Working on a friends 1966 loboy. Got her running but after warm up oil pressure is low. 20 lbs at 1800 rpm and 0 at idle. (Cold about 30 full and 10 idle.) She has fresh 30w oil. I am really a Case guy and my VAC is happy at 18 lbs (manual says anything above 12 is OK) so the 20 doesn't scare me but going to zero at hot idle...
I want to give my friend some idea how bad this is going to be with out tearing her down. Can I check the main bearing clearances just dropping the oil pan and removing the bearing caps?? (Manual indicates you can replace the bearing shells with out pulling the crank if i read it right) Also can you remove and check the oil pressure bypass spring and plunger without pulling the engine?
Last question when I depress the clutch pedal the engine slows down (100-150 rpm)...That seems backwards to me. She shifts and drives OK...
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Two loboy questions
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Re: Two loboy questions
You can remove the main and rod bearings without removing the crankshaft.
The oil pressure regulator valve is not your problem. The spring is designed to limit high oil pressure to 35 - 37 lbs. The oil pressure regulator valve opens up at or above the designated oil pressure.
Reduced RPMs when you depress the clutch, normal. The throwout bearing is a solid piece of "graphite".
Before you get to far into the engine, conduct dry then wet compression tests.
The oil pressure regulator valve is not your problem. The spring is designed to limit high oil pressure to 35 - 37 lbs. The oil pressure regulator valve opens up at or above the designated oil pressure.
Reduced RPMs when you depress the clutch, normal. The throwout bearing is a solid piece of "graphite".
Before you get to far into the engine, conduct dry then wet compression tests.
I have an excuse. CRS.
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Re: Two loboy questions
Thank you for the information. I should have added that she doesn't smoke and seems to have reasonable power. The reason I asked about the pressure relief was i was thinking it may not be seating correctly and bleeding off too much oil. I shall run a compression test and /or a leak down test before Ii drop the pan and check the mains.
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Re: Two loboy questions
Did the compression test and a leak down test.
Results cold hot
1 110 120
2 105 110
3 110 115
4 108 119
None did well on the leakdown test. In all cases it was rings as she vented out the crankcase filler. Valves seemed to do OK no big leakage out carb or exhaust.
She starts and runs well seems to have power doesn't smoke and while the leakdown and compression may not be good I am not sure why that would cause the oil pressure to drop so severely when hot.
I guess next step is to drop the oil pan and do a plastigage on the main bearings. This isn't my tractor and the owner probably isn't going to work it really hard but 0 oil pressure at idle cannot be a good thing
Any thoughts would be very much appreciated
Results cold hot
1 110 120
2 105 110
3 110 115
4 108 119
None did well on the leakdown test. In all cases it was rings as she vented out the crankcase filler. Valves seemed to do OK no big leakage out carb or exhaust.
She starts and runs well seems to have power doesn't smoke and while the leakdown and compression may not be good I am not sure why that would cause the oil pressure to drop so severely when hot.
I guess next step is to drop the oil pan and do a plastigage on the main bearings. This isn't my tractor and the owner probably isn't going to work it really hard but 0 oil pressure at idle cannot be a good thing
Any thoughts would be very much appreciated
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Re: Two loboy questions
Compression and leak down readings - not that bad. My guess is well worn rings.
I would do a plastigage reading on the center main and two adjacent rod bearings. You can then present your readings/opinions to the owner.
My opinion, pull the engine and rebuild this winter.
I would do a plastigage reading on the center main and two adjacent rod bearings. You can then present your readings/opinions to the owner.
My opinion, pull the engine and rebuild this winter.
I have an excuse. CRS.
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Re: Two loboy questions
Thank you. A further question if I may. I am more used to Case tractors. Case VACs have oil pump issues. Are cub oil pumps trouble prone? From a quick look at the manual it looks like the engine has to be pulled to check or replace it.
Winter might not be long enough. projects are backing up
Winter might not be long enough. projects are backing up
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Re: Two loboy questions
AI have never heard of more than one or two cub oil pumps being bad, and I question the accuracy of the diagnosis in both those cases. Yes, you do have to split at the rear of the engine, pull the pressure plate, then the flywheel to get to the engine oil pump. It is mounted on the rear of the camshaft.
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you are part of the problem!!!
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Re: Two loboy questions
Still chasing the low oil pressure when hot.
Dropped the pan (nice how they make the back three bolts a bit hard to get to.
Checked all 3 main bearings just now. None of them has any scarring discoloration etc. Popped the shell out on one and it was stamped "std".
Did the plastigage thing and got the following
#1 .0021
#2 .0029
#3 .0025
By my reading of the manual the are all in the acceptable range. I haven't pulled any rod caps yet as I don't see how they would affect oil pressure (or lack thereof).
Once she is warmed up about 18-20 psi at 1800 rpm drops to about 10 psi at 700 rpm then goes to zero psi below that
Dropped the pan (nice how they make the back three bolts a bit hard to get to.
Checked all 3 main bearings just now. None of them has any scarring discoloration etc. Popped the shell out on one and it was stamped "std".
Did the plastigage thing and got the following
#1 .0021
#2 .0029
#3 .0025
By my reading of the manual the are all in the acceptable range. I haven't pulled any rod caps yet as I don't see how they would affect oil pressure (or lack thereof).
Once she is warmed up about 18-20 psi at 1800 rpm drops to about 10 psi at 700 rpm then goes to zero psi below that
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Re: Two loboy questions
Have you tried a new or known working gauge to verify the readings?
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Re: Two loboy questions
The crankshaft has passages bored through it that carries oil from the mains to the rods, It does only go through in spurts, but worn rod bearings will contribute to low oil pressure.pfrederi wrote:....... I haven't pulled any rod caps yet as I don't see how they would affect oil pressure (or lack thereof). ..........
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