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Seeing as the weather in London this week is practically tropical, meaning it isn't snowing, I decided to change the leaking valve cover gaskets.
I had done this job before, 15,000 miles ago to be precise, and here's a word of warning: do no buy the aftermarket Jagbits kit. It's rubbish. Half the thickness, made of inferior materials, it failed fairly quicky and fairly spectacularly.
This time I bought original, as I should have done in the first instance.
Alas, my question here is about the chain tensioners.
I did this job before, on this same car, approximately at the same time as gaskets. And, like with the cover gaskets, I bought aftermarket parts. Today, with the cover off, I decided to check on the aftermarket tensioners. Engine off, obviously!
So, my question is: is the chain supposed to have any slack when the engine is still? The passenger's side tensioner is completely retracted, no pressure, and it doesn't push the chain at all, the chain is essentially just resting on top of it, but if you pull it with your finger it has about a centimetre of play. I'm assuming that with oil pressure, when the engine starts, the tensioner pushes up, thus stretching the chain tight. But shouldn't the inner tensioner spring keep the chain tight even when the engine is off? Or is a bit of slack normal?
Any answers will be very much appreciated, as this is obviously the time to do something about it, ie get a pair of updated Jag tensioners and replace.
Thanks, Gary. Indeed, you are right. It's not "aftermarket", it's "OEM" part no. AJ88400-SET (https://www.jagbits.com/product/AJ88400-SET.html). Which is even more of a misnomer, since OEM is widely touted as "equal to or exceeding manufacturer's" specs.
Let me happily demonstrate the difference. Black is the Jagbits "OEM", red is original Jag:
I think you are fine. But the design changed between the AJ26 and later AJ27s, so it would be useful to know what year you have. Mine was tighter on bank one (right). But ran like a top for the 20K I put on it.
Very strange but I will surely look into this and forward these pics to our UK manufacturer asking for an explanation. We have been selling them for years and have never had a complaint.
I think you are fine. But the design changed between the AJ26 and later AJ27s, so it would be useful to know what year you have. Mine was tighter on bank one (right). But ran like a top for the 20K I put on it.
Thank you, Jhartz. Apologies, I should've mentioned: it's a 2001 car. I remember the original parts taking out to be plastic, and the upgraded aftermarket to be aluminium or some metal alloy.
The Black gasket looks like an AJ27 gasket. The Red one is an AJ26. Mine has aftermarket seals and they are the same as factory. I also have the cheapest of cheap tensioners fitted and have no slack in the chains... But then again, I use quite a sticky oil...
I have the gasket in a factory Jaguar package and it is black identical to the one I shipped not orange. Part number is AJ88400 i also looked at other suppliers online every one is black like mine.
Those are two different gaskets. The thicker red gasket (with round spark plug seals that are attached to each other) are for 1998 engines. The thinner black gasket (with round spark plug seals that are separate) are for 1999-2003 engines.
I'll have to check with Jaguar here in Blighty to confirm they've sent me the right parts for my car, but that's tomorrow - they're closed for the day. FYI, one side is red, the other is grey, and as far as fitment is concerned, they're a glove. Still, I must concede that other websites I checked show it to be black.
I'm positive it's a 2001 car throughout though, so it's all strange.
But the fact that the OEM Jagbit part failed after so many miles remains. By failed, I mean both covers started leaking oil onto the heat shields quite simultaneously.
YES, the secondary chain could have some slack in it if the exhaust cam comes to rest in certain positions at engine shut down. 'Certain positions' meaning that the cam lobes would allow a little bit of travel clockwise. If you put the timing tools on (crank pin and hold down bar on the camshafts) and there's still some slack, then you need to do a little tighten up. I just went through this last week. I got my 'chain slack' down from 4.5mm to 1mm on the A Bank.
Chain Tensioners - a penny-pincher's question!
