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)

[eyesright]

Warn

I located the relief valve seat by looking up the bore. It didn't make sense the times I inspected it before, tryiing a spacer under the piston, different spring, honing the piston top, etc. but your photos and explaination made it all clear.

So I got some marking fluid which showed a bung on the seat. The seat, incidently, appeared at most to be 1 mm on one side and probably 2mm on the other. for what ever reason, the bores didn't apper to be concentric. In any case, just a small seat like that actually is a comparatively large area since its on the outer circumference and should make a differrence in opening and closing pressures.

So with wet/dry paper glued to the top of the piston and trimmed to the bore, I spun it by hand against the seat. I ended with 600 grit and the seat shined! Nice and smooth.

So I run it and ....same low oil pressure, about 5 @idle, 15-20@ speed and oil temp slowly climbing to 220F. Went Ace hardware and found a stiffer spring, the gauge was about 20% larger and it was 1 cm longer. Maybe under heat it faded but anyway...., same pressures and temp!

Well, shucky darns! So my options are still

!) clearance problems

2) pump problems

3) some other relief/regulator problem

4) cheap gauge/sender

5) or NO problem... VW Porsche made this one this way and its going to run like crazy for 200K miles. I've put 1000 break-in miles on it now and my know-it-all advisor/pal says I if it was really a problem I'd probably know it by now.

I think I will order a new piston just to rule out the piston bore being part of the problem. Any comments anybody?