wood-gee Posted April 30, 2015 Share Posted April 30, 2015 I changed my head gasket recently, and since I've got everything back together engine has what I can only describe as either a knock or metallic clanking sound. The video below shows a bit of what I mean - you can here on the edge of the normal engine sound a kind of knocky / clanky sound (damn am I a good describerer). Has anyone had something similar happen, or any obvious idea what it could be? https://youtu.be/VOFnNRx--yY The noise is RPM dependant, but not as frequent as each cylinder, so I wondered if it were coming from just one. I have had the manifold gasket loosened off then tightened a few times having first made a mistake on the bolts and then after a few trips test driving it realising I'd used too long bolts on the bottom which bottomed out without clamping. It was down on power, but I've since adjusted valve clearances, fixed a hole in the air filter to turbo pipe and reseated an injector I was unhappy with, and its now very much back on power, feels lovely and smooth to drive, but still makes the knocking sound, any suggestions? Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 30, 2015 Share Posted April 30, 2015 I can't listen to the video at work, so haven't heard the noise. Check that your injectors are properly clamped down, I had that once on the 300TDi, and it was an RPM and load dependent knocking. Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted April 30, 2015 Share Posted April 30, 2015 It sounds a little breathy to me. Is there any excessive crankcase pressure? Are you sure that the exhaust or inlet manifolds are sealing correctly? Could be a lose injector as elbekko said, but I would think you would notice the gasses coming out past the injector if it was. What headgasket did you use? Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 Crankcase pressure seems fine - there's not much by way of gases coming out when I pull off the filler cap and it isn't blowing oil out. I used an elring head gasket (I think that was the brand), so one of the good ones as far as my internet research showed. I think there's a definite risk that the manifold gaskets aren't sealing correctly given that I've had them tight and loose a number of times as mentioned, I was considering buying a new one and changing it tonight just for completeness. There's no obvious gases on the injectors - I snapped a stud and put one in on a bolt originally after the change, and this didn't seal properly, and the escaping gases were really obvious, but I didn't check which orientation the injector washers were meant to be when I first reassembled it, so the back two could potentially be upside down - not sure if this would have any negative effect? Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted April 30, 2015 Share Posted April 30, 2015 Did you strip the head when you did it then? By the way, Elring gasket is good. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 I didn't, as background on it, I thought I had an overheating problem, and having pursued every other potential cause thought it might be that. Only since did I find that it was a not obvious electrical fault, so a somewhat expensive lesson in fault diagnosing. But back on point, I pulled the head off, found nothing obvious (as one would expect based on it actually being electrical), used a machined flat block and some fine wet and dry to make sure the head was flat then reassembled, so the only bits I took out in the process were injectors and heater plugs. As an aside on that, how do the heater plugs seal in the head? Quote Link to comment Share on other sites More sharing options...
Tetsu0san Posted April 30, 2015 Share Posted April 30, 2015 They just tighten up and seal, nothing special. But the sounds you are getting seem too loud for the small leak you may have from an injector or glow plug. But it's hard to tell on a youtube clip. From the issues you had with the manifolds I would start looking there. Although it doesn't sound like valves you might want to check the valve clearances, especially if you removed the rocker and maybe put the pushrods back in in a different order. But another thing would be to remove the airbox and see if you can hear a loud booming from there, this would indicate leaking valves or valve issues. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 Thanks, I'm borrowing a torque wrench from work to torque the rocker shaft correctly to do the valve clearances properly tonight and will change gasket//try what you've suggested with the air box as well and see where I am after that. Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 30, 2015 Share Posted April 30, 2015 Hold your hand in front of the air intake (not against!), and feel if it's pulsing more than it should. That could point to a broken rocker/rocker shaft. That also makes one hell of a knock. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 The air intake is definitely pulsing pressure a bit, whether this is more than it should IDK, but I'm fairly sure it's more than it did pre head gasket change which is another reason I wondered about manifold gasket leaking, should it pulse at all? I've had the rocker cover off a few times since though and there's no broken rockers, what else could break in the shaft, or could it be that I've attached it wrong? I assumed the was nothing really to mix up on it; my procedure was lay rocker shaft on get rockers in position make sure washers are lined up a la parts book make sure dowel is lined up in end tighten bolts, doing a bit on each one at a time As I mentioned earlier, I didn't tighten it up as per manual, just to what felt 'tight', so was going to retorque and recheck valves tonight Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 30, 2015 Share Posted April 30, 2015 It wouldn't be the first one that looks fine, but falls apart when you take it out. Your method seems fine though, IIRC it's tightened to 25 or 35 Nm? So hand-tight. Tightening should be progressive inside to outside. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 According to the workshop manual I looked at last night I think it was 5Nm then 60 deg, although I had done it to 25Nm originally, so it probably won't make a grand deal of difference. I'll inspect the shaft to see if there's anything obvious when I have it off, and hand't realised about inside to outside so that's a great tip. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 Nipped home for lunch to do a quick bit of work on car and discovered no 1 valve doesn't have a valve stem cap on! (Don't know how I missed this before, probably couldn't see for looking). Going to pick one up after work tonight and hopefully she'll be fixed! Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 This would also concur as no 1 was the only valve really out when I did the clearances Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 And to quote glencoyne 'if valve clearances are too wide, the valve stem can punch the centre out of the cap, resulting in slight loss of power and a loud tapping noise from under the rocker cover. ' Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 So it would appear after closer inspection that actually the cap had just fallen off, sadly my excitement was misplaced Quote Link to comment Share on other sites More sharing options...
elbekko Posted April 30, 2015 Share Posted April 30, 2015 If the cap wasn't there while it was running, that would definitely explain the knocking. If the cap came off while running, check your pushrods... Quote Link to comment Share on other sites More sharing options...
wood-gee Posted April 30, 2015 Author Share Posted April 30, 2015 I think it came off when I removed the rockers to check the pushrods this morning sadly. On a more positive note I showed it running to one of the mechanics at work this afternoon who said it sounds the same, if not a little better than his 200 tdi 90. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted May 1, 2015 Share Posted May 1, 2015 My money is on the vacuum pump. Quote Link to comment Share on other sites More sharing options...
elbekko Posted May 1, 2015 Share Posted May 1, 2015 Finally got to hear the video. Doesn't sound worrying, maybe a little too much valve lash. Quote Link to comment Share on other sites More sharing options...
wood-gee Posted May 1, 2015 Author Share Posted May 1, 2015 What does a shot vacuum pump sound like out of curiosity? Quote Link to comment Share on other sites More sharing options...
reb78 Posted May 1, 2015 Share Posted May 1, 2015 I'm struggling to pick up much difference to mine on the video also. 1 Quote Link to comment Share on other sites More sharing options...
wood-gee Posted May 2, 2015 Author Share Posted May 2, 2015 I've now pretty much concluded it was paranoia as to having done something wrong, as I did a big drive home to my parents yesterday and it felt as good as it ever had 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.