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I am attempting to remove the bolt that holds the crankshaft pulley. However, even with a long bar, the car in sixth gear and the brake on, it was not possible to undo the bolt. I found online that another way to loosen the bolt is to rest the bar against a part of the chassis and then turn the engine over. However, having tried this, the starter motor didn't have enough power to loosen the bolt.

I have been thinking of another way to loosen the bolt, and I have thought of my own method. I can't find any information about such a method online, so I am looking for some advice about whether this method would work.

My proposed method is to take the car to a small hill and place the bar against a part of the chassis. Then, with the engine off, press the clutch and then once the car is barely moving (1mph or less), lift the clutch up to crank the engine over, with the hope being that this can exert a little more torque than the starter motor on the bolt.

My main worry with this method though is that it may cause damage to another component. Other than the obvious risk of damage (shearing the bolt and/or damaging a part of the bar), would this method pose any more of a risk to another part of the car/engine than the cranking over method?

PhysicsGuy123
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  • Welcome to Motor Vehicle Maintenance & Repair! What is the year/make/model/engine of the vehicle you're working on? There are different methods of removing different crankshaft pulley bolts, so having this information will be of great help in helping you. – Pᴀᴜʟsᴛᴇʀ2 May 29 '19 at 11:51
  • A sharp shock load can break the crankshaft, and before you ask, yes I have seen it done. Many other questions about this on here - have a search... this is but one : https://mechanics.stackexchange.com/q/27253/10976 – Solar Mike May 29 '19 at 11:58
  • You have made a close inspection to make sure that someone has not welded the bolt into place... – Solar Mike May 29 '19 at 12:14
  • @SolarMike, the bolt certainly isn't welded in place. How much of a shock load would generally be needed to break the crankshaft - would even cranking it over on the starter motor have the power to do this? My assumption was that my method would be slow enough that the force put on the engine's components would be comparable to stalling the engine, but obviously I wanted to ask on here first in case this assumption was incorrect, as I don't want to damage something else while trying to fix this. – PhysicsGuy123 May 29 '19 at 13:18
  • @Pᴀᴜʟsᴛᴇʀ2, it is a BMW 1 series, 120d. – PhysicsGuy123 May 29 '19 at 13:18
  • It is not the magnitude of a shock load that is the issue - it is the peak duration... – Solar Mike May 29 '19 at 13:32
  • @SolarMike - Okay. So is this why people would suggest using the starter motor to loosen the bolt, but not my method? – PhysicsGuy123 May 29 '19 at 14:53
  • I always found a 3' bar and a locked flywheel sufficient... Mind you I am known amongst my friends for being able to break stuck fasteners... – Solar Mike May 29 '19 at 14:57
  • @SolarMike, could I just ask one final thing regarding the risk of damaging the crankshaft. Am I incorrect in assuming that the bar drive would break before the crankshaft, as surely this would be the weakest point? – PhysicsGuy123 May 30 '19 at 17:05
  • You've tried the usual penetrants? Heat it up with MAPP gas? – Huesmann Jun 03 '19 at 19:37

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Use an impact gun to remove the bolts. If one isn't available, take a look at the ring-gear for the starter motor attached to the fly-wheel at the bellhousing end of the engine and see if you can wedge something in there. In the past I've had success with a large flat-blade screwdriver tight against the ring-gear to stop the engine turning at the flywheel end.

Please don't explore the method you've described any further. There are too many risks. What if the wrench jams and stops the engine from turning whilst the car is building momentum down the hill? What if the method works and you find yourself at the bottom of a hill with a partially disassembled engine? What if the shock causes your timing belt to jump a tooth with the engine still turning?

I bought a very inexpensive electric impact gun from amazon. If you don't have one and don't want the expense of buying one, approach local garages / vehicle owners clubs / tool hire places and see if you can beg / borrow / hire one.

My father always says "The right tool for the right job" and this feels like an instance where this advice is sage.

Good luck.

Steve Matthews
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  • Yes, this was another plan, but the problem with this is that the access to the bolt is very small, so an impact gun would not work without taking several components off of the front of the car, and obviously this just adds to the complexity of the job. I was hoping to find an alternative which allows me to remove it without doing all of this, but it seems that the alternative methods are dwindling, hence why I am looking at the option I mentioned. – PhysicsGuy123 May 29 '19 at 13:14
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    You can put a wobble bar on an impact gun. – Steve Matthews May 29 '19 at 14:50
  • Thanks for the suggestion. How would this work with the hammer action - would this not mean the hammer action is not in the direction of the bolt? Could this risk shearing the bolt at all? – PhysicsGuy123 May 29 '19 at 14:55
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    It'll be fine, I've done this plenty of times for hard to reach bolts. – Steve Matthews May 29 '19 at 15:05