- Sat Sep 12, 2020 8:21 am
#92922
In some earlier threads we already discussed the fail of the O-ring at the oil pump output stud and some of the consequences, especially for the rockers. Often problems in this area are indicated by a ticking sound. Such a sound may have different reasons, but most of the times it is oil pressure related.
The overall oil pressure and oil volume circulating in the engine largely depends of the oil pump output stud O-ring. We remember that the O-ring is situated between the oil pump output and the oil filter input. The O-ring sits in a little groove at the oil pump and is compressed by the rh engine cover to form an oil tight seal. Unfortunately, in the factory the O-ring is fixed by super glue to the oil pump what makes the O-ring brittle and prone to leakage. One more reason for leakage in this place is the fact that the area where the O-ring sits is not machined but of a coarse cast structure at the oil pump stud. At the engine cover side, the area is machined as it should be for a good seal. In the UCE the sealing properties greatly depends of the distance between the oil pump stud and the machined surface of the engine cover. But this distance depends of the thickness of two gaskets – the gasket between the oil pump body and the crank case as well as the thickness of the gasket between the crank case and the engine cover, as both distances will determine how much the O-ring is compressed during tightening the engine cover screws.
So far, we already discussed the issue, but there is one more important fact that explains why the O-ring may fail.
When we have a look inside the oil filter compartment we can see that the whole where the oils enters the oil filter compartment is not centred in the compartment, but offset. That means that the oil cannot flow straight inside the oil filter. Below the oil filter element there is an O-ring, sealing the oil filter bottom against the oil filter compartment. The O-ring will prevent oil from bypassing the oil filter element and going unfiltered to the crank, gears, hydraulic lifters and rockers. The cross section of the O-ring is about 2.5 mm, compressed may be 1.5 mm. As the oil input in the bottom of the oil filter compartment is off-centred, the oil has to squeeze to a narrow gap to enter the oil filter. Obviously, the factory realized that the free oil flow is reduced by this fact, they machined a recess around the hole in the bottom of the oil filter compartment to form a bigger gap. As the depth of the recess is only 2 mm the oil has to squeeze through a 3.5 mm (1.5 mm of the compressed O-ring plus 2mm of the recess) gap. Not a good idea for an oil flow amount of up to 9.6 litres per minute (at 4500 rpm). The pressure just before the gap rises, while the amount of oil after the gab decreases.
Now we are coming back to the already doubtful O-ring at the oil pump output stud. It is placed just before the gap and is the weakest link of a weak chain. The increasing oil pressure due to the small gap already make it more vulnerable for leakage.
So, what is a solution for the problem ?
If we can realize a larger gap between the bottom of the oil compartment and the bottom of the oil filter element, the oil amount flowing will be increased and at the same time the pressure the small O-ring has to withstand lowers. It should be the first step to solve the problem. I placed a spacer of 15mm height between the oil filter element and the bottom of the oil filter compartment with an O-ring on both sides. As I already realized a screw connection between the oil pump output and the oil filter compartment for a better sealing I need some space here for the flat nut inside the oil filter compartment. In my first approach I had a less high spacer ring below the oil filter element that worked fine, increasing the cap already to about 6 mm. To fit the oil filter compartment cover it had to be modified. The stud holding the spring had to be shortened. To avoid a modification here I meanwhile found a better solution that allows me to realize a gap of about 15 mm by a higher spacer ring below the oil filter element. I machined a spacer ring that is placed between the oil filter compartment and the oil filter compartment cover. The side of the spacer ring that touches the engine cover has a groove for an O-ring to seal the joint. The unmodified oil filter compartment cover seals the opposite side as it would do in the factory setup. Probably only the increased gap between the oil filter element and the oil filter compartment bottom may solve the issue with the overstrained oil pump output O-ring, leading to a better oil flow. Otherwise, you additionally may realize the more secure screw connection between the oil pump and the oil filter compartment as I realized it. In my case, there is a very good oil flow at the rockers, even at idle, and all irregular noise from the valve drive has gone.
A test ride of two hundred kilometres was very satisfying with no issues at all. I will have an eye on this modification and will report if there are new facts.
The overall oil pressure and oil volume circulating in the engine largely depends of the oil pump output stud O-ring. We remember that the O-ring is situated between the oil pump output and the oil filter input. The O-ring sits in a little groove at the oil pump and is compressed by the rh engine cover to form an oil tight seal. Unfortunately, in the factory the O-ring is fixed by super glue to the oil pump what makes the O-ring brittle and prone to leakage. One more reason for leakage in this place is the fact that the area where the O-ring sits is not machined but of a coarse cast structure at the oil pump stud. At the engine cover side, the area is machined as it should be for a good seal. In the UCE the sealing properties greatly depends of the distance between the oil pump stud and the machined surface of the engine cover. But this distance depends of the thickness of two gaskets – the gasket between the oil pump body and the crank case as well as the thickness of the gasket between the crank case and the engine cover, as both distances will determine how much the O-ring is compressed during tightening the engine cover screws.
So far, we already discussed the issue, but there is one more important fact that explains why the O-ring may fail.
When we have a look inside the oil filter compartment we can see that the whole where the oils enters the oil filter compartment is not centred in the compartment, but offset. That means that the oil cannot flow straight inside the oil filter. Below the oil filter element there is an O-ring, sealing the oil filter bottom against the oil filter compartment. The O-ring will prevent oil from bypassing the oil filter element and going unfiltered to the crank, gears, hydraulic lifters and rockers. The cross section of the O-ring is about 2.5 mm, compressed may be 1.5 mm. As the oil input in the bottom of the oil filter compartment is off-centred, the oil has to squeeze to a narrow gap to enter the oil filter. Obviously, the factory realized that the free oil flow is reduced by this fact, they machined a recess around the hole in the bottom of the oil filter compartment to form a bigger gap. As the depth of the recess is only 2 mm the oil has to squeeze through a 3.5 mm (1.5 mm of the compressed O-ring plus 2mm of the recess) gap. Not a good idea for an oil flow amount of up to 9.6 litres per minute (at 4500 rpm). The pressure just before the gap rises, while the amount of oil after the gab decreases.
Now we are coming back to the already doubtful O-ring at the oil pump output stud. It is placed just before the gap and is the weakest link of a weak chain. The increasing oil pressure due to the small gap already make it more vulnerable for leakage.
So, what is a solution for the problem ?
If we can realize a larger gap between the bottom of the oil compartment and the bottom of the oil filter element, the oil amount flowing will be increased and at the same time the pressure the small O-ring has to withstand lowers. It should be the first step to solve the problem. I placed a spacer of 15mm height between the oil filter element and the bottom of the oil filter compartment with an O-ring on both sides. As I already realized a screw connection between the oil pump output and the oil filter compartment for a better sealing I need some space here for the flat nut inside the oil filter compartment. In my first approach I had a less high spacer ring below the oil filter element that worked fine, increasing the cap already to about 6 mm. To fit the oil filter compartment cover it had to be modified. The stud holding the spring had to be shortened. To avoid a modification here I meanwhile found a better solution that allows me to realize a gap of about 15 mm by a higher spacer ring below the oil filter element. I machined a spacer ring that is placed between the oil filter compartment and the oil filter compartment cover. The side of the spacer ring that touches the engine cover has a groove for an O-ring to seal the joint. The unmodified oil filter compartment cover seals the opposite side as it would do in the factory setup. Probably only the increased gap between the oil filter element and the oil filter compartment bottom may solve the issue with the overstrained oil pump output O-ring, leading to a better oil flow. Otherwise, you additionally may realize the more secure screw connection between the oil pump and the oil filter compartment as I realized it. In my case, there is a very good oil flow at the rockers, even at idle, and all irregular noise from the valve drive has gone.
A test ride of two hundred kilometres was very satisfying with no issues at all. I will have an eye on this modification and will report if there are new facts.
On the eighth day, God created Harley-Davidson.
And he saw that it was a shit.
And he saw that it was a shit.
