Bent valve and wiped cam?

[Conundrum2006]

This question is for a friend on a XJ board. His son has a 2010 Liberty (KK) with a 3.7, it has under 100k milage, in the last 10 months he drove it all over the country. Apparently he had a bad head gasket replaced under warranty. A week later the Jeep is back in the shop this time the shop says it has 2 bent valves and 2 wiped lobes all in the same side. They replace the valves and tensioners, the cam was replaced with a “good used one.”

Does any of this make sense? He just trying to help his son figure this out before the warranty expires in a few weeks.

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[Conundrum2006]

Here is the rest of what he posted on the 2010 KK 3.7

Some of this was confused because his son was the go between on the information.
One of my first theories was the shop swapped in a bad head but supposedly they didn’t swap the head. I did mention to him the compression they shop claims is good was too low for this engine.

Anyway here’s the reset of story.

All the work was done by a very old established motor rebuilder (with a not so good reputation in the old days). They replaced the Cam with a used one. They did NOT swap heads, they just cleaned/serviced the valves only on the heads (My guess is that means they cleaned it and replaced the valve stem seals). They said nothing about resurfacing the heads or block, but in answer to my questions he said the heads themselves were fine, no cracks. My son had the jeep all over the country last year, 10 months many miles with only one part replaced, the oil pressure sender went bad, and one coil pack replaced to solve a specific cyl miss fire code, that was done about 2-3 months before the head gasket failed. It was leaking/loosing coolant very slowly about 8 weeks before the head gasket job. Lost maybe 2 gallons of 50/50 blend in weeks, about 2000 miles. He also replaced 5 spark plugs when he replaced the coil pack. Could not access the 6th spark plug.

The motor shop guy told me all 6 cylinders have 155 psig compression.


But now I am wondering how you bend a steel valve stem, in an aluminum head, with out damaging the head???? And the piston???

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[tjkj2002]

Steel valve guide inserts and you only about 50% of the valve "stem" is inside that guide at any time so plenty easy to bend a valve without damaging the insert or head.

Just to add the only way to bent a valve is from mechanical damage,something let loose and caused the bend.It's not like a head gasket,seals,or any other gasket that just fails after time.Most likely cause was to much coolant in the oil caused lack of upper end lubrication and the cam lobes wore to much causing a rocker to fall off causing the bent valves.

 

[Conundrum2006]

Thanks, I passed the information on.




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