I’ve a S1 with an engine I rebuilt 5-years ago that had oil pressure that was getting lower and lower - verified with mechanical gauge. Only down about 1000 miles a year, so certainly shouldn’t have had any wear. Anyway, the oil light started coming on at lights, so I first thought to check the oil/filter. The oil had some flakes of metal and the oil filter was full of metal 
Removed engine and stripped the engine (again). The main bearings were completely coming apart . The rod bearings were excessively warn and the cam bearing were a bit more warn that I’d expect. What I also found though was that the self adjusting chain tensioner had lost it’s rubber and was pressing the metal part against the chain. The chain had created large grooves in the tensioner as a result. I replaced all the tensioners during the rebuild, so should have been good. I was left wondering if the metal from the tensioner caused contamination of the oil, that then led to excessive bearing wear and perhaps even a blockage causing oil starvation. Interestingly the worst bearings were the upper middle mains - not sure of the significance of that. The crank was machined to .01 during the rebuild and matching bearings supplied by machine shop. The machine shop has a good reputation particularly with XK engines, so unlikely their mistake. I’m of course going to have to start again with the rebuild, but wondered if anyone had any thoughts on this, especially that failed tensioner. Was I just unlucky and fitted a defective part, causing all this damage, or is there something else that could have happened?
I would say you were lucky, when my ‘S’ lost the nose of the Reynolds tensioner it popped out and dropped into the lower timing chain Sprocket, instantly snapping the chain. Sounds like you have found the problem.
Hi Derek,
There have been many reported problems with Rolon brand timing chain tensioners all over the British car forums for the past several years (other British cars use the same tensioner as Jags). The problem is exactly what you experienced - the rubber head pops off the things.You didn’t mention what brand you had but the Rolon’s head is just flat on the bonded part. It doesn’t wrap the metal part of the piston in any way. The OEM Reynold part’s rubber head wraps around the metal at the top and bottom.
People reuse their old tensioners because of this - or just fit the old piston that rides against the chain into the new body. I just rebuilt my Series 1 engine and luckily found a NOS Reynold or I was going to reuse the old piston again.
Did you find alot of metal missing from the timing chain or what was left of the tensioner piston? Definitely could explain bearing failure if it found it’s way unfiltered into the sump.
@Robin_O_Connor surprised to hear of a Reynold timing tensioner slipper-head failure - was it the original?
~Mike
72 XJ6 (x2)
73 XJ6
85 XJ6
84 XJS
Derek I note your mention of the middle main bearings.
Check the cap and block for heat discolouration,
The block might need line boring.
Peter B
This was 25+ years ago, to be fair I would have to say that I cannot recall if the nose lost its slipper or if the chain had developed sufficient slack to allow the piston to fully eject from the body. I just know the result was like somebody turning the ignition off at 60mph in the fast lane of a motorway.
Not the best place to have it happen
I did the timing chains and the lower tensioner in our Mk2 last year. Had heard of all the tensioner issues and was hence wary about replacement. There is a great deal on this subject in the archives. In my case the chain was slack and noisy as the previous worker had not released the helical ratchet adjuster. I have since run about 1500 miles on a French made tensioner sold by my local Jaguar dealer - effective through the Jaguar Heritage arrangements. The slipper does indeed have rubber that returns around beveled edges on the steel foot. There will be pictures in the archive from my good self IIRC. Best of luck, Paul
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Do I understand that the damaged described happened with only some 5000 miles after rebuild, Derek…?
…in which case something went wrong during the rebuild, but exactly what is of course unclear. If indeed the tensioner wear described occurred after new parts were fitted; either the parts were defective/poor quality as mentioned by others. Or reassembly somehow went wrong - or a problem present went undetected…?
The whole point of the oil filter is to catch particles large enough to cause damage. In doing so, it clogs up, resulting in low oil pressure, loss of oil circulation and bearing overheating and coming apart. Or the other way around; the bearings failed, causing low oil pressure, and the tensioner failure was a separate fault - but both contributing to filter debris…?
Questions arising; were the oil channels in the crankshaft cleaned up, blind plugs removed - and indeed, did you check bearing clearances? That bearings matching the regrind were supplied by a reputable shop, but still only a clearance check can verify that necessary clearances was to spec. And that can only be checked when fitted in the engine. It is certainly something to be considered on your second rebuild - any sign of blueing of the crankshaft bearing surfaces…?
The bearing damage in such a short time due to particulate produced by the abrasion at the tensioner assembly is not inconceivable - it just should not happen. Though the tensioner damage was very bad; we have had tensioner assembly damaged reported without any bearing issues. This, and general wear debris, is supposed to be caught by the filter - but rapid and extensive wear may overwhelm the filter and oil change regime…?
I suggest that before reassembly; you clean up the oil passages in the crankshaft - and indeed the cam feed passages. Whether cause or effect; debris may cause clogging - which should be cleared up. Debris may also have caused damage to the oil pump - which should be routinely checked…
With new bearing shells provided; the running clearances should be verified. In a situation with severe bearing damage ‘immediately’ after rebuild - unless positively checked during assembly; tight bearings will quickly fail…
The chain tensioner problem should be addressed as a separate issue - whether or not it is a/the cause. It sure would be nice to know what went wrong, to prevent a repeat - and some effort to this end would be worth while…
Frank
xj6 85 Sov Europe (UK/NZ)
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Oh, just checked and it was indeed a Rolon part. The original is long gone, any suggestions about a good replacement?
I don’t see any heat discolouration outside of some of the bearings. During my last rebuild the liners were bored to .040 so no room left there now.
Hi Derek, per my above post the picture below is the one I used. It’s a french made Reynold - sold by my local Jaguar dealer in Blakehurst NSW. Note the returns on the slipper foot. Others may have different ideas. Regards, Paul
Thanks Paul, it does look a better design.
Hi Frank,
Yes <5000 miles after rebuild. Engine was actually running very well, except the oil pressure was on the decline.
I had the crank cleaned and new bling plugs fitted as part of the regrind - I think this time I’ll just do the cleaning myself, so that I know for sure it was done. The crankshaft doesn’t seem discoloured, but is scored. I’m going to take it back to the machine shop today for a verdict. I worry as some of the scoring looks very deep.
The filter really did contain a lot of metal.
I checked the new oil pump and it has scoring too. It’s measurements, were at the limit now, so I think I’ll be replacing that again.
I confess that I didn’t confirm the running clearances (first rebuild rooky mistake in hindsight). I hand turned the crank as the only test and it seemed smooth and free to me.
I think I will just need to be more careful about what parts I use this time, confirm clearances (not just assume machinist is correct) and make sure everything is very clean.
Thanks all.
By line boring I mean the main journals Derek, not the bores.
I have past experience with 4.2 blocks of center main journal distortion.
Peter B.
Thanks Peter,
Just dropped off the crankshaft and they said these should be checked too, after I mentioned the way the bearings failed. Not something that was checked originally, so will be interesting to see what the result is. If this were to be ground, then I guess that would mean some very special bearings to compensate.
The Reynold tensioner that @Breen60 shared is the good one. They made the originals.
~Mike
@Robin_O_Connor That is definitely high up in the ‘worst-case-scenario’ list
I was not precise Derek. I refer to the journal housings the crank sits in.
Check the center main housing for ovality. If your crank is standard
and needs to be ground, oversize bearings are available.
Peter B.
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This widespread scoring does indeed indicate metal particle intrusion, Derek - from what parts is somewhat intriguing. As a crude test, if you still have the old oil and filter; use a magnet to see if the particles are magnetic…?
Particles should be caught in the filter, but they first have to circulate through it. Oil is drawn from the sump though the sump strainer into the pump - then flows to the filter before entering the oil channels, so there should be no coarse particles entering the channels. Which is supposedly the only way they could enter the bearings…?
The wear in the chain/tensioner area may be the metal source - one stray though, apart from a bad component, is that the chain was excessively tensioned? The hydraulic adjuster is only meant to take up the slight slack that should be present after tension adjustment…
Two scenarios; the tensioner particles clogged up the filter causing the pressure to drop - and the bearings failed as a result. Scoring the pump as a byproduct, but maybe causing the pump to fail - and the oil pressure to drop…?
Or the bearings failed due to insufficient running clearances, or whatever - causing drop in oil pressure. Scoring the pump as a byproduct - the tensioner problem being an ‘irrelevant’ parallel event, or being rapidly abraded by contaminated oil…?
With low oil pressure developing; did you try an oil and/or filter change? Changing the filter is a relevant check with low oil pressure…
It would sure simplify rebuild matters if the chain of events were known - the range of suspects are rather wide…
Frank
xj6 85 Sov Europe (UK/NZ)
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ODo you know if the machine shop, or someone, performed two critical operations:
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were the galley plugs removed before hot tanking, scrubbed with wire brushes, then tanked and rinsed again?
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were the oilway plugs removed from the crank and properly cleaned?
That is very unfortuantely, and yes a timing chain tensioner letting go would indeed wreak havoc on internals. this kinda sound like tensioner guide bits getting caught up in the oil pump pickup, which would diminishing oil pressure causing the bearing wear your describing.
I’ll be doing one of these in my Series II. Ugh.
I thought I’d do a general update. I had the block line checked and it was found that the middle cap was .002 out and the two either side were .0015 out. As my previous build included crank grind and new bearings, that probably left me with no clearance in the middle. I do wonder however what came first though, was the line out before causing the failure, or was the bearing failure (for another reason) the cause of the line distortion, perhaps from heat. Line has been honed now and the crank has be ground again (.03 mains, .02 b/e). I’ve made sure all oil ways are clean have begun assembly. I fitted the crank and this turned very freely - 1 finger on crank weights. I used some plastiguage and this shows .002 for all. I then fitted the pistons. The pistons and bores have only been cleaned as the previous rebore was still fine and the pistons were new before (Mahle 9-1 +40). The ring clearance shows .025 - I must confess I didn’t check it originally. My manual says it should be only .012 but google suggests things vary with new piston manufacturing techniques/materials which can increase or decrease depending on applications. I certainaly wasn’t burning oil before, wasn’t smoking and had plenty of power, so not totally sure if that’s OK or not. I’ve fitted the pistons now and they turn a little stiffly. You can just about turn the crank with a long bar with 1 finger if you keep the motion going. I you pause on a down stroke, then you’ll need about 23ft lb to move it on. I checked the b/e clearance with platigauge and got .015 .0175 .02 .02 .0175 .015. Interesting pattern, but the manual has the minimum as .015 so these numbers seem OK.