My secondary chain on the left side of my engine broke due to tensioner failure. The valves hit the piston. My cylinder wall looks good, the top of the piston has some dents and the head is not useable. Could I buy a good head and put the engine back together, or are the dents in the piston a problem? One of the dents is fairly deep but not through the metal.
Thanks John

 

Sorry!

There is no way to definitively determine if piston damage is terminal without putting the engine back together and trying.

I had the same experience 25 year ago when a timing belt broke on a Volvo Diesel and breaking the cam with the the valve/piston interference. Put a new head on it and drove it for another 70,000 miles.

I would try it.

 

Go for it.

 

Given the time involved I would not! If I were you I would get some new pistons and then stick it back together! At the very least its not going to be correctly balanced, worst case you have bits of metal scoring the cylinders and damaging the piston rings.

Having said that, never tried it....

I have heard horror stories of timing chains going on XK's, I actually took mine to the garage a few months back and asked them to change the chain as a precautionary measure as I have 100,000 miles on the clock but the guy there said not to bother as he had never seen one go on an XK.

 

Maybe a picture would help?

I'd be inclined to give it a try.

 

Tokyorich,

Your mechanic is giving you very bad advice. Your original tensioners are just as likely to fail as anyone else's, and when they do, you will be the one paying for it...not him.


.

 

You do not need your chain replaced, but you do need to replace your secondary tensioners at a minimum or else you will likely suffer the same fate.

 

Hmm, thanks for the advise! Will get that sorted.
Any idea how much a Jag specialist would charge for that - ball park?

 

I would be concerned about using pistons that are beat up. I seem to remember from old auto shop days that a rough surface will develop hot spots and could burn through (not a pleasant thought). Just my two cents.

 

+1. I had an old Rover 2000TC a long time ago. Did an engine rebuild on it but since I was on a budget I reused the old pistons with new rings. A couple of years later one of the pistons broke. The top part detached from the rest of it when I was accelerating onto a motorway. Rather nasty surprise

 

Got a quote from my Jaguar specialist at ~£1,500 including VAT for metal primary and secondary tensionners, along with the replacement of the chain. The replacement of primary tensionners (the most vital ones) should be ~£1,000 max including gaskets etc.

My nearest Jaguar dealership gave me a rough estimate at £2,500 for primary and secondary tensionners. They told me they would not fit any upgrade (metal ones) but rather fit new plastic ones as per the technical specifications prescribed by Jaguar...

It's labour intensive, hence it costs a few quids. But it's certainly money well spent if you intend to keep the car for a long time. Mine has 77k miles, I have no idea whether the replacement/upgrade has already been carried out or not but, to be on the safe side, I have budgeted for it later in the year.

 

The secondary (upper) tensioners are the ones most likely to fail and the least expensive to replace. Metal ones are the last and best version. You are getting some odd advice from both sources.

Back to OP, it looks possible to replace a piston with the engine in the car, something to explore. If the damaged one lets go, it's a new engine for $ure.

 

So I seems like 01 xk8s are suspect for tensioner and or chain going out? My car was running fine, I went into a shop and when I came out the car would not start. Mechanics I took it too think its a timing belt and seized up engine. Could this be true?

 

At 75k I replaced the secondaries as a preventative measure. At 93k I developed a bad chain rattle and did the primary - the guides were split and disintegrating. I should have done all at the same time. I also replaced the front crank seal which had developed a slight leak.

All is now well at 106k and I sleep well at night.

Sam

 

Welcome to the forum,

It certainly could. There is no belt its chains, but there is a potential for disaster, they will have to investigate to find out, no attempt should be made to start the car,

While they are doing that maybe you can slip over to the new members area and post an intro?

 

I just replaced all the tensioners and chains at 88k. The cahins had stretched over the years. The car seems to run better now.

I will likely replace them all again at 160k miles.


OP, I would rebuild the engine if there was any loose metal found when you pull the head or drain the oil.

 

noterman, I wouldn't reuse dented pistons, I did that on a motorcycle once and ended up with a rod through the case. Engine gone.

Toykorich, The dealer in Halifax told me the same thing. Never seen a secondary tensioner fail. However this is a picture of my passenger side tensioner when I removed it. 54000 miles and it crumbled in my hand like a wet sweet tart.

 

If it's a 4.0 and cranks but won't start then it might be bore wash. That's where petrol has washed oil off the bores and there's not enough compression.

The fix is either to remove all plugs and add about 50ml oil to each cyl then turn engine to smear it around or else WOT cranking. That means 100% (not less!) throttle as the PCM then does not add any fuel. Failing to be 100% will continue the fault. You crank and crank and crank in bursts of say 30secs until it tries to start then drop throttle to 3/4 till it runs. May need to recharge battery a time or two.

 

Not all 4.0 are nikasil, just the AJ26, 97-98.

 

You get bore wash regardless of Nikasil or not.