roco16

Okay, so I finish my 4th oil pan gasket, do the oil cooler seals, koni conversion, control arms, ps rack, etc... I put the 951 back together after it sitting 5 weeks or so, and get this horrific knocking sound:

Wav file (1.2mb):
Sickening Knocking
http://www.geocities.com/roco1669/roco16.wav
Quicktime MOV (poor sound, 450kb)
Movie
http://www.geocities.com/roco1669/roco16.mov

(you may have to copy+paste into your browser window, a Geocities thing)

When the car was first started, it was fine for about 3 sec or so, then intermittent knocking, then constant knocking. Since then, the knocking has paused only momentarily if I blip the throttle (as heard in the sound file). The noise is definitely coming from the top of the motor, not the pan. It sounds roughly from the 2-3 intake runner.

So, after reading 30 or so posts in the archives about similar noises, these are the brainstormed possibilities:

1. Rod Bearings (unlikely, changed them 6k ago)
2. Dry Lifters
3. Pre-ignition, 'detonation' or 'knock'
4. Something fallen into the engine during reassembly
5. Wrist pin slop
6. Fuel Pressure/Injector problem

And here's what I have checked out as being a-ok by me:
-Timing. The car is in time, no problem
-Distributor/rotor. I increased my likelihood of arthritis again in taking that assembly apart. All was normal, tight...
-Oil pressure. Steady 4.5 bar at ~cold idle
-Compression. Quasi normal for my car: 133, 135, 130, 130
-Mechanical binding. Turned the motor over by hand, no problem
-Drained the oil. ZERO metal flakes
-Opened the camhousing holes and dripped ATF on the lifters/followers and cam lobes, no change
-Injectors are firing. Pulled the fuel rail and turned the car over to confirm all injectors are firing, and about the same

Any help is appreciated.
-Robert

dgz924s

No sense diagnosing that! Only answer is tear it down, But to me it is the rod, wrist pin perhaps. Could be pick up tube. No easy fix here so dig in!

Jason_86_951

Ahhhgg the horror.
Sounds like a broken or siezed lifter. I'm just guessing though.
I wish you luck on a speedy and cheap repair.

NeedPorscheSpeed

I'm sorry you are having trouble, Roco. My '86 Turbo is also knocking quite loudly, and it is emanating from the head. I tried to download your files, but your bandwidth has been temporarily exceeded. I'll try again later.

cruise98

Robert:

Use a mechanics stethoscope or even a long screwdriver to try and pinpoint the location of the noise. It could be a collapsed lifter, wrist pin, piston, or something else. Compression seems even enough.

roco16

Thanks guys,

Alternate URLs for the movie and sound file:

http://www.geocities.com/roco16669/roco16.mov
http://www.geocities.com/roco16669/roco16.wav

Copy+Paste them into your address bar if they come up w/ the 404 Error (dont ask why).

Other thoughts:
Would cylinder compression vary if a lifter is siezed/ collapsed?

Cruise- I tried the stethoscope test with a long 1/2" breaker bar... I couldnt make much of it, other than center camhousing/head.

I'm going to take off the intake manifold tonight and verify the intake valves are opening/closing ok, as well as run some cleaner through the injectors. If no change, the I guess I have to pull the cam housing and check for bad lifters.

Cwigg666 - That means I'm going to need our timing tool back to re-install everything...-thx

Thanks for everything guys,

-Robert

cwigg66

You got it bro! What time are you going to be doing it tonight... think I'll deliver the tool myself and help you get on the road with the Pcar

Jeremy Himsel

I had the same noise happen to my turbo after letting it sit a few weeks. Really bad knock. I was able to isolate to the #4 exhaust valve lifter. Anyway, from sitting, it just bled down and couldn't regain pressure while running. I pulled the DME relay and cranked over the motor until I had good oil pressure (15 to 20 sec.). The lifter pumped back up and was fine. 8 months later all is well. Give it a shot.

roco16

Jeremy-
I read what had happened to your car in one of the archives. I really hope what is happening to me is from the same cause, but since reassembly the car has run a total of about 3-4 minutes, and maybe 40+ sec or so from starter only (compression testing)... all of this to no effect. I also have good oil pressure from the get-go. Did you ever replace the lifter? Was there any damage to it or the cam?

Chris-
I get off work around 6-7ish. Will be pulling the cam housing tonight, so if you want to stop by anytime after 7, that's awesome. Pretty heart-breaking noise, eh?

cwigg66

Man I think you car is possessed with the devil.

Peckster

I would at least pull the cam tower to see what's up. Sounds like a lifter should have pumped up by now.

Jeremy Himsel

[QUOTE=roco16]Jeremy-
I read what had happened to your car in one of the archives. I really hope what is happening to me is from the same cause, but since reassembly the car has run a total of about 3-4 minutes, and maybe 40+ sec or so from starter only (compression testing)... all of this to no effect. I also have good oil pressure from the get-go. Did you ever replace the lifter? Was there any damage to it or the cam?


Roco,

I ran mine several times for about 20 minutes tracking down the problem. Perfect oil pressure, just a solid knocking sound. Once I determined it wasn't a rod knock, I wasn't concerned with running it. I never had to replace the lifter or remove the cam tower. All it took was a good turn over cycle to get the oil pressure up through the motor. Once I saw good oil pressure on my gauge while cranking, I went another 10 seconds or so. Once I started the car the knock was gone. All is well now. Let us know how it works out.

Chris_924s

My heart just dropped when I hear the wavfile.. I just hope it's a simple oil pressure problem.

I wouldnt wish that noise on anyone.

adrial

I think pulling the cam tower is a good idea.

The following is just a datapoint...

I started up the car for the first time after the rebuild and tried to hold it to around 2000rpm...valvetrain was real noisy.

I shut the car off after it warmed up, later in the day I started it up and took it for a drive...lifters were quiet as soon as the car started. It didnt take very long for it to catch. The engine had 2 bar oil pressure prior to starting the first time.

JimV8

It could be something as stupid as a failed exhaust manifod gasket. My jeep broke an exhaust maniford stud and it makes a hell of a mechanical racket. I was told by various experts that it was piston slap, broken oil pump, rod bearings, then I took a close look...