bebbetufs

The minute I started up my rebuilt engine there was a distinct knocking sound. I did not notice at the time because I was too preoccupied checking for oil pressure, leaks, etc. After breaking the engine in (hard) and driving about 40km I noticed the sound and reviewed the startup video.

The knocking has been present since startup. It seems to have remained the same. In the stethoscope it was clearly loudest in the middle of the pan, directly beneath #2 cylinder.

I now have the pan off the engine but so far I haven't identified any faults. There is some metal dust in the bottom of the pan, but I assume that is normal considering the engine is still undergoing break in (I changed the oil after 30kms). There are no pieces of metal and all the rods seem the same as far as I can tell, although I still need to remove my DIY windage tray to say for sure.

If any of the bearings are bad should I be able to identify which by shaking/moving the big end, or do I have to remove the caps to make sure?

V2Rocket

I hope you cranked it over a few times (30-40 seconds worth) with the coil unplugged to build oil pressure before firing it up the first time.

Rod knock is a pretty distinct noise but if the bearings are still in ok shape it should go away almost immediately (1-2 seconds until there is oil pressure), not after 40km.

bebbetufs

I used Red Line assembly paste. Freshly polished cranck, rods, and align-honed block. Rod clearances are around 0.043mm. on all 4 rods.

I had 5 bar oil pressure before startup. I packed the pump with petroleum gelly and primed the oil galleries via the oil filter bracket. I also filled the oil cooler before cranking. Pressure built quickly, but I then had startup problems for three days until I found the KLR to be bad. I minimized cranking as much as possible during troubleshooting.

I'm confident I did everything one could do to build pressure as quickly as possible given the circumstances.

I still don't know if the sound is from a bearing or not. It could be from my DIY scraper/ tray combo, but so far I cant see any signs of contact. Cylinder walls look fine.

Here's the video my mate took immediately after firing up the engine for the first time. The video exaggerates the noise. I could not hear the noise from inside the cockpit, and I did not notice it while bleeding the cooling system, nor during the breaking-in drive or the safety stops I did to check oil level and coolant levels. The noise was not commented by the local dealer when they did the MOT and it remains the same after 40kms. Still, I'm not running the engine like this.

The main question remains if I should be able to identify a bad bearing by feel, or if the cap has to come off?

Auto_Werks 3.6

if you can identify by feel its going to be so hosed that you're essentially done. probably going to have to pull the caps, and i guess that means you need new nuts. if you already have the pan down, i would go ahead and pull the caps.

bebbetufs

Thank you.
I'll go ahead and pull the caps tomorrow. Thankfully the Wossner rods have reusable bolts. However, if a bearing is bad already I'm not going to be able to trust this engine. I built this for track use and I need to know it will hold up. I will have to pull the engine and disassemble it to find the cause of the failure.

Interesting that you can have knocking and not being able to feel it. Even at 0.092 there should be no knocking as this is the max clearance/wear allowed by Porsche. I would expect clearances above that to be easily felt. Is it the oil film which makes it so difficult to feel any movement, or is the problem that all of them will have movment so there is no way of knowing a bad rod bearing from a good one?

Tiger03447

Here's hoping that the rod bearings all look great and that this issue is soon put to rest. :>))!
Fingers crossed for you.

Jay Wellwood

Exactly what I'm thinking. Any 'play' in the connecting rod attachment to the journal that can be 'felt' would indicate clearances are well beyond allowable.

bebbetufs

Thanks everyone.

I can't feel anything from any of the rods. I started by removing the cap of #2. Apart from one tiny scratch the bearing is pristine and so is the journal. I cannot feel any slop in the wrist pin either. I'm starting to lean towards windage tray/scrapers, but there are no tell tale signs on them.

I'm on my way to pull the rest of the caps now.

topley

I'm curious if you ever found the problem with this. Any resolution? BTW did you ever do the "disconnect a spark plug" test to see which cylinder it was?
Jay

bebbetufs

Thanks for asking.
No, I gave up and packed up the car for the season. I will revisit the problem if I can find some motivation. I am still at a loss as to what is causing this, even after this long thread in the NA forum.

JustinPSI

Valvetrain noises can mimic rod knocks..as well as loose/bad flywheel/flexplate hardware or the units themselves. Heard a few faulty dual-mass flywheels sound just like some I-beams smacking around

bebbetufs

Thanks for chipping in.

Listening with the stethoscope the noice is definitely from the bottom end. It is not the crank itself, it is silent. It is not the auxilliary equipment as the noise is there with all the belts, except the timing belt, removed. The bellhousing area as well as the block around the RMS is silent. The noise is loudest on the flat part of the oil pan, directly above the x-member, between cylinder 1-2. at about 30degrees cw from BDC.

The intensity increases when the engine warms. Removing plug leads makes no difference. The noise frequency is double the crank speed.

If anyone would like to try to help please lead the very detailed description in the other thread.