Timing Chain Tensioners

[BigCat83]

I'm getting ready to drop the cradle on my '97 Eldo for Timeserting and headgaskets, etc.

While I'm in there I'm going to replace everything I have access to; what about the timing chain tensioners? Should I or shoud I not replace them? Have they been known to fail with mileage?

On my late Jaguar XJ-S V-12 they were considered maintenance items, should I consider them the same on my Eldo?

Thanks guys!

[JasonA]

No. The entire timing system is engineered for the lifetime of these engines. I don't think anyone on here as ever even heard of someone with problems with the timing chain system. Nothing in the timing system is considered a normal maintenance item.

[Ranger]

I recall the Guru saying that though you will see some wear grooves in them Normal), they will outlast the engine.

[Cadillac Jim]

I had a 1990 Quad 4 HO, which is similar internally to half a Northstar, but with 80 bhp/l and a 6800 rpm redline. The rev limiter was at 7200 rpm and I often flirted with that on the 1-2 and 2-3 shifts. The cam tensioner is worth about 50,000 miles when the car is driven like that. A Northstar with the same setup and a 6,200 rpm redline should be good to go for over 100,000 miles – but not 200,000 miles. The Northstar timing chain dampers and tensioners are better than those of the Quad 4 HO, however.

From experience with much older engines, mostly not applicable to Northstars, there are certain items that should be changed whenever you see them in other work requiring teardown, regardless of mileage. The idea is that some items are basically wear or throwaway parts, and it's expensive to get to them, so when you are looking at one of these, you replace it with a new one. These parts include, but are not limited to, the following.

• Coolant, oil, power steering fluid, brake fluid, or any other replaceable fluid.

• Any gasket.
• Spark plugs. If the plug wires aren't easily changed, they fall into the same category.
• Anything made out of rubber or plastic that ages, like coolant hoses or some valve seals.
• Belts, whether they be v-belts, multi-rib belts, or fiberglass belts. This includes the serpentine belt.
• Thermostat.
• Points and condenser (showing my age, here). The distributor cap and rotor, if any, are too easy to get to for them to be included in the change-it-when-you-see-it category.
• Cam chain tensioner (!!!).
• Timing gear (not sprocket). Any timing gear changes must be made as pairs, because a new gear will cause a worn mating gear to wear quickly and vice versa. Chain-driven cam drives also must be replaced as a unit – a chain and all sprockets that it traverses, including idlers. Reason is same as that for mating gears.
• Piston rings. If they change, change the pistons and hone or bore the cylinders.
• Piston pin retainer clips and other such small parts. Once stressed for removal, put in a new one. If it't not removed to remove the piston pin or piston, leave it alone.
• Plain bearings.
• Crankshaft seals.
• Transmission seals.
• Any filter; if it's not a throwaway, clean it.
• Water pump and seals.
• Oil pump.

It's your car, you decide.

[Regis]

Ok so back to the Northstar. I'm with Jason and Ranger. I believe we all read the same informational post laid down by a certain individual. The timing chain has been referred to as the million mile chain. But heck you might as well look at the tensioners. "Yup there they are!" At least you can say you saw them lol.

[Cadillac Jim]

Well, you're right. I'm so conservative about engines and car repair in general that I question the cost-effectiveness of my own advice ("It's your car, you decide.")

I would look at the tensioner and the miles on it, and think ahead about how many more miles I want to put on that engine before I pull it down for the chain tensioners. According to the guru, such an examination will result in a "leave it alone" decision. But, I would look at it, particularly if I didn't buy the car new. Who knows what evil lurks in the innards of a used car?

[KHE]

The tensoners will last several hundred thousand miles - they are hydraulic ratcheting tensioners. When I had my STS engine apart for Timeserting at 105,000 miles, the tensioners still looked new. Unless you have money burning a hole in your wallet, I wouldn't bother replacing them. The chain guides will have two grooved in them - that is normal and should not be used as a bias for replacement.

[BigCat83]

Thanks,

I'm second owner and have taken very good care of the car. I started having overheat problems after an Italian tuneup on the way home from work one night. I have changed the coolant so I'm concerned about what has caused this situation...

I plan on keeping it as my commuter for years to come - 200K or more miles, so my thoughts are that as I'm in the motor anyway and if the tensioners look worn or deteriorated I'll replace them.

I only plan on getting into the motor to this degree only once so I will replace everything that can be replaced - whether it needs it or not. Any future motor work will be a rebuilt motor.

The third car in the family will either be a black on black XLR or a black on black XJS V12 convertible...

[Cadillac Jim]

From what KHE says, you probably will be better off leaving the tensioners alone. Post some pictures here and let us see. You do have a good macro mode or macro lens?

[JasonA]

Some engines with cheaper designs will require maintenance of the tensioners sooner. I once had a Nissan truck with Nissan's KA24E engine. It was a great engine, but the timing chain tensioners and guides were notoriously weak on those engines. I don't know about the Jag -- it may have a cheaper design also.

The Northstar tensioners are good virtually forever. People with hundreds of thousands of miles on theirs have never reported problems. The only issue on these engines with any degree of consistency is the head gaskets, and even that is not common when considering how many of these cars are out there.

[KHE]

Thanks,

I'm second owner and have taken very good care of the car. I started having overheat problems after an Italian tuneup on the way home from work one night. I have changed the coolant so I'm concerned about what has caused this situation...

I plan on keeping it as my commuter for years to come - 200K or more miles, so my thoughts are that as I'm in the motor anyway and if the tensioners look worn or deteriorated I'll replace them.

I only plan on getting into the motor to this degree only once so I will replace everything that can be replaced - whether it needs it or not. Any future motor work will be a rebuilt motor.

The third car in the family will either be a black on black XLR or a black on black XJS V12 convertible...

You will not see any wear on the tensioner portion that contacts the chain. Where you will see the marks I was referring to is on the nylon chain guides. You can replace them but keep in mind, the new ones will look the same in short order. The grooves only will go as deep as the amount of overhang on the chain links to the chain pins - thousands of an inch.

I really would not waste the money replacing the tensioners or guides. Where I would spend the money while you have the engine out is on re-sealing the crankcase half and oil pan with the updated seals from GM with the anerobic sealant. Also, if the HVAC cover is brittle, the time to replace that is while the engine is out.

[Cadillac Jim]

Those with more open-engine experience than I have spoken, and all of them say to leave the valve train drive (sprokets, chains, guides, dampers) alone.

[BigCat83]

Thank you Gentlmen; I shall leave the tensioners alone.

Jaguar makes great engines but they never seem to get the timing chain tensioners quite right.

The V-12s wore and the new 4.0 V-8s wore, though I understand the original "weak" style has been replaced by a more robust tensioner...

[Cadillac Jim]

Ford has done wonders for Jaguar.

[BigCat83]

Ford has done wonders for Jaguar.

Yes they have. Ford finally taught the Brits how to build cars AND make money at it. I really enjoyed my XJ-S. I love my Eldorado. They are similar to one another yet different enough to compliment one another - A matched pair you might say...

Anyway, thank you everyone for the valuable advice.