Good afternoon everyone,

I've recently acquired a low mileage, Anthracite, XJR and it's beautiful. Well, beautiful in every way apart from the engine rattle under load around 1800-2100 RPM...

I've replaced the upper timing chain tensioner in hopes of remedying the noise, to no avail. I have run the engine with belts removed as well and the noise persists. It has become clear through my research that the alternative is going to be to replace the lower tensioner arm (and dampers while I have the timing cover off).

I have been able to find all four dampers, the oil seal, and the two tensioner arms from SNG Barratt. However it is my understanding that the crankshaft spacer must also be replaced or else the seal may begin to leak.

Does anybody know of a source for these spacers? Any other advice regarding this project will also be appreciated.

Thank you, Michael

 

If your speaking of the spacer that the seal rides on, Just turn the old in reverse of the way it came off which gives the new seal a new place to ride on.

Thank you.

Larry Louton

 

Depending on where you get the seal from, often times a supplier makes the sealing lip offset slightly to cause it to seal on the adjacent unworn portion of the surface. It may well be that your spacer has no or minimal wear and will be fine. Also some seal Mfg's make a "speedy sleeve" that presses over the surface and gives the seal a nice new place to ride on. Pay careful attention to the dampener, crankshaft snout key way and the key. A failed dampener can cause the sound you describe by not controlling the harmonics and causing excessive noise through chain slap.

 

Thank you everyone,
Larry, that is a simple solution, I will definitely try that (assuming the original wear point isn't directly in the center).
Darren, that is also a very real possibility as the car has only 44,000 miles on it. I just wonder, are you referring to the harmonic balancer as in the crankshaft pulley? Or are you talking about the dampeners that the chains ride along and are bolted to the engine block/head, because I will be replacing all four of those.

Both are good solutions that'll hopefully work for me.
Thanks again, Michael

 

The pulley assembly is the harmonic balancer assembly. When they start to fail it makes it difficult to control the crankshaft harmonics, Typically you'll initially see evidence of failing when you observe the accessory drive belts start to vibrate excessively as you vary the RPM. The vibration of the belts will come and go as you cross over the harmonic resonance point of the crankshaft. This will also show up as reduced belt life on the alternator (which is essentially a spinning flywheel) Those same harmonics also get passed on to the timing chain and likewise will vary with RPM. Though initially it can be difficult to diagnose and is often overlooked as a cause, I have over the years discovered many failing/failed dampeners. It is the elastomer insert that fails through shearing wear or change in durometer hardness that alters the effective frequency range. In some cases I have seen it actually increase the tolerable crankshaft harmonics to the point of crankshaft failure. We used to use a timing light and multiple timing marks to see a failing dampener on larger engines. On smaller engines we used 2 crankshaft position sensors and 2 timing trigger points. One point was attached to the hub and the other was attached to the dampener outer ring and used an oscilloscope to see the timing points separate and come together. We currently do the same thing on modern vehicles using the cam and crank sensor scope patterns though not quite as effective.

 

Darren, I hadn't thought of the harmonic balancer as being the culprit. I will definitely check for deterioration and wobble within the pulley before removing the timing cover (and after removing the pulley before moving into the timing cover). I also assume a timing light test at varying engine speed would show a timing mark on the pulley jumping around if the balancer was deteriorated. I do like the idea of using multiple hall effect sensors and an o-scope. That seems like a good way to show any disparity between the hub and the pulley...If only my toolbox included an oscilloscope... I appreciate your advice. - Michael

 

I kept things simple but actually a timing light is not a good way to do this unless you have a fixed frequency trigger for the light. A strobe light is better (I just happen to have a timing light tester used for calibrating timing lights) As for using a timing strobe, you make several reference marks on the hub and dampener rings. The using the strobe and gradually raising engine rpm you look for the match marks to become misaligned slightly. If you are lucky, the ring will actually slip and when the engine is off you'll se the marks mis aligned.

Here are some articles that go into more depth than space would allow here.

https://www.enginebuildermag.com/201...s-and-dampers/

https://www.enginelabs.com/news/unde...ith-fluidampr/

https://fluidampr.com/troubleshootin...nic-balancers/