peterwells
Active Member
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- May 13, 2005
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Car in question is a 2008 5.4 3V Expedition, it had a misfire, garage said it had zero compression on cylinder 5, I figured it wasn't worth replacing the engine so decided to bring it home and take a look myself. Performed compression test (cyl/press) 1/180, 2/200, 3/120, 4/150, 5/210, 6/210, 7,185, 8/200. This vehicle has been roundly abused, including overheating at around 175k miles (today it has 200k). Next was a leak test on cylinders 3 and 4, both showed zero leak; I'm scratching my head at this. I was thinking with low compression on adjacent cylinders maybe it was a head gasket issue but the leak test ruled that out. I reperformed the compression test on cylinders 3 and 4 and saw no change on cylinder 3 but cylinder 4 improved to 175 psi.
Two things to add, firstly this is a spare vehicle that we keep around because its size makes it useful for hauling stuff, it's probably going to do less than 3k miles/year; having siad that it has new struct, tyres are good, new TPMS, new chassis mounts, etc. Secondly, I'm thinking a weak valve spring might explain the low compression with zero leak - it's quick for me to pull the valve cover and check.
What would you do? I can pull the head if need be but given the plan for the vehicle can I hobble by with it as is?
All advice appreciated,
Peter
Two things to add, firstly this is a spare vehicle that we keep around because its size makes it useful for hauling stuff, it's probably going to do less than 3k miles/year; having siad that it has new struct, tyres are good, new TPMS, new chassis mounts, etc. Secondly, I'm thinking a weak valve spring might explain the low compression with zero leak - it's quick for me to pull the valve cover and check.
What would you do? I can pull the head if need be but given the plan for the vehicle can I hobble by with it as is?
All advice appreciated,
Peter
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