TDI Knock/Wrap

Hi all, I have an 02 with about 170k miles that i just rebuilt the engine on. All was going great accept that i didn't prime the oil pump with assembly oil when i put it in. When i started the engine the first time i had an oil press gauge on it and it didn't build press, so i shut it down, pulled the pan and primed the pump. The next time i started it the press built instantly. I broke in the cam and took it for a 5 mile spin, but i was hearing a little tap. I freaked out, thinking bad stuff happened with the no oil experience when i first started it, and pulled the pan and checked the bearings. The bearings had a coating that was very lightly scratched, so i replaced them. But, the knock is still there. I put almost 700 miles on the rebuild so far and i don't really think it's getting worse.



Now to explain the knock, it is way more obvious when its cold. It's heard best if you stand at the drivers door (behind the engine). You can hear it very faintly when you're cruising at 50-70 mph,but as soon as you let off of the throttle it disappears. Sometimes when its cold at lower rpms the noise is there whether you're on or off of the throttle, this is typically at about 1800 or less. The noise is by far most noticeable at idle and just off of idle.


My mods include a VNT17 turbo, Bosio Sprint 520 nozzles, Colts Stage 2 cam, headstuds, bar 3 sensor, high flow oil pump, South Bend Stage Daily SMF, and Kerma Tuning.


I don't have a vag-com yet, one is on the way. I have hammered the iq some, so who knows where it is. I spilled some fuel on the front of the engine and i noticed some bubbles around two of the injectors (the others didn't get wet), so i'm going to replace the injector seals. The oil pressure hot is around 20. I looked at my cam and lifters, all seems okay. My alternator pulley seems to be good. Any help is greatly appreciated!

Sounds a great deal to me like fuel knock. My car has it when hot or cold. When you let off throttle usually if it's in the valve train or bottom end or whatever you'll keep hearing it. These engines, from my understanding, when they are cold they will not completely cut fuel when you get off the throttle. I could be wrong but that's my understanding.

I'd wait till some others put in their two cents but it sounds like fuel knock to me.

If it does it in the driveway, remove some covers and use a stethoscope or hose-in-ear to isolate the noise.

Thanks for the input. Yesterday i went to pull it into the shop to replace the injector gaskets (it was about 40 - 45 deg F outside) and it sounded fine. I'm going to see what happens when i get my vag and set everything where it should be. Will a SMF make any difference in noise? 'cause that's what my SB Stage2 kit had in it. I'll keep you posted w/ what i find. Thanks!

Update

I got my vag and checked everything. The timing and the iq were both low. The inj. balance was pretty good i think- the biggest diff. I noted was from .90 to -.90. I put the timing in the mid 60s and the iq i took from 12 up to 2. This thing SCOOTS now (it does smoke a little off the line, though). The knocking was still there @ idle until i took it for a bash after my adjustments, then it was very, very hard to notice. I don't know what about the temp makes the diff. i guess the oil and fuel would likely be hotter? Still would like some input.

Tap could be lifters still pumping up. I know when I changed them in mine and my dad's car it took at least 25 minutes of fast idle in my driveway to get them all to burp the air out. Now they're as quiet as can be. I'm guessing it's a combination of new lifters and not priming the pump is what took yours longer.

I started having glow plugs 1&2 codes setting. So i pulled 'em out and they all had some sort of moisture that i couldn't identify by smell and 1&2 were a tad bent! I can't see a mark like were the piston would've hit but like i said they're a little bent. When i had the machine work done on the heads the guy decked them, I think it was .005 inch. He also decked the block a few thousands and when i measured piston protrusion it was calling for a one hole head gasket. What had been on it was a two hole. It never occurred to me that the glow plug length could be an issue. I want to get a compression gauge and check it out. Another thing is on top of everything is that my colts cam has a higher lift than the stocker! Still open for suggestions.

I'd imagine that the glow plug protrudes into the cylinder where the swirl chamber is on the piston.

Protrusion for a 1 notch is max 0.039 in. A 1 notch gasket is 1.55mm (0.061 in).
.061 - .039 = 0.022 in (0.56mm)

Half a mm clearance between the piston crown and the cylinder head.
I'm pretty sure the glow plug sticks out of the head by more than half a mm, so the glow plugs would surely be smashed up, if they weren't in the swirl chamber.
Also if your block was decked I'd assume the protrusion would be higher not lower, the deck is moved down relative to the tops of the pistons, so a thicker HG would be needed. But, the bearings were all changed as well which would change stuff.

jackfolstam said:

I'd imagine that the glow plug protrudes into the cylinder where the swirl chamber is on the piston.

Protrusion for a 1 notch is max 0.039 in. A 1 notch gasket is 1.55mm (0.061 in).
.061 - .039 = 0.022 in (0.56mm)

Half a mm clearance between the piston crown and the cylinder head.
I'm pretty sure the glow plug sticks out of the head by more than half a mm, so the glow plugs would surely be smashed up, if they weren't in the swirl chamber.
Also if your block was decked I'd assume the protrusion would be higher not lower, the deck is moved down relative to the tops of the pistons, so a thicker HG would be needed. But, the bearings were all changed as well which would change stuff.

Click to expand...

I agree the head gasket should be thicker.

If none of the rods are bent then I would think all of the glow plugs should be bent.

Replacing the bearing alone shouldn't raise or lower the piston protrusion.
The mains should spin at the same location.
If the rod journals weren't cut they will still be at the same offset from the center of the crank.

If the crank was cut incorrectly it could throw things out.

I replaced the injector gaskets and checked physical cam timing, no change. I swapped the bent glow plugs with the straight ones and it didn't bend them, so i don't why those where bent, maybe they got dropped. I just ran it for a while, but just today i noticed some of the injectors where seeping fuel up around them, so i talked to Kerma and them wanted them back to check them out. I'll wait and see.

I've traced this prob to something mechanical. I think it's piston slap. I pulled the head and measured the bores. The clearance is supposed to be .00157 and they're .002 to .0025 over that which means they're double what their supposed to be. Could this amount be making the noise?

Yes it would, slapping pistons can knock like that.

Hi, guys. I got a used block and was planning to have it bored to exact tolerance, but after waiting a year for on the machine shop and the money, I decided to buy a used engine and put my rebuilt head on it. I did that and the only things I swapped from the old setup were the head, cam, injectors, oil pump, turbo. The only parts that i used from the used engine that I bought where the short block and IP.

At first after I got it on the road, i thought it was fixed, but the more I drove it the more i noticed the knock was still there. I had noticed that when I took the head off back about a year ago, that the fuel injectors where not hitting the piston swirl bowl correctly. I wonder if it is a fuel injector issue. The noise is most noticeable at idle, and low engine speeds. The noise is also still there, howbeit a lot more faint, when the engine is coasting. Has anyone else had trouble with Sprint 520 that were supposed to be mounted and balanced by Kerma?
At this point I'm just driving it, because it doesn't seem to be anything mechanical.

Do you have stock never opened or messed with injectors you could try?