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.

[Cap'n Krusty]

How is a larger oil pump, which will definitely increase flow, going to increase oil pressure. I agree with the previous post. I may be wrong but, IMO, low oil pressure is a result of insufficient restriction somewhere in the system. That means something out of tolerance, like an OP relief valve, bearing clearance too great, or damage to an oil passage resulting in a leak.

The Cap'n

[worn]

Here is a drawing about what it looks like. Sorry I am playing with a tablet pen.

[FourBlades]

Keep in mind this is just a guess...

The oil pressure relief system includes a spring and a piston.

The PET lsits 2 springs and 2 pistons by part number.

Could you have the wrong spring or piston for your engine block?

Maybe the spring is just fatigued from 40 years and opens too easily letting your pressure bleed off?

John

[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]

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.

I am not ruling out the bearings. They are new, I measured the case lots of different ways - Pawn shops have micrometers that even include calibration standards.

As the Capn says there is oil leaking out somewhere. And while it might be the bearings, it might also be something else. My initial idea was that the pressure relief couldn't possibly be the problem, but I am looking at a valve that has tons of clearances all over - at the non-existent seat, and with at least ten fold more side clearance than any of my bearings. I was shocked at how the thing was made after I looked at it closely. I figured that the idea of the relief system letting out pressure was simply wishful thinking (cannot say I'm not wishful) - but now I am really not so sure.

In answer to the capn. Given some leak of pressure, a larger pump will bring a higher equilibrium pressure for a given size escape hole. So the oil pressure should go up in a system that is below the rated delivery pressure of the pump. If the bearings are loose, this is probably just making the gauge feel better because the oil film depends on close tolerances.

If someone has a shot case, I would love to cut it apart to have a better look at the relief and other parts of the oiling system.

Capn - have you ever seen a case with an inadequate relief bore?

[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.

[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.

[worn]

How is a larger oil pump, which will definitely increase flow, going to increase oil pressure. I agree with the previous post. I may be wrong but, IMO, low oil pressure is a result of insufficient restriction somewhere in the system. That means something out of tolerance, like an OP relief valve, bearing clearance too great, or damage to an oil passage resulting in a leak.

The Cap'n

I found a wonderful post on the Samba in which they tested 100 newly rebuilt VW engines at different temperatures, monitoring oil pressure and flow using both a 26 and 30 mm pump. It is worth reading for most of us:

http://www.thesamba.com/vw/forum/viewtopic.php?t=280293

For me, several parts were of interest. For one thing it shows what happens when you change pump size. So they answer the Capn's question. I am regretting the Melling already, but it was enough work to get in that I am giving it a try. Car is almost buttoned up. Maybe I will end up with lower viscosity oil in the end.

The second part was in a warm engine, they uniformly found low oil pressure at idle - about 10 psi. 100 engines, very low variance.

For me the most interesting part was the design of the pressure relief valve. These were two valve engines, although not type 4. The VW engineers were very careful about how these should be made, and a very clever bevel modulates opening pressure to make it higher than closing pressure. I can say for certain - mine ain't shaped like it is supposed to be! It is either completely worn out, or more likely, never made right to begin with.

I understand there were design changes between the motors described in the article and the ones we run, but read the post, it is completely worth it. (IMG:style_emoticons/default/pray.gif)

[r_towle]

Check the case main bearing seat size.
Check the main bearing thickness.
Check the main bearings in the case all torqued down, no crank.

I recall Jake mentioning that the main bearings halves were slightly large and needed to be hand files down on the top edges to allow the case to close all the way.

Rod bearings may also be having the same issue, not sure.

Pretty sure Jake measures everything with bearings and not with bearings to verify the bearings are right.

With his higer volume of motors, he sure has seen all the wierd product issues coming onto the market.

Just because the bearings are new does not mean they are right.

Rich

[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]

Check the case main bearing seat size.
Check the main bearing thickness.
Check the main bearings in the case all torqued down, no crank.

Just because the bearings are new does not mean they are right.

Rich

Thank you Rich. It isn't as though I don't believe I can make a mistake. I work in a checklist environment and I have made many many of them. Believe me, I know I get things wrong on a regular basis.
My worry though is what happens if I take it back apart and there is nothing that I can find wrong in the clearances? So I want to cover other avenues first. The tranny build went just like that, but I spent months on the engine measuring. When I was a post doc at Berkeley my advisor told me something that stuck forever - if you do an experiment and get a result, and then do it again the most likely outcome will be the same result.

Also, the fact that we have data about 100 VW engines is pretty mind blowing to me. No, it is the fact that it is data we get to look at.

Thanks again Rich. The advice I get here is always appreciated.

[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.

[yeahmag]

Interesting for sure:

http://www.headflowmasters.com/vw-oil-pres...valve-body.html

[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.

[r_towle]

Check the case main bearing seat size.
Check the main bearing thickness.
Check the main bearings in the case all torqued down, no crank.

Just because the bearings are new does not mean they are right.

Rich

Thank you Rich. It isn't as though I don't believe I can make a mistake. I work in a checklist environment and I have made many many of them. Believe me, I know I get things wrong on a regular basis.
My worry though is what happens if I take it back apart and there is nothing that I can find wrong in the clearances? So I want to cover other avenues first. The tranny build went just like that, but I spent months on the engine measuring. When I was a post doc at Berkeley my advisor told me something that stuck forever - if you do an experiment and get a result, and then do it again the most likely outcome will be the same result.

Also, the fact that we have data about 100 VW engines is pretty mind blowing to me. No, it is the fact that it is data we get to look at.

Thanks again Rich. The advice I get here is always appreciated.

So , I appreciate that you measured quite a bit of the motor, but what I am asking is not typical.

Did you measure the roundness of the main bearings mounted in the torqued case with no crankshaft in place?

This would produce an oval measurement if the bearings are as Jake has found some of them to be, which is to large.

Did you do the same process to the rods on the big end, bearing in place, measure for round.
Again, same condition, same results.

Using an internal bore measuring device, done in a systematic way will produce the results of round or oval...

Just putting that in the back of your mind...again, its not a typical thing to ever do when building a typical motor...but with Jake finding these bearings coming from the factory to large, I now do this extra set of steps just to be sure.

Mind you, I build maybe two a year....
Jake builds alot more, so he will see more issues.


Lastly, I would look into the heavier spring and new piston for the pressure relief system.
http://vwparts.aircooled.net/Bugpack-Oil-P...lief-p/3041.htm

Not the exact part, but call them, they are cool and they have the right one...
I would go for that...20 bucks that may help..

Rich

[worn]

Check the case main bearing seat size.
Check the main bearing thickness.
Check the main bearings in the case all torqued down, no crank.

Just because the bearings are new does not mean they are right.

Rich

Thank you Rich. It isn't as though I don't believe I can make a mistake. I work in a checklist environment and I have made many many of them. Believe me, I know I get things wrong on a regular basis.
My worry though is what happens if I take it back apart and there is nothing that I can find wrong in the clearances? So I want to cover other avenues first. The tranny build went just like that, but I spent months on the engine measuring. When I was a post doc at Berkeley my advisor told me something that stuck forever - if you do an experiment and get a result, and then do it again the most likely outcome will be the same result.

Also, the fact that we have data about 100 VW engines is pretty mind blowing to me. No, it is the fact that it is data we get to look at.

Thanks again Rich. The advice I get here is always appreciated.

So , I appreciate that you measured quite a bit of the motor, but what I am asking is not typical.

Did you measure the roundness of the main bearings mounted in the torqued case with no crankshaft in place?

This would produce an oval measurement if the bearings are as Jake has found some of them to be, which is to large.

Did you do the same process to the rods on the big end, bearing in place, measure for round.
Again, same condition, same results.

Using an internal bore measuring device, done in a systematic way will produce the results of round or oval...

Just putting that in the back of your mind...again, its not a typical thing to ever do when building a typical motor...but with Jake finding these bearings coming from the factory to large, I now do this extra set of steps just to be sure.

Mind you, I build maybe two a year....
Jake builds alot more, so he will see more issues.


Lastly, I would look into the heavier spring and new piston for the pressure relief system.
http://vwparts.aircooled.net/Bugpack-Oil-P...lief-p/3041.htm

Not the exact part, but call them, they are cool and they have the right one...
I would go for that...20 bucks that may help..

Rich

Thanks for the in depth reply. The answer is often but not always. With the round bearings on the mains I quickly found that plastiguage wasn't gonna help. So I did measure roundness mostly with a set of snap gauges and an internal mic, not the ideal tools.

I won't have the hard data for a few days but tonight I found what appears to be the smoking gun. How much smoke remains to be seen, but it looks to me like folks are underestimating the complexity of the relief system, and that may extend to factory machinists. At this point I can clearly say that at high temp my oil relief should have been sendinding oil all to the cooler. It was instead bleeding oil into the sump at a rapid rate. Nothing to do with the pistons or the springs, but instead either case wear or sloppy machining. Look at the samba post - it is an eye opener about where and at what pressure oil in this class of engine goes.
I cannot thank you and others enough.
Warren

[cary]

Did you get a case yet?

I have one that had a hole blown out the side where the PO or wrench forgot the slotted oiling washer under the distributor. (IMG:style_emoticons/default/mad.gif) (IMG:style_emoticons/default/mad.gif)
I JB welded the case after it was out just to see how it would work.

I'm pretty certain I have both halves. I'll look tonight. I'm heading to the shop to collect my backpacking gear.