Broken timing belt

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makaraft
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Broken timing belt

Postby makaraft » Thu Jul 05, 2018 12:52 pm

So I rebuilt the C223 in my 81 LUV in spring of 2017, but due to a deployment wasn’t able to crank it until two weeks ago. It sat in a storage unit over the winter here in Utah, fully assembled with all new parts installed, including the timing belt. Fast forward to yesterday, I took it out on about a 15 minute ride and 10min it the engine stops. All my rockers are broken and pushrods bent. I’m guessing the timing belt broke. Is there anything else I need to replace to prevent this from happening again? I didn’t think the timing belt would break because it was new.

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puttputtinpup
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Re: Broken timing belt

Postby puttputtinpup » Thu Jul 05, 2018 1:58 pm

I've only changed a couple of timing belts, so it doesn't quite qualify me as an expert in timing belts. I'd begin by trying to determine the cause of the break. Others with more knowledge may chime in, but I don't believe we've seen cases where all push rods and rockers break. It's usually only 1 or two.

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JoeIsuzu
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Re: Broken timing belt

Postby JoeIsuzu » Thu Jul 05, 2018 2:15 pm

I think this happened to my engine right after Jerry overhauled it. I think he said it looked as if the camshaft had seized up. Maybe he can weigh in here with more information.

Jack

makaraft
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Re: Broken timing belt

Postby makaraft » Thu Jul 05, 2018 3:12 pm

What did you do for the cam shaft seizing?

makaraft
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Re: Broken timing belt

Postby makaraft » Thu Jul 05, 2018 3:13 pm

Here’s a picture of under the valve cover. I’ll rip into the timing cover when I get a chance.
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JoeIsuzu
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Re: Broken timing belt

Postby JoeIsuzu » Thu Jul 05, 2018 4:24 pm

makaraft wrote:What did you do for the cam shaft seizing?

I'll have to ask Jerry to fill us in.

Jack

makaraft
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Re: Broken timing belt

Postby makaraft » Fri Jul 06, 2018 12:26 am

Well guys, we have a good puzzle here.

Got home from work and pulled the timing cover. Everything is in tact, belt is installed with TEETH IN TACT ( no chewed up rubber in the bottom ). Pulled the tensioner and it spun freely, pulled the belt and all components (fuel pump, cam and crank) spin freely. I’ll get a leak down tester within the next few days and check compression, but everything down here looks good EXCEPT the timing is off.

Now, I set the timing last year, it sat all winter and I finally cranked it two/three weeks ago. It’s been running fine up and down the street, and the day it took a crap I took it on a longer drive, maybe 2-3 miles. What could’ve caused this? Has anyone seen this before?

Attached I have a picture right when I took the timing cover off, of the belt and the timing compartment without the belt.
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makaraft
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Re: Broken timing belt

Postby makaraft » Fri Jul 06, 2018 12:37 am

This is the book I used when I re-assembled after the engine tear down. Maybe I missed/messed up a step in the timing procedure? If I had tensioned the belt incorrectly, could the belt have skipped some teeth, causing the melt down? I’m losing my mind here, guys.
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puttputtinpup
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Re: Broken timing belt

Postby puttputtinpup » Fri Jul 06, 2018 6:33 am

The cam sprocket spins freely, but is the entire cam turning or could it be busted? Drop a push rod down in the furthest spot on the cam, turn the cam sprocket and see if the rod goes up & down.

makaraft
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Re: Broken timing belt

Postby makaraft » Fri Jul 06, 2018 9:46 am

Checked. All pushrods go up and down when the cam sprocket spins.

So if I had set the timing correctly but not tensioned the belt correctly (more slack between the crank and fuel sprockets instead of slack between the fuel and cam sprockets), do you think the belt could’ve just jumped and thrown the timing off? Or say put too much tension in the belt?

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puttputtinpup
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Re: Broken timing belt

Postby puttputtinpup » Fri Jul 06, 2018 3:10 pm

Not sure. We have a How-To for changing the c223 timing belt. Read through that and see if you may have missed something when installing the belt.

I know when i did my belt, after placing tension on tje belt with the tensioner, I rotated the engine one cycle to seat the belt. It seems Jerry had me rotate it a bit backwards a bit, then forwards? Not sure about that. Then set the tension again double-checking if all timing marks lined up okay.

Maybe Mark, Paul, or Jerry would have a theory about your issue.

dorf
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Re: Broken timing belt

Postby dorf » Fri Jul 06, 2018 5:50 pm

Wrong belt
Defective belt
Really old stock belt
Aftermarket junk belt

Yikes...just my 2 cents

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puttputtinpup
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Re: Broken timing belt

Postby puttputtinpup » Sat Jul 07, 2018 5:35 am

dorf wrote:Wrong belt
Defective belt
Really old stock belt
Aftermarket junk belt

Yikes...just my 2 cents
the belt turned out to be fine. My 1st guess is it didn't have enough tension on it and jumped a few teeth.

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Re: Broken timing belt

Postby FiatSpider2 » Sat Jul 07, 2018 8:18 am

puttputtinpup wrote:
dorf wrote:Wrong belt
Defective belt
Really old stock belt
Aftermarket junk belt

Yikes...just my 2 cents
the belt turned out to be fine. My 1st guess is it didn't have enough tension on it and jumped a few teeth.


A defective or old stock belt can stretch, deflect and jump and still be intact and look good to the eye. First thing to check is the timing marks before you remove the belt if after an incident like this you find the belt seemingly intact. Another possibility is that when warm the cam soft seized which can happen especially if the engine sat unused for months without a sufficient coating of zinc rich assembly oil on all parts removed and put back into the engine or replaced.
FiatSpider2 (4FB1 Isuzu Diesel powered 1978 Fiat Spider)

makaraft
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Re: Broken timing belt

Postby makaraft » Sat Jul 07, 2018 12:37 pm

Right on. Thanks for the replies. All components were installed with plenty of assembly lube and it has ran fine with oil in t for a couple of weeks. Reading back through the timing procedure I may have skipped some steps and not tensioned it properly. I’m ordering a rocker arm assy, push rods and a new tensioner bearing. I’ll re install everything and be more meticulous about following the book.