Strange Tapping Sound with Engine Running

[JETaah]

According to my sources, in thousanths the gasket thickness goes:
1 hole = .061
2 hole = .064
3 hole = .067

The piston protrusion match up is;
.036 - .039 = 1 hole
.040 - .043 = 2 holes
.044 - .047 = 3 holes

the recess in the piston for the valves in two different engines that I have checked out is .038"+ or - a tad.

The projection of a valve on a VW rebuilt head that I recorded was about .032".
The correct match-up of gasket to engine allows an approximate clearance of .020".

Bottom line is if the the valve is shutting completely The worst case scenario of mismatching gaskets is not going to cause the valves to strike the piston.

 

[JETaah]

And BTW, you did mismatch the gaskets.
The relevant hole match-up is the round hole.
All this is covered in the Bentley.

Try out these part numbers to be sure.

038103383 H = 1 hole
" J = 2 hole
" K = 3 hole

also - the obvious - I made the mistake myself but caugh it in time - is the gasket mounted with the "TOP" marking on the part number tab showing? If not, I beleive the oil channels from the the block to the head ain't happening.

 

[rowl]

Thanks Martin, good information, and news for me.

It could simply be a compression issue then that may be resolved, or at least diagnosed, by adjusting the injection timing to see if the sound subsides?

 

[rowl]

I am a little confused with the gasket issue. I have this picture because I sent it to Jack at VWDIESELPARTS questioning the very issue. He assured me they are both one hole. According to the Bently the hole to go by is the one on the right looking at the top of the gasket, and yes it was put on with the top facing up. Jack supports what the Bently says and claims the shape of the hole has nothing to do with the gasket you have, only the location of the holes and the number.

This picture is the top side of both gaskets. Notice the VW part number on the old one, indicating the top, and the replacement gasket is stampted "top".

 

[JETaah]

Hmmm that is confusing. Can you read the suffix letter on both gaskets?
I cant on the pictures. I would have to think that its the deciding factor. or simply measure them if you can.

 

[Drivbiwire]

First of all why did you NOT replace the rods and pistons as a set...MANDATORY when working on a VW due to crank balancing and obviously piston and head clearances relative to the deck of the block

The gasket you removed is a two hole (Origninal) the one they sent you is a single hole (you have a problem now not that you did not before).

solution:

Replace the #4+#3 rod with a matched rods from VW also replace the pistons as a pair again #3+#4.

This is not a Chevy where you can just slap in a single piston and rod. Also if a rod is bent ALL the rods should get replaced as a set not to mention the pistons.

As you can see the hassle of having to go back in is not woth the hassles you would have saved doing it right from the get go.

DB

 

[rowl]

I have the old one at home. I will get the number off of it when I get home.

 

[rowl]

Why do you say the old one is a two hole? Because it has two round holes on the left side? According to the Bently these holes mean nothing. The hole that matters is the hole on the right side. Look at the Bentley. Am I reading it wrong?

 

[moondawg]

Thanks Martin, good information, and news for me.

It could simply be a compression issue then that may be resolved, or at least diagnosed, by adjusting the injection timing to see if the sound subsides?

Yes, it could be. Compression leaks can sound like clicking/tapping. Have you pulled your injectors and looked for carbon deposits? Turned over the engine slowly by hand to see if you hear any undue hissing?

To me it sounded like something that was happening in time with the piston, and not the camshaft... but it's hard to tell from a recording. Maybe a spun mainshaft bearing?

Lots of possibilities! It will be interesting to see what the gremlin is!

moondawg

 

[JETaah]

Just checked ....
I have three gaskets here.
one with three round holes on the left of the slots "AN"-- the another with three round holes to the right of the slots "K".

part numbers are not the same but according to the crossreference they are replacements for one another.

The clencher is that the middle of the gasket sandwich matches in thickness where the third, a two round hole gasket, is .003 thinner "J".

 

[rowl]

I have not pulled any of the injectors. I have turned it over several times by hand and I can hear the compression leak off as the valve slowly opens, but nothing that sounds necessarily wrong. What would you consider undue hissing?

 

[jorpet]

OK, I have listened to this and believe it sounds very similar to what mine sounded like after a timing belt change. I finally decided it was way to advanced and simply broght it back until it sounded "right".

I would attempt to back it off until you get rid of the harsh tapping sound or until you get to a no-start condition. If you get to a no-start condition and then move it minutely ahead and can get it to start and the sound is still there, then you know that it is a mechanical sound and not due to timing. If the sound goes away (which I suspect it will) you can then check it with the VAG-COM and re-time it. The sound should not come back.

 

[rowl]

Are you referring to the timing in adaptation and not the timing on the TDI graph? Sorry, I have only had my Vag-Com for about 5 days and I am not quite up to speed on it yet.

 

[jorpet]

I am talking about adjusting it at the pump. I talked to GeWilli about it and had talked to him when I did mine. He asked if I would listen to the .wav file since I had brought my timing back into spec by sound before I could get to a VAG-COM.

My suspicion is that even if VAG-COM says it is in the graph it is not, not sure why. It is an easy enough test to retard the pump a bit at a time until the sound goes away or you get to a point of no-start. As I said, if you get to no-start and it was still making the hammering sound then there is a mechanical cause for the sound. I don't really think there is since it sounds very much like mine did when it was way, way, way, way to advanced.

At any rate, it should be worth trying, doesn't cost anything and you can either eliminate the pump timing as the cause or eliminate a mechanical problem. Either way it narrows down where you need to look.

 

[rowl]

I will try to retard it. The funny thing is, when I got my Vag-Com it was advanced off the scale, about 112-115. It started and ran good. I backed it down to the top of the scale and it was smoother and still starts and runs good. I will try to retard is some more and see how it sounds. It really has the sound of a pre-ignition knock vs. mechanical issues.

Thanks for the feedback.

 

[moondawg]

I have not pulled any of the injectors. I have turned it over several times by hand and I can hear the compression leak off as the valve slowly opens, but nothing that sounds necessarily wrong. What would you consider undue hissing?

hissing from other places than the valves!

My thought was mainly around the injectors... although if you had a serious leak from the head gasket, you might hear that too... but i'd figure it would run rougher if that were the case.

Just ideas... It does sound like you're hot on the trail with the advanced/retarded timing.

the saga continues....

moondawg

 

[MOGolf]

Yes, you count the ROUND holes to determine the gasket.

 

[GeWilli]

rowl, any updates?

There's doubt that a one holer will cause enough change in the volume to advance the timing but i'm wondering if it could be just enough to make a difference.

Some people talk about reducing the CR by going one hole more on the headgasket.

if ya need more sound bytes posted lemme know...

 

[jorpet]

GeWilli, I thought about that today, but that shouldn't cause pre-ignition. The pump timing should be set to send fuel when you want it to go "bang". Increasing the compression will not make the fuel ignite much faster and can't cause it to advance beyond when the fuel is injected. Unlike a gasser where the fuel is already there and a rapid rise in pressure will cause pre-ignition.

The higher pressure will create higher temps and will ignite the fuel faster, not unlike what happens with higher cetane fuel. The knock sensor should be able to handle the little bit of timing advance from the increased pressure.

 

[rowl]

I haven't had a chance to do anything yet. I have classes on Monday nights. It will be this weekend before I can mess with the timing.

If I now have higher compression due to the head gasket, what are all the implications? Higher temperatures, poissibility of burning a piston, etc. Can I reduce this risk by retarding the timing a little and possibly cutting the fuel back in some way with the Vag-Com? I hate to tear the thing down to replace the head gasket again, but on the other hand a days work doing that is better than ruining the motor. I guess I am at least safe nothing is hitting according to Jettah. Let me know what all of you think, and thanks to everyone for the feedback, help, and concern.
Tim

 

[rowl]

Jettah can you check your part numbers again. Here are all the numbers off my old head gasket.

KLG DF 220599
038 103 383 AM (This doesn't match any of the numbers you had)
Mine definately has an "A", I got a magnifying glass and made certain.

Try out these part numbers to be sure.

038103383 H = 1 hole
" J = 2 hole
" K = 3 hole

2000 Jetta GL

 

[JETaah]

With a few quick calculations I figured out that you can get back your compression ratio to where it should be by cutting 13/16 of an inch from each glow plug. Heck, down in Texas you probably don't need them anyway.

 

[JETaah]

"AM" is superceded by "J"

 

[rowl]

Ha Ha! You are about right on that. It is 68 F right now and I am sitting here in shorts with a nice breeze blowing in the window! However, I did go to Northwest Arkansas at Christmas in the Jetta and it was single digits one morning. Fired righ up though! Wish I could spare 13/16" off the glow plugs!

 

[rowl]

"AM" is superceded by "J"

I guess that confirms the 2 hole replaced with 1 hole, but then again everyone was sure about that already. I guess we will see what happens when I get to work with the timing and fuel quantity.

Thanks for the help.

 

[rowl]

I traded vehicles with my son and had a chance to play with the timing and fuel last night, but there was no change to the tapping sound. The engine would change sounds, but not the tapping. This morning I started it up, and no tapping, it returned when I started driving, so I am not sure.

Thick cold oil? No tapping? Lifter? wrist pin?
Cold fuel? Injector?

I am not quite sure what to do now, but pulling the head and pan may have to happen. I hate to do it, but something is not right and I have to find the culprit. I will probably turn it over slowly with no glow plugs just to make sure I can't feel anything; if one of the injectors is the problem I don't know how to find out short of taking them to a guy 50 mi. away, and that will have to be Monday.

Any other suggestions?

 

[rowl]

Well I got my Dad's 03' Jetta over to the house today and listened. His has the same sound, but it is not as prominent as mine. I put the Vag-Com on both and there were a few differences in blocks 03 and 04. Not a lot of difference, but I adjusted the settings until they were the same. The tapping is more prominent, but in reality I am thinking the difference is probably from the slightly higher compression making it have a little more of a diesel knock. The diesel knock sounds identical in both cars. I am a little more comfortable with it now since I hear it in his too, but I am still a little concerned.

Any thoughts?

 

[GeWilli]

Did ya happen to get a sound clip of the timing changes when you did it?

It the timing it mechanically perfect (pump pin and cam lock and flywheel mark lined up) and timing wise (vag-com) looking good i'd say there is something... could just be the headgasket. But many folks feel its not enough but i'd support that it could be.

What oil are you using?

 

[rowl]

I didn't recrod it because it didn't really do anything. Sounded about like the A/C compressor kicking on and off when I changed the timing. The tapping remained.

I am using Rotella 5-40 synthetic.

I noticed something interesting in measuring blocks 013.
Cyl.1 Cyl. 2 Cyl. 3 Cyl. 4
-0.14 -0.05 -0.05 +0.26

Does this indicate my #4 injector has something wrong?

 

[runonbeer]

that #4 nozzle's the one you got from me eh? try swapping with one of the others I supplied.
For the group to consider: the nozzle in rowl's #4 cyl is from a '99 A3 Jetta, approx 90K on it. been sitting for about 2 yrs. in a jar of PS.