Sealing rings at top/bottom of cylinders

[Tcash]

[Clatter]

The 2nd relief valve is found on early type 4s only.

The tool to remove is a ‘triple square’ like the CV bolts.
It’s also used on auto transmissions and different late model VW/Audi.
Can’t remember the exact size, but it is used in several other scenarios,
So you should have an easy time borrowing/buying one.

Smack the relief valve plug with a hammer,
And it will smush the crush ring,
And make it easy to remove
(Should it be stuck and give you trouble).


EMW sells a solid spacer kit to eliminate/replace the spring,
And hence the entire 2nd relief plug altogether.
The spacer pushes the relief valve solid against its seat,
Effectively turning your dual-relief case into single.
Pretty sure you just found a reason they do this..
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[Wildthings]

[Volswagon]

The motor I'm rebuilding is also a '72 CB block. It appears Mark Stephens put a notched piston with a stock spring in the 1st relief, and a limiting rod inside the spring at the 2nd control valve.
I've never had a pressure or temp. gauge installed, I'm apprehensive about this T4store 30mm pump I'm installing.
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'75 Bus https://www.thesamba.com/vw/forum/viewtopic.php?t=697183&highlight=

[RalphWiggam]

Ill pick up a 13mm triple square at lunch today and have a look at my second pressure relief valve tonight.

Ill also call EMW and talk to them about why someone should use their 2nd relief blocker kit. I would assume it is for people who switch to hydraulic lifters in an early case.

[SGKent]

The late case does more than just eliminate the second pressure valve. It also recirculates the over pressure oil that is dumped and sends it back to the oil pickup.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[RalphWiggam]

Just talked to EMW. They confirmed that their secondary relief blocker kit would do nothing for hot oil pressure.

I couldnt find a 13mm triple square bit anywhere. I found 12mm and 14mm (of course).

I read somewhere on here that a 3/8" socket extension fits perfectly. I will try that.

[raygreenwood]

[SGKent]

[tommu]

Is there a consensus on the late, single piston being grooved or solid? I pulled a solid piston out of my GEX rebuild which I obviously do not trust

I have seen some second hand reference to solid pistons in late single valve cases but nothing documented from an official source.
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[SGKent]

I believe slotted. On a single relief the slot lets a set amount of oil bypass the gallery (and loop back around to the oil cooler again on late G series engines). On prior engines the excess that went thru the cooler was dumped back into the sump. Either way it let the engine cool more oil than it was using. We think our engines are air cooled but in reality they are both air and oil cooled. (Except Skills and his Subie friends who are water cooled).

021 115 411 A http://www.busdepot.com/021115411a

There is a lengthy debate and discussion here. https://www.thesamba.com/vw/forum/viewtopic.php?t=623487
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

[RalphWiggam]

Both of mine are slotted. Here are some pics of the second oil control valve I pulled out from under the #1 cylinder.

Should mine not be slotted? This valve was a bit scored on the top so I sanded it down and polished it back up. It was moving very nicely in its bore. I don't think it has anything to do with my low oil pressure when hot.

[Wildthings]

[SGKent]

make a block of wood the size of the dimension in Bentley where it reads at X pounds. Then get the bathroom scale. Put the spring and block side by side on something solid and zero the scale. Push the spring down. As you push it you will see the weight go up slowly until it reaches the thickness of the block of wood, then it will go up suddenly. That instant before it jumps is the weight of the spring at the Bentley height. Personally I think it will be close. Were it me I would replace that plunger as it is pitted. You can sand it on 1500 grit paper to smooth the top until it is smooth in the meantime.

I replaced mine and saw pressure go up and temps fall about 10%, & mine looked nicer than your valve. That said I would replace both of the valves then test oil pressure again. I got mine from VW Heritage but Bus Depot says they have them now.

When those valves leak you are getting the slotted leak which VW planned for and the valve leaking too so it drops the PSI enough that it is a problem when hot.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[tommu]

Here's Colin's method too measure spring pressure:

http://www.itinerant-air-cooled.com/viewtopic.php?t=12459&start=15

Ray, Steve thanks for the feedback on the correct Piston. A new genuine slotted one just arrived from Heritage Parts so I'll use that.
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[busdaddy]

A bathroom scale on a drill press table works too, set the spindle stop to the required height.
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[RalphWiggam]

Put my new set of Duralast Gold plug wires on last night along with the new mechanical oil pressure gauge.

Took it for a spin to get it real nice and hot. Same issue. Once the oil get to about 205 or so I only see about 25psi at 3500 rpm. The idiot light is now coming on at the majority of stop lights when the engine is hot. I was by myself so I couldn't read the mechanical gauge at different revs.

I'm going to grab some VR1 Racing 20w-50 tonight and see what that does. I'll try again to get all of the air out of my 18" sender extension. I'll also check the main pressure relief and pull the oil screen and make sure everything is ok while I'm changing the oil.

Anyone have any other ideas? Am I just delaying the inevitable of having to install a 26mm oil pump?

Relevant Info:
- 150 miles since full rebuild
- Running SAE 30 break in oil
- Dual relief case
- Fuel pump bushing and shortened rod are in place (using electric fuel pump)
- Replaced o-ring on oil pump during rebuild
- Gears and housing in oil pump looked good during rebuild
- No gasket on oil pump flange to case (used loctite 518)
- Both pressure relief pistons are moving freely
- Using Mann 920/17 oil filters
- Running a remote oil pressure sender/idiot light setup with 18" stainless hose from the idiot light port in the case
- Dual pole and single pole VDO senders indicate about the same

[SGKent]

send the pump to Phil to be re-machined. That is the only thing I could recommend. Whether that will fix the issue or not I don't know. You are losing pressure somewhere. 20-50 will improve the issue but it isn't the only issue you are having.
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“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

I agree with SGKent.

You note....that pump and gears "looked" ok. Did you do any measurements?

The pump has two main factors that can create low volume.....both represent qbout 50% of volume losses in my experience....one is gear end play.....as Steve was getting at.....haging it remachined or lapping like I did can correct that.

The gear mesh combined with any excessive slop of the gears on the shaft is the other 50%. Having either one but not both.....means only a little bit of loss. Having both can be significant.

The other question I have to ask....simply because I cannot remember.....how were your crank bearing to journal tolerances on both mains and rods?

We tend to work hardest at the main to crank bearing journal tolerances in order prevent excessive movement to prevent both pounding and oil pressure loss.

But in reality the rod journal bearing tolerances are even more critical....for both straight running of rods and that due to their oscillation movement and being at the end of the line of the oil flow chain through the crank.....and because of those factors....need to somewhat be the "thumb" over the end of the hose.......larger than ideal oil tolerances on the rod bearing can be a prime cause of low oil pressure.

A good overall rule of thumb for ideal rod bearing oil tolerances is a MAXIMUM of .001" for each 1.0" of rod journal diameter. So the rod journals are 2.16".....so the absolute max for the oil tolerance and mechanical movement and oil film is .0021".

Though the factory tolerance is 0.0008" to 0.006".....that .006" is insane...unless you have the absolute minimum rod side clearance (axial play). Most of us have somewhere in the upper 75% of rod side play tolerance....unless we are using brand new aftermarket rods.....so that means that our rod bearing to crank journal oil tolerance needs to be as tight as possible.....about .002" max.....for best oil pressure.

But none of this is tragic. Its why there IS tunability in both oil viscosity or rebuild your pump and/or the ability to even go to a 26mm pump if your pump is a bit worn.

If you wrote down what your pump and your rod and main journal tolerance measurements were.....then you probably have your answer as to WHY your oil pressure is low.

I also applaud the way you have gone about this. I know its time consuming and tedious.....but its the correct. Way. Too many people just automatically throw a thicker oil at an engine....without real diagnostic work to all of the potential other issues.....like verifying oil pressure gauges and senders....and absolutely verifying that oil pressure relief and control valve pistons and springs are spot on.

Knowing what its NOT.....will point you to what it actually is. What I disagree with...especailly with what you spent.....is just automatically throwing big pumps and heavy oil at an engine when that may not be the issue. Both have their trade offs. Ray