Low oil pressure at idle. Only 12,000 miles on new rebuild.

[IdahoDoug]

Nice input on the spring and shim. Agree, at hot idle is the lowest oil pressure an engine sees. And it would be just flat wrong to claim the old spring is not holding the bypass valve shut, so a new spring does hold it shut. Why? It would mean that at a pressure of perhaps 5psi, the spring is so weak it is opening. Which if you apply your noodle(s) you will realize that means at 25 while running down the road, the valve is WIDE open and actual pressure going to the bearings and such would be - what - 15? 18?

So this simply does not pass the sniff test. As xflyer notes, these bypass springs are in virtually every automobile engine on the planet. Since the failure or even weakness of these springs would lower oil pressure, it's safe to say the manufacturers pay more than just casual attention to their quality and lifetime of function or they'd be rebuilding engines left and right. This is a super simple and durable system every single car has - it is not unique to the WBX.

So, don't shim these springs. You are literally INCREASING the chance of damage to your engine by raising the cold max pressure with thick oil. And that is quite literally all you are accomplishing. Zero impact at operating temperature. I want my Samba buds to understand this, so if there are further questions I'm happy to continue. I've had a little experience with production engines as the former WorldWide Engine Planner for GM.
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1987 2WD Wolfsburg Vanagon Weekender "Mango", two fully locked 80 Series LandCruisers. 2017 Subaru Outback boxer. 1990 Audi 90 Quattro 20V with rear locking differential, 1990 burgundy parts Vanagon. 1984 Porsche 944, 1988 Toyota Supra 5 speed targa, 2002 BMW 325iX, 1982 Toyota Sunrader

[Ahwahnee]

Yeah, what ^they^ said.

And I believe the case against Fram was further exacerbated by a website where a disgruntled former Allied Signal engineer had an ax to grind.

[michaelasnider]

[DanHoug]

here's some photos that should illuminate the situation....

this is the bore of the oil relief plug + spring assembly. if you look closely, you'll see that there is a dual relief channel that runs alongside the piston chamber. these channels begins about 1/8" off of the piston seat and go all the way past the oil relief port, which is about 1/2 way in the bore. so it takes is about 1/8" piston movement before the bypass channels are reached. if the piston was a tight fit in the bore, little oil would flow into the bypass channels if the piston moved against spring pressure less than 1/8". but it is NOT a tight fit, and the sealing appears to be done largely on the seat the piston rests. as soon as the piston lifts off the seat, there is SOME bypass oil flow. time for pictures....

bore showing dual bypass channels located 1/8" above piston seat

this is the stack of parts, note the piston rests on TOP of the spring but goes OVER the guide on the plug

this is how far the spring extends above the plug threads with piston installed. even if the spring is short, there is compression on the spring because they are never THAT short.

now... "I'd like to buy an argument" <Monty Python>

Hooke's Law says that a spring's force is proportional to the extension. this means that as the screw-in plug compresses the spring, additional length provided by adding a washer will result in a proportional increase in pressure of the piston against the seat. i THINK we're all good up to this point.

the question is whether the oil pressure raises the piston off the seat at low oil pressure, because lifting it off the seat just a tiny bit WILL bypass some oil because the piston is loose in the bore. empirical testing by some people on this list has shown that increasing the spring pressure a washer thickness did indeed result in a small increase in hot idle oil pressure. this suggests that the oil pressure relief system has some effect before the piston moves the 1/8" to uncover the bypass channel.

"Time's up. Good day."
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-dan
60% of what you find on the internet is wrong, including this post.

'87 Westy & '89 Westy both 2.1 4spd

Past projects can be found at--
www.thefixitworkshop.com

[3xvanagon]

Super interesting, so I took the crush washer out today of the plug which effectively raised the seat of the plug and spring by the same height as a washer would and noticed zero change in oil pressure hot or cold. I can't see how a washer on the plug seat (where the spring sits) would have any different effect?

[DanHoug]

[3xvanagon]

Depends on how you define as hot idle. I find a huge discrepancy between hot city driving (30+ minutes) , and a long haul on the highway (30+ minutes)

City
Idle-9 psi
Fourth gear 3000+ rpm 25 psi

Highway
Idle-7 psi
Fourth gear 3000+ rpm 22 psi

Oddly, In both instances it seems very gear dependent, for instance in 3rd gear at 3000+ rpm I see ~5psi higher.

When people speak of "acceptable" psi values, I'm also curious how they are measuring (long highway hauls, city driving, in what year, etc)... At least for me, this provides varying results.

Compression on the engine is fantastic 155-160 across all 4, so I suspect maybe I had a top end rebuild from PO. I did replace the oil pump with a high volume one from gowesty for good measure, which seemed to keep oil pressure higher between 2-3k psi and a maybe 1 psi higher in "hot" scenarios.

[DanHoug]

you've got some real data, many don't report to that level! your 3rd gear oil temps are less because the engine is under less working load... your van is going slower for the same rpm so the engine is doing less work.

your oil pressures are getting to the low end... below the 10psi/1000 rpm wear limit (set forth by VW or else 'common wisdom'). i'm rebuilding a motor for a van that runs great but has about 22 psi hot at 3500 rpm and none showing on the gauge at idle but the oil light doesn't flash so it is above the low switch threshold of 2-5psi.

[xflyer]

Comparing those oil pressure readings with oil temp will probably explain the differences between the "city" and "highway'' driving.
On a side note to that, I found that running the oil level about 4-5 mm above the "low" mark on the stick lowers the oil temp by about 30 deg F. A lower oil temp will likely increase the sought after oil pressure.
Was the cause of the low pressure on the engine being rebuilt found?
Also my 85 (2.1 conversion) did this once, oil light on at operating temp idle. Turned out the problem was a cam bearing that was falling apart. Used to see that long ago on the 40hp 1200 motors (first ones with separate cam bearings) with a lot of miles and questionable servicing. Replaced bearings and its been fine since then (15 yrs ago).
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C

[DanHoug]

[ThinkingD]

Just weld a nut onto the oil pressure relief valve cover. No more removal problems, or need for a BMFSD.
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87 Titian Red Westfalia 2.0 VW I4 SOHC manual Ottawa, Ontario

[xflyer]

Hopefully you are replacing the infamous 2.1 rod bolts.
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C

[xflyer]

"weld a nut onto the oil pressure relief valve cover."
Good idea. What I learned was to tap the plug with a steel hammer. This loosens it without strange tools, cursing, and bloodletting.
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1989 Campmobile, 1984 7 passenger beater Vanagon
Both with cool A/C