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)

[nathansnathan]

I've experienced this same thing, low oil pressure on newly built motor. My conclusion after years of thinking searching, etc, the problem for me is wear in the bore of the oil pressure relief valve and oil pump bodies being too small on the newer type 1 pumps.

It was Adrian from headflow masters who really showed me how the relief valve wears. He had made a tool to check them, a screw driver welded to a relief piston. About half way up the bore you feel the groove it gets stuck on. What feels like a little lip with your finger, when the tool reaches that point, you can cock it out by way more than you think.

Different conditions can happen with wear there, too. If the seat isn't holding you will see low pressure at hot idle. Oil seeping by in the loose bore causes problems off idle. There are other ways it can fail, if it becomes cocked in the bore, it either won't open or it won't close depending on which end it gets stuck at.

I was pretty enthusiastic about Adrian's ball valve sleeve insert when he showed it to me. Reviews on shoptalkforums are not favorable, but it is just 1 guy that had a bad experience from what I can see. Adrain said the same, said he'd give me one for free if I let him install it. I was totally going to take him up on it, but didn't make it back down to Vista for like a year after, got a different case going in that time. I am still thinking about the ball valve.

Something that I couldn't figure is if it is knurled on the outside, because that one guy said it was, and that it never would come out, so it it gets screwed up on install the case is trash. It doesn't look knurled in the pic on Adrian's site, though. Still thinking about it...

[worn]

Yeah Nathan, I looked at that site too. I am way tempted.

It looks like the oil relief system is highly dependent on oil viscosity since there is no seat for the piston. The Welmeister kit seems to solve this by making longer pistons - that also mess with spring pressure. I suspect that the longer piston restricts escape flow more than stock.

I have to say I did not install the Melling pump as it came out of the box. I sanded down the clearances and then had to clean up a lot of sand casting in the flow passages.