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]

FWIW I'm just now rereading the Haynes manual, 6.7, page 20,

"For SAE 30 @ 70C (158F) the pressure at the switch for engine revolutions of 2500 rpm should be 42 psi. If this pressure sinks below 28 psi then remedial action in the bearing circuit or pump is indicated."

I pulled my fresh home rebuilt engine chasing oil leaks at the oil filter mount and rear crank and will post on that when I get it back in the car this week I hope. But I have been following this thread because my pressure seemed low during the 600 break in miles I put on it last month. In my college days driving a VW Bug many miles I remember hearing that an oil light at idle wasn't unusual. Of course it helps to read the manual every now and then so now I'm worried again. And is the oil hot @158F or just on the way to hot if 200F is a more normal temp range.

If I had a direct read oil temp and direct read pressure gauge instead of my electric VDO's maybe I'd feel more secure, and maybe I just need to replace the oil pump while the engine is out....

So I'm keeping an eye on this thread and will add my results

[worn]

FWIW I'm just now rereading the Haynes manual, 6.7, page 20,

"For SAE 30 @ 70C (158F) the pressure at the switch for engine revolutions of 2500 rpm should be 42 psi. If this pressure sinks below 28 psi then remedial action in the bearing circuit or pump is indicated."

I pulled my fresh home rebuilt engine chasing oil leaks at the oil filter mount and rear crank and will post on that when I get it back in the car this week I hope. But I have been following this thread because my pressure seemed low during the 600 break in miles I put on it last month. In my college days driving a VW Bug many miles I remember hearing that an oil light at idle wasn't unusual. Of course it helps to read the manual every now and then so now I'm worried again. And is the oil hot @158F or just on the way to hot if 200F is a more normal temp range.

If I had a direct read oil temp and direct read pressure gauge instead of my electric VDO's maybe I'd feel more secure, and maybe I just need to replace the oil pump while the engine is out....

So I'm keeping an eye on this thread and will add my results

Oh I have no problem making more than 28 psi at 2500 rpm at that temp, it is more like 40. But at full warm up, it sinks towards oil light pressure on the electric gauge at 900 rpm. FWIW, when my electric VDO says 8, my mechanical one from VDO on the case says 15, if that means anything. In the TR6 I just built I get way more than 15 at idle. So I am worried, and it sounds like I should be.

It is worth looking at the Samba article though. The valve illustrated looks quite functional. But the one in my engine contacts the plunger in a rim that does not exceed the chamfer of the plunger (which you can hardly see). I did prussian blue and it marks a shoulder about a half mm wide all around. The case from the motor I am replacing has a contact ring of about 2 mm all around. Neither seems like a great sealing surface for hot oil.

Again, if there is a junked case out there, I would like to dissect it with my band saw.