OK, just a simple question.

Bought a TL with leaking rocker cover gaskets, 136,000 km on the clock.
Finally got around to doing the front bank, new gasket, tube seals (also leaking), and platinum plugs.
Probably do rear bank next weekend.

Anyhow:
The gasket was as brittle as anything, broke into a number of pieces removing it. The Felpro replacement - also rubber -was nice and floppy when it went in. Similarly, the tube seals were rock hard, new ones nice and soft at the top lip.

In comparison, my TJ with similar Km, has no leak either at the tube seals or rocker cover gasket.

Anyone have a possible explanation for this difference?

I'm guessing the TL was a highway car and the engine spent a lot of time running hot, while the TJ did town km and didn't get as hot or as often - just a guess though, don't know the previous history of either car.

Just curious really, can't think of why there should be such a difference. How long do these bits last for other people, before leaks start up?

Is it possible the TJ's rocker cover gasket may have been replaced already prior to your ownership?
I did the ones on my TJ six months ago, and the gasket itself was somewhat brittle, but still flexible, and the tube seals were quite hard, but did not break into pieces. Like yours, mine did not have history of it being replaced prior.

Even the last of the TJs are edging a decade old, I'd be expecting many would have had a replacement rocker cover gasket or two by now. Its possible the TL could have still had its original ones.

Yes, good point. The TL bits I replaced were definitely original, but the TJ ones may have been replaced by the previous owner, it did have fresh plugs in the front bank when I bought it, but not a fresh cam belt - it was at that stage Km wise. I must get a spare set of gaskets and tube seals, just in case the TJ starts leaking too. Cupboard of spares for services and "just in case I need that bit soon" is filling up nicely. lol

So I'm figuring the gaskets and tube seals need doing roughly at 10 years/100,000 km? I guess plug and belt change time is a good time to do them in that case.

So I'm figuring the gaskets and tube seals need doing roughly at 10 years/100,000 km? I guess plug and belt change time is a good time to do them in that case.

I think it varies. Like any external seal, the durability of it would vary with regard to how the engine is treated. Short runs, and the engine heating and cooling within a small timeframe is more detrimental to seals than extended runs, as it causes the rubber to become brittle quicker.

But if you're putting it into a preventative maintenance perspective, then 5 years/100,000km I think would be a more accurate yardstick.

But if you're putting it into a preventative maintenance perspective, then 5 years/100,000km I think would be a more accurate yardstick.

Oops! Yeah, I meant 5 years rather than 10. lol Do them at cam belt change time. The TJ is due for a new belt in 3 years time, I will do them then if they last that long and see if original or aftermarket.