TDI Pumpe Duse PD Cam Bearing Oiling and Related Wear (eddif)
This thread will give information necessary to understand the cause of cam wear, cam-bearing wear and cam-bearing wear indications on the TDI Pumpe Duse. It is somewhat involved, difficult to see, and time consuming, but worth the effort.
The VW Pumpe Duse TDI PD engine is a great engine, but suffers from insufficient lower cam bearing backup. IMHO. The lower cam bearings do not have support under their whole area. The problem occurs when the original design had the cam pushed up by valve spring pressure. In the pushed up position the cam had full cam bearing area, but the followers had cutouts that reduced the lower cam bearing area. The PD design had an added injection roller rocker that overcomes the valve spring pressure and forces the cam down onto not fully supported cam bearings.
The reduced cam-bearing backup area causes the cantilevered cam bearing area to deflect downward. This downward deflection causes the end two bearings to cock in their bores and cause early copper release on the belt end bearing. The three center bearings deflect equally during use and cause limited support during operation. This pressure causes minute head cam bore wear and the second and third bearings sets have reduced life. The cam is forced, over time, to the front of the car (over the cam-bearing oil slot) obstructing oil flow to the cam bearing and followers.
There are multiple approaches to the problem and this article is intended to show the solutions I think will work, and to invite other solutions. Of course any modifications to a car that came equipped with a warning sticker about oil type and usage causing severe danger, are at your own risk. VW marketed a design they never totally made trouble free, and you are listening to my opinions. In my own private vehicle cam bearing replacement helped restore oiling to the followers and allowed copper streaked lobes, on a failing cam, to make a recovery and survive more miles. The copper came from worn cam bearings. Most of the cam-bearings looked fair, but cam bearing cocking caused early release of the copper layer, of the belt end cam bearing. After cocking is resolved and more oil is supplied, copper release should be delayed and life should be longer.
This first labeled view is from the timing belt end of the engine. The link view is from the flywheel end of the engine. Backwards from our situation, so I reversed the drawing and show a drawing that agrees with the link.
The link describes a crankshaft, but a camshaft is still a moving shaft in bearings. The main difference is the injection roller pressure that directs the camshaft position. The higher oil hole will allow the oil wedge to develop over more miles, and may allow longer cam bearing wear.
I have a plan for cam bearing modification to allow longer life. The first step is to simply connect the two stock oil delivery slots together with a slot. The slot will probably be .75 mm deep in the Babbitt side of the cam bearing and 5 mm wide. These dimensions are open to change and Hurst89 and others are welcome to calculate the dimensions to overcome rotational oil turbulence , meet flow parameters, to keep too much oil flow from going to the upper bearing oil slots. We may make the lower shell cut different (deeper) from the top shell cut, to allow a top bearing change after 90,000 miles. Hopefully as the top new oil flow pushes the oil into the wedge it will self regulate by interaction with the old oil slot still in position. When the old hole is uncovered, a little, it will flow more oil again. Here is the point that the old hole may have to be blocked and the new hole uncovered, but time will tell. No, this is not all tested and firm, but is open to others trying for the best design. If I waited around till it was completed, the cars would all be junk.
The quality of the following drawings, are sure not to impress anyone but will possibly help others understand.
Since it is posted some copy write legal aspects exist. You are welcome to use this information for personal repair on your car. Any other use will require permission before use.
http://www.zddplus.com/TechBrief11%20-%20Internal%20Combustion%20Engine%20Lubrication.pdf
http://machinedesign.com/article/gro...more-lube-0522
The above simple left hand drawing shows the original position of the camshaft when the engine is new. The right hand drawing shows the position as the bearing wears and the oil supply begins to decrease. If the cam continues to move almost all oil is cut off to the bearing and most of the oil flowing down to the followers almost stops. Always look for the cam position rather than the amount of wear. Wear indicates position of operation in the PD. When the cam-bearing oil hole is blocked oil supply decreases. Always remember copper release in the PD defines cam-bearing wear / failure.
The next view is flipped to allow link to agree with drawing.
The following cam-bearings show the general shape, The area from green line to red crescents is the unworn portion often seen on a used bearing.. The red wedge area is a .50mm deep removal of babbitt and steel removed to stop cocking / flexing of the bearing in the bore. When the babbitt is removed the oil film will not carry load in that area, but the bottom is retained to direct oil to the cam follower face. The white area between the green line and the red area should carry load after removing the red area surface. The red square area is a .75 mm deep and about 5 mm wide, where babbitt and steel are removed to allow oil to flow to the top bearing. The right bearing has the Square area removed, but not the red crescent / crescents and is the top bearing. The left bearing is the drive belt end lower cam bearing. If you move the cut to the left side you have a flywheel end lower cam bearing. The center cam-bearing fits in the lower center three positions. The right cam bearing is the upper cam bearing for all positions. Eventually I hope we post actual bearings cut for service, Anytime anyone can help by posting better drawings feel free to post away.
lower belt end ……... lower middle three … ….Top all positions
This thread asks for your questions. The PD has multiple failed camshafts and we seek to find a solution that allows more miles than the stock engine. Oil slots in the follower bores (from the lifter oil supply hole) will supply more oil at the follower / lifter / tappet ---- cam-lobe interface area. A groove in each bottom cam bearing may help, and in fact the square is a type of groove. This thread is about maintaining or possibly increasing cam and cam-bearing oiling. Any method of increased oil supply will help. This thread will also try to find if, when the cam bearing oil holes are covered, the follower oil gallery pressure rises. If the follower oil pressure rises, the follower pressure on the cam lobe follower interface point may increase, also causing increased wear. Eventually I hope to use 150 HP injectors to reduce loading. This article / thread is open to solving the problem and not about making a point.
eddif
This thread will give information necessary to understand the cause of cam wear, cam-bearing wear and cam-bearing wear indications on the TDI Pumpe Duse. It is somewhat involved, difficult to see, and time consuming, but worth the effort.
The VW Pumpe Duse TDI PD engine is a great engine, but suffers from insufficient lower cam bearing backup. IMHO. The lower cam bearings do not have support under their whole area. The problem occurs when the original design had the cam pushed up by valve spring pressure. In the pushed up position the cam had full cam bearing area, but the followers had cutouts that reduced the lower cam bearing area. The PD design had an added injection roller rocker that overcomes the valve spring pressure and forces the cam down onto not fully supported cam bearings.
The reduced cam-bearing backup area causes the cantilevered cam bearing area to deflect downward. This downward deflection causes the end two bearings to cock in their bores and cause early copper release on the belt end bearing. The three center bearings deflect equally during use and cause limited support during operation. This pressure causes minute head cam bore wear and the second and third bearings sets have reduced life. The cam is forced, over time, to the front of the car (over the cam-bearing oil slot) obstructing oil flow to the cam bearing and followers.
There are multiple approaches to the problem and this article is intended to show the solutions I think will work, and to invite other solutions. Of course any modifications to a car that came equipped with a warning sticker about oil type and usage causing severe danger, are at your own risk. VW marketed a design they never totally made trouble free, and you are listening to my opinions. In my own private vehicle cam bearing replacement helped restore oiling to the followers and allowed copper streaked lobes, on a failing cam, to make a recovery and survive more miles. The copper came from worn cam bearings. Most of the cam-bearings looked fair, but cam bearing cocking caused early release of the copper layer, of the belt end cam bearing. After cocking is resolved and more oil is supplied, copper release should be delayed and life should be longer.
This first labeled view is from the timing belt end of the engine. The link view is from the flywheel end of the engine. Backwards from our situation, so I reversed the drawing and show a drawing that agrees with the link.
The link describes a crankshaft, but a camshaft is still a moving shaft in bearings. The main difference is the injection roller pressure that directs the camshaft position. The higher oil hole will allow the oil wedge to develop over more miles, and may allow longer cam bearing wear.
I have a plan for cam bearing modification to allow longer life. The first step is to simply connect the two stock oil delivery slots together with a slot. The slot will probably be .75 mm deep in the Babbitt side of the cam bearing and 5 mm wide. These dimensions are open to change and Hurst89 and others are welcome to calculate the dimensions to overcome rotational oil turbulence , meet flow parameters, to keep too much oil flow from going to the upper bearing oil slots. We may make the lower shell cut different (deeper) from the top shell cut, to allow a top bearing change after 90,000 miles. Hopefully as the top new oil flow pushes the oil into the wedge it will self regulate by interaction with the old oil slot still in position. When the old hole is uncovered, a little, it will flow more oil again. Here is the point that the old hole may have to be blocked and the new hole uncovered, but time will tell. No, this is not all tested and firm, but is open to others trying for the best design. If I waited around till it was completed, the cars would all be junk.
The quality of the following drawings, are sure not to impress anyone but will possibly help others understand.
Since it is posted some copy write legal aspects exist. You are welcome to use this information for personal repair on your car. Any other use will require permission before use.
http://www.zddplus.com/TechBrief11%20-%20Internal%20Combustion%20Engine%20Lubrication.pdf
http://machinedesign.com/article/gro...more-lube-0522
The above simple left hand drawing shows the original position of the camshaft when the engine is new. The right hand drawing shows the position as the bearing wears and the oil supply begins to decrease. If the cam continues to move almost all oil is cut off to the bearing and most of the oil flowing down to the followers almost stops. Always look for the cam position rather than the amount of wear. Wear indicates position of operation in the PD. When the cam-bearing oil hole is blocked oil supply decreases. Always remember copper release in the PD defines cam-bearing wear / failure.
The next view is flipped to allow link to agree with drawing.
The following cam-bearings show the general shape, The area from green line to red crescents is the unworn portion often seen on a used bearing.. The red wedge area is a .50mm deep removal of babbitt and steel removed to stop cocking / flexing of the bearing in the bore. When the babbitt is removed the oil film will not carry load in that area, but the bottom is retained to direct oil to the cam follower face. The white area between the green line and the red area should carry load after removing the red area surface. The red square area is a .75 mm deep and about 5 mm wide, where babbitt and steel are removed to allow oil to flow to the top bearing. The right bearing has the Square area removed, but not the red crescent / crescents and is the top bearing. The left bearing is the drive belt end lower cam bearing. If you move the cut to the left side you have a flywheel end lower cam bearing. The center cam-bearing fits in the lower center three positions. The right cam bearing is the upper cam bearing for all positions. Eventually I hope we post actual bearings cut for service, Anytime anyone can help by posting better drawings feel free to post away.
lower belt end ……... lower middle three … ….Top all positions
This thread asks for your questions. The PD has multiple failed camshafts and we seek to find a solution that allows more miles than the stock engine. Oil slots in the follower bores (from the lifter oil supply hole) will supply more oil at the follower / lifter / tappet ---- cam-lobe interface area. A groove in each bottom cam bearing may help, and in fact the square is a type of groove. This thread is about maintaining or possibly increasing cam and cam-bearing oiling. Any method of increased oil supply will help. This thread will also try to find if, when the cam bearing oil holes are covered, the follower oil gallery pressure rises. If the follower oil pressure rises, the follower pressure on the cam lobe follower interface point may increase, also causing increased wear. Eventually I hope to use 150 HP injectors to reduce loading. This article / thread is open to solving the problem and not about making a point.
eddif
