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Wo ist die Rennstrecke?
 
DonE's Avatar
 
Join Date: Mar 2004
Location: Brooks, GA
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Nope

I have a stethescope and listened to the lower valve covers (sounds normal) and the uppers (both sides have a slight tic, drivers side more than pax side). I listened to the cam chain covers and they were real quiet. I listened to the case - very quiet. I pulled the covers and started the motor to confirm lots of oil from the spray bars. I checked the timing of each cam in case valve touching piston - no problem. I checked the valve lash (again) and no problem. I checked side to side play on rockers and all within spec. The car runs great except for the tic sound. I am completely stumped.

Old 10-03-2008, 07:31 PM
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The scavenge pump is on the drivers side. Is it perhaps making excessive noise?

EDIT: OOPS, just read back through this and noticd that GJF mentioned it in post number 7.
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Last edited by sand_man; 10-04-2008 at 12:16 PM..
Old 10-04-2008, 02:24 AM
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Sand_man's idea is good but the scavenge pump is a rotary gear pump and should not produce a "tic" sound.

I would do a compression test on the offending side, it is very easy to do. Remove the coil wire. Pull all the plugs on the driver's side and turn the engine over for 10 seconds with the gauge hose in each successive spark plug hole.

If the pressures are all within +/- 5 PSI, then you almost have to do a tear down to learn the source of the unusual sound.
If one of the cylinders is low, then you may have a partially stuck (bent? dirty?) valve. Then a leakdown test will point to the intake or exhaust.

As an alternative to mechanical investigation, try Sea-Foam or Berryman's fuel system cleaner. It costs about $5 and after a half a tank of gas, you would know if it is deposit related. As a bonus, it would clean all the gook out of your fuel system. And you are about to dump your oil anyway...

Good Luck,
Mark
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Last edited by lucittm; 10-26-2008 at 06:19 PM..
Old 10-04-2008, 05:45 AM
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DonE,
Correct me if I'm wrong, but the sounds appears after the engine is up to temp or after short driving period? It is quiet when the engine is cold? You said the sound it makes is like a "card in the spokes" after you have driven it?
If rocker arms and lobes look normal, then it's got to be an exhaust leak....header flange gasket, header weld cracked, turbo flange gasket(s), wastegate flange gasket, cracked ceramic on spark plug, or.......busted head stud? But you did state your compression was good.
I'm also assuming the sound is the same whether the clutch is in or out.
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'85 930 Factory Special Wishes Flachbau
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Old 10-04-2008, 11:20 AM
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To test for possible exhaust leak:

Use a lift and raise the car with engine running. Find a rubber hose and put one end into your ear and poke with other end around exhaust flanges. If you have a leak, you'll be able to hear it.

If car starts ticking when hot, it might be an exhaust crack which expands when hot.

It can also be a loose rocker.
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Old 10-04-2008, 02:24 PM
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Wo ist die Rennstrecke?
 
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Quote:
Originally Posted by WERK-I View Post
DonE,
Correct me if I'm wrong, but the sounds appears after the engine is up to temp or after short driving period? It is quiet when the engine is cold? You said the sound it makes is like a "card in the spokes" after you have driven it?
If rocker arms and lobes look normal, then it's got to be an exhaust leak....header flange gasket, header weld cracked, turbo flange gasket(s), wastegate flange gasket, cracked ceramic on spark plug, or.......busted head stud? But you did state your compression was good.
I'm also assuming the sound is the same whether the clutch is in or out.
You are correct on your assumptions. With the ticking, it sounds like one cylinder. When I place the stethescope on the valve cover, I can hear a metallic ticking. I assume that if it were exhaust related, I would not be able to hear the ticking through the valve cover.

This sprang up, from literally over-night, when I replaced the cam sprocket and cam chain idler sprocket. I had to time the cams, but that was it.

I placed the stethescope on the aftermarket turbo sump pump and it was dead quiet while running. If I had to bet, I would say that the sound seems to be coming from the intake side of cylinder #3. Also, I checked all head stud torque. I can not find any exhaust discoloration on anything either (header primary, spark plug, exhaust gasket, etc).

Goran - loose rocker, how? The lash is set properly, the rocker has little or no side to side play, the rocker shaft is in place and solid. Did I miss something?

It has to be something in the valve train for the #3 cylinder. It's dead silent for the first 30 seconds, then you can hear the tick. At idle, you have a very difficult time hearing it. At 2000 rpm, you can hear it if you know what to listen for. The hotter the engine, the less pronounced the tick. There is lots of oil from the spray bars too.
Old 10-04-2008, 10:01 PM
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What about the heat deflectors between the cylinders? Are they tight? I think you've covered everything...
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Old 10-04-2008, 11:21 PM
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DonE,
Wow, this is baffling! If it were a out-of-spec valve lash adjustment, the tick would get louder when the engine warms up since lash grows with temperature. It does sound like you isolated the area, that's the good news. What's that leave? Bad valve, valve guide, busted inner or outer valve spring.....I still lean towards a pin hole leak on the exhaust, but that's just me.
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'85 930 Factory Special Wishes Flachbau
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Old 10-05-2008, 06:58 AM
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Quote:
Originally Posted by DonE View Post

Goran - loose rocker, how? The lash is set properly, the rocker has little or no side to side play, the rocker shaft is in place and solid. Did I miss something?

It has to be something in the valve train for the #3 cylinder. It's dead silent for the first 30 seconds, then you can hear the tick. At idle, you have a very difficult time hearing it. At 2000 rpm, you can hear it if you know what to listen for. The hotter the engine, the less pronounced the tick. There is lots of oil from the spray bars too.
OK, I assume that you already inspected the rockers. Did you have a chance to inspect valve guides as well?

If this happened overnight and was triggered by tensioner job (with cam timing redone) I would say that issue probably lays within valvetrain. It would be good if you could isolate the cylinder. Then you could remove the valve cover and check for valve guide wear and wear on tappets and rocker shafts.

When you timed the cams, did you turned the engine by hand (with plugs removed) to check for valve/piston interference?


So far, I believe you could narrow the source to few things:

1. Small exhaust leak which expands/tightens with heat
2. Rocker/shaft issue, maybe it starts wandering when it heats up or shaft is pitted?
3. Slightly bent valve due to collision with piston. (timing job)
4. Excessive valve guide wear.

It's really a puzzling problem.
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Old 10-05-2008, 09:43 AM
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You can isolate it from being an exhaust leak by pulling spark from one cylinder at a time while motor is running. If it's a small leak when the spark goes dead, so will the leak noise. Motor will run tad rough for a few seconds but it'll help yay or nay an exhaust leak.
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Old 10-05-2008, 11:15 AM
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Quote:
Originally Posted by BoxxerSix View Post
You can isolate it from being an exhaust leak by pulling spark from one cylinder at a time while motor is running. If it's a small leak when the spark goes dead, so will the leak noise. Motor will run tad rough for a few seconds but it'll help yay or nay an exhaust leak.
That's a good idea. It will also detect a worn rod bearing or loose piston tap if that is a cause of tick.
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Old 10-05-2008, 01:33 PM
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Wo ist die Rennstrecke?
 
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Thanks Adam - good suggestion.

Goran - yes, I timed the cams and turned the crank by hand.

Would an exhaust leak have such a pronounced tic through the upper valve cover?

Anyway, I'll pull the plug wires and see if it changes the noise.
Old 10-05-2008, 04:20 PM
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Quote:
Originally Posted by DonE View Post
Thanks Adam - good suggestion.


Would an exhaust leak have such a pronounced tic through the upper valve cover?

It could yes, if it were coming from a bad sealing surface between the head and cylinder. Sometimes exhaust leak locations can be deceiving as the sound tends to travel and throw your ears off. At least it does with my ears
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Old 10-05-2008, 04:36 PM
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DonE,
Any word on your "tick"?
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'85 930 Factory Special Wishes Flachbau
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Old 10-26-2008, 10:38 AM
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Wo ist die Rennstrecke?
 
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Nope.

I've decided to disassemble the left side valve train - the cam chain pulleys, tensioner, all rockers. I'm also going to remove the plugs. Then I'll re-time the cams, adjust the valve lash and put everything back together, hoping I fixed it somehow.
Old 10-26-2008, 06:09 PM
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Don,
When you get it back together I want a ride in that beast at the track!
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Old 10-26-2008, 06:19 PM
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Quote:
Originally Posted by DonE View Post
Nope.

I've decided to disassemble the left side valve train - the cam chain pulleys, tensioner, all rockers. I'm also going to remove the plugs. Then I'll re-time the cams, adjust the valve lash and put everything back together, hoping I fixed it somehow.
Don,
Sorry to hear that. I have one other idea.... check your valve guides. A bad guide will give that annoying tic as well. You don't have to remove your heads to do so, but the springs and retainers have to be removed by pressurizing the cylinder and using a special clamp to remove them. Good luck to you sir.
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'85 930 Factory Special Wishes Flachbau
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Old 10-27-2008, 08:17 AM
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Don,
Before you pull it apart again you could try one more thing with stethescope.
I managed to isolate a very similar hard to find noise with a screw driver to ear.
Try placing scope on each cylinder and see if noise is in the bore.
I found a slightly loose wrist pin on my SC this way. Once found I could actually feel a very slight tap on the screw driver.
Same symptoms as you describe - and nothing on cold engine.
Broken valve spring?
Alan
Old 10-28-2008, 01:07 PM
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Wo ist die Rennstrecke?
 
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Found it. The number three cylinder, exhaust valve guide. I can move the valve stem side to side with a screwdriver. It's probably less than a mm, but there is definite movement compared to all the others (no movement, absolutely none).

I guess its time for another engine drop. If I didn't drop the engine at least once per year, I just wouldn't feel right....
Old 11-02-2008, 07:50 AM
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Altho it may be worn, and worth replacing, I'm not sure that would cause a knocking noise.
How did you isolate it?
I just query it because would hate to see you put engine back in and still find noise there.
What makes you certain this is the source?
Alan

Old 11-02-2008, 09:26 AM
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