XK8 chain tensioners

The secondary chains for the 4.0L and 4.2L are all a single row design.

The 5.0L, and now the new 3.0L V6 SC both have one chain per bank driving both cams, there is no secondary chain.

Cheers,

Thanks for the additional history Steve. It's obviously a lot more complicated than I thought. Sounds like the only safe bet is a car from 2005 or 2006. I wonder, did they ever go to double row secondary chains on the 4.2L? What about the 5.0L?

I wish it were that simple, Ken.....
The 4.2L introduced in 2002 as a 2003 MY engine, does have multi-row primary timing chains, but the secondary cam to cam chains are still single row. Double row primary chains came in with the Constantly Variable Valve Timing introduced in the 1999 NA AJ27, and the 2000 SC AJ27 engines.

As to the tensioners themselves, that's kinda murky, too. The aluminum housing tensioners were announced as available for service replacement in a bulletin in early 2005. Exactly when they were introduced for all of production, I have never been able to pin down. I know they were not used in every 2003 model, for instance. I used to believe they came in sometime in 2004, but I was proven wrong by a gent who owned a 2002 XJR100. That car, and the XKR100, [which were 4.0L engines] were limited edition cars for Sir William Lyons 100th birthday. I did not believe there were any of the aluminum tensioners that could have been used in production that early. He sent me pictures and sure enough, his were date coded 2001. I have since found others dated that early. I have as yet found no rhyme nor reason for when they do or don't show up in cars earlier than 2004. Up to then it's kind of like Gump's box of chocolates, ya never know what yer gonna git.

Like I said.......murky!

Cheers,

It's my understanding that all 4.2L engines, introduced in MY 2003, have double-row chains and all-metal tensioners, and are not susceptible to the dreaded spontaneous chain failures common on the 4.0L engine used from 1997 thru 2002.

Brad, the entire xj / xk V8 line of that era 97 to 2006 , replace at 75,000 tops, unless you want valves crashing into pistons.....It happens ALL the time...........
Normal routine is the tensioners, thermostat housing and the gas cap. All 3 were prone to go. Loved the style and the power, but if you do not do the above, the engine will be terminal with NO warning.
GTJOEY1314

We long ago settled on a recommendation of 6-7 years or 60-75K miles for the two earlier design tensioners. I encourage friends and clients to change them out using those limits. That is probably a bit conservative, but I like to head off failures..... it's worked so far.

The current design parts were released for service in early 2005, though I have seen them show up as production installed in some cars earlier than that. I have no idea as to why or when that happened, some sort of factory testing, I suppose.

Cheers,

Peter,

When does "Old School Maintenance" say these should be replaced? When did they start using the new design?

Cheers,

S498 = Throttle Body Inspect and replace, on certain VIN numbers.
S499 = Frt Suspension Bushing inspect and/replace, if not already replaced prior.
S841 = Replace Evap Pipe with lined pipe to prevent corrosion

All these actions have expired as of ca. 2005.

Unless you can find some documentation to support the tensioners having been replaced, your only option is to pop the cam covers and inspect for the latest design.

Cheers,