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Bill725

Legacy Daihatsu Diesel Oil Change Question

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Bill725

My local Simplicity dealer has a bent connecting rod from a Daihatsu diesel laying on the parts counter. I was told the reason the connecting rod is bent is because the cylinders hydraulically lock with oil when adding oil. The owner changed his own oil and started the engine up right after adding the oil causing the bent connecting rod. I was told B&S recommends waiting a minimum of 20 minutes after adding new oil to allow the oil in the cylinders drain into the crankcase. My question is: How does the oil get into the cylinder?

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RAC

Valve guide would be the only way on any engine. And then only if you're dumping it in too fast probably and flooding the oil galley in the head. Fill it slow enough that oil doesn't pool up in the head under the valve cover and should minimize any chance.

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wwbragg
6 hours ago, Bill725 said:

reconnecting rod is bent is because the cylinders hydraulically lock

OK.  There are a lot of people who know more than I.  But that just doesn't make sense.  Oil in the cylinder would only last for one cycle or one compression stroke.  The next stroke is the exhaust stroke which would expel the excess oil.  Furthermore, that first compression stroke is powered by the STARTER, not repeated combustion.  Is the starter really powerful enough to bend a rod when thus impeded?  OK, a diesel has much higher compression.  And I can see the starter simply refusing to turn over, blowing a head gasket or even ejecting a glow plug, but bending a rod???  I'm interested to see if others support the explanation rendered by Bill's dealer or if the is some other explanation.

Edited by wwbragg
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SmilinSam

My son  who is a professional diesel mechanic, and has been in and out of his Daihatsu briggs fixing it, said only 2 ways to bend a rod. Hydraulically locking a cylinder from below by filling  crankcase with too much oil, or from above.by filling with diesel fuel - like from and injector gone bad. Thats what he said anyhow......

If what was said by the dealer above and briggs is true,  its a new one on him. The oil shouldnt be running down the guides into the cylinders. .................another reason not to own one of those engines.

Hes apparently not been impressed with them anyhow...

Edited by SmilinSam
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wwbragg

Well, there it is.  "In the mouth of two or three witnesses every word may be established."  I can understand the combustion chamber filled with fuel.  That would result in one heck on explosion.  Amazing that the rod is the weak point in the system.  So instead of warning the operator not to overfill the crankcase or add oil too quickly, why not just design a safety valve?  I know, I know - it's cheaper.  I'm just sayin'.

Edited by wwbragg
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RAC

So if a sufficient amount of oil could actually leak down the guide whilst filling (would take a pretty bad guide I'd have to think) and it was on a cylinder on the intake or just past TDC on exhaust then it'd be in there on the compression stroke. If one of the other cylinders fires then.... Don't know how much it'd take,  teaspoon maybe??? 

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wwbragg
1 hour ago, RAC said:

Don't know how much it'd take,  teaspoon maybe???

I'm beginning to appreciate Briggs' "no oil change ever" engines discussed in the next topic.

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Talntedmrgreen

The issue is that folks may fill into the breather.  Oil does not flow INTO the cylinders.  That's ridiculous.  There is also no 20 minute wait time.  Perhaps that's a rule of thumb for the shop, so the teenagers working out back don't damage equipment?  These motors are very easy to maintain, and the oil change is much easier than on the Kawasaki.  

The oil galleries up top are admittedly small.  With many multi-thousand hour motors out there to help verify, however, they do the job.  The issue is, with oil added too quickly and/or not vented, the oil level up top becomes too high and will plug the breather, which in turn, creates a pressure issue on startup.

 

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MikeES

Just another logic thought...If the top of cylinder fill up with enough oil to cause hydraulic lock, it would take MUCH longer than 20 mins for that new oil to drain down past the rings. 

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