Dreaded knock sound is starting

[gmcman]

Well just when I'm ready to turn 200K, I'm hearing this knock or tap..whatever. I started hearing it before my last oil change, wasn't terrible but seemed to go away above idle. I have had a cold start tick every once in awhile and I was starting to think of a weak oil pump, I have a gauge set and just looking right now to figure out how to get the adapter and someone has pointed me to a possible lead but I will get to that hopefully this week.

I never really had an issue with piston slap, at least I never really heard it. Problem is I also have an exhaust leak at #6 due to a broken bolt but I don't think this is an exhaust noise...however with this motor anything is possible.

The knock is at roughly 4-5 times per second, which is about 300 RPM at idle. I have pulled each coil and also the subsequent coil in the firing sequence, no change in pitch. I even disconnected 3 CYL at a time and no change in pitch. I really want it to be a weak lash adjuster but it's hard to pinpoint. I hear it near the valve cover and almost sounds "plasticky" for lack of better terms. The sound seems to come from where the head meets the block but could be traveling everywhere.

Could be a worn piston skirt but the last oil filter and this oil filter I had cut open and there's barely anything in the filter....no specs of gold, no metal that I can tell...just some small bits of black grit deep in the pleats.

I have a video and wanted a hot engine clip but my battery died on the camcorder but when hot the noise is faint. I will know more when I get a oil gauge hooked up but when I used a stethoscope around #4&5 it sounded like an xylophone. This could very well be the noise and sounds dull on the outside but inside through the scope it sounds just like an xylophone and whether or not that's the knock I'm hearing I don't know and could very well be a work skirt.

The thrills begin.

[video=youtube;Q3vIeIjtMXU]https://www.youtube.com/watch?v=Q3vIeIjtMXU[/video]

 

[gmcman]

Here's an audio clip from the stethoscope, clearly sounds like what may be a piston or pin rattling but not in rhythm with the knock, not sure if it's even related.

[video=youtube;lZSzesODIxQ]https://www.youtube.com/watch?v=lZSzesODIxQ[/video]

 

[jrSS]

That's not piston slap.

 

[gmcman]

That's not piston slap.

No, sure doesn't sound like it...what I was questioning was the "ringing" sound in the audio clip...you need good speakers or headphones to hear it.

Here's a vid of the motor when hot, much lower noise.

[video=youtube;HkS9M8J7wxg]https://www.youtube.com/watch?v=HkS9M8J7wxg&feature=youtu.be[/video]

 

[triz]

And you have ruled out the pulleys?

 

[gmcman]

And you have ruled out the pulleys?

I ran it with the serpentine belt off and there was no change.

 

[gmcman]

I saw this on the internet and figured I would give it a try. Only think I could think of is valves being pulled tight against their seats or the rods loading up drawing more vacuum...not sure but the added vacuum in the valve train could also starve areas of oil so what do you all think?

[video=youtube;5lWx1sq8Gu8]https://www.youtube.com/watch?v=5lWx1sq8Gu8&feature=youtu.be[/video]

 

[CaptainXL]

My suggestion would be to drain a quart of oil and add a quart of diesel to the crankcase. Drive it for a bit warmed up and see if the noise abates.

If it does then it's the valve adjusters. I had this noise and fixed it by flushing my engine a number of times over a year or so.

I would also make sure you are using a GM PF-61e filter (because the TSB says that noises like this can happen not using them).

Also make sure you are using 5W-30 and if your CPAS is old (or just cleaned and old) then replace it.

 

[bobdec]

My WAS (wild ass guess) is plugging the PVC intake is increasing the valve and crankcase plenum vacuum. Thus sucking more oil through the oil passages to the lifter/crank/cam/CPAS passages. +1 on previous post to increase oil flow would be my first recommendation specially since it goes away at higher RPM.

 

[CaptainXL]

My WAS (wild ass guess) is plugging the PVC intake is increasing the valve and crankcase plenum vacuum. Thus sucking more oil through the oil passages to the lifter/crank/cam/CPAS passages.

I really think this is more likely the effect. The biggest things that might affect pressure (aside from worn bearings) are the oil pump and the finer passages such as those used by the overhead cams and the exhaust camshaft phaser unit. The vanes in it could be on the way out. So you might need a new phaser.

 

[gmcman]

Man....I just filled it with Castrol Edge......I may drain it out and use some Rotella high detergent along with some diesel or ATF... If I had to make a hunch, if it's in the valvetrain then it's on the intake side...whether or not the phaser influences that side is beyond me unless the bearings are worn.

When I look in the oil fill hole, there's a good stream of oil running off the cam gear. Would there be any chance that the increased vacuum is influencing the bottom of the pistons and pulling them down?

So diesel wont harm any seals? Would diesel be more aggressive than ATF?

 

[CaptainXL]

So diesel wont harm any seals? Would diesel be more aggressive than ATF?

No it won't harm anything for as long as it will be in there. Which is typically 15 minutes at idle. It will only drop your oil viscosity slightly. Remember we have 7 quarts of oil in the pan. One quart of thinner oil (which diesel is btw) will not make any difference.

#2 diesel is the main product in many engine oil flush products. You can use one of them name brand ones if you like. It's just cheaper to use a quart of diesel than pay $5 for a quart of engine detergent/flush you can buy at AZ.

Your looking to either:

1. unblock a passage that is keeping oil from getting somewhere.

...or

2. Unstick something that isn't moving right. Like valve adjusters or camshaft phaser, or timing chain tensioner being stuck....etc.

Any success (however partial) means you have something gummed up and need more flushes.

I restored my friends '78 Camaro with a 305. We drained all the oil and filled engine all the way up to the lifter galley with kerosene. Let it sit for a week, drained, dropped pan to clean then refilled. Worked like a charm. Of course you want to make sure the cylinders are dry before firing up.

 

[Mooseman]

I would swear that was my engine. When cold, it almost sounds like a diesel running but once warmed up, it's quieter but not completely gone. Been doing this for over two years and even changed my cam phaser and CPAS. I'm thinking the chain or adjuster is loose.

 

[gmcman]

Capt, I think I will try the diesel if I can't get any results from the Rotella, but I had already purchased it and was going to give the mild cleansing a try to start with. I may try the diesel at the time of the oil change.

I pulled the Syntec Edge and filled with 5 qts of Rotella T6 5W-40 and 1.5 qts of Maxlife ATF leaving the oil filter alone. I idled it for about 30 min and was noticeably quieter, drove it for 5 miles and let it sit. We'll see how it fares over the next hundred miles or so.

Here's a vid of the motor after 30 min of idling with Rotella and ATF mix and some short driving....much quieter so far.

I took some dipstick samples also and will post updates.

[video=youtube;RXW1Zk6WEWE]https://www.youtube.com/watch?v=RXW1Zk6WEWE&feature=youtu.be[/video]

 

[CaptainXL]

Here's a vid of the motor after 30 min of idling with Rotella and ATF mix and some short driving....much quieter so far.

I took some dipstick samples also and will post updates.

Like I said if you notice any difference...keep at it. It sounds like in your case you might be close.

I would skip the diesel in your case and nip it in the bud and pull out the big boy stuff.

My prescription: 5 quarts oil + 2 quarts K&W engine flush (stronger than diesel) use as directed.

View attachment 34202

 

[triz]

Man that sounds a whole lot better.

 

[gmcman]

Man that sounds a whole lot better.

Yeah, I sure hope it continues in this direction. I was already getting a list at the dealer for a front cover, rod bearings, pickup tube, screen because if the pan was coming off, then the bearings were getting replaced, no doubt about it. Would be a mountain of labor saved and since the pan was off...may as well change the pump since GM went to a revised pump in 03.

 

[CaptainXL]

Yeah, I sure hope it continues in this direction. I was already getting a list at the dealer for a front cover, rod bearings, pickup tube, screen because if the pan was coming off, then the bearings were getting replaced, no doubt about it. Would be a mountain of labor saved and since the pan was off...may as well change the pump since GM went to a revised pump in 03.

Dude you don't need any of that stuff. Most engines with proper maintenance last for a very long time. Bearing wear should be close to nil. I bet if you took them out now they would look like new. Really the only thing that wears appreciably in an engine now a days is the cam, valve train and piston rings.

If you are that paranoid about your engine grenading on you then I would get an oil analysis done over the next couple years from Blackstone Labs.

 

[gmcman]

Dude you don't need any of that stuff. ...If you are that paranoid about your engine grenading on you then I would get an oil analysis done over the next couple years from Blackstone Labs.

Oh I agree, it was just the fact if I had an oil pressure issue and possibly a pump issue then I was going to change out the rod bearings regardless while I was in there....mainly for peace of mind.

I will definitely get a Blackstone report after all this flushing goes on.

 

[davenay67]

Whilst we're drinking the snake oil.

The Auto-Rx product is not cheap but has a lot of followers.Big on the VeeDub forums where the 1.8T is a big sludge-maker.

Auto-Rx Plus Non-Toxic Sludge Remover and Cleaner for Engines and Transmissions

 

[CaptainXL]

Whilst we're drinking the snake oil.

The Auto-Rx product is not cheap but has a lot of followers.Big on the VeeDub forums where the 1.8T is a big sludge-maker.

Auto-Rx Plus Non-Toxic Sludge Remover and Cleaner for Engines and Transmissions

Chemical engine flushes are not snake oil. They actually strip the gum, varnishes and oil from the metal immediately. However it has been noted that Auto-RX can take years to work (if ever) and is questionable.

In a fully warmed up engine there is actually no metal to metal contact anywhere. At least there shouldn't be. Every surface rides along a pressurized stream of oil that acts like a bearing. All we are trying to do is increase the flow of oil from blocked passages. We don't care about making the engine spotless.

 

[davenay67]

Chemical engine flushes are not snake oil. They actually strip the gum, varnishes and oil from the metal immediately. However it has been noted that Auto-RX can take years to work (if ever) and is questionable.

In a fully warmed up engine there is actually no metal to metal contact anywhere. At least there shouldn't be. Every surface rides along a pressurized stream of oil that acts like a bearing. All we are trying to do is increase the flow of oil from blocked passages. We don't care about making the engine spotless.

You, of course, have a different experience of the product. But I know of quite a few folks over the VW forum I frequent who experienced sludge thick enough to choke the oil pump. After the Auto-Rx 2 phase approach and a new CCT their engines were back to good health again.

As always, YMMV....

 

[CaptainXL]

I know of quite a few folks over the VW forum I frequent who experienced sludge thick enough to choke the oil pump. After the Auto-Rx 2 phase approach and a new CCT their engines were back to good health again.

As always, YMMV....

I give you that. But never in my life have I come across a board where people say AutoRX cleans out sludge in a fast manner. They say to give it time.

We are talking about fixing something with a $5 can of chemical cleaner immediately, not using a slow acting product. In that sense Auto-RX is way slower and can be seen as not able to produce the results we are looking for in the short term.

 

[gmcman]

I received my sandwich adapter so I installed it with a fresh PF61E filter and took a reading on hot engine oil. The results are interesting...I don't think the pressure should be this low at idle, as well as this high at 4K RPM.

Haven't dug into the manual yet but wanted to share my findings, what is the consensus on these numbers? If the hose was another couple feet longer I could have placed the gauge inside but the shoe trick worked.

[video=youtube;ZZhSBjqRB8M]https://www.youtube.com/watch?v=ZZhSBjqRB8M&feature=youtu.be[/video]

 

[Mooseman]

Manual gives only a minimum of 12PSI at 1200RPM so for that, it looks healthy but it sure looks high at higher RPM. It may be normal for this engine though since the stock gauge is just a lie, we have no idea what is normal on these engines but I haven't heard of any normal engines running pressures that high.

 

[Texan]

You have convince me that the cluster gauge does not show the real numbers.
I would think 25 psi @ 600 RPM is great, based on the old days. I am surprised
at the 85 psi at 3500 RPM, but that may be normal now days. The only vehicles
I ever saw that ran that high were British Jag's, Lotus, ACBristol back in the 60's.
It will be interesting to see what others have to say. Thanks for sharing.

 

[gmcman]

Still trying to pinpoint my knock, tap, whatever you want to call it.

Before I went to the dealer I put about 16oz of water down the large vacuum hose hoping to clean the combustion chambers somewhat and I have a half a tank of BG44K through the engine which hopefully softened any carbon I may have.

So I finished and went to the dealer and picked up a trans filter, gasket, and some upper engine cleaner but had to administer it DIY style. Since I can't use the fuel rail the other way is to mix 2oz cleaner to 14oz gas and (carefully) spray into the the TB.

Knock is still there but not as loud, I'm really hoping it's a carbon noise so time will tell. Still could be a lash adjuster and I will tackle this next weekend.

As far as oil pressure...... I left the gauge attached and did a cold test and I thought the gauge was whacked...was idling around 80 PSI and easily hit 100 PSI @ about 1500 RPM. Finally did settle to normal after it warmed up.

 

[gmcman]

Something came to mind with these sandwich adapters for the oil filter in regards to pressure readings. The pressure ports, or all the ports for that matter, are in the same channel as the outside of the filter media...or the oil that comes from the pump. I would only think that once the oil passes through the media the pressure is reduced and that is where I would want to know what the pressure was. You could have a clogged filter and the pressure would still be registering normal.

A friend who has an 06 says his pressures read about what mine do so apparently the pressures seem to be normal.

Does the factory gauge read from the oil flowing after the media?

 

[Mooseman]

Neither. The factory gauge is an outright fabricated reading by the PCM. There is only an on/off switch to tell it if there is any pressure, just like old fashion idiot lights. The pressure you see on the dash gauge is a lie.

 

[gmcman]

Neither. The factory gauge is an outright fabricated reading by the PCM. There is only an on/off switch to tell it if there is any pressure, just like old fashion idiot lights. The pressure you see on the dash gauge is a lie.

I agree but is the factory sender inline with filtered oil or pre filter? If post filter then that's the port to use and not a sandwich adapter.

 

[gmcman]

I have been driving it to work this week and the noise is still there but is still slightly less than before all this oil/fuel treatment.

I had a theory today and thought I would try something. I want to hypothesize that there is an oil delivery issue to the lash adjusters/cam journal area and when cold there is significant pressure at idle to get through any slight restriction. Once the fast idle begins to slow then there is a drop in oil flow and being cold the oil is losing the battle over the restriction. Once hot then the flow is restored slightly resulting in a quieter noise.

I'm not saying there is no oil flow at times but just restricted. I have a video of the oil pressure at a cold start and it's suprising to say the least....fast idle is about 85 PSI and I can easily push it over 100 PSI. This is why I think it's a flow issue to the lash adjuster.

So on my way home a used a good stretch of road with no lights for about 3-4 miles and kept the revs around 4-6K, accelerating and slowing the entire time....basically an Italian tune up. I did this until my temp gauge started to move past the 210 mark.

Grabbed a cup of joe and some gas and did this again, and I swear the valvetrain is quieter. The knock is still there but it's not as loud, the quietest it has been when hot.

I will see what happens tomorrow on a cold start but I still think it's in the valvetrain....hope so anyway. I plan on removing the valve cover this weekend (hopefully) and see whats going on.

 

[gmcman]

I won't bore you with a 7 min video but the pressure did settle down to about 30 PSI at idle. However when cold I was surprised to see how high it really was. You can see the fluctuation in the needle when the lash adjuster is sticking...Here's the first minute, ambient temp is 48 deg.

I uploaded the wrong video, this is slightly longer and shows that 100 PSI could easily be reached, this is also pre-filtration.

https://www.youtube.com/watch?v=H1y7p6VV5aE&feature=youtu.be

 

[Ed H]

My fingers are crossed it is a simple fix.

 

[gmcman]

My fingers are crossed it is a simple fix.

I tell ya...you and me both. The knock is there but it's not nearly as long in duration during warm up as it was, once hot it's much quieter. Time permitting this weekend I'm going to pull as many lash adjusters as I can access and attempt to clean them with some kerosene or similiar. Hopefully I can pinpoint the faulty one and replace it...the rest I will try to clean if possible.

 

[gmcman]

So my progress is I had removed the valve cover and looking to pull a few lash adjusters. Turns out my removal tool doesn't work so I'm looking for one now.

Anyway after the Rotella/ATF cleaning and while that may or may not have scrubbed it down since I didn't look inside before the treatment, after about 800 miles since I filled it back up with synthetic and 200K miles on the clock, it looks pretty good.

Not sure what the brown stain is though

 

[gmcman]

So I have puled the lash adjusters from cyl 1&2 on the intake and they are basically petrified. When I run my finger on the cam lobe you can feel a very slight indentation before the ramp of the lobe, not on all but on a couple. I don't know if the indentation is normal but I assume not, since it's only on a few so far.

Safe bet the adjusters aren't collapsing and almost acting like a solid lifter. I have to work them for about 5-10 min with acetone, mineral spirits, and constantly trying to work them until they start to give. After awhile I can get the small roughly 1/8" of travel out of them.

New adjuster is measuring 1.470 inches, 3 of them measure 1.461 as I pull them and one measured 1.457..I want to assume that's the bad one. I will at least replace that one and if I had some extra coin I would do all of them, no question. However at about $12 a piece it's pricey.

 

[xtitan1]

For those like me who have no idea what a lash adjuster is, this Wikipedia article is pretty helpful: http://en.wikipedia.org/wiki/Hydraulic_tappet

Just reading that it definitely sounds like a lash adjuster that is not opening fully (because it is seized) would for sure cause a knocking sound. Apparently this may also be what causes the diesel sound on cold start as the oil may drain out of it while parked so that it isn't fully extended until the oil is worked back in there after running the engine for a little while.

Kind of makes me worry because I was an idiot and didn't realize that I tripled my mileage this year so I went 10k miles on dino.

 

[Texan]

I assume that first picture is existing and second picture is new lash adjuster. I do see a few differences.
Do you know the history of this vehicle? I wonder about the oil change history. Would a super heavy duty
engine flush (snake oil) cleaning clear this up?

 

[gmcman]

The newer adjusters are diiferent looking. I was going to do the KW flush Capt XL recommended but I needed to see what was going on first. These adjusters are really gummed up bad...you cannot compress them without a clamp.

I'm the orig owner and the oil changes have been at a decent interval, generally M1 and 5-7K. Sometimes it's a bit too long but I did run conventional for awhile and I think with a couple long drain intervals at about 8K which is my fault in conjunction in using non-synthetic....I'm likely the main contributor.

I could not get the front exhaust adjuster out unless I removed some parts so I"m not going there. However......when I pulled the #2 adjuster on cyl 1 on the exhaust side....this on raised a brow.

Once it loosened up I could easily push it down twice as far as the other adjusters and was gritty...even got stuck for a brief second so I"m really hoping this was the culprit. If not, at least 15 of them are cleaned as I could not reach the last 2 cylinders with my tool. The rest had about 1/16" of travel and this one was 1/8....and easy to depress, almost no resistance. This is the one I replaced with the new one.

Sent my bro for an intake manifold gasket and it's going back together, 14 Cleaned adjusters and 1 new one.....if this doesn't fix it I know it at least did some good.

 

[Texan]

Thinking again. The exhaust side probably runs hotter than the intake side. Oil and heat create coke and other gunk.
I think you said that you were approaching 200k miles. The high oil PSI really surprised me. I believe that the oil pump
has a by-pass relief valve. I wonder what it's relief PSI spec is? Did you check how far the new lifter plunger would travel?
To me, this has been a very interesting story. I am at 134k miles, and now debating if I should run some "snake oil" through it.
I am now retired, and drive less than 5k per year, I may install a real oil pressure gauge on my TB just to see what happens.
Keep us informed.