Hey all, okay. So, family friend is ASE certified and we usually take our car problems to him, besides the Rover of course. My parents take their Lincoln Navigator for tune-up stuff, etc. Real good guy. Anyways, while I'm up here at school I had him look my truck over after a few minor overheats and make sure I had a solid foundation to fix upon, I didn't want to buy a new radiator and find out I had a cracked block. Anyways, I didn't need the truck back in any short order so I left him to fool around with it and plug up a diagnostics machine on it. After what began as a simple combustion test he came up with this, absolutely zero CO2 gas in exhaust emissions, as is shown below:


I mentioned cylinder 7 sometimes steam cleaning blah, blah, blah so he ran a relative compression test which resulted in an interesting find. Cylinder 3 is significantly lower than the rest of the cylinders.



Further investigation, significance on Cylinders 3 and 7 for comparison's sake.


This test is ran through the alternator and heavy battery usage is a result. So the battery was charged and test ran again. Results are above what they were, but compression is hardly over 100 PSI, >100 PSI=No Fire (Complete Misfire)



Overview of all Cylinders:



Cylinder 7, healthy:




Cylinder 3, not so healthy:



After frequent scans and manipulating the cylinder in any way possible and listening through a stethoscope it's obvious the amount of air escaping the cylinder was much more.

Diagnosis: Cylinder 3 Piston Ring Leak
This misfire doesn't make itself obvious very much since the cylinder warms up and expands, filling the gap. Every now and again it will be a dead miss though.

Just thought I'd share this as a neat insight into the Rover V8 and how-to completely 100% gather a firm overview of what's going on inside, down to decimals.

 

its a computerized compression tester. we use the same things with a regular compression tester and a leakdown tester. Simple diagnosis just seen as on a computer screen.

 

old school poured in a tablespoon of oil and re-did manual compression test to see if it went up (rings). Computer much more accurate.

 

that's cool.

 

Isn't it though? I was pretty impressed. A wealth of information for anything pertaining to the truck

 

I dont think it is a ring leak.

 

why's that and what do you think it is?

 

Impressive courage. Elaborate?

 

i need them to hook up that machine to me....

 

Two main metal things hold compression in a cylinder - the rings, and the valves being seated properly. And of course the head gasket (which can leak into several places - external to air, internal to another cylinder, internal to coolant, internal to oil). And the spark plug, which is the cheapest to change. If something mechanical in the valve train is holding that one cylinder open very slightly, it also would not hold compression. While in theory you could be detecting wear on the rings, the norm would be for all cylinders to wear at a similar rate, so one may fail, but some others would be lower than normal, not just one lonely guy very wimpy. Not that it can't happen, but a trip under the valve covers is a lot cheaper than pulling out pistons. Seems like the "add oil and repeat" might be useful to "see" if readings improve. IMHO some more diagnostic inspection is needed.