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-   -   Oil pressure/temperature problem (https://vansairforce.net/community/showthread.php?t=160463)

tullow 05-18-2018 02:46 PM

Thanks to you all for your help and suggestions, haven't replied for two days as I wasn't able to work on the plane since then.
What I have done -- I've flushed out the oil cooler and nothing significant came out. I've checked the ball in the relief valve and it's in perfect condition. However I imagine that the spring may have lost it's original strength (does this happen?)
so maybe I should replace it. I borrowed another vanatherm valve and installed it.I've checked and cleaned both oil screens, they were quite clean apart from some small carbon particles. Unfortunately I haven't been able to find another oil pressure gauge to T into the system to check the panel instrument.
Having done all this I flew this afternoon with more or less the same problems
i.e. On engine start oil pressure rises to 80+ psi until the oil starts to warm up, short taxy, engine checks at 1800rpm with oil pressure about 75psi and temp
140?.
On take-off pressure and temp. are in the green. Climb to 3000 ft. OAT 14?c
After a few minutes at 140 kts, pressure is now down to 65psi and slowly descending and temp. around 200?. When I throttle back for approach pressure drops to 55psi and when taxying back to the hangar after landing with about 1000rpm the pressure was only 40psi !! . The temp. was never over 200?.
After shutdown I pulled the prop through all cylinders and there were no obvious
"hard points" and the fore /aft movement of the prop/crankshaft seemed normal.
Mahlon,
What 3 plugs on the rear face of the case are you referring to?.
During my rebuild of the engine I only replaced the two main crankcase halves ( one of which was cracked) so the rear accessory housing with it's plugs and accessories were mounted as before. The main bearings and crankshaft are as before i.e. have been "mated" and run for about 150 hours so the main bearing clearances are as before the strip-down.
The mystery continues!
Thanks again.
Mike

n82rb 05-19-2018 09:23 AM

Am I reading it correct that you did not replace the bearings when reassembling it? Anytime the case is split they need to be replaced. As per lycoming.

https://www.lycoming.com/sites/defau...aintenance.pdf

I'm going to guess that bearing clearances do not meet spec anymore if they were reused.

Bob burns
Rv-4 n82rb

mahlon_r 05-19-2018 10:32 AM

The three plugs go in the rear of the crankcase halves. They are 1/8 pipe plugs. Two go in on the right half at the end of the lifter gallery and one on the end of the left half lifter gallery.
They may have been preinstalled in the case halves but lots of overhaulers remove them during the overhaul and you need to put them back in. If your cases were new than they were not likely installed. If you look in a parts book at the case assemblies you will see them shown and their locations.I am not sure but I think you might be able to see the right case half ones with the vac pump drive removed. Maybe not..... but I think it might be possible.

Good Luck,

Mahlon

lr172 05-19-2018 09:49 PM

Quote:

Originally Posted by mahlon_r (Post 1261055)
The three plugs go in the rear of the crankcase halves. They are 1/8 pipe plugs. Two go in on the right half at the end of the lifter gallery and one on the end of the left half lifter gallery.
They may have been preinstalled in the case halves but lots of overhaulers remove them during the overhaul and you need to put them back in. If your cases were new than they were not likely installed. If you look in a parts book at the case assemblies you will see them shown and their locations.I am not sure but I think you might be able to see the right case half ones with the vac pump drive removed. Maybe not..... but I think it might be possible.

Good Luck,

Mahlon

To add to this, two of the plugs back there are caps to the main oil galleries (left and right). These galleries are straight, drilled out bores with a plug on each end. During cleaning, both plugs are removed and a brush is run through the bore. Industry convention is the engine assembly mechanic installs these, not the machine shop. They often include a bag of plugs. You should be able to pull the plugs on the front end of the galleries. Then pull a mag and shine a bright flashlight into the inside of the accessory case. Then look in the front gallery opening. If you see light, you found your problem.

Larry

Walt 05-20-2018 08:05 AM

I'm pretty sure a missing plug would lower oil pressure to less than what you are seeing, my guess like some other folks suggested is excessive bearing clearances, I've seen this before.


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