VDP SC has ~180K miles on it. Rough idle started a few days ago. Did some troubleshooting eventually did a compression test. #5 cylinder as 0 compression... none.

No obvious signs of head gasket issue as oil and coolant look normal.

I'm going to try to get my hands on a bore scope. If that is not available, possibly try compressed air in cylinder to see if I can detect where air is leaking.

Open to thoughts on what could be causing this, would like to be able to diagnose without removing valve cover or head.

Anyone had a similar experience? Thoughts on what has likely failed?

 

Have the secondary tensioners been updated? It sounds like an exhaust cam may have skipped a couple of teeth. Another possibility is that overheating resulted in a dropped valve seat.

 

Yes, secondary tensioner has been updated. Out of curiosity if the exhaust cam had skipped a couple teeth is it possible that only one of the four cylinders on that bank would have lost compression? In my case cylinder 6-8 have between 120-140psi.

Dropped valve seat could be a possibility. I had a very brief overheating, was in stop and go traffic noticed Ac wasn't blowing cold. Looked down at gauges and temp gauges was rising (literally caught it while it was on the rise). Turned Ac off and temp returned to normal. Turned out one cooling fans was down as the harness came out of the hold down clip and got rubbed through by serpintine belt.

I would imagine that a dropped valve seat would be pretty obvious with bore scope. Attempting to locate one.

 

Just my advice to you is don't waste your time with a bore scope. Either way the head has to come off. That brief overheating along with 180K on the factory head gaskets (albeit, I got to 234K miles) is a lot to ask for on any supercharged engine. I would send the heads out to a reputable machine shop and get the MLS head gaskets along with new range rover head bolts and you'll be good to go for a long time. If you love the car like I do, then just either do it yourself or have it done by a skilled technician. Be prepared. $$$$$

 

Agree in all likelihood heads are going to need to come off. Will be back with an update in a bit. Are the RR head bolts less expensive? Is that why you recommended? I assume it is not recommended to reuse the old ones.

 

The original cylinder head bolts can be used twice. That is if they do not have centre pop marks on the boltheads, this shows they've been torqued twice.

For safety, a new set insures no sheared bolts left in the block. The Range Rover 4.4 V8S/C bolts are identical and I originally suggested using these to forum members as they were a fraction of the cost of Jaguar's, but here in the UK they are now priced in line with Jag so if you can find a set at RR pricing get them.
The later MLS 4.2 head gaskets are a great upgrade.

It does sound like a head gasket but before stripping the top of the engine maybe get a drop of oil down the bore via the sparkplug hole to see if you can get compression, they do suffer from bore wash.
Another good test is a sniff test it connects to the header tank and analyses coolant for exhaust gases. A good indy shop should have this kit. Good luck.

 

Well, I pulled the valve cover. Intake valve on upper right hand side (of picture) has not returned to the normal location indicating a possible bent valve, hung valve or broken spring. Perhaps there are other possibilities as well.

I verified this by using feeling gauges between the shim and cam shaft lobe with #5 at close to TDC. The other intake valve for cylinder #5 was at ~~.012 the stuck valve has a clearance of ~~.075 .

Plotting next steps. Before I start tearing into it more it would be good to know how much damage has been done. Specifically want to make sure that the piston hasn't been destroyed or the cylinder walls are really messed up.

 

Put the piston on Bottom dead center, use a bright flashlight to look at the top of the piston. If the piston isn't shiny on any spots, then chances it'll just need a valve and seat. I think either way it'll need a valve and seat unless the head was hammered. I'd take a chance and pull the one head for eval. If it's gonna be ok get a complete valve job done on both heads along with new valve stem oil seals. It'll run like new again.

 

My guess would be that the valve tapped the piston and your damage will be a slightly bent valve. I had one valve where you could barely tell it was even bent, but it wouldn't fully close.

 

And that would open up the question as to whether a cam
sprocket has skipped a tooth or two.

 

It is hard to see, but looks the flats on the cams are aligned.

 

OR a valve floated? Or both cams are off a tooth or two? Looking forward to seeing how this turns out...

 

Actually, i think the flats are not at all aligned and there is at least 1, maybe 2 teeth off.
Tensioners are old style, almost certainly cracked and broken. Primary probably also. Get chain tensioner kit from rock auto, S175.
Can pull oil pan off and look for bits.

Bolts, landrover bolts are 1/3 the cost of jag. Got them for $3.30 each from dealer. They have a 12mm RIBE internal drive and much more satisfactory

 

Dsetter- you know I think you are right. The intake cam looks just slightly off from the exhaust...

 

I bet a beer with you they are aligned, the perspective of the picture fools you .
Of course I hope I am right, as that will be a big plus for the OP.

PS. Tensioners are surely not first generation, probably 3rd, perhaps 2nd..

 

I'm fairly certain I didn't jump any teeth. Secondary tensioners were replaced I'm not sure if they are second or third gen. I'll take a better picture of them.

I just got my $20 borescope off amazon and now have pictures from the inside!! While lighting and focus isn't great I'm pretty sure that I had a valve seat drop. I will post the pictures this evening and maybe yall can help me confirm.

 

PS just prior to this whole ordeal I had the timing cover gasket replaced by a jag mechanic. Does the radiator fan have to be removed to do that?

 

Yes! I assume you mean the front cover, and it would be pretty difficult to remove the front cover from the engine without removing at least the fan, I would certainly remove the radiator too. Are you thinking maybe you had an overheat due to the fan not running? Sounds like one of an number of possibilities.

 

Yes, the front cover (timing chain cover). The motor did overheat (briefly), the cause was that the fan wire was not in the hold down clip and got severed by the serpentine belt.

 

Ill take that bet, happy to drink yours or mine! I agree the perspective makes it harder to determine and I keep trying to move my head to look at the picture from a better perspective.
Still, ooking at the picture again on a better screen, there still seems to be some offset between the two cams.

I do agree the tensioners are metal bodied, so are more recent, so that is a good thing, the runner color looked like the older old style.
Otherwise, all the inside metal looks clean and not many deposits inside.