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TACK TACK TACK TACK


mws
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We swapped timing belt and installed Thorley's on my old (now my nephew's oldest son's) '87 grey V6 pathy with just over 200K miles. The new belt had lines, the pulleys lined up exactly like stock AND I did the counting so I am 99% sure the cams are propertly timed. Being an anal retentive and experienced shade tree mecanick, I triple checked everything. Belt was perfectly tensioned (90 degree twist passed with tensioner at 5:30). Was running like a champ at shut down, considering its miles. Been running Mobil 1 and Syntec for last 30K miles - 10W30.

 

We also did some rewiring and replaced radiator, etc. It took two weeks to complete the job (had to take a weekend off for dirt biking!) and we finally started it up. After flooding it due to a wire not being connected, it finally fired up. But now features a very loud TACK TACK TACK TACK TACK sound - like a slightly amplified diesel engine. Appears to emanate from passenger side. Shut it off and checked oil - nothing on stick. Was 1.5 quarts low (she has always burned a bit and the nephew, well, clearly was not topping off often enough). Topped it off. Idiot light was working and never lit up while running, so I don't think it was ever significantly starved.

 

Ran it for about 3 more minutes. Still TACKING and barely idled - very rough. Sounding very much like it is missing on at least one cylinder.

 

#1 suspect: Collapsed lifter that just won't pump up. Like completely bled down and not opening valve at all. Is that possible with this design?

#2 suspect: Timing belt woodruff key sheared and pulley shifted on start up and now we have a valve kissing a piston.

#3: Miss-set belt and my two witnesses didn't catch it.

 

#2 just seems like a longer shot than #1. Abd #3 even a longer shot.

It is running like it is completely missing 1 lung, not just "off" power a bit. It is running ROUGH. It will rev up to 3K, but reluctantly.

 

Has anyone had a lifter collapse or not refill? How loud was the tap, and did it sound like a diesel, but louder?

 

Current plan: Dump in some Seafoam, run it for 1 minute, let it sit, and then run for 3 minutes at idle and see if it clears up. If so, change oil and schedule a lifter change in the future.

If not, pull valve cover and watch rockers while turning over engine.

 

Ideas? Suggestions?

How messy is the VG30 to start up with valve cover off? It would be nice to watch it run and verify exactly what lifter may be collapsed.

 

Thanks for ideas and suggestions!

Martin

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Great idea on the fuse! :aok:

 

I don't have a way to accurately record a sound clip, and they end up so distorted on PC's, but I'll see what we can do.

Edited by mws
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I know you triple checked everything but it almost sounds like the belt is one tooth off. I've heard a motor run with a belt being one tooth off, and two teeth off. Sounds just like what you are describing, but it could be a lifter. Though, I'd check the tooth count between the pulleys once again just to rule it out.

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I had some tap a little in the old engine... it was noticeable but not extremely loud (nothing like the Subaru tick :blink: )

 

Along with counting TB teeth... If you have a Stethoscope listen to each lifter and see if you can pinpoint where the noise is originating from.

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Here is an obvious one... Did you put that long timing cover bolt in the bottom behind the HB?

 

SeaFoam and maybe a lighter weight oil.... Did you also do a oilfilter relocation kit? might be a little low on pressure...

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Long bolt? Can you elaborate, please? I take it there is at least one bolt longer than the others and if put in behind the the HB it hits either the HB or something inside the cover?

I was not involved with the cover replacement as I was working on re-wiring some things.

 

It has had filter relocation for some time now.

 

I have Seafoam now and will try it one of these evenings.

Edited by mws
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Slick did it(She has a Pic) and someone else more recently put one of the longer timing cover bolts in the bottom hole behind the HB. if so that will make a ton of noise. Just slide under the font end and look up(assuming the skid is removed) you will be able to see it.

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You know I had totally forgotten about how irritating of a sound that bolt makes! that mounting tab is on the oil pump, and on my old engine it was bysted just like in the picture, which allowed it to bend and ride agains the HB pulley!

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Seafoam experiment is not resolving the problem. I added 1/2 can and have run it 3 times for about 4 minutes then shut off and let cool to let the methanol work on crud. No change.

 

She is scheduled for a little exploratory surgery tomorrow...

 

Running with the hood closed made it sound much more like a classic lifter tap. Just a really loud one!

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After flooding it due to a wire not being connected, it finally fired up.  But now features a very loud TACK TACK TACK TACK TACK sound - like a slightly amplified diesel engine.

 

Is it possible that a cylinder filled with fuel and hydro-locked resulting in a damaged rod or piston?

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Dammit! After all the checking and double checking, somehow the belt was off by 3 teeth on the crank. I can only surmise that it slipped during the tensioner adjustment. I though we had triple checked the tooth count before buttoning it back up, but clearly didn't. We were rushing things a bit as my nephew wanted to get home... I know better, but still allow myself to slip up every now and then...

 

So 3 teeth off will result in TACK TACK TACK.

 

And a bent valve (I hope). We reset the belt, started it up, and still have an intermittent mechanical noise. Passenger head is off, will be pulling drivers side soon. No damage to pistons, but there is a cleaned spot (knocked carbon off) in the intake valve relief and what look to be witness marks on the intake where they were kissing the piston. No obviously seriously bent (they were all closed when removed) but haven't chucked them up and measured with indicator yet.

 

Trying to find the silver lining.... At least this will let us clean up valves and install new seals! Maybe that will reduce oil consumption somewhat...

And we're getting REALLY good at stripping the front of the engine to get to the belt...

Edited by mws
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