lo-fi Posted February 2, 2016 Share Posted February 2, 2016 It is sounding like a resonance thing. No throttle plate, no overlap and short duration will create quite a pulse in the intake, and the defender must be an NVH engineers worst nightmare... Just to clarify, you can only feel air flowing out of the air box filtered side through a little bleed hole? The booming only happens at certain revs/load? You could rig up a simple manometer with some tube and a couple of clear bottles which should be sensitive enough to measure small changes. Maybe have a go with that and see how it relates to the booming sound? Quote Link to comment Share on other sites More sharing options...
Mo Murphy Posted February 2, 2016 Share Posted February 2, 2016 The only time I've had an issue with intake noise on my current 200 Tdi was when I forgot to reconnect the rubber hose from the wing intake to the air box after working on it. That made a very unpleasant noise at speed. Mo Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 Just to clarify, you can only feel air flowing out of the air box filtered side through a little bleed hole? The booming only happens at certain revs/load? No, if i remove the crank breather (from cyclone filter) near the turbo i can feel it there too! not i must say from the cyclone pipe, but from the air intake pipe! Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 2, 2016 Share Posted February 2, 2016 What air filter do you have fitted? Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 ^ standard paper filter. I've driven without filter makes no difference. Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 OK here is a vid i done a while ago. you need a good set of speakers as the booming is very low frequency Quote Link to comment Share on other sites More sharing options...
Aragorn Posted February 2, 2016 Share Posted February 2, 2016 the external shots sound completely fine. The internal booming is very odd though, what about engine mountings? Perhaps one of them is knackered an not isolating the engine vibrations from the chassis? I've had a similar noise in a car before when an exhaust mount broke and the mid section was touching the floor pan. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 2, 2016 Share Posted February 2, 2016 Sorry if you already said, but what exhaust are you running? Have you tried removing props? Diff pinions OK? what about the engine/gearbox mounts, are they standard or 'uprated solid' ones? As above, the induction sounds OK, with all you have done you would expect it to have changed, if not cured it, suggest you look elsewhere. Sounds very much like it could be something touching it shouldn't be... Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 exhaust is standard too. rear and middle silencers, both renewed made no difference. down pipe is solid pipe, not flexi type. changed offside engine mount (gen part) no difference. i think i might try putting new gearbox mounts next. getting fed up shelling out on replacement parts that don't cure it!! removing props makes no difference either! Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 2, 2016 Share Posted February 2, 2016 What are the exhaust mounts like? Does it happen only in gear/underload/off load etc? Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 new exhaust rubbers! tick over i can hear it quietly as I'm tuned into it now! rev it in neutral can hear it easily. worse under load, high box low box diff lock whatever, its still there! it can only be heard from inside, I've walked alongside as my mate drove it in low box so it was really bad inside, but i could not hear it outside! Quote Link to comment Share on other sites More sharing options...
steve b Posted February 2, 2016 Share Posted February 2, 2016 Is it a single or twin box exhaust ? I'm wondering if the main box has lost it's filling . Can you strap that camera underneath near the main box and do the drive test again? The engine itself sounds normal from the video but the droning is clearly audible inside . It would bug me too cheers Steveb Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 2, 2016 Share Posted February 2, 2016 steve its a twin box system, but both have been changed made no difference. Quote Link to comment Share on other sites More sharing options...
steve b Posted February 2, 2016 Share Posted February 2, 2016 ...how completely nuts , I can see why you are frustrated with it . In that case what are the engine and gearbox mounts like ? cheers Steveb Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted February 2, 2016 Share Posted February 2, 2016 Bodywork resonance perhaps? Have you done any soundproofing or added damping to any panels? Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 3, 2016 Share Posted February 3, 2016 You don't have a snorkel, do you? That tends to make a booming noise with valve related oscillations. Quote Link to comment Share on other sites More sharing options...
Souster Posted February 4, 2016 Share Posted February 4, 2016 If it can't be heard externally in your video then surely it's body work resonance like retro said. Not sure if it's already been asked, but have you made sure the intake hose isn't rubbing on the bulkhead, or the intercooler hose with the metal straight piece that clamps to the inner wing isn't resonating is it? Apologies if it sounds daft or you've already checked Quote Link to comment Share on other sites More sharing options...
Kurt Posted February 5, 2016 Author Share Posted February 5, 2016 New head gasket I fitted was leaking!! Possibly because I had missed water in the bottom of some bolt holes in the block..... i did think some of the bolts felt a bit springy as I was torqueing it down. Checked head and block faces with an engineers straight edge whilst it was all apart again and both were good to go just gave the block face a carefull going over with 2000 grit paper. After a couple of days of running all seems fine. Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 5, 2016 Share Posted February 5, 2016 That's a good way to crack the block - the pressure exerted by head bolts in a wet hole would be enormous. Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 5, 2016 Share Posted February 5, 2016 New head gasket I fitted was leaking!! Possibly because I had missed water in the bottom of some bolt holes in the block..... i did think some of the bolts felt a bit springy as I was torqueing it down. Checked head and block faces with an engineers straight edge whilst it was all apart again and both were good to go just gave the block face a carefull going over with 2000 grit paper. After a couple of days of running all seems fine. so kurt, is your booming gone? i used compressed air to blow water out block threads! Quote Link to comment Share on other sites More sharing options...
g-mack Posted February 5, 2016 Share Posted February 5, 2016 Update: fitted new down pipe with flexi today. Made NO difference!!!!! been having a good look and listen again today, its definitely being caused by the back pressure! the booming climbs and drops with the revs, basically sound like an exhaust! Quote Link to comment Share on other sites More sharing options...
Kurt Posted February 5, 2016 Author Share Posted February 5, 2016 That's a good way to crack the block - the pressure exerted by head bolts in a wet hole would be enormous. I know.... i cringed when i realised my error. Think i must of been suffering brain freeze from the weather when i did it.that and battling the fading light. Quote Link to comment Share on other sites More sharing options...
Kurt Posted February 5, 2016 Author Share Posted February 5, 2016 so kurt, is your booming gone? i used compressed air to blow water out block threads! Yep thats was i resorted to this time around. Was a bit of a faff lugging the compressor about but i wasnt about to take anymore chances. And no the booming remains! Quote Link to comment Share on other sites More sharing options...
Snagger Posted February 5, 2016 Share Posted February 5, 2016 How about the exhaust manifold and turbo? Are the secure and well sealed? Quote Link to comment Share on other sites More sharing options...
Kurt Posted February 5, 2016 Author Share Posted February 5, 2016 ^ My exhaust/turbo appears fine. On second manifold gasket at the moment correctly torqued up with clean mating surfaces. Just thinking out aloud here but could this be a symptom of a worn camshaft/bearings? I am imagining valves not opening properly at the correct time could somehow cause this backpressure in the inlet manifold as those with a snapped rocker shaft may have found as suggested earlier in this thread? Quote Link to comment Share on other sites More sharing options...
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