another rebuild disaster? sharp PANGing sound coming from head

[burpod]

i was going to post a more detailed thread involving this, but currently just trying to figure out this issue and get some ideas before i pull the pan off again or take the head off.

my ahu, that previously skipped a timing belt, i rebuilt with forged rods, asv pistons, machined i-shaft, new ported head and rebuilt at machine shop. after some relatively minor issues that i resolved, car was running great, loads of power, and after 2800mi on it, i was starting to really push the boost and fuel, thinking i was good to go. after a hard run, lost boost, 15 seconds later bad groaning and strainging sounds, pulled over. then i looked at my oil pressure gauge and it was 0. shut it off. still oil in the dipstick so first thought was i-shaft broke. i thought engine was toast. went back with my flashlight and checked vacuum pump and sure enough, i-shaft had broke, the end at the vac pump was loose.

following day i got the courage to check a cam bearing, and to my surprise it looked perfect, so did the cam and lifters. so pulled them pan, everything looked fine, engine turned over nice and smooth as it should. some little nick marks on the bottom of rod #4 where it had been hitting the now loose i-shaft, no longer rotating with the tb. discovered the i-shaft sheared off right at the beginning where it had been machined down. with the stress of the belt it also spun the outer bearing, and the TB was all messed up. however, before removing the belt etc, i did verify timing was still spot on! phew! i was beginning to think i dodged a bullet and perhaps could get away with making a new i-shaft and putting it in, despite seeing some nicks on the bottom of rod #4. since the shaft was loose at that point, perhaps i wrongly thought it would be OK.

put in a new outer i-shaft bearing (inner one looked fine). so made a new i-shaft on my homemade "lathe" (more on that later), verified it wasn't hitting anything, got it all together, including wasting 3 hrs dealing with a motor mount bolt that broke while tightening it. fired right up, i can't say for sure but thought i felt a couple hiccups during the first few seconds. got my timing to just below the middle line (so when warmed up it would likely be just above). seemed to sound OK, i don't think it was making the very loud metallic pang/tapping sound at first. so took an easy 8 minute test drive. a number of times it would suddenly lose boost, like the n75 just quickly closed (or opened, what i always get it mixed up), letting out a little woosh. i think i saw some vacuum fluctuation on my vaccuum gauge, but it's not mounted and just hanging around in the dash so was hard to tell for sure. but it sounded like a momentary loss of vacuum, and then would start boosting again fine. when i got back after the engine was warmed up, checked timing with VCDS again, just above the middle line, and noticed it was making a very sharp tapping/panging sound from the head. like ball peen hammer on an anvil i guess i would describe it. very metallic. goes up with RPMs and very distinct.

long story short, i've checked all these things:
-oil pressure seemed normal as i drove it, went up and down with RPMS, was about 75psi when i first started it, warm 75F day
-verified physical timing again, spot on.
-tensioner looked good
-all other pulleys look and feel good
-checked glow plugs and injectors, no leaks around the base.
-loosened each injector line as it was idling, sound still there, just started to sputter when injector lost pressure
-i couldn't depress any of the lifters by hand
-no exhaust leaks
-no other funny sounds or stupid little things like loose heat shield that i could find
-inspected end of i-shaft at vac pump - looks perfect, no evidence of collision, same with outer end of the shaft, bearing looks perfect
-took cam out, all lifters look perfect, they all rotated, cam looks perfect
-without taking more out, the springs and upper retainers all look and feel normal
--however, even after engine had been sitting overnight, i cannot compress any of the lifters by hand. i though they were supposed to drain out after a few hours? i noticed this when i rebuilt the engine before.

could these lifters be bad? too much oil pressure in them?
dreading having to take the pan or head off again, but i'm running out of ideas.
i've read injector pumps when going bad can make a loud ticking sound, but this is much more of a sharp PANG, TAP sound and really sounds like its coming from the head. not as loud underneath the car or putting my head up to the oil pan. the car was also running perfect just prior the i-shaft breaking.

any ideas? if i get motivated i was going to post a better thread on the trials and tribulations, but wife is fed up (so am i) and just want to get it running again because i have a million other things i need to be doing....

 

[burpod]

i'll also try and post some pics, but right now the only thing i can think of is the tiny little couple nicks i saw at the bottom of rod #4 could have caused some sort of severe damage that i could not feel. but since everything rotated so nicely and no other carnage i could find, i thought i would try my luck. really hoping it's something that won't require another total rebuild...

one other thing to note - my oil light has been flashing since the rebuild (cursing myself now for not fixing it sooner) - one reason why i didn't pull over as quickly as i could have. since i did some major re-wiring during my first rebuild i've had some wiring issues i haven't resolved yet. i attributed it flashing to either a bad used sensor i picked out of the bag or some other wiring glitch. i fixed a couple bad solder joints on some grounds during our road trip last month, but some little issues are still lingering that are on the back burner.

my oil pressure sender is on the filter housing. i never removed the oil pressure switch on the housing, but replaced the one in the head after head was rebuilt - don't know if it was the one i had in before or a different one, possibly defective.

and one other thing - i noticed my vac pump was really worn, the slot where the oil pump fits in. i put in a different used pump that was better, but no change. perhaps that could have been cause for my strange boost-woosh loss...

 

[burpod]

the video doesn't do it justice, just like all the other videos i've watched of similar isssues. not nearly as pronounced as if you were actually here, but maybe it gives some clues... it's bad enough i don't think it should be driven until i figure out why.

 

[burpod]

machined, now broken i-shaft, can see it spun the bearing too - i assume that happened after the break:

my new i-shaft i made on homemade lathe - i took it down to just under 24mm at the beginning, and had to "machine" off some of the gear, rods #1 and #4 would hit the stock shaft:

head w/lifters:

lifters were brand new INA, 2800mi ago. now that i look at the pic, i do see darkening in the centers of some, but nothing unusual? and as i mentioned before, even after sitting overnight, i can't compress any of them by hand. when i first installed them, same thing except for one or two i could. really hoping somehow new lifters would solve the problem, but somehow doubt it.

i do have a supposedly good, clean low miles 11mm pump i could put on, but i also doubt that's the issue, as it ran fine just prior and shouldn't have been affected by any of this other crap.

 

[burpod]

well i'm now starting to think it's nothing very serious internal to the head (except lifters?) or block. after not finding anything odd with the cam out, no broken valve springs or anything strange looking, i put it back together. started up no problem, no smoke, engine sounds smooth except for the loud ticking. maybe i'm going crazy, but maybe it's not as loud as i think? with the hood closed and driving, it sounds more like a tick. varies directly with rpm. perhaps 10ish? ticks a second at idle. ticks in gear when coasting. when listening under the hood it's a sharper tapping sound. wish i had a stethoscope, i tried using some pipes to help but wasn't working. i tried the soapy spray test around injectors and glow plugs again, and did find that #1 glow plug had some slight bubbling and snugged it up and no more bubbling. didn't make any change. timing perfect again, as well as vcds injector timing right around the middle, not much deviation.

i did find why i had the weird boost problem - breaking solder joint on my JB ecu wire leads which finally broke completelyi (had recently been using a different one i did years ago for my mk1). swapped in my other ecu, got the courage to go drive around a little bit. aside from the ticking/tapping, which is much harder to hear at higher rpms, it drove great. steady strong boost up to 20psi and 3600 rpm, engine smooth, good power and no smoke.

checked injector balance which i had forgot to really look at before. initially it was much higher than i remember ever seeing, something like 1.4, 1.6, 1.6 and even up into the 2.x. after driving around, they were down to .8, 1.34, 1.29or so. iirc, previously i had never seen anything over 1.

maybe it is just my IP? although it really sounds like it's coming from the head. or lifters somehow are messed up? currently i'm thinking i should just try new lifters/cam. being that it drives and sounds so perfect except the ticking, i can't imagine it's something seriously wrong with the head/block.. could easily be wrong though.

 

[burpod]

so the other day, continuing to believe what's wrong must be related to my i-shaft breaking and loss of oil, i tried a set of new lifters. fire it up, still klacking. the new lifters i got, i could compress partially by hand and see oil squirt out the side-hole. my "old" lifters, even after sitting over night several times rightside up, i could not compress whatsoever! so i really thought that could be a possible problem, but apparently not..

took another look at the gear end of the i-shaft through the vacuum pump area. got paranoid it might be just barely hitting by a hair, as i saw the nick in the rod end (although i believe that happened when the shaft broke and was sitting loose in the bearing). so took it out again and removed a little more material from where i thought it could possibly be a problem. nope, still klacking. i didn't really think it was possible as surely the shaft would break, but maybe it was just ever so slightly knicking against it. also, measuring against the broken one i removed, it didn't seem possible this was it.

swapped in my old pp764s... still klacking. didn't have much hope that would be it, as loosening an injector while idling didn't do much.

before i swapped in another injection pump, brought it to my friend chris (GTiTDi) - ultimate vw guru . using his proper stethoscope, he seems to think my pump is in fact the culprit and that my drivetrain head/block sound fine - what a relief. so i have hope again. sounds like line to injector #1 is especially noisy, i could hear it myself with the real mechanics stethoscope so feel fairly confident his diagnosis is a good one.

go figure that the last thing on my list to try is the likely issue, and most unrelated to the i-shaft breaking and oil pressure loss. have high hopes the pump swap will be a success.... had hoped to do it tonight, but ran out of fuel with the wife and kids in the car on our way home from a walk . so spent time dealing with that. still haven't fixed my fuel gauge issue and had been so consumed with fixing the engine i forgot where i was for mileage.... the fail train just keeps chugging along! it's an unstoppable force. forgot my spare keys and phone in my friends car who helped us out, of course.

 

[burpod]

well, not that anyone is listening, but might as well document this.

swapped injection pump with a super clean low miles one i had scored a while back. i had high hopes on this.. but alas, no difference, still the loud clack/click/ticking sound.

took another look at the intermediate shaft, and got paranoid again maybe it was just barely hitting one #1. i looked at the new outer bearing i put in and some some wear already on one area. since #1 was where we hear the most noise, i thought, aha! perhaps it's just ever so slightly scraping it such that it didn't break it? also, looked at the inner bearing, and it didn't look as good as i thought it had initially. so i machined it down more from 24mm at the base to 23 and tapered down. still clacking!. am i going crazy? took it out again, and brought it down to 22 and even a little closer to the base. still clacking... tried using some tape at the gear end to check for clearance, even though i was sure it was fine, couldn't get it to snag. maybe this i-shaft somehow got warped? fairly sure all the extra times i machined the shaft had nothing to do with it, and my initial version clearanced it fine.

checked glow plugs, egt probe. can't find any leaks. have gone over everything i can possibly think of short of pulling the head and oil pan again, which i didn't want to do yet. drives great, tons of power but also sounds like a problem with the head that could end in a serious catastrophe and ruin it all.

so i finally had to pull the plug and abandon ship. wife not happy with all the hours and late nights under the car. took the 1856 and put it on my rabbit ahu and got that running without too many issues after sitting for almost 8 yrs. i'm trying to resist waiting a little bit before i swap in the .260 injectors and turn up the boost. just running the 26psi original tune i had for it now. it really scoots! i forget how much i actually like the cable clutch setup it has...

 

[Zak99b5]

Ive been reading. Your skill set is above mine, so I have nothing to add.

I liked the cable clutch in my ‘84 GLi, till one day the housing failed and I couldn’t shift. Car was only 4 or 5 years old at that point.

 

[burpod]

oh, since the only next step i could think of was pull the head, and i was resigned to not being able to fix the problem now. i took the intake manifold off - and looked inside at the valves with a mirror and flashlight. 3 and 4 looked normal, i think. #2 looked like it had some gray powdery-ness around the base. exhaust getting in there? #1 had a strange black area at the base, hard to tell, maybe it was just oil on an odd casting area that i could reach with my porting, although i didn't port much of the intakes.

but i feel something must be wrong in the head. although could also be the block.. but i didn't have the heart to pull the pan again. going to have to fight this battle after the summer i think. too much else to do, i already spent wayyyyy more time on this any sane person would

 

[burpod]

hahaa well, my skill set also seems to include some severe screw ups. such a shame though... after some minor kinks and quirks, it was running fantastic, tons of power. then the i-shaft snapped... either some sort of collateral damage i couldn't see without taking block apart, or something else failed due to too much boost/fuel, i'm not sure..

 

[Lightflyer1]

I have been reading too just to follow along on the journey. Good luck!

 

[burpod]

So the 1856 and .260 injectors are in the rabbit now with the original 26psi tune, just about done with all the basic maintenance and little issues that have arose after sitting almost 8yrs. Drives awesome. Mk3 is filling up with random parts and tools plan to
get back to fixing it after the summer. Going to try my tuning again on the rabbit this time and hopefully not blow IT up

If anyone has any bright ideas what could be causing that ticking/clacking in the mk3 I'm all ears, but for now it's just going to sit...

 

[AndyBees]

And, I've been reading too ...

 

[Seatman]

Maybe the thingymajig is hitting off the thingamybob but without pulling the thingamywotsit there's no way to tell!

Yeh I've no idea but have also been reading lol

 

[burpod]

I'm hoping it still could be something easy and stupid, but I doubt it so strange that it seems to drive so well, no stumbling, smoking or anything that would lead one to believe there was a possibly serious piston/valve issue.. who knows, I'm not a real guru, just somewhat dangerous

 

[Seatman]

It does sound very camshafty in the vid, any chance you could idle it with the intake off, see if it sounds more distinctive? Might be louder and more obvious if it is an inlet valve at least.

Don't think the same method would work for the exhaust though lol