Hello everyone, I'm new to the forums (and jaguars in general). I recently came across a non-run/drive 2016 Jaguar XF with the 3.0 supercharged V6 with a little less than 60k miles. I decided to take a chance on it (sight unseen) since I got it at a pretty good deal, but it looks like its going to be a little more work than I thought.

First off here are the codes:
P0328 - Knock/Combustion Vibration Sensor 'A' Circuit High
P0333 - Knock/Combustion Vibration Sensor 'B' Circuit High
P0300 - Random/Multiple Cylinder Misfire Detected
P0303 - Cylinder 3 Misfire
P0305 - Cylinder 5 Misfire
P1315 - Persistent Misfire

Here's what happened:

The battery was dead and the coolant was only at around 15% of the reservoir when the tow dropped off the car, so I replaced the battery and topped off the coolant. While filling the coolant reservoir, it would not fill beyond roughly 20% before excess coolant started leaking out underneath the car.

Afterwards, I tried starting the engine and got a crank/no-start condition. While cranking, it sounded like the car had a dead skip to it, seemed to me like a low compression issue.

With the low compression sound and the low coolant I started to get worried if the engine overheated so I went to do a compression test.

I took out the coils and plugs, the passenger side bank was drenched in oil, but the driver side was dry (likely just a valve cover issue).

The sparkplugs looked to have normal wear except for cylinders 3 and 5 (same cylinders throwing misfire codes). The ends of the plugs were completely black and covered in carbon/sludge.

I then performed a compression test. I used a pretty cheap tester, so take the raw numbers with a grain of salt (mainly looking for variance between the any cylinders), but every cylinder measured around 75 psi except cylinders 3 and 5, which showed 0 psi. Not low compression, just zero. Also when just listening to it crank, I could hear a free-spinning/whirring sound rather than normal compression pulses.

From what my research tells me, the cylinder layout on this engine is:

Passenger side (front to rear): 1-2-3
Driver side (front to rear): 4-5-6

That means the two cylinders with zero compression are:

Cylinder 3 (rear passenger side)
Cylinder 5 (middle driver side)

What's interesting to me is that they are on different banks, which seems like an important observation.

The fact that both cylinders have:
Misfire codes
Black/carbon-fouled plugs
Completely zero compression
Are located on opposite banks

makes me think there may be a common failure point here rather than two unrelated issues occurring at the same time, which is hard to imagine since they are on different banks.

Has anyone seen this combination before on the 3.0 SC V6? What do you guys think could cause true zero compression on cylinders 3 and 5 simultaneously, especially when they're on opposite banks. Could this point toward a timing-related issue, valve damage, or something else specific to these engines? I am not sure if the coolant issue might be linked with this.

Any thoughts would be appreciated. I am a hobbyist mechanic who has mostly done easy to moderate maintenance jobs. I have no experience working on engine internals, so this will be a good learning experience trying to diagnose the issue, even if the engine ends up as junk (hope not).

 

Sounds like it may have been badly overheated. At this point with that little compression, I would suggest just pulling the heads and inspecting, but that's a major job.

Do you have a borescope? Would be worth taking a look inside those cylinders, seeing if you have melted pistons or damaged valves.

Where was the coolant pouring back out of?