Hi All, I have a cams out of time issue that has at least bent the exhaust valves, I have removed the timing chain cover and found no apparent problem other than the valvetrain out of time. The guides, tensioners, chain and sprockets appear undamaged. Cams and followers look like new. I checked the crankshaft sprocket for a sheared key and discovered it was two independent sprockets. Both were in perfect condition and properly keyed to the crank. Both banks appear to be out of time by the same amount. I find this confusing because both banks are totally independent from each other, yet they have both jumped time and by the same amount. This is why I looked at the crankshaft sprockets and their key. I did notice that the sprockets teeth seem to be rather small in height for the size of the chain and would seemingly enhance the propensity for the chain to jump, but the tensioners seem to have the chains very tight at rest and I can't believe they would be any less with oil pressure. Before I move ahead with this I'd like to hear from someone that has experience with this issue that I hear is common with these engines. The car has only 70,000 miles and I'm thinking this is far to soon to be seeing a problem like this. If it is a jumping chain, does anyone make replacement sprockets with longer teeth?

 

Hi The cable guy,

Welcome to the Jaguar Forums. It's great to have you with us!

You posted the same information in four different threads. Please do not start any more threads on this topic, but instead add any additional information here.

Before we go any further, a little housekeeping. Please visit the New Member Area - Intro a MUST and post a required introduction.

Second, please tell us the year, model and engine of your Jaguar so we can provide the most accurate replies.

Cheers,

Don

 

Sorry, I don't know how that happened. I thought I was posting on just one thread, the one I was starting. Perhaps I don't know how this works, I'm new to forums. Year and model are in the post.

 

Where?

Another tip: Please remember to add line returns from time to time. Large blocks of text are hard on the eyes and discourage others from reading your entire post.

Cheers,

Don

 

Can you tell us why the valves are bent?
Was the tensioner repair done without locking the cams into postion first?

Trying to understand why it happened?
No there are no longer teeth gears so forget that and that's not your problem anyway.

The engine does not jump time unless something caused it? You need to figure that out first.
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As stated, a leakdown test revealed exhaust valves not closing even though normal lifter/follower operation was observed during cranking. 70,000 miles on car with NO indication that engine has ever been opened. NO visible wear or damage to valvetrain, including chains, sprockets, phasers, tensioners and crank key, with the exception of normal break-in wear on chain guides. This suggests slightly bent exhaust valves.

My question for you is; since these engines are known for this and similar problems, despite being apparently well engineered, except for the sprockets, what is the common reason for timing to jump? Remember, the chains are tight, there is no visible damage to sprockets, chain, guides, or tensioners. Both banks jumped the same amount despite having independent chain systems. How does that happen? I'm trying to not only fix the problem, but prevent it from happening again. So, if the problem is caused by improperly engineered sprockets and or tensioners, then I would be looking for aftermarket parts that are properly engineered.

This is how hot rodder's turn stock engines into powerhouses. I'm not looking to hop this engine up, I just want to know that its not going to prematurely jump time again. On typical American V8 engines of the '60s '70s and '80s the timing chains had no tensioner, and when they wore and got sloppy timing would flutter about causing rough running and eventually the chain would jump and it would be $25 for chain and gears, $12 for gaskets and a couple hours in the garage. This Jaguar is not like that, so I want to get it right the first time. Thanks in advance for your help.

 

Year? Model?

 

This engines jump time after failure of tensioners, i didn't hear about badly engineered sprockets yet
How did that happen? you bought car like that? or were driving home after purchaser?
Chance it jumped both banks with good tensioners is absolute zero, so we don't have complete picture here

 

OK, so, apparently a whole paragraph that I painstakingly typed into this forum thingy disappeared. It was the part where I described how I rescued a 2000 Vanden Plas with 70,000 miles from the salvage yard. It was there because the engine had no compression. I removed the valve covers performed a leak down test while insuring that the cam lobes were not pushing the followers down and determined that the air was flowing out of the exhaust. This in conjunction with the fact that the cam timing is off, as indicated by rotating the crankshaft to top dead center on number one cylinder and observing the flats of the camshafts were not in line with each other, tells me that the chains must have jumped, and I'm sure those tiny sprocket teeth helped that to happen. We call that under engineered, but then, Jaguar has made some really bad calls lately so I suppose I shouldn't be surprised. That's too bad because this is such a nice car, I really like it and if this is how their engines are to be, then I will entertain an LS swap, but I'd really rather just fix this one.

HOWWWever, as this V8 engine has an independent chain drive for each cylinder head, one would expect one side to jump and not bother the other side, But that is not the case. This engine has apparently beaten those tremendous odds and both sides have apparently jumped time as indicated by no compression on any cylinder and the cam flats misalignment is about the same for both banks. The chains, sprockets, guides and tensioners look to be good. The chains are tight and there is no visible wear or damage to any component with the exception of normal wear in the plastic runners of the guides and tensioners, and that is minimal. I cannot push the tensioner pistons back into their bores, suggesting they are full of oil and working properly. Somehow, this engine jumped time on both banks. I could replace the bent valves easily but I'm not looking forward to doing this job again in 10,000 miles, so I would like to know if anyone here has dealt with this problem before. This can't be the only one.

 

In more than three decades of Jaguar ownership, I can't recall any owner reporting slipped chains due to small teeth on the sprockets. On the other hand, I can recall dozens reporting chains that skipped or fell off the sprockets due to cracked and failed plastic upper chain tensioners. Are your tensioners the upgraded metal-body ones?

It's certainly possible that for some reason, a previous owner rotated the crankshaft counterclockwise as viewed from the front of the vehicle, which could cause both chains to skip. If your upper tensioners are the latest metal-bodied type, perhaps whoever installed those got the timing wrong....

Cheers,

Don

 

Guides are alloy with plastic runners. Tensioners are metal with a plastic pad. Are you saying the originals were all plastic? Remember, the engine did not show signs of being disassembled recently. The holes in the crank damper/pully for the puller had lots of gunk. I had to run a tap through it to clean the threads so I could get the puller bolts into it.

Can we attach pictures here? I can get some pics but I have to drive over to where the car is. That probably won't happen in the next few days as I have company coming for the holiday.
-Larry-

 

the engine has been opened and slapped together with ebay parts. a 2000 build engine is going to have plastic wraped
metal guides, a bicycle/roller chain, and plastic primary tensioners.

it was probably mistimed

 

Hi Larry,

I get the joke of your username now.

Yes, we can attach photos. In the menu bar above the text window, click on the icon that is a square framing mountains and the sun. Then you can browse your computer or phone for a photo to upload. There is a size limit, which the system will tell you about if you try to exceed it.

Cheers,

Don

 

Camshaft flats don't align at top dead center but at plug in the flywheal that fits instead of CPS which is fair bit off

 

My theory is that someone replaced guides/chains with pistons at TDC and cams at the 'flats' or some other timing combination.

Engine lost compression so the car ended up in the salvage yard??????????

Just a guess?

 

I must admit that I knew about the flywheel positioning procedure but I presumed it was a top dead center position. I didn't have a way to lift and support the car at the time so I just put it to TDC from above. Why on Earth would Jaguar to do something like that. Well, even so, I could, with the aid of a socket extension in the spark plug hole see that the cam lobes were depressing the exhaust followers when the piston was at TDC. After the holidays I will lift the car, position the flywheel and check the flats, just to be certain.

 

I think if you can post pictures it will help?
As posted above by very experienced members valves don't just bend and again no the sprockets are not designed wrong. Please leave that be it's just plain wrong.

Xalty repairs Jaguars for a living and has seen many, many things.
I think the fact it was a junk car from the salvage yard says a lot? Hard to say what the car went thru before it landed in the junk yard.
But thanks for any information you can post because all the details do help.

With the additional information I would be scoping the cylinders to check for additional damage beyond just some bent valves. You might be running into a bigger set of problems than you originally thought?

Would you be against installing a used engine? Might be the quickest and cheapest way forward if you want to keep the car.
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The engine timing is set at 45 degrees AFTER TOP DEAD CENTER #1 so that NO valve will touch a piston when the chains are disconnected.(no piston at TDC anywhere in the engine)

Please download and read THOROUGHLY my old copy of ENGINE COURSE 168 in .pdf.

I had my paper copy of three ring binder student guide converted to Adobe Acrobat .pdf a few decades ago.
I offered it to the internet and it is everywhere if you look to download.

The document 168 is a newer version of my ENGINE COURSE 180 that only had the AJV8.
The 168 covers the V6 as well as the AJV8.

About once a month I got calls on the Jaguar dealer shop phone about how the engine would not run when another shop set the timing to TDC pistons but 45 ATDC cams. (flats aligned)

I had to explain that the engine was NOT TIMED TDC.
Next thing I heard on the phone was OH ****.

 

To motorcarman's point, it's best to review the procedure beforehand so the camshaft timing is correctly set.

Just in case you don't have the Engine Course 168, here is a link so you can download it from Dropbox:

https://www.dropbox.com/scl/fi/nfvwk...=higqa2mf&dl=0

 

Since I know the valves are bent, or at least not closing, I am going to pull the heads anyway. I have built/rebuilt a few engines in my life so this is not intimidating to me, and yes, the idea of a replacement engine has been considered and remains a backup plan. If I find cylinder or head damage then that plan my be employed. The car is beautiful except for a small dent in a front fender that likely came from the yard. It was simply too nice to see it parted out. Many of the replacement engines I found on car-parts.com had many more miles than the 70k of this one, so my first choice is to repair if possible and practical.

In my years, I have dealt with a lot of chains and sprockets, from my bicycles and motorcycles to industrial machinery

Since this is my first foray into the realm of Jaguar I thought it best to seek advice from those who have been there, so here I am.