils,and adjusted valves,yet one cylinder still refused to fire properly--one engine even had what appeared to be a bad head gasket replaced and it still skipped!....a compression test revealed low compression on that cylinder ,only 75 lbs instead of 150 like the others had...it wasn't until the head came off for the second time that the guy noticed one piston stopped about 1" short of TDC before it started back down again!..guess that will lower the compression ratio a lot!...the rods in both engines looked like banannas...
..Hydrolock was the suspected cause...one engine was a Nissan 4 cyl,the other a 3 cylinder briggs and stratton inline diesel in a tractor..the Nissan had a bad head gasket and it filled the cylinder with coolant ,and when it was started the next day it bent the rod...the tractor engine has a factory "defect" that allows oil to get directly into one cylinder when adding fresh oil,and will hydrolock easily if your not careful when adding oil..
y5mgisi
1 ton status
Crazy stuff.
so looks like the crank was hitting the piston, probably the piston was cocked in the bore, and the rod was running at an angle on the crank, affecting the side of the #7 rod as well?????
I would start with a diff engine if you don't want to check these parts out thoroughly before running again.
I would start with a diff engine if you don't want to check these parts out thoroughly before running again.
pvfjr
1/2 ton status
Well money is tight after buying the truck, and I don't have much to lose by trying to fix this engine. It is in the truck still anyway, and I'd have to put it back together in order to move the truck to a place where I'm allowed to swap the engine.
So, I'll just put a new (used) piston and rod from a friend at a machine shop in it. I'll replace both #7 and #8 bearings to be safe. Luckily, the crank looks just fine, and the abnormal bearing wear was quite minimal. I'll check everything out as best as I can, and plasti-gauge everything real thoroughly. It sounded pretty clearly that there was only noise coming from a single cylinder, and all the others look good and feel good. I really feel like this engine still has a lot of life left in it, so I'll see what I can get out of it. All the other parts looks so good, I just can't bring myself to trash it.
And yeah, that crankshaft counterweight was definitely scraping past the piston when it was at the bottom of the stroke. That's what the noise was coming from. If you look closely, you can see a crack in the piston right at the wrist pin too.
So, I'll just put a new (used) piston and rod from a friend at a machine shop in it. I'll replace both #7 and #8 bearings to be safe. Luckily, the crank looks just fine, and the abnormal bearing wear was quite minimal. I'll check everything out as best as I can, and plasti-gauge everything real thoroughly. It sounded pretty clearly that there was only noise coming from a single cylinder, and all the others look good and feel good. I really feel like this engine still has a lot of life left in it, so I'll see what I can get out of it. All the other parts looks so good, I just can't bring myself to trash it.
And yeah, that crankshaft counterweight was definitely scraping past the piston when it was at the bottom of the stroke. That's what the noise was coming from. If you look closely, you can see a crack in the piston right at the wrist pin too.
Yuppers
Newbie
What ended up being the problem. My 05 5.3 is making the same noise and I don’t want to admit that it’s a rod knock
Up here you can score a 4.8 or 5.3 for as little as $400 on craigslist or facebook marketplace,so many rotted out trucks of that vintage are being parted out now and scrapped by people--salvage yards still want at least double that for one though,and many have 200+ thousand miles on them..for that money,it's easier and cheaper to just buy another engine than fix the one that's knocking..
There has been quite a few old school 350's and 454's showing up for sale lately too,after none being around for several years,I guess many are swapping in LS engines into older muscle cars and trucks now that there's a glut of them available..
There has been quite a few old school 350's and 454's showing up for sale lately too,after none being around for several years,I guess many are swapping in LS engines into older muscle cars and trucks now that there's a glut of them available..
