Hi all,
My Defender 110 TD5 has been a bit sluggish for a while, and the posts on this forum and others have been extremely helpful in narrowing down the cause - but as there are quite a few posts on TD5s lacking power, I thought it might be helpful to others to see one with closure and the issue resolved - but also to draw attention to a potentially serious issue which could have resulted in quite serious engine damage had I not discovered it when I did.
So I went through all the usual things, checked fuel pressure, checked boost pressure, checked the waste gate was properly adjusted, cleaned out the intercooler, cleaned the MAP sensor which was really badly clogged and fitted an EGR bypass kit. Changed the MAF sensor, checked for oil in the red plug, changed air and fuel filters, changed the accelerator pedal for a second-hand unit, fixed the low ratio sensor in the transfer box (which was permanently telling the ECU it was in low ratio so the throttle response was poor). I also fitted a straight-through pipe to replace the centre exhaust box, although this wasn't really related to fixing the issue, just because it was given to me by a friend whose wife wouldn't let him keep it...
All of the above made small incremental improvements, but none actually seemed to get to the bottom of the issue entirely. Then came the breakthrough. Aside from any previous issues, it started to develop the early signs that the injector seals were on the way out, fuel pump was running more than normal, and it was intermittently cantankerous at starting. On taking the rocker cover off to sort the injector seals I discovered the problem shown in the attached photo.
The pins around which the cam followers rotate in the rockers on no1 and no4 cylinders have lost their retaining dowels, and have migrated almost all of the way out of the rockers. The cast webs in the cylinder head have prevented them from escaping altogether, with the result that the rockers still act on the injectors as they should, albeit with quite excessive play. The engine appears to have been running like this for quite a long time with no untoward noises, in fact no symptoms at all other than the slight loss of power, as confirmed by the grooves worn in the aluminium by the ends of the escaped pins.
According to my local dealer, Land Rover don't sell the retaining dowels except as part of a complete replacement rocker shaft assembly. So my solution was to remove all 5 retaining dowels, cam followers and pins from the rocker shaft - run a 3.5mm drill bit through the dowel holes, then tap them with M4 threads - then refit the whole lot with M4 grubscrews and loctite retaining them. So far it's up to about 400 miles on this fix and it doesn't appear to have exploded again yet, and I'm pleased to report that it now goes like stink.
The truck is 1999, V reg, ex electricity board, was then owned by a local business and I am its 3rd owner, it appears to have been professionally maintained with quite a bit of documented history prior to my ownership. It has done 185k miles and had a new head fitted at 120k by the previous owners.
I hope this is helpful to someone. I really wish I had found this issue sooner, and for the sake of 10 minutes of anybody's time, if there is any suspected issue then it must be worth popping the rocker cover off and having a look underneath just in case.
