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Murrmayde
New User
Dec 20, 2015, 5:42 PM
Post #1 of 8
(1798 views)
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Broken Crankshaft
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Can a faulty or improperly installed cam and/or crank sensor cause a broken crankshaft or an engine to seize? I've been told my 85-year-old mother's 1993 Mercury Grand Marquis with only 115,000 lightly traveled miles, has a broken crankshaft. It's been only 3,000 miles, over 15 months, since a shop "fixed" cam and crank position sensors. They "fixed" it once, and then, a couple weeks later, the same problem caused the car to stop running again. They then "fixed" it again.
My mother hasn't driven the car for years, but she is most comfortable in it when going to doctor appointments and grocery shopping, so family members drive her places in it. Lately, I had noticed the same symptoms again. I was planning to take it back in to have them look at it, but before I could, the engine just stopped one day last week. I had it towed to the place because their work was still under warranty. All they would tell me is that the engine was seized. They didn't go into detail about the crankshaft being broken. I had it towed to another place I trust, and they said the crankshaft is broken.
Am I out of line with my suspicion that the first shop may have done a crappy job with the sensors that would cause the engine to seize? After all, they did a crappy job the first time they "fixed" the problem.
By the way, the car never made any noises or exhibited any symptoms that are identified as symptoms of a seized engine or broken crankshaft. And the oil was clean and the level was perfect. The car had been regularly serviced.
Thank you for your input... 
(This post was edited by Murrmayde on Dec 20, 2015, 5:59 PM)
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Murrmayde
New User
Dec 20, 2015, 6:54 PM
Post #3 of 8
(1781 views)
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Re: Broken Crankshaft
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Thank you. I have not yet asked those questions of the mechanic who diagnosed the broken crankshaft. You have given me good questions to ask of him.
The mechanics who first diagnosed the seized engine, without mentioning a broken crankshaft, told me they put some sort of giant leveraging tool on some part of the engine in order to try to loosen the engine. Could that have caused the crankshaft to break?
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 20, 2015, 7:07 PM
Post #4 of 8
(1778 views)
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Re: Broken Crankshaft
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The forces involved to twist a crankshaft to break would need to achieve an insane amount of torque. Not even sure how much torque would be required to do that. Maybe around 400 ft/lbs? It would also require one part of the crank to be stationary.
Enough side force can break a crank. You can actually drop a cast iron crankshaft on its side from enough height and snap it in half. Don't understand why any mechanic would try unsiezing an engine once it was locked up by twisting on the crank. The engine would have to come apart to see what was seized on it and would probably need to be overhauled or replaced.
You really need to find out where the crankshaft broke. Either way it probably needs an engine. Seeing how old the vehicle is, it would probably be better to find her another car.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 20, 2015, 7:13 PM)
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whisperer
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Dec 21, 2015, 12:04 AM
Post #5 of 8
(1767 views)
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Re: Broken Crankshaft
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Is it possible there was some miscommunication here? Is it actually a broken crankshaft bolt? That seems to make more sense. Did the first shop say they put a big breaker bar on the crankshaft (the bolt) to try to break a seized engine free?
The result is the same, the engine needs to come out. With a car like this, if there is a sentimental reason to keep it going (your mom likes it) I might look at finding a used engine to get some more miles out of it and keep it running for a while.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 21, 2015, 2:00 AM
Post #6 of 8
(1764 views)
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Re: Broken Crankshaft
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Please don't take it the wrong way but low use cars this included with I think 1st year of the 4.6 which is excellent but not going to like low use for intricate cam timing. Fuel lasts about 3-6 months at best sometimes and be a problem alone.
Not to say your Mom or any older person but there's a mindset of rev the snots out of them cold, perhaps hard of hearing too involved and it will bust up probably rods and more requiring another engine of exact same one. If it doesn't turn by crank bolt for real is almost certainly game over for that engine.
You can find them in good shape or shop can but car has to be run now and then, gas used up an if low enough use, use stabilizer all the time. Teach Mom to do nothing but turn the key to start it not play with the gas pedal. If it doesn't start call for help.
Seriously, if not used and driven it's going to have problems both engine oil pressure leaked all the way down, battery low in a month if no problems otherwise. Drive it or get someone to do it on purpose routinely. It's that or tricks your Mom isn't likely to understand or want to deal with so wont go there,
T
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kev2
Veteran
Dec 21, 2015, 8:06 AM
Post #8 of 8
(1750 views)
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Re: Broken Crankshaft
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A "seized" eng or a broken crank would be something to clear up. Oil change maintenance sounds like a question to get answered- as mentioned a rare failure
the sensors alone would not cause this - but why were sensors changed?
my thoughts - someone else was using vehicle... OR the sensors were messengers of a deeper issue and changed out of misdiagnoses.
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