08-08-2011, 08:53 AM #1
- Join Date
- Jun 2010
787 PTO loctite is not holding on the PTO, PTO keeps coming lose? why? Used Impact
I used an impact gun and red loctite on my 787 rear PTO flywheel. It keeps coming lose and spinning out of the back of the engine causing a vibration and winning noise.
It is a lightweight flywheel pto, I even tried a 2nd one and it did it again. I guess the impact gun can't get the job done. How do I lock the motor down so that I can really wrench on the pto and keep it tight.???
08-08-2011, 09:11 AM #2
Here is a back yard trick. APPLY THIS AT YOUR OWN RISK! Use 1/4" string. Remove PTO spark plug and cover spark plug hole with your finger. Rotate crank slowly in the direction you want to tighten, when you feel compression stop rotating. Install string into PTO spark plug hole untill you can't get anymore to fit. Then torque PTO to spec.
08-09-2011, 01:41 AM #3
Drop the pto into a pot of boiling water for 5 minutes and torque it up to spec. When it cools it shrinks even tighter onto the tapered shaft. Been doing this for 15 years without any problems.
08-09-2011, 08:56 AM #4
- Join Date
- May 2008
- Elephant Butte New Mexico
best practices for pto attachment
while I haven't used the boiling water trick, it sounds interesting.
The service manuals are pretty clear on this issue, the "rope trick" is actually discussed in most brnad manuals for this sort of thing. Using an impact wrench is verboten btw.
The key the way I've experienced it is to use a _fresh_ bottle of thread lock, not one that has been left open on the bench a bucnh of times (me=guilty) I see thread lock as cheap insurance against comebacks, so I use lots and lots of it everywhere i can. i sometimes regret it when I have to redo something ( hear me out there SBT?)
proper surface prep is critical . Clean the threads on the crank and pto with solvent. AIR dry ( the air coming out of your compressor will typically have a mix of oil and water, unless you have a really good seperator on it) apply thread lock in liberal amounts.
You need to set up your "engine lock" rope before you begin the prep of the pto and crank. I'll repeat the prior warning..be careful and work slowly, you get the rope into the exaust port, it's going to ruin your day.
screw the pto on, get your prop tool and breaker bar in place and lay on it till you are worried about breaking something. that;s about right.
Now the big trick is WAIT WAIT WAIT. Give the threadlock a chance to setup. I let mine go overnight after having an unforunate PTO unscrewing ruin a weekend) If you've done it right, the next guy that wants that PTO off is going to have to heat it and rap it with a hammer ( thanks to oside for that trick)
this should keep the pto where it belongs. Apply grease (one shot) after installing the driveshaft.
use of an impact gun is not suggested under any circumstance. never use an impact gun with standard sockets. that's a trip to the hospital. If you must, wrap the socket in fiberglass tape and wear some eye protection. Back when I was just starting out, there were some unfortunate events at the honda dealer I worked at with imact guns. The owner of the dealership actually bought a bunch of the correct sized impact sockets to keep his workmans comp claims down. ( we had three in one summer, one fellow lost an eye..I never forgot that day)
I have large respect for the ability on an air powered tool to ruin your day. You should too.
08-09-2011, 09:56 AM #5
Boiling a PTO. I got to try that the next time.
08-13-2011, 11:33 AM #6
- Join Date
- Jul 2011
Loctkite as makes a primer especially for metals that don't rust. like SS."something about metal salts that speed process and lack of in non ferros" And also a product for locking bearings to shafts..I have used heat and cold for expanding and shrinking metals for many years. A good heatgun has a million uses.
08-14-2011, 03:50 AM #7
A proven way to install a PTO onto a crank either on the bench or in the hull is to remove the coupler from the pto, now drop the PTO into a pot of boiling water leave it for 5 minutes.You will need gloves to do the rest. Install 2 stainless bolts into the rear of the pto as this will prevent the crank from spinning.Install the now hot pto onto tapered shaft and torque up to spec.You can place a steel bar between the stainless bots and this will stop the crank from rotating while you torque it up. You need to torque it up reasonably quick, as it cools the pto shrinks and tightens even further around the crank.No need to remove heads or use strings as those methods can twist cranks and cause run out.
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