I picked up a Jaguar to work on for my auto shop students at the high school I teach at. It was not running when I received it and after taking the valve covers off the chain connecting the two cams on the drivers side is broken. The tensioner is also destroyed. How do I put a new chain in? Remove the cams? Thanks for your help.

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1998 XK8 4.0L

 

Welcome to the forum faSStcars,

I've moved your question from General Tech Help to XK8/XKR forum. This is the place to pos technical questions about your model.

Graham

 

Bear in mind it's an interference engine so may be damaged beyond repair.

 

I would start looking at a new engine.

 

Motorcarman said he ran across several cases where the exhaust cam parked in a position that kept the valves closed, so it's worth taking the heads off first. Hopefully one of the moderators will arrange for you to down the the repair manual.

 

As RJ said - they can be rebuilt. I was able to have mine rebuilt following tensioner failure/chain break.

 

This link will give you info on the engine.
http://www.jagrepair.com/images/Auto...Code%20168.pdf

I had an Xk8 in a similar condition. I had to replace the head and one of the pistons. I had spare parts that helped to keep the cost down.

 

I was hoping since they were at idle when the car stopped that it might be ok. I understand what your saying though. I could try using my fiber optic camera to try and see the valves or do a leak down test. Or what do you recommend for checking the cylinders?

The flat part of the exhaust cam is almost flat even with the deck surface but that could be were it stopped or when it ended up after a piston smacked a valve. Although being a technician for years before becoming a teacher I have very little experience with European cars so I appreciate all you input. If my students and I can determine what direction to head we can start to fix the engine. The car is in pretty good shape so I feel it's worth it.

Thanks also for the repair guide. I'm sure it will come in handy.

 

It might be interesting to use a bore scope to check out the cylinders, and a good lesson for students. I don't know if you can see the valves with one though.
If you have the facilities and the time, it might be a good project.

 

If the exhaust cam is not holding any valves open you can do a leakdown, but the boroscope will tell you if any valves have hit pistons. Pulling the head to inspect would certainly be a good idea, but does add to the cost of repair. If you rotate the engine by hand, turn on clockwise as seen from front to avoid bearing damage- that according to Jaguar, not personal opinion.

 

The bore scopes have a mirror attachment so you can look backwards. Usually what I do is check the condition of the piston and look for impacts in the carbon. Then use the mirror attachment to look at the valves and try to see a bend. I could also close the valves on each cylinder and try and pressurize the cylinder listening for air. I think I also read on the forum to turn the motor clock wise only right?

Our school shop is 3 bays. I have space but I don't want to tie things up to long.

 

1. Remove cam chain and any bits of the tensioner
2. Remove exhaust cam
3. run compression test

I have had (multiple) AJ's with broken chains that ran just fine when I replaced the tensioner and chain after they had snapped. word of caution- replace BOTH tensioners- do NOT just do one. Ask me why.

Also, look up the "zip tie" method of replacing the tensioner and chain- it is much quicker and less expensive than pulling the timing cover etc.

You can usually skip the compression check if you can see one of the buckets is lower than the other (bent valve) or a shiny mark on the piston. There ARE indentations in the piston that are valve head shaped so don't be fooled by them.

 

Also, check the filter on the oil pump for pieces of that brown plastic. That can give you a hint as to the general health of the primary chain guides.

As a general point, this situation could be a wonderful teaching opportunity, but don't underestimate the effort/cost involved:

• There is a structural sump design, so the engine has to comes out if you need to replace a piston. This is not simply about removing the oil pan and reaching up.
• You likely need to replace the primary chains and guides as they crack just as much as the secondary tensioners.
• You might need machine work to fix whatever head damage, or just because you are already there.
• There are special engine tool kits involved for this engine work (check eBay).
• New parts are not insanely expensive, but are certainly not cheap either, and costs do add up. Think new water pump, valley hoses, octopus hose, gasket kit, etc.
• There is some magic involved with the crankshaft bearings. Stampings on the block tell you what went in at the time of manufacture. Pulling that apart might possibly bring complications.
• On the plus side, the documentation is readily available (workshop manual, engine course, etc.) and there are experts on this forum that have been through this before.

From reading this forum (I have no direct experience), folks hit with this dreaded "secondary tensioner failure" typically replace the entire engine with a used engine of similar vintage. This engine was used across a number of models and there are some cross compatibility. Others just sell the car as the cost of a replacement engine plus labor cost are more than what the car is worth (likely the conclusion reached by previous owner). As a side note, if this is an early AJ26 engine, there is some possibility of replacing it with a better AJ27 engine (more advanced VVT), but I am unsure of the specifics.

Last, keep in mind that the car came with the ZF 5HP24 transmission, which itself has a propensity to mechanically fail (a-drum failure). If you were to take the engine out, it might be a good time to consider a rebuild of the transmission and a replacement transgo valve. Fortunately, it is a very popular transmission and there is plenty of parts kit and information out there that cover it. Another great teaching opportunity...

Best of luck, keep us posted.

 

Thanks guys for the advice. Mondays are always busy with two kids in Boy Scouts. The school doesn't have a lot of testing equipment so I'm grabbing my compression gauge and camera to look inside the engine. I will know more tomorrow and keep you posted. Before tearing into this motor I did look around for used engines and in my area I can pick one up for around $700ish. Depending on what I find I may just do tensioners and chains like dsnyder suggested. Even though this is a school project it is100% paid for by me and I can afford to put an engine in it but it might be a couple months so hopefully we will see no damage.

 

I checked the cylinders today with the bore scope and found no indication of contact from the valves. The lifters also all look to be the same height. I checked the compression ratio and was getting various readings so I shot a little oil into the cylinders and they equalized for the most part. Since the motor had not been run in such a long time and the exhaust cam was stationary the cylinders looked they may have been washed with gas. I may try and replace either the one secondary tensioner or both. Dsnyder I'm guessing you have some experience with this failure. When you say find the zip tie method are you talking about here on the forum or you tube? There is some type of clicking coming from somewhere in the front but I can't see anything and all the guides on the primary chain look to be intact still and tensioned. Not sure but it could have something to do with the missing chain.

 

I read in some other posts about a secondary chain that had a master link so is that a real part. Car Quest has the tensioner for $132 and the chain for around $28 but I think it's a one piece chain.

 

Given the age of the vehicle, the primary and secondary timing chains, tensioners and guides should be changed at the same time. The primary chain guides crack and pieces fall off into the sump.

Use the correct tools and procedures as outlined in the Workshop Manual. If you don't have the Workshop Manual, you can download the Engine Repair Course here:

http://jagrepair.com/images/AutoRepa...Code%20168.pdf

Pay particular attention to the top of page 74, page 26 in the course, regarding the correct camshaft timing. The correct camshaft timing IS NOT TDC.

Under no circumstances is the engine to be rotated in an anti-clock direction when viewed from the front of the vehicle. Damage to the main and rod bearing is the result.

Use the correct crankshaft holding tool for the AJ26. Do not use the crankshaft holding tool to hold the crankshaft whilst removing the front pulley bolt. Use a piece of serpentine belt around the pulley groves and a chain spanner to hold the pulley. A 24mm socket can be used to loosen the pulley bolt.

 

Someone else will correct me if I am wrong, but I can't see how the zip-tie method can be used here when you have a broken chain. The zip-tie relies on the timing already being correct and allows you to change the secondary tensioners without anything moving.

Sounds like a great school project, we just made door latches and ashtrays in school (and a bolt for the door when the bell rang).

 

Zip tie method to be used on the OTHER side

 

Also, I like the idea of showing students there are more than one way to skin a cat (no pun intended)