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Oil pressure/temperature problem
Hi all,
I recently discovered a small crack in the crankcase of my IO360 A1A which was seeping oil. So I removed the engine and did a complete disassembly and rebuild with a new crankcase. The only other work entailed grinding the valves and cleaning the pistons and cylinder heads of the carbon that had built up. Now the engine starts and runs perfectly as it always has done BUT and it's a big but, the oil pressure and temperature are way off the normal figures that I had become used to i.e. - 55psi/ 220? instead of the previous 75 psi/ 175?. in cruise at 2000ft OAT 15?c/60?f at 140 kts. I have changed nothing on the baffles or oil cooler installation. I have added the maximum permitted number of washers to the oil pressure relief valve to try to bring the pressure up to normal. I checked the Vanatherm valve in boiling water and it "opens" by 0,165 in.(Is that enough?) So apart from an oil cooler that has suddenly become clogged (and why would that happen?) I'm running out of ideas. Any information or ideas would be very much appreciated. Mike |
Hmm, maybe you should take a look at the sensors and ground wiring just to make sure you're getting an accurate reading. When you R&R an engine you remove wires and grounds, just make sure they are all back where they belong.
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Oil Pressure
I always try to ?T? in a mechanical direct reading gauge to the existing system and compare readings simultaneously.
Don Broussard RV9 Rebuild in Progress 57 Pacer |
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Did you check Main bearing clearance? Also are you sure you installed all three 1/8 pipe plugs on the rear face of the case?
Good Luck, Mahlon |
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https://www.vernatherm.com/ BTW, there's a page here everyone should see...the core of our units: https://www.vernatherm.com/thermal_actuators.html |
THERMAL ACTUATORS (WAX MOTORS)
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Something in the oil circuit is flowing more oil than designed is the most likely cause of the low oil pressure. I would inspect the mating surface for relief ball. Make sure there are no nicks or gouges. Did you re-use your relief spring? If not, make sure it is correct. After that excessive bearing clearance is the next likely suspect followed by an opening somewhere in the circuit. Larry |
Does your oil pressure start out low or does it drop from the suspected high oil temps? Low oil pressure running at normal oil temps (~ 185F) would be a separate problem then low oil pressure when the oil gets very hot (ie: 220F). Perhaps you need to separate your two issues to see if they are not related or connected. Very high oil pressure can increase oil temps but this is not your issue. Loose clearances will lower pressure but not increase temps, tight clearances will increase temps but will also increase pressure. I agree that you should check these readings against other instruments just to be sure.
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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 |
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 |
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 |
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Larry |
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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