poohbear Posted June 5, 2008 Share Posted June 5, 2008 I have a knock which I thought is diesel knock but am now not sure whether it's the big ends decomposing and was wondering if any one on here can ease my paranoia the best description I can give is as follows: It's a regular loud metallic 'knock' that is separate from the usual cold engine 'rattle'. I think it is coming from the bottom of the engine rather than the top. It is prominent at idle and also when accelerating where it becomes more mettallic, but disappears on overun and at high speed (although I think it is being masked by road/wind noise). As the engine warms up it seems to ease off but as the engine reaches normal operating temperature it is back again. I have tried adjusting the fuel injection pump timing in both directions but it is always there. I have recently replaced a split smoke inhibitor membrane that was feeding diesel directly into the fresh air side of the turbo - at the same time I renewed the fuel filter. The oil has also been replaced recently with Halfrauds 10W/40 part synthetic. Everyone I ask that has heard it at idle says that 'it just sounds like an old diesel' but I'm not convinced. I have had problems with the engine trying to run away due to the diesel introduced into the turbo, and wondered if this could have damaged bearings or the such? Am I just being paranoid or is there anyway I can diagnose this 'knock'? If this is diesel knock and I can't cure it through pump timing what are my options? Quote Link to comment Share on other sites More sharing options...
draper40 Posted June 5, 2008 Share Posted June 5, 2008 It does sound like a big end problem. I had one and witin 20 miles my engine blew up and I now have a rebuild on my hands! Pete Quote Link to comment Share on other sites More sharing options...
steve b Posted June 5, 2008 Share Posted June 5, 2008 I'd be inclined to check the exhaust manifold gasket first, and then the cyl. head gasket.....200Tdi's do blow at the back occasionally and it does bang.....if it is a really metallic knock then I'd pull the sump and check the shells. If it is that then you will wreck the crank if you carry on using it ..........much easier to sort it out with some new shells before it goes too far . It's worth measuring the crank if you get this far to see if it needs a grind - a micrometer is the only real way to measure accurately , but a vernier caliper will give you a good idea. Let us know how you get on , there is a recent thread by Scotian on here about similar things.......I'm sure someone can provide a clicky linky...... cheers Steveb Quote Link to comment Share on other sites More sharing options...
poohbear Posted June 5, 2008 Author Share Posted June 5, 2008 Just had a thought...... I'm wondering if the all the work I have done on the fuel system is a red herring. As I said earlier I have just changed the oil which I did as a standard procedure having bought the truck just over a month ago. Being a suspicious type of fellow I'm wondering whether the previous owner had used an oil 'additive' to hide the sound of worn big ends! Man the paranoia is really setting in now Quote Link to comment Share on other sites More sharing options...
tjolliffe Posted June 5, 2008 Share Posted June 5, 2008 Don’t want to state the obvious or anything (i mite just be being really dum ), but why don’t you just take the sump off and have a look. That will confirm/refute your suspicions instantly. Only a couple of hours under the truck and a tub of oil to do that and would give you the answer you want...... Quote Link to comment Share on other sites More sharing options...
Les Henson Posted June 6, 2008 Share Posted June 6, 2008 Big end knock is noticeable when pulling away or going up a hill in a high gear. At idle or sustained revs they don't tend to do it. Main bearings knock all the time (more like a rumble though) If your big ends are knocking you need to sort it fairly quickly - the more they wear - the faster they wear if you know what I mean. There's also the risk of damaging the crank journals, which would mean a regrind or replacement. Same applies if it's the mains. Excessive big end wear can splay the big ends - meaning new conrods/end cap as well. The eventual outcome would be a thrown rod and an unwanted window in the side of the block Les. Quote Link to comment Share on other sites More sharing options...
DaveB Posted June 6, 2008 Share Posted June 6, 2008 I hope you get the knock sorted. I am interested in you comment about the engine running away because of diesel in the turbo. I very occaisionally get this problem with my Td5. How does the diesel get into the turbo and how did you resolve the problem? Quote Link to comment Share on other sites More sharing options...
Les Henson Posted June 6, 2008 Share Posted June 6, 2008 The engine runs on the engine oil, Dave. It's called running away because if you turn the ignition off - it dtill runs and only stalling the engine or blocking the air intake will stop it. The engine revs higher, which cause more engine oil to be sucked in, which makes it rev even higher. If you don't manage to kill the engine it will self-destruct. Les. Quote Link to comment Share on other sites More sharing options...
poohbear Posted June 6, 2008 Author Share Posted June 6, 2008 Dave - as Les said the engine runs away when it is finding fuel (oil/diesel) via other means than the usual fuel circuit. In my case diesel was getting into the turbo through the pipe which is connected between the fuel injection pump and the turbo impeller housing, I'm guessing in a normal operating situation this adjusts the fueling/timing relative to boost pressure? Anyway I've fixed that problem but now my big ends have started to rattle. Just as you get one thing sorted something else comes up to grab your attention away from work/kids/washing up etc. Its almost as if the truck craves attention! Les - I appreciate your comments regarding speed of degeneration, I think I have heard the frequency of the knock double over the last couple of runs, although the knock is definately there at idle and under load but eases at higher rev's and less load. As I have mentioned it is more pronounced than the usual cold start rumble and is still there when the engine is hot although it does ease as the engine warms - I'm assuming this must have something to do with oil viscosity verses temperature? By a strange co-incidence I actually have a spare 2.5TD lump sat in my garage just missing most the ancillaries and which is supposedly a reliable non smoker. I think I'll do a transplant when I return from my holidays - I'd like to get this engine fully prepped before the swap to reduce down time - anybody got a 2.5TD flywheel and bellhousing they need to get shot of? Quote Link to comment Share on other sites More sharing options...
Les Henson Posted June 6, 2008 Share Posted June 6, 2008 Poohbear - what engine have you got fitted at present? Les. Quote Link to comment Share on other sites More sharing options...
western Posted June 6, 2008 Share Posted June 6, 2008 think there's a clue here a spare 2.5TD lump sat in my garage Quote Link to comment Share on other sites More sharing options...
Les Henson Posted June 6, 2008 Share Posted June 6, 2008 If that was the case, then he wouldn't need anything to fit it would he - just take the necessary bits off the old engine in order to fit the spare. Although I could be wrong................ Les. Quote Link to comment Share on other sites More sharing options...
western Posted June 6, 2008 Share Posted June 6, 2008 Yep, he could if the existing knocking engine is the same. Quote Link to comment Share on other sites More sharing options...
poohbear Posted June 6, 2008 Author Share Posted June 6, 2008 Yep - got a 2.5TD (original motor with 136K), bought a second lump when I thought the Turbo seals where on their way out - was cheaper than a new turbo and also came with a steering pump I needed. The only problem is that the guy I bought it off needed the flywheel and bell housing as he was doing a 200Tdi conversion from a disco (Anyone need a disco bell housing by the way?). Ideally I would prep the engine on the bench - timing belt, tensioner crank oils seal both ends etc, etc. If I had a spare flywheel and bell housing I could swap the engines really quickly as it would be one in - one out, or does it not take a lot of bother to swap the bell housing and flywheel as part of the swap? Quote Link to comment Share on other sites More sharing options...
western Posted June 6, 2008 Share Posted June 6, 2008 once the old knocker is out of the vehicle, it's fairly easy to change the flywheel/bell housing over to the good engine. Quote Link to comment Share on other sites More sharing options...
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