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AZTechBrian
AZTechBrian, ASE Certified Technician
Category: BMW
Satisfied Customers: 708
Experience:  Owner
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2007 BMW 550 - Engine will only rotate +/- 45 degrees from

Customer Question

2007 BMW 550 - Engine will only rotate +/- 45 degrees from TDC I have owned this car for six years with minimal problems. This car has 155,000 miles on it and has been burning oil. I took it to the dealer who confirmed valve stem seal needed to be replaced
and it would cost $8-12K. I decided to complete this project myself with the engine still in the car. The good news is that I have removed the valve covers, timing chain covers, removed the alternator, purchased the timing tools, locked the flywheel at TDC,
replaced the valve stem seals. Before installing the camshafts, I decided to try and rotate the engine since this is required for the timing of the camshafts. The bad news is that the engine will only rotate +/- 45 degrees from TDC. The engine seems to get
stuck at cylinder number 5 TDC and cylinder number 2 TDC. The valves are all seated so that they should not be getting in the way. I do not thing that anything is impeding the pistons since the car ran well before I started this procedure. I do not see anything
external impeding the crankshaft. Please let me know the specific list of items that I need to check. Thanks in advance for your help.
Submitted: 1 year ago.
Category: BMW
Expert:  K. Wiggins replied 1 year ago.

Hello, if the cams are not in and all valves are seated the compression from the pistons has no where to go so to speak. If you remove the spark plugs it should then rotate.

Customer: replied 1 year ago.
Hello K. Wiggins,Thanks for your response. I failed to mention that the spark plugs were removed. Please let me know your other ideas.Best Regards,Mike
Expert:  K. Wiggins replied 1 year ago.

I'll open this back up to other experts. With plugs out and valves up I'm stumped to be honest.

Expert:  AZTechBrian replied 1 year ago.

Hello. How did you keep the valves seated in order to remove the springs to replace the seals? compressed air?

I am reasonably certain that something has either fallen in one of the cylinders, or something is catching up on the flex plate. Can you insert a bore scope in each cylinder and just make sure there is nothing there? Please let me know what you find with your inspection.

Expert:  AZTechBrian replied 1 year ago.

If I don't reply right away, I will asap. Thanks!

Customer: replied 1 year ago.
Hello,Thanks for your quick response. You are correct. I used compressed air to keep the valve seated when I was using the spring compressor.I had a problem rotating the engine prior to changing the valve stem seals, I have not lost any parts and did not find any parts in the cylinders.I have not checked the flex plate. How should I do that and are there any other items that I should check?ThanksMike
Expert:  AZTechBrian replied 1 year ago.

the part that the starter engages to turn the engine is the flex plate. the torque converter is bolted to it. Try looking at that to see if something is catching back there.

Since you have no accessories attached, or even a timing chain, the only part outside the engine that's turning that you could check would be the flex plate and torque converter. If those check out fine, and definitely nothing in any of the cylinders then the problem has to be internal.

You say that you had a problem turning the engine before doing the valve stem job?

Customer: replied 1 year ago.
Thanks for your additional thoughts. I will check on the flex plate next week.Yes, I had a problem turning the engine while I was removing the valve stem seals. Is there any significance that I can only rotate it +/- 45 degrees from TDC. I would have thought that it would stick/hang-up in one direction but not both directions. Could the timing chain be caught up on something?
Expert:  AZTechBrian replied 1 year ago.

Is there any way anything could have gotten into the timing cover?

Customer: replied 1 year ago.
The only thing that fell in is small plastic parts from the gasket and valve cover gasket bolts. Could these small plastic pieces be part of the problem?
Expert:  AZTechBrian replied 1 year ago.

you had valve cover gasket bolts fall in? That could definitely cause problems

Customer: replied 1 year ago.
I did not have valve cover bolts fall in. The BMW's have a known problem when the gaskets become brittle and break apart. Thus, small pieces of the gasket may fall into the engine. I have drained the oil to remove the plastic components before I start the engine. I did not know if these small gasket pieces would get into the chain.
Expert:  AZTechBrian replied 1 year ago.

I would think that gasket material stuck between your chain and crank gear would cause it to bind up, but am not sure if that's what's happening. Do you have a camera you could look in there with? The same camera used to look in the cylinders would be perfect

Customer: replied 1 year ago.
I will use the camera to check next week. Thanks for the ideas.
Expert:  AZTechBrian replied 1 year ago.

your welcome. you'll find it. something has to be caught up either in the chain or in a cylinder somewhere. Just a matter if finding it.

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