Relief, Oiling system in a type 4 Options

[worn]

If anyone has read my previous threads my two week vacation turned from driving to lying on the creeper under the new engine and transmission. Low oil pressure after warm up. I ordered a new Melling 30 mm pump and we shall see, but at the same time I looked into the pressure relief system - especially where it shunts oil away from the cooler because it is easier to see in the car.

What I found surprised me. First, looking at two different cases (72 1.7 and 76 2.0) I found that the piston seats on a shoulder in the bore that is at most a mm wide, and is not at all uniform in width across the piston face. OK, maybe it isn't supposed to seal.

Second I found that by the time you have opened the valve to shunt past the cooler, you are also dumping into the sump. That is there is a small overlap between the outlet to the oil gallery and the grooves cut in the bore leading to the sump exit.

Finally, the piston is simply loose in the bore. I can understand a fear of seizing, but there is no way that with my system oil isn't streaming into the sump, and it will stream faster as it thins - much faster.

I also spent a long time cruising the Samba - they ought to know whats up. What I found is a recurrent theme of new engines built in a variety of ways making low oil pressure. Many people were happy with what I ended up with - 10 psi at idle. On a new engine.

It is steel against untreated aluminum, so wear would be expected, but mine do not look worn - just poorly made. Maybe they are worn and I cannot tell. I got a face full of oil on one attempt at examination, so I may have missed things.

It seems an ideal situation for machining or sleeving during the rebuild, and I actually found a manufacturer of a sleeving kit with a ball bearing valve.

Thoughts ladies and gentlemen? (IMG:style_emoticons/default/idea.gif)

[reharvey]

I've been following your posts about the oil pressure problem because I went through this very same thing many years ago after a rebuild. I tried to find a solution in the way you have but the bottom line was to much bearing clearance. As soon as the oil heated up the pressure dropped off. Hate to be the bearer of bad news but my only solution was to take the motor back apart. You'll find that if you use 20w50 oil along with a can of STP it'll keep the pressure up and you may be able to just drive it for a while. I did for over a year with no problems. Good luck.

[worn]

I've been following your posts about the oil pressure problem because I went through this very same thing many years ago after a rebuild. I tried to find a solution in the way you have but the bottom line was to much bearing clearance. As soon as the oil heated up the pressure dropped off. Hate to be the bearer of bad news but my only solution was to take the motor back apart. You'll find that if you use 20w50 oil along with a can of STP it'll keep the pressure up and you may be able to just drive it for a while. I did for over a year with no problems. Good luck.

What was the cause of the excess bearing clearance? I would like some ideas before I pull it back apart.

[reharvey]

I've been following your posts about the oil pressure problem because I went through this very same thing many years ago after a rebuild. I tried to find a solution in the way you have but the bottom line was to much bearing clearance. As soon as the oil heated up the pressure dropped off. Hate to be the bearer of bad news but my only solution was to take the motor back apart. You'll find that if you use 20w50 oil along with a can of STP it'll keep the pressure up and you may be able to just drive it for a while. I did for over a year with no problems. Good luck.

What was the cause of the excess bearing clearance? I would like some ideas before I pull it back apart.

I rebuilt another motor to replace the one with oil pressure problems. Years later when the old motor was torn apart we found that the # 3 main bearing was a mess. Don't know what went wrong but it had deep grooves in it and was worn out. By the way--I tried the Melling pump in the old motor and it made things worse. The oil pressure was lower than with the stock pump. Ray

[worn]

I've been following your posts about the oil pressure problem because I went through this very same thing many years ago after a rebuild. I tried to find a solution in the way you have but the bottom line was to much bearing clearance. As soon as the oil heated up the pressure dropped off. Hate to be the bearer of bad news but my only solution was to take the motor back apart. You'll find that if you use 20w50 oil along with a can of STP it'll keep the pressure up and you may be able to just drive it for a while. I did for over a year with no problems. Good luck.

What was the cause of the excess bearing clearance? I would like some ideas before I pull it back apart.

I rebuilt another motor to replace the one with oil pressure problems. Years later when the old motor was torn apart we found that the # 3 main bearing was a mess. Don't know what went wrong but it had deep grooves in it and was worn out. By the way--I tried the Melling pump in the old motor and it made things worse. The oil pressure was lower than with the stock pump. Ray

Thanks. I am interested in doing a post mortem on the 2.0 I took out to see what the deal was. After several autocross runs the OP would poop out. No problem getting to the event though.