When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Our '04 XJR has developed a knock and rattle from the right bank near cylinders 1 and 3, more likely cylinder 1. The noise is loud and sounds a lot like rod knock, but disconnecting the right bank coils one at a time makes no change in the sound. I have not yet pulled the plugs or checked compression. This video doesn't fully capture how impressive the sounds are:
Here’s the background: My wife has been driving the car the past couple of months, and Saturday night she mentioned it was making a noise at startup. I had her start the engine and heard what sounded like timing chain rattle that went away almost immediately. I checked the engine oil, which was ½ quart down from max full, so I didn’t worry too much and told myself I’d have to do some further investigation. I topped up the oil for good measure.
Sunday morning I drove the car to church to see how it was behaving. Same brief rattle at startup that went away immediately. Car ran and drove great the 22 miles to church and almost all the way home. But when I was exiting the highway, I heard what sounded like a drive belt shredding and flapping against other objects in the front right of the engine bay.
I stopped in a parking lot, shut off the engine and raised the hood, expecting to find a belt in tatters. Of course, there are so many obstructions it is difficult to see much with the exception of small areas of a couple of the pulleys. I couldn’t see anything obviously wrong with the belts, and since the temperature gauge was reading normal I decided to try to limp the car home, hoping that the remains of the belt would hold for just 5 more miles and keep the water pump and alternator turning.
I drove very gingerly, mostly in the 30-40mph range and very light on acceleration, watching the coolant temp gauge for even the slightest flicker of warming. I had to climb one steep hill (maybe an elevation change of 200 feet or so) and reached about 50 mph coasting down the other side, but I just let the engine coast rather than downshifting to engine brake as I normally do. At some point after the coast downhill the belt flapping sound ceased and was replaced by a regular knocking sound.
Oh boy, I thought. Since the remaining mile or so home was nearly flat ground, I carefully nursed the car home at around 25-30 mph.
I changed out of my church clothes and popped the hood. Again looked for signs of a shredded belt but couldn’t see any. I removed the air intake pipe between the MAFS and throttle pipe, and I removed the screw that secures the coolant reservoir and moved it around so I could inspect the belts. They looked just fine, with no signs of problems.
So I started the engine and listened. Loud knock from front of Bank 1. Listening with my stethoscope, it’s coming from the cylinder 1 area, possibly cylinder 3. When the engine is revved the sound is more of a rattle. The sound is louder when probed at the cam cover than at the PCV valve. I probed several points on the supercharger and it is not the source of the noise. I raised the front end and probed various points. The knock is clearly audible from both the lower and upper sumps, and all the way at the back of the upper sump near the bell housing. My belt tensioner pulleys are getting a little noisy, but are not the source of this noise.
The engine has done 127K trouble-free miles with regular oil and filter changes (Castrol Edge full synthetic since I bought the car at about 70K). I installed new OE plugs at around 96K. Changed the supercharger oil three months ago and the old oil didn't actually look too bad for age and didn't smell much worse than the new oil.
Aside from some adaptive cruise codes that have been present since I bought the car, the only codes flagged were P0171 (Bank 1 combustion too lean) and P0138 (Bank 1 downstream O2S circuit high voltage). No codes for misfires or timing issues as might be seen if the timing chain had slipped a tooth, and no knock sensor codes. When my wife revved the engine (more than I wanted her to) while I was recording the video, the exhaust seemed a bit smoky, but the engine was cold and ambient temps were in the low 30sF, and also I had unplugged each coil in that bank so at least one of the cylinders may have had some residual fuel wash, so the exhaust may or may not be significant.
So what are my suspects? A broken valve spring seems most likely. What about a timing chain tensioner? What else could have sounded like a disintegrating drive belt flapping and slapping around?
My plan is to inspect the plugs, use my borescope to inspect the tops of the pistons, and run compression tests. If inconclusive, I'll remove the cam cover for a look.
If it's a valve spring, can it be replaced without removing the head by supporting the valve by the typical compressed air method?
One, pop off the cam cover (I would think to pull both) but do the offending side first and visually check the valve springs & chains for slack and the tensioner/guide rail if you can peek down. These tensioners should not have issues but who knows.
If you find any slack do not restart the engine!
Second, disconnect the belt running the supercharger and run the engine and see if the noise persists. (Maybe the noise is supercharger bearing related) - hopefully.
oh , sorry to hear that !!
i think your right . it sounds like valve train. it doesn't sound hollow like a gudgeon or big end would sound .
it may be the shim/lash cap or bucket is sticking in the sleeve ,
if thats the case your cam lobe will be slapping it from a distance .
which would also sound this terrible , and could also result in the piston striking the valve as well . if that hasn't already happened .
you need to get that valve cover off for sure . it sounds like what ever it is it will stand out like a sore thumb when you expose it .
and maybe stick a bore skope in to see wether its worth engine replacement or tear down ! best of luck .
Sorry to hear that video Don. My spine twitched. And I thought I was having a bad month!
Unfortunately, I'm going to follow this post closely.
You still have to love this car unconditionally.
This is very sad news indeed. Look into the bore on cylinder 1 & 3 and see if you see collision on the piston top. If you do, removing the head is next. If you get the valve cover off and find that one of the buckets are low, it would be best to remove the head to replace the valve and possibly the seat. Again, so sad to hear this.
I'll try to document this journey since it seems that whatever the problem may be it is uncommon or rare on Jaguar V8 engines and we may all learn something. I had hoped to get the cam cover removed today but kept getting interrupted by real work.
Also, I was slowed down by the cylinder 7 coil screw seized in the brass insert in the cam cover (CC). As I turned the screw to remove it, the brass insert began rotating in the CC. I considered my options. One would be to see if penetrating oil would help the screw release, but I figured that the oil would also lubricate the brass insert and cause it to spin even more freely.
Another option would be to try to remove the CC with the coil still secured, but I was concerned that there might not be enough clearance to pull the CC far enough away from the head to get the coil boot free, and after seeing the plugs from cylinders 1, 3 and 5, I was anxious to see the plug from cylinder 7.
Or, I could have cut or grind the head off the screw and dealt with the shank after the CC was removed, but access to the screw was limited, and while I wasn't worried about damaging the coil, there would have been a high risk of damaging the CC, and I'd rather not have to find and pay for another one.
Speaking of the coil, I could have cut through the mounting arm, and I seriously considered doing so since this is an old aftermarket unit replaced by the previous owner, and I have some spare Airtex-Wells/Ford Motor Company coils (the same coils Jaguar now issues).
In the end, I decided to pull the brass insert out of the cover by prying up on the coil mounting arm with a screwdriver while spinning the screw and brass insert with an impact driver to heat up the plastic of the CC so the brass insert would release. Here are some photos:
Impact driver setup:
Left hand gently prying up with screwdriver under coil mounting arm, right hand holding impact driver to spin the coil screw and brass insert to heat up the plastic in the cam cover to help the brass insert release:
The brass insert seized to the coil screw:
Hopefully I'll be able to separate the brass insert from the screw without damaging the insert so I can reinstall it in the cam cover with some plastic bonder or epoxy.
I'm sure there will be more bad news the further I get into this disassembly, but the first bad news was the spark plugs, which are coated in partially baked-on oil. There was oil in the cylinder 5 plug well, but wells 1, 3 and 7 appeared to be dry. When I changed the plugs 30K miles ago there was no oil on the old plugs. At least there is no apparent damage to any of the plugs.
From left to right, the plugs from cylinders 7, 5, 3 and 1:
I'm surprised there were no signs the engine was running poorly and no codes for misfires or such.
I forgot to mention last night that my borescope can't take photos or video and I didn't take the time to try to photograph its screen, but examining the piston tops was interesting. They are covered in a fairly good layer of carbon, not surprising at 127K miles, I guess, but something I'll want to address.
The good news is that if a valve had been coming into contact with the top of a piston, I would think that it would have made marks in the carbon layer. None are visible on the cylinder 1 piston top, which I can see in its entirety.
Cylinder 3 is too high to see the entire top, so today, depending on what I find when I get the cam cover off, I may rotate the crank for a better view of the #3 piston.
That cylinder #5 plug was that very easy to take out Don?
Reason I am asking could there have been some "blow by" to cause that oiling up? A long shot I know.
Good question, jackra, but that was actually the tightest plug! Go figure!
I'm guessing the valve stem seals have been leaking, but perhaps also the coils on that bank may be weak. Three of them are OE and the fourth is a no-name aftermarket unit replaced by a previous owner. As part of this process I may go ahead and spring for new coils to replace the ones I haven't done already. I think I only need three more to have the Airtex-Wells/FoMoCo coils in all eight positions, because I've replaced three in Bank 2 and have a couple of spares left. As Six Rotors confirmed, these are the coils Jaguar now supplies as replacements, and they're available from Rock Auto cheap.
Okay Don, since you have shown the plugs weren't damaged, and appears that the top of piston isn't smiley'ed, which it surely would have been if contact was happening, the next item up for bids is to remove the valve cover and examine the cams, valve buckets, and timing chain and tensioners.
In my opinion, the noise sounds way too fast to be a valve bucket or cam directly, which is half of crank speed. It sounds too fast to be piston or rod. What it actually sounds like is a chain dragging against something.
Didn't have a lot of time today but managed to remove the cam cover for a first peek. Here are a couple of photos:
On first inspection, the timing chains are very tight with no discernible slack and no discernible wear on the secondary chain tensioner.
No obvious damage to any cam lobes.
I'll pull the plugs on the other bank so I can rotate the crank and examine the chains for any signs of rubbing, per David's advice, along with the lobes and of course to see if there's a bucket that does not ascend when it should. I'll also get the borescope down into the timing case to see if I can see anything unusual going on.
And if none of that is conclusive, I'll test all the connecting rods for movement.
I'll also remove the supercharger belt so I can give it a spin. abonano had suggested running the engine without the supercharger belt but I forgot to do that before I pulled the plugs. If I can't find anything else, I may reinstall the plugs and coils to perform this test (briefly) to see if the noise is still present.
It was a beautiful day in Tennessee today, but not a beautiful day in our driveway.
In preparation for manually rotating the engine so I could inspect for what I had begun to hope was a broken valve spring, I removed the coils and plugs from Bank 2. I disconnected some coolant hoses and removed the reservoir for better access.
I disconnected the supercharger belt and spent some time listening with my stethoscope as I spun the pulley. The S/C was definitely not the source of the engine noise.
Access to the bolt that secures the harmonic balancer to the crank is obstructed by a couple of rigid pipes (high pressure A/C lines probably - I didn't take the time to identify them). Working by feel alone, I found that a 24mm socket fit the bolt. I fitted a short extension and ratchet and slipped a long curtain rod tube over the ratchet handle for better leverage and control.
I wanted to establish TDC on cylinder 1 so I could tell when I had rotated the engine through its entire cycle, to be sure I inspected all the valve buckets at the point when they were in their highest positions (valves fully closed).
I inserted a long wooden dowel in the cylinder 1 spark plug hole until its end rested on the top of the piston. I then rotated the engine and watched the dowel rise. When it just began to descend from its highest point, I made a mark on the dowel to indicate TDC. I used one of the air spring studs as a reference point for my TDC mark.
Once I had cylinder 1 at TDC, I thought to myself, I may as well rule out a connecting rod/bearing problem before I begin checking the valves. Here's the result:
03-14-2017, 09:05 PM
Knock & Rattle: Connecting Rod
