GBMUD Posted October 27, 2011 Share Posted October 27, 2011 1987 Ninety with a mid-late 90s 300Tdi auto. It has been converted to a purely mechanical fuel system. So, tomorrow morning I am supposed to be going green laneing up to North Wales for the weekend. This week I have been seeing to a few electrical issues and, having sorted it all, I tested the Landrover by driving up to collect SWMBO from Bristol - a mix of A and B roads and motorway driving; it all went well. Since I was a little early I went down to Morrisons (where I buy all my fuel if possible) to buy a cheap tank full of diesel. I know I got diesel as I almost picked up the unleaded nozzle but caught myself before picking it up. In any event, 43l of petrol would be pretty evident in a 90 tank! I drove about 2 miles back up the motorway, collected SWMBO and then drove into Bristol city centre (motorway then city centre ringroad) where I parked for about 30 minutes. All was as normal. As we left Bristol city centre in a huge, mostly stationary, traffic SNAFU I became aware of an odd engine noise. At first I thought it was the air cleaner housing rattling against the head - it would stop as I pulled off and the engine revs rose. However, when I finally managed to stop to look at it, it became apparent that the noise was being made by the engine itself, a really harsh knocking. The knocking disappeared when the engine was under load - notice more about load than revs - and then reappeared upon slowing down. When we finally made it to the M4 it seemed to drive normally for the 8 miles or so to our junction but as soon as we slowed it reappeared, sounding worse than ever. I stopped in a layby just off the M4, turned the engine off and got a spanner from the back with the intention of slackening each injector pipe in turn in the hope of isolating a duff injector. When I opened the bonnet and SWMBO restarted the engine it ran normally, (almost) like a Swiss watch. Several start/stops failed to get it to do it again so we set off. After about 2 miles there it was again, but not a regular knock this time, as if it was only doing it occasionally and then managing several 'good' revolutions. I left the engine running and loosened each injector in turn but each seemed to behave the same - with the intermittent knock it was more difficult to tell - knocking a couple of times as I undid the union and then idling 'normally' with a misfire due to the disconnected injector. Since it seemed not to be too bad, and since there was nothing I could seem to do, we set off again to come home. The engine returned to normal and was fine all the way back with a few starts and stops at shops - since I had to buy a headlamp bulb anyway, I picked up some injector cleaner in Halfrauds but the car is now running quite normally and quietly - well, as quiet as a Tdi - and i have not yet added it. So, to recap, my question was: What makes a diesel make a really heavy knocking noise that disappears under load and then clears 'just like that?' I cannot say for certain whether it was one or all four cylinders doing it, but I wish they wouldn't! I am quite worried about it as it was clearly not a sustainable noise/symptom and, as I say, I am supposed to be going away this weekend and can well do without any problem which kills the car! Any suggestions? Thanks Chris Quote Link to comment Share on other sites More sharing options...
brighouse shed Posted October 27, 2011 Share Posted October 27, 2011 having had diesel co. cars now for the last 20 years doing c40k miles pa this is something i get once in a while. from my experience it's always at Morrisons/tesco/asda etc. My theory for what it's worth is it's after the site has been filled and the residual has been stirred up be it water or general crud. I think "proper" stations clean the tanks out more regularly plus they always buy their own fuel. the supermarkets all fill up with whoever needs to shift some and so they don't get Shell/Exxon/BP support team checks. I find the first 100 miles a bit like you describe then i guess the in line filters have got rid of the crud or it's settled in the tank. usually a couple of fills with Shell city diesel or BP premium stuff and i'm back to normal. I can only suggest filling up now to dilute the stuff in your tank and also checking your filter doesn't need a clean in case it's full and not stopping anything. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 27, 2011 Author Share Posted October 27, 2011 Mmmm, the tanker came in right behind me so I guess the tanks were more empty than full. I like the idea of muck/contamination in the fuel, but my other vehicles have never suffered and I almost always use the same station - and there is always a queue so there must be plenty of throughput. If the fuel were a problem then surely the symptom would have manifested itself sooner rather than waiting for me to do 10 miles or so? Still, I have no better suggestions... Chris Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted October 27, 2011 Share Posted October 27, 2011 It's the wiring you modified rattling together Chris Mo Quote Link to comment Share on other sites More sharing options...
Pete Attryde Posted October 27, 2011 Share Posted October 27, 2011 Chris, Did this sound like a small bloke with a big hammer in the bellhousing (particularly at tick over)? Much louder than tappets. As the only time I had a similar noise manifest itself was when the flex plate cracked. Unfortunately there is no easy way to check the plate with out dropping the gearbox. Pete. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 27, 2011 Author Share Posted October 27, 2011 Chris, Did this sound like a small bloke with a big hammer in the bellhousing (particularly at tick over)? Much louder than tappets. A bit. The noise of a cracked flex plate would not go away though, would it? Pretty sure this was a piston/pre-ignition sort of noise... Chris Quote Link to comment Share on other sites More sharing options...
Les Henson Posted October 27, 2011 Share Posted October 27, 2011 Sounds like intermittent detonation to me Chris. A small amount of petrol in diesel will make a diesel engine do this - the petrol will ignite as soon as it's in the cylinder (hot engine will ignite it immediateley), so a pre-ignition effect in a way. The cylinder will fire early and give the effect of a knock. Les. Quote Link to comment Share on other sites More sharing options...
jbs Posted October 27, 2011 Share Posted October 27, 2011 Since using "good diesel" from normal fuel pumps in my 90 I've noticed better MPG (OK by a small amount) but also better running of it when I use texaco etc and not asda/tesco/sainsburys fuel, as it seems substandard to me I'd rather put the good stuff in, ok I'm paying a bit extra but it gives me peace of mind to be able to get on and do and not worry about the quality of my fuel in my 90 Quote Link to comment Share on other sites More sharing options...
Pete Attryde Posted October 28, 2011 Share Posted October 28, 2011 A bit. The noise of a cracked flex plate would not go away though, would it? Pretty sure this was a piston/pre-ignition sort of noise... Chris I've thought about this a bit more and I'm fairly certain the symptoms don't fit for the flex plate being broken. The noise from the flex plate being broken would go away if the engine revs (not load) were raised slightly (although putting the engine under load will also stop the noise.) I think the noise of the flexplate comes and goes because the broken bits rattle against each at tickover but as the engine smooths out at higher revs they wedge against each other stopping the noise. When it broke on me, I could drive it fine (no odd noises) until I stopped at road junctions etc when the little bloke would re-appear with his hammer. Hope this helps Pete. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted October 28, 2011 Share Posted October 28, 2011 Sounds just like my disco did with a knackered vacuum pump. With a weakened return spring, it doesn't quite return all the way and follow the cam at the extreme. Therefore you get a 'knock' when the cam hits the follower again. Goes away with revs. Quote Link to comment Share on other sites More sharing options...
C18RCH Posted October 28, 2011 Share Posted October 28, 2011 I filled up at a sainsbury's once and got 50L of water! It was only because my landy was a TD5 with ae fuel contamination warning light that no serious damage was done. Sainsbury's never offered to pay the repair bill despite having a receipt and statement from the AA saying where I was recovered 2 miles down the road from the garage and that they removed 50L of water from the tank. I still to this day boycott Sainsburys but I have also found supermarket fuel to be lower quality than shell, bp, esso etc Quote Link to comment Share on other sites More sharing options...
Diablo Posted October 28, 2011 Share Posted October 28, 2011 When I worked at sainsbury's they bought their fuel from BP (this was probably a couple of years ago). Not that that means it's the same stuff you'd get at a BP station mind. I'm surprised they didn't pay out for that. I've seen them pay for dents made by trolleys before, and that's some idiot's fault for smashing it into someone else's car, not really Sainsbury's fault. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted October 28, 2011 Author Share Posted October 28, 2011 Now broken down on the M4, lost all drive. Exact cause unknown but it is a pretty big coincidence. No noises though. Tried forward and reverse, high, low and diff lock. Chris Quote Link to comment Share on other sites More sharing options...
simonr Posted October 28, 2011 Share Posted October 28, 2011 Is your truck an Auto, Chris? I can't remember! While I was reading your first post - I was thinking it sounded like a flex plate or torque converter bolts coming undone. I'm glad someone else mentioned it - as I was less convinced when everyone else thought fuel. Loosing drive altogether would tend to confirm it's the flex plate / torque converter. I bet you'll still get there before me! Si Quote Link to comment Share on other sites More sharing options...
simonr Posted October 28, 2011 Share Posted October 28, 2011 In relation to the fuel thing. As the runner of one or two company vehicles, I have kept accurate fuel & mileage records. I have found that Fuel from BP/Shell (and probably the others) gives on average 4% more mpg compared to Supermarket fuel. The BP fuel is generally about 1% more expensive - so it is still more economical. I have no scientific explanation for this - only the data. In Horsham, there is a Shell station very close to Tesco and they sell fuel for the same price as Tesco - that's generally where I buy my fuel now! Si Quote Link to comment Share on other sites More sharing options...
Les Brock Posted October 28, 2011 Share Posted October 28, 2011 Oh Bum ! Quote Link to comment Share on other sites More sharing options...
simonr Posted October 28, 2011 Share Posted October 28, 2011 I've just had a lucky one - The Land Rover Gods are grinning at me! I went to the shop and on the way back - a minor bang and no drive!. Stick it in difflock and it carries on. Get back to work and find that both rear drive flanges have stripped splines! The interweb says this is a common problem because the hubs are not oil lubed. Fortunately, the X-Deflex flanges are (more by luck than judgement) the same type - so I've put on a couple of them instead. Setting off for wales in 30 mins! Si Quote Link to comment Share on other sites More sharing options...
disco_al Posted October 28, 2011 Share Posted October 28, 2011 Now broken down on the M4, lost all drive :( not good - hope you get sorted easily . Quote Link to comment Share on other sites More sharing options...
brighouse shed Posted October 28, 2011 Share Posted October 28, 2011 Sorry looks like dirty diesel was a bum steer Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted October 29, 2011 Share Posted October 29, 2011 Now broken down on the M4, lost all drive. I often feel like that on the M4 Well, as Jules would say, you've got maximum value for money out of whatever was making the noise. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.