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Old 02-03-2014, 07:36 PM
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2004 Jeep Grand Cherokee no compression cylinder #1, with knock

I have a 2004 Jeep Grand Cherokee Overland, with 4.7 HO engine. Cylinder #1 has no compression and there is knocking at the top of the engine. I believe that one of the valves my be stuck open or slighty bent. Anyone ever see anything in this nature on a 4.7?
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Old 02-04-2014, 05:17 PM
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Its dead...

Yeah Ive seen that on 4.7d...4.6...4.0s...3.8s...and plenty of 7.5s. Trash it.

Or sell it to me. Ill buy the crank and heads.
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Old 02-07-2014, 06:09 AM
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Re: 2004 Jeep Grand Cherokee no compression cylinder #1, with knock

It can be that a valve is stuck open, or that one valve will not open. A rocker arm can fall of when a valve is sticking due to carbon buildup on the valve stem. Also a failing lash adjuster or broken valve spring could cause this.
Also comon on this engine is a dropped valve seat. This happens more after overheating, but many cases are known that it just happened without overheating. In attached picture you can see the valve seat stuck between the valve. This situation mostly has secondary damage to piston and/or cylinder wall.
So i would start pulling the cylinder head cover and check for a fallen of rocker arm and check for play on the valves.
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File Type: jpg IMG_03511337656077.jpg (64.2 KB, 10 views)
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Old 03-19-2014, 01:22 PM
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Re: 2004 Jeep Grand Cherokee no compression cylinder #1, with knock

I have the same trouble with my GC WJ 2002 4.0l no compression on first cylinder and knoking noise. I remove the head, everything seem in good condition but alot of sludge??? The hole for oil circulation are completly jam. The camshaft probably heat to much without this circulation. Probably the answerd.
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Old 03-19-2014, 10:57 PM
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Re: 2004 Jeep Grand Cherokee no compression cylinder #1, with knock

Not familiar with this engine myself, but according the manual the camshaft is pressure lubricated via oil galleries, so any clogging in the head would not prevent lubrication of the camshaft. Oil is fed to the hydraulic lash adjusters and from there goes through the hollow pushrods and lubricates the valve train. The oil then drains back via the pushrod guide holes to the pan. Which hole(s) where plugged in the head?
The formation of sludge points towards a bad working PCV system and/or lack of the required oil changes. Plugging of oil canals will destroy the engine sooner or later.
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