UPDATED: 5/10/11. Please read my post on the second page. I am having some weird things going on. Engine is apart right now.

My 99 xk8 upper chain snapped on me today. Just parked my car, and when i went to start it again, it would not start. Brought it home, took off the front cover and saw that the chain snapped. When i cranked the car, it would crank fine; didn't make a whining noise or anything. I also did a compression test on that side of the motor and the numbers are all consistantly high, i think 120 or 140, but they were consistant. Did i get lucky with just failed tensioners and a broken chain, or do i need a new motor. I know that when the tensioners go bad, it is just a matter or upgrading to the metal ones, but not sure about the damage a snapped chain can cost. car only has 55k miles on it!!!!

 

Sounds like you got lucky!

I would make the assumption that the slipper came off the tensioner which is the usual way a chain breaks. Put it back together with new metal tensioners and see what happens. By pulling the valve cover I assume you are going to do the work yourself. You probably know you can lift the intake cam and install the new chain from the rear rather than pull the primary chain or use a repair link.

 

thanks for the reply testpoint. this was just the affirmation i needed to rest tonight. I was going to replace the chain guide as well as the chain and the metal tensioner; i hope there is a way to do this from the rear, (that would take me about an hour), but i don't think there is. I am going to do the work myself as well.

I only checked the compression on the side of the motor that the chain snapped, i cant imagine how one side of the motor would effect the other side, or would it? just too lazy right now to check the other side.

again, thanks for your reply.

 

You can get the upper chain with a master link if you want to avoid removing the primary sprockets.

They are usually sold as part of a kit: 2 upper tensioners, 2 secondary chaings, 2 master links.

edit: testpoint has a better option than using a master link!

 

I had mentioned the intake cam method of replacing the chain. You tilt up the cam from the rear and slip the chain to the front. Personally, I would not use the repair link solution.

 

Sounds like a much better/stronger option.

Earlier post has been edited to add a notation to that effect.

 

How do you measure compression if the upper chain is snapped, meaning that exhaust cam is not spinning. Am I missing something here?

 

you are right, i meant to say pressure tested.

Testpoint and Plumsauce, thanks for the tip. I was planing on using the blackonyx right up for replacing the chains and tensioners, but i would much rather just lift the cams up and get them on that way. I searched for this way but can't find a write up anywhere. Are all we are talking about is loosening the cam mounts and slightly tilting them up, then tightening them down to get the chain tight? Sounds simple enough. Would i still need a cam alignment tool, or can i get away with a straight edge to line up the flat spots on the cams? and finally, should i still go under the car and lock the flywheel at the triangle marker, or is that not neccessary if i can get the flat spots on the cams aligned?
I'll be going to pick up the parts later this evening and getting to work tonight.

 

The difference for you is that the secondary snapped.

Logic would indicate that:

-- the intake cam has maintained its timing relationship with the rest of the engine through the primary timing chain

-- lifting the intake cam will require that you somehow maintain the timing existing timing relationship - perhaps through zip ties, thus the "ziptie plus" method would be born.

-- then to "retime" the exhaust cam, given the above, you might be able to rely on the flats.

caveat: others may disagree violently with the above, or may point out a stupid assumption

 

The intake cam must remain aligned with the crankshaft but that is not a big issue. Unless you do something I cannot mentally conceive I do not know how you can screw that up. You will have to 'carefully' loosen the intake cam bolts, a little at a time until all are removed. Cams have been reported to have been broken from uneven pressure. Personally, I cannot envision that. I have broken a cam but not that way.

Once all the cam bolts and bearings have been removed you can lift up the rear of the intake cam and slip the chain to the front. Please be sure to maintain the bearing caps in the same order and the same top/bottom alignment as they came off for reinstalation.

It is not necessary to remove the exhaust cam bolts as you must use the Jaguar tool or a home made version of it to correctly align the intake and exhaust cams. No, a straight edge is not going to do!

Once the intake cam is bolted back down, carefully, you are back to the point that you can use any of the links to tensioner replacement unless one of those unimaginable things occurred.

 

I don't know if this fits in this area, but here goes; I have a 2003 xk8, been reading about these chain tensioners. Do I have anything to worry about? Should I have them inspected? Car's histor does not show it had its 50K service when I got the car from a dealer. the dealer I got it thru (Honda) took it in on trade and did a "Basic" inspection and service...thoughts on having the 50K service with a car that has 53K on it?

 

No, this is not exactly the politically correct place to ask your question . . . but that's OK. Welcome to the forum.

Your '03 does not have a tensioner problem.

The 'Big' service interval is at 60k miles so you have a few miles to acquaint your self with Jaguar's recommendations and the owner's thoughts on the subjects.

Check out the FAQ sticky above for more information than you ever wanted to know.

 

Thanks again for the replies. One last question hoping either testpoint or plumsauce share their info: So, like i said, i tried to start the car when this first happened. THis would mean that the intake cam was spinning, while the exhaust cam remained stationary. Am I still to leave the exhaust cam alone? wouldn't the intake spinning and not the exhaust screw up the timing between the two?

 

Yes, but ... what is being said is that the intake camshaft has maintained its correct timing relationship with the remainder of the engine components.

You must maintain that timing relationship while you maneuver the secondary chain into place from the rear end of the intake cam as suggested by Test Point.

Once that is done, you must then install the secondary chain onto the exhaust cam as well and during that process you will have to time the exhaust cam with the intake cam which has the correct timing. In other words, let the intake cam, and the remaining good pair of cams on the other side take the lead.

When you rotate the engine to get position on the cams, you must rotate it only in a clockwise direction as viewed from the front of the engine. The crankshaft bolt is 24mm. You will need the appropriate socket in a 1/2 inch drive and a long breaker bar. Having the plugs out helps in reducing the required effort. You might as well buy a fresh set of plugs for reinstallation. You do not need to unplug the ignition coil wiring. Just pick up the whole mess like a double handful of spaghetti and place on rags at rear of engine or down near the rear of the exhaust manifold. If you interrupt the job, make sure that you do not slam the hood on the coils. It gets kind of expensive.

Plug every single place with paper towels or rags, including sparkplug holes, where things could drop into the engine. *BUT* remember to retrieve every single piece during reassembly. Check twice before buttoning up.

Think of the whole timing exercise as "dead reckoning" of sorts or a game of chess. You have a known good starting place(the good side), a way to the next good point(the intake cam), and a lost lamb(the exhaust cam). If you protect and take advantage of #1 and #2, you can successfully orient #3. But, you *must* protect #1 and #2 at all times.

When you are finiished the cams on both sides should have the flats in alignment simultaneously. If not, you did it wrong. Do not start the engine until remedied.

Some people have done the exercise with straightedges. Not everyone is comfortable with it.

BTW, some people advise pulling the fuel pump relay to inhibit fuel flow during the initial crank to oil up the tensioner and cam journals. A better way is to pull the fuel injector fuse because it does not allow residual fuel in the rail to fire the engine as the fuel injectors do not open at all without the fuse.

++

 

Plumsauce, you are the man!!! After i slip the chain on the intake cam, i'll spin the crank until the flat spot is horizontal, then i will have to manually spin the exhaust cam until that flat spot is horizontal, verify with my straight edge, and then slip the chain on the exhaust. Sounds good? I have done this once before but it was on my bmw, which was much simpler, or maybe i'm just making too much of this.

 

I'm just looking over your shoulders here, trying to learn something. Stuck on one point:

In preparing to re-align things, we're going to lock the intake cam at the standard reference point, bringing one (two?) piston to TDC. At least I think that's right. Let's say that's done.

Now: the exhaust cam is currently sitting at some unknown phase, but we know it is such that none of the exhaust valves extend down far enough to whack a piston as it passes through TDC.

Here's where I'm stuck: we have to rotate the exhaust cam independently to bring it back into phase with the intake cam. As we do that, how do we know we won't pass through a cam position where an exhaust valve will extend down and hit a piston, one or more of which is now locked at TDC?

(If the answer is simple, please pretend otherwise so I won't feel too stupid.)

 

I used the "tool" method when I changed out my secondary tensioners so I didn't get the experience of removing the cam, but, I see Dennis' concern about banging the valves when getting the engine to TDC. I think that removing the exhaust cam and then finding TDC would eliminate this problem. Reinstall the cam with the flats aligned and the chain should be on the correct teeth of the sprocket. Follow what the other posters have said about carefully tightening down the cam and turn the engine by hand checking that it all turns up aligned. The intake cam pulls the exhaust cam so it should be timed right.

 

If he were to align and lock the crankshaft, and therefore the three cams at the correct point that puts all the pistons out of reach of the valves. Cam alignment is not done at TDC of anything. I think I read that is really about 45 degrees past #1 TDC.

THEN you can turn the exhaust cam without fear of hurting anything.

 

Aha! Thanks.
(But couldn't you have made that seem more complicated )

 

I shouldn't have used TDC (I stand corrected) I was more referring to the mark on the flex plate. My concern is that turning the engine to get to this position 3 cams will be turning and the 4th will be in an unknown postion with the posibility of some valves being extended. He has to loosen the cam anyway using the zip tie method so why not remove it and get the engine lined up.