Crankshaft Wont Reach TDC In Either Direction
03-23-2017, 04:49 PM
#1
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Crankshaft Wont Reach TDC In Either Direction
Hi guys, I have a 2001 A8 that I was attempting to change the timing belt on using a FIT guide found here on the forum.
I used the camshaft locking pin and crank locking bar as described in the thread and removed both once the replacement was done. At this point it was time to give the engine the recommended two full rotations but the engine stoped turning about 45 degrees before TDC.
I removed the belt to attempt moving crank independently and it will not reach TDC in either direction, at this point I have the cams at TDC using the locking bar but the cam stops short of TDC in both directions. I attempted to move the cams in all types of directions at this point, trying to find a position that would allow the crank to reach TDC but it just not reaching it.
Do you guys have any ideas on what the problem could be?
I used the camshaft locking pin and crank locking bar as described in the thread and removed both once the replacement was done. At this point it was time to give the engine the recommended two full rotations but the engine stoped turning about 45 degrees before TDC.
I removed the belt to attempt moving crank independently and it will not reach TDC in either direction, at this point I have the cams at TDC using the locking bar but the cam stops short of TDC in both directions. I attempted to move the cams in all types of directions at this point, trying to find a position that would allow the crank to reach TDC but it just not reaching it.
Do you guys have any ideas on what the problem could be?
03-23-2017, 07:03 PM
#2
AudiWorld Senior Member
Just a little more info...
The engine was running fine before you took it apart for maintenance?
After securing the cams, did you loosen the big bolts on the front of the camshafts and pop the pulley's free? If so, did you remember to tighten them? If you forgot, then the crank and cams are no longer in time with each other. That's a problem. The nose of the cams and the cam pulleys meet at a smooth tapered press fit for adjustment purposes. The crank rotates twice for every one revolution of the camshafts. Lots of people replace the belt without ever disturbing these bolts.
Did you use the plug in the side of the block to lock the crankshaft too?
You may want to remove the cam covers if you haven't already done so. Sometimes the cam pulley marks are bogus, they can lie to you, but the little notch on the end of the camshafts under the cam covers never lie. They are hard to see down in behind the variable intake cam timing adjusters. A flashlight and maybe mark them with a dab of whiteout. Also, you can see if the plastic pads for the cam adjusters are intact.
This is an interference engine meaning you can bend valves if the pistons hit them at speed. That said, if you turn it SLOWLY by hand, the hydraulic lifters may deflate and allow you to get things lined up properly again. You do that at your own risk.
You probably want to remove the spark plugs. If you led a very good life and have good karma coming your way, maybe a leaking fuel injector has filled a cylinder with fuel and the inability to turn the crank to TDC is hydro-lock. Fluid does not compress. Or maybe you had the intake manifold off and some water got in the cylinder head. Crazy idea, but removing the plugs will allow you to clear it. This is really really really unlikely though, but I've had it happen with a V4 motorcycle years ago with a stuck carb float. Regardless, I would remove the spark plugs so when you turn the crankshaft by hand, you won't be fighting against the engine's compression. Also you won't have to guess if any resistance you encounter while turning the engine is compression or a piston bumping into a valve.
Frustrating, but patience is your friend. I ran into a similar situation a few years back, panicked, pulled the cylinder heads and found no damage, but LOTS of carbon...so cleaned it, lapped in the valves and replaced the valve stem seals, head gaskets, head bolts, every seal within reach, etc etc... Totally unnecessary overkill, But I did replace the cam adjuster pads too.
If you think you are totally and irretrievably lost, you could actually remove the camshafts. Crazy? Yes, but it will close ALL of the valves. Then you rotate the crank to TDC. Confirm it with a dipstick in cylinder 5 (front of engine, driver's side). Since the cams are out, replace the 4 adjuster shoes and then reinstall and re-time the camshafts. Very tricky. If you are doing the belt change cookbook style - following all of the steps, but not exactly certain about what is actually going on - then this part would be way over your head for the moment. Just know that if you are totally screwed, this could save your butt.
Let us know how you get on.
After securing the cams, did you loosen the big bolts on the front of the camshafts and pop the pulley's free? If so, did you remember to tighten them? If you forgot, then the crank and cams are no longer in time with each other. That's a problem. The nose of the cams and the cam pulleys meet at a smooth tapered press fit for adjustment purposes. The crank rotates twice for every one revolution of the camshafts. Lots of people replace the belt without ever disturbing these bolts.
Did you use the plug in the side of the block to lock the crankshaft too?
You may want to remove the cam covers if you haven't already done so. Sometimes the cam pulley marks are bogus, they can lie to you, but the little notch on the end of the camshafts under the cam covers never lie. They are hard to see down in behind the variable intake cam timing adjusters. A flashlight and maybe mark them with a dab of whiteout. Also, you can see if the plastic pads for the cam adjusters are intact.
This is an interference engine meaning you can bend valves if the pistons hit them at speed. That said, if you turn it SLOWLY by hand, the hydraulic lifters may deflate and allow you to get things lined up properly again. You do that at your own risk.
You probably want to remove the spark plugs. If you led a very good life and have good karma coming your way, maybe a leaking fuel injector has filled a cylinder with fuel and the inability to turn the crank to TDC is hydro-lock. Fluid does not compress. Or maybe you had the intake manifold off and some water got in the cylinder head. Crazy idea, but removing the plugs will allow you to clear it. This is really really really unlikely though, but I've had it happen with a V4 motorcycle years ago with a stuck carb float. Regardless, I would remove the spark plugs so when you turn the crankshaft by hand, you won't be fighting against the engine's compression. Also you won't have to guess if any resistance you encounter while turning the engine is compression or a piston bumping into a valve.
Frustrating, but patience is your friend. I ran into a similar situation a few years back, panicked, pulled the cylinder heads and found no damage, but LOTS of carbon...so cleaned it, lapped in the valves and replaced the valve stem seals, head gaskets, head bolts, every seal within reach, etc etc... Totally unnecessary overkill, But I did replace the cam adjuster pads too.
If you think you are totally and irretrievably lost, you could actually remove the camshafts. Crazy? Yes, but it will close ALL of the valves. Then you rotate the crank to TDC. Confirm it with a dipstick in cylinder 5 (front of engine, driver's side). Since the cams are out, replace the 4 adjuster shoes and then reinstall and re-time the camshafts. Very tricky. If you are doing the belt change cookbook style - following all of the steps, but not exactly certain about what is actually going on - then this part would be way over your head for the moment. Just know that if you are totally screwed, this could save your butt.
Let us know how you get on.
03-24-2017, 02:51 AM
#3
AudiWorld Super User
Hi guys, I have a 2001 A8 that I was attempting to change the timing belt on using a FIT guide found here on the forum.
I used the camshaft locking pin and crank locking bar as described in the thread and removed both once the replacement was done. At this point it was time to give the engine the recommended two full rotations but the engine stoped turning about 45 degrees before TDC.
I removed the belt to attempt moving crank independently and it will not reach TDC in either direction, at this point I have the cams at TDC using the locking bar but the cam stops short of TDC in both directions. I attempted to move the cams in all types of directions at this point, trying to find a position that would allow the crank to reach TDC but it just not reaching it.
Do you guys have any ideas on what the problem could be?
I used the camshaft locking pin and crank locking bar as described in the thread and removed both once the replacement was done. At this point it was time to give the engine the recommended two full rotations but the engine stoped turning about 45 degrees before TDC.
I removed the belt to attempt moving crank independently and it will not reach TDC in either direction, at this point I have the cams at TDC using the locking bar but the cam stops short of TDC in both directions. I attempted to move the cams in all types of directions at this point, trying to find a position that would allow the crank to reach TDC but it just not reaching it.
Do you guys have any ideas on what the problem could be?
"FIT guide found here on the forum" ??? ...where is that?
The very terminology in your post worries me ... "camshaft locking pin", no. "Crank locking bar", no. Maybe turn this over to a real mechanic before you do any more damage(?).
03-24-2017, 10:04 AM
#4
I removed the belt to attempt moving crank independently and it will not reach TDC in either direction, at this point I have the cams at TDC using the locking bar but the cam stops short of TDC in both directions. I attempted to move the cams in all types of directions at this point, trying to find a position that would allow the crank to reach TDC but it just not reaching it.
....why do I feel like we are being trolled...?
03-24-2017, 10:54 AM
#5
Pull all the plugs out if they are in, and pull the belt. Then if you can easily turn the crank to 45 degrees BTDC or ATDC you should have no piston at TDC (90 degree crossplane crank). Check down the plug holes for pistons near TDC. In this configuration you should be able to rotate the cams over, maybe see if you can get into this condition and then we can talk about retiming the motor from here.
03-25-2017, 08:32 AM
#6
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The engine was running fine before you took it apart for maintenance?
After securing the cams, did you loosen the big bolts on the front of the camshafts and pop the pulley's free? If so, did you remember to tighten them? If you forgot, then the crank and cams are no longer in time with each other. That's a problem. The nose of the cams and the cam pulleys meet at a smooth tapered press fit for adjustment purposes. The crank rotates twice for every one revolution of the camshafts. Lots of people replace the belt without ever disturbing these bolts.
Did you use the plug in the side of the block to lock the crankshaft too?
You may want to remove the cam covers if you haven't already done so. Sometimes the cam pulley marks are bogus, they can lie to you, but the little notch on the end of the camshafts under the cam covers never lie. They are hard to see down in behind the variable intake cam timing adjusters. A flashlight and maybe mark them with a dab of whiteout. Also, you can see if the plastic pads for the cam adjusters are intact.
This is an interference engine meaning you can bend valves if the pistons hit them at speed. That said, if you turn it SLOWLY by hand, the hydraulic lifters may deflate and allow you to get things lined up properly again. You do that at your own risk.
You probably want to remove the spark plugs. If you led a very good life and have good karma coming your way, maybe a leaking fuel injector has filled a cylinder with fuel and the inability to turn the crank to TDC is hydro-lock. Fluid does not compress. Or maybe you had the intake manifold off and some water got in the cylinder head. Crazy idea, but removing the plugs will allow you to clear it. This is really really really unlikely though, but I've had it happen with a V4 motorcycle years ago with a stuck carb float. Regardless, I would remove the spark plugs so when you turn the crankshaft by hand, you won't be fighting against the engine's compression. Also you won't have to guess if any resistance you encounter while turning the engine is compression or a piston bumping into a valve.
Frustrating, but patience is your friend. I ran into a similar situation a few years back, panicked, pulled the cylinder heads and found no damage, but LOTS of carbon...so cleaned it, lapped in the valves and replaced the valve stem seals, head gaskets, head bolts, every seal within reach, etc etc... Totally unnecessary overkill, But I did replace the cam adjuster pads too.
If you think you are totally and irretrievably lost, you could actually remove the camshafts. Crazy? Yes, but it will close ALL of the valves. Then you rotate the crank to TDC. Confirm it with a dipstick in cylinder 5 (front of engine, driver's side). Since the cams are out, replace the 4 adjuster shoes and then reinstall and re-time the camshafts. Very tricky. If you are doing the belt change cookbook style - following all of the steps, but not exactly certain about what is actually going on - then this part would be way over your head for the moment. Just know that if you are totally screwed, this could save your butt.
Let us know how you get on.
After securing the cams, did you loosen the big bolts on the front of the camshafts and pop the pulley's free? If so, did you remember to tighten them? If you forgot, then the crank and cams are no longer in time with each other. That's a problem. The nose of the cams and the cam pulleys meet at a smooth tapered press fit for adjustment purposes. The crank rotates twice for every one revolution of the camshafts. Lots of people replace the belt without ever disturbing these bolts.
Did you use the plug in the side of the block to lock the crankshaft too?
You may want to remove the cam covers if you haven't already done so. Sometimes the cam pulley marks are bogus, they can lie to you, but the little notch on the end of the camshafts under the cam covers never lie. They are hard to see down in behind the variable intake cam timing adjusters. A flashlight and maybe mark them with a dab of whiteout. Also, you can see if the plastic pads for the cam adjusters are intact.
This is an interference engine meaning you can bend valves if the pistons hit them at speed. That said, if you turn it SLOWLY by hand, the hydraulic lifters may deflate and allow you to get things lined up properly again. You do that at your own risk.
You probably want to remove the spark plugs. If you led a very good life and have good karma coming your way, maybe a leaking fuel injector has filled a cylinder with fuel and the inability to turn the crank to TDC is hydro-lock. Fluid does not compress. Or maybe you had the intake manifold off and some water got in the cylinder head. Crazy idea, but removing the plugs will allow you to clear it. This is really really really unlikely though, but I've had it happen with a V4 motorcycle years ago with a stuck carb float. Regardless, I would remove the spark plugs so when you turn the crankshaft by hand, you won't be fighting against the engine's compression. Also you won't have to guess if any resistance you encounter while turning the engine is compression or a piston bumping into a valve.
Frustrating, but patience is your friend. I ran into a similar situation a few years back, panicked, pulled the cylinder heads and found no damage, but LOTS of carbon...so cleaned it, lapped in the valves and replaced the valve stem seals, head gaskets, head bolts, every seal within reach, etc etc... Totally unnecessary overkill, But I did replace the cam adjuster pads too.
If you think you are totally and irretrievably lost, you could actually remove the camshafts. Crazy? Yes, but it will close ALL of the valves. Then you rotate the crank to TDC. Confirm it with a dipstick in cylinder 5 (front of engine, driver's side). Since the cams are out, replace the 4 adjuster shoes and then reinstall and re-time the camshafts. Very tricky. If you are doing the belt change cookbook style - following all of the steps, but not exactly certain about what is actually going on - then this part would be way over your head for the moment. Just know that if you are totally screwed, this could save your butt.
Let us know how you get on.
Yes I removed the plug and inserted the locking bolt.
Yes I used the cam locking bar
Yes I loosened the cam bolts
NO I DID not pop the cam puppies loose after loosening the bolts and it seems that this was my error.
At this point my timing is off and I would like to correct it without pulling the cam covers if possible.
03-25-2017, 08:41 AM
#7
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No I'm not a mechanic by trade but with the right tools and instructions there's usually not much that I can't accomplish. Yes I make mistakes, I'm human. All I'm looking for is help from more experienced guys like yourself to correct my mistake.
Thanks!
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03-25-2017, 08:49 AM
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Thanks
03-25-2017, 10:13 AM
#9
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Pull all the plugs out if they are in, and pull the belt. Then if you can easily turn the crank to 45 degrees BTDC or ATDC you should have no piston at TDC (90 degree crossplane crank). Check down the plug holes for pistons near TDC. In this configuration you should be able to rotate the cams over, maybe see if you can get into this condition and then we can talk about retiming the motor from here.
Thanks!
03-25-2017, 12:28 PM
#10
AudiWorld Senior Member
Don't forget to pull the spark plugs...
...remove the plugs so you know that any resistance you encounter is not compression. Also, you might want to remove the cam covers. The cam cogs don't tell you much. Do you have marks on the cam pulleys that your are certain indicate they are in the right position. If not, pull the cam covers.
