Excessive case pressure - rebuilt engine

[BDorsey]

Hi all,

Another cross post with he Vanagon forum. Hope nobody minds.

I have just over 1000 miles on a rebuilt AC 2L FI California spec. engine, all stock. I am getting oil out of the dipstick tube, pushrod tubes and oil filler junction - like a spray of oil all over around the fan, not just a drip. I rigged up a spring to hold the dipstick in the tube (b/c it is somewhat loose-fitting) and that reduced the oil spray but there is still leakage around the fan shroud (oil filler? main seal?!?) and the push rod tubes.

I am fairly positive that there is no restriction in the case ventilation system as I have replaced the "PCV" valve on top of the crankcase vent with one similar to this: https://www.thesamba.com/vw/forum/viewtopic.php?t=769148&highlight=pcv and checked the flow through this. It seems to flow fine.

I suspect higher than normal crankcase pressure because if I remove the PCV valve and hold a piece of paper over the breather it blows straight up. But, I honestly don't know what 'normal' pressure is.

I have checked compression and all cylinders are 130-140 psi.

The builder said to change the 20W-50 I have in there for 10W-40 and see if that helps but I am skeptical that oil type is the problem. Shouldn't the oil stay in the engine when using the recommended grade?

I could use some info on 'normal' crank pressure and possible causes for high pressure besides excessive blowby (assuming good compression = normal blowby).

Thanks!
Brian
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1982 2.0L Aircooled Country Homes Camper

[busdaddy]

Barfing it out all over isn't normal.....

Describe your break in procedure for us please.
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[aeromech]

Well,
If everything breatherwise is stock then I’d have to suspect the piston rings. That said, just run 10W30 oil. Use an additive with zinc for cam break in
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[BDorsey]

Hi

The builder did the cam break in. Trying to follow Jon from aircooled, I drove fairly hard for the first 500 miles and pushed it hard on some local hills thinking his would seat the rings. Then I changed the oil and have mostly driven around town while working out FI issues but still trying to drive it somewhat hard.

When I realized changing the pcv valve didn’t stop the leaks and observed the amount if air coming out of the breather, I did a session of hill repeats thinking the rings might not be seated. I loaded down the engine on the ups, varying the speed, and let compression slow me on the way down to put pressure on both sides of the rings. I have read that is a good method.

It was during this session that enough oil came out of the dipstick tube (and maybe oil filler) to coat the access door and get flung around by the fan. I may have painted too extreme a picture when I said spraying everywhere. I wouldn’t say it is puking everywhere, especially with the dipstick secure, but it hasn’t stopped leaking.

Hope this is helpful.

Brian
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1982 2.0L Aircooled Country Homes Camper

[BDorsey]

Aeromech,

I figured bad or unseated rings too but the compression is great in all four pistons. Could both things be true?

Brian
_________________
1982 2.0L Aircooled Country Homes Camper

[BDorsey]

Sorry Aeromech, I also meant to ask, are you are saying that the oil grade can be the cause of leaks?

Thanks
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1982 2.0L Aircooled Country Homes Camper

[jmstu76]

I had a friend mistakenly hook up a hose meant for the fuel evap system (hose was meant to go to the charcoal canister) to his case vent. Obviously it pressurized the case big time and oil was pushed out all over out of various seals. Once we got the hoses routed correctly no more oil was pushed out.

Just a thought...
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James

'76 Deluxe Sage Green Westy
2258 cc GD case 78mm CW crank, 2.0 H-beam rods 5,325” 22mm pin, JE forged pistons with 15cc dish, JE rings, type 11 clearanced oil pump, CB Eagle 2205 Type-2 “Torque Special” hydraulic cam with matched lifters fed by CB Dual Weber 40 IDF MX with 6” foam air filters, currently 55 idle, 130 main, 200 air correction, 32 mm venturis. 27in General Grabber AT2 All Terrains, Berg Shifter, stock '76 exhaust HPC Ceramic Coated. 11/18/2020

[aeromech]

Don’t use thick oil on a new rebuild. Something to consider is that maybe you have an incorrect dip stick. Do an oil change an install a known quantity of oil. Then look at the dip stick
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[BDorsey]

Thanks Aeromech. I did not know about thinner oil in a new engine. I will change it and test the dipstick as well.

Thanks!
_________________
1982 2.0L Aircooled Country Homes Camper

[busdaddy]

[Wildthings]

With the PCV valve installed but the hose removed, do you get air blowing out of the valve?

Make sure the hose itself isn't clogged.

Hook up a hose to the dipstick tube and see if it seems to blow excess air.

You don't have added rock box vents do you?

How about taking and posting pictures of your engine compartment showing all your hoses.

[BDorsey]

OK, I have some observations and answers to good questions posed here.

Aeromech - I changed the oil to 10W40 as suggested by the builder. I put "exactly" 3.7 qts in - measured with the scale on the side of the 5 quart oil bottle. This volume only reaches the FIRST (i.e. low oil) notch on the dipstick. I compared the length and notch positions with those here https://www.thesamba.com/vw/forum/viewtopic.php?t=770023&highlight=dipstick and they were all maybe 1/8" LONGER on my dipstick. But, this could be down to tape measure accuracy or wear on the rubber plug. The curious thing is that inaccurate notches in this direction should result in the correct volume measuring too high.

So, my question now is whether to trust the dipstick or the spec in Bentley for oil volume. Relatedly, how much change in case volume is possible during the rebuild process? Could this change the required oil volume? AAHHH so many variables!

In any case, I cleaned the oil off the engine and took a ~15 mile test drive. There is some oil leakage but it looks like less. So that is progress. Read on for more progress!

Wildthings - my old PCV valve did not allow much airflow at all, but the new one does. But, the post from which I learned about this particular part is ambiguous about the orientation of the valve. So, I tried to feel if one way allowed more flow than the other. It seemed there was a difference so I change it around and that is when I think I made an important observation. Previously, there was positive pressure from the oil filler tube when I removed the cap at idle. But with the pcv valve reversed there is now a slight negative pressure and removing the cap affects the running EDIT: - vacuum leak! This tells me the positive pressure is reduced but I actually don't see why it would affect engine performance.

I think this may be significant and could possibly solve the problem.

Any thought about oil volume and measurement or the case pressure (or anything else) are much appreciated!

Thanks
Brian

PS Here are a couple pics of the engine, as requested. These are with the PCV valve in the NEW orientation.

[/img]
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1982 2.0L Aircooled Country Homes Camper

[aeromech]

1). Install a known quantity of oil. Whatever the book says is the capacity. Check the dipstick after shutdown. Does it match the marks? No? Make a new mark on the dipstick and use that. Done.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[Wildthings]

FWIW, I have been running an additional quart of oil in my Type 4 engines for 35 years and have never had a problem with oil blowing out of the dipstick tube or anywhere else because of doing so.

[aeromech]

In my opinion, 40 weight oil is too thick in a new engine during winter
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[SGKent]

if you build up positive pressure in the crankcase then it WILL puke oil out, blow dipsticks out, etc..

You need a neutral, or minimal negative pressure in the crankcase to draw crankcase gases out.

I would look closely at the prior posts on the PCV valve conversion to be sure you have it the right way. If it is installed the right way, any positive pressure will push the valve open and let crankcase gases flow out. The ONLY time a working and properly installed PCV valve allows pressure to build to where oil is puked is if there is massive blowby thru the rings or valve guides, hole in the piston.

Based on what you wrote, it is likely you had the valve backwards but please double check against prior posts on the conversion. You can't tell which way it goes by sucking or blowing on it. You need to look at the arrows, or design.

Break-in oil is typically SAE 30. SAE 40 in winter is really thick oil. Maybe in summer SAE 40, 10W-40, 20W-50, 15W-50 etc works fine but winter with the high oil pressure it builds, you can blow out an oil filter or gallery plugs that way. When we go to Yosemite it can be 95F - 100F in the valley and the long climb into the Sierra Mountains suits SAE 40 or 20W-50, but in the morning up there sometimes it is close to 35F the next morning if a spring cold front has gone thru, so I have to let the engine idle until it is warm or the oil pressure goes ballistic. You can't drive a cold engine with thick oil in the cold without excessive oil pressure. And in cold weather it may never warm up enough to thin out properly. You need 10 PSI per 1000 RPM. That is a really safe guidline. Plan your oil viscosity around that pressure.
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[BDorsey]

This is great. I am learning.

Wildthings - your experience is reassuring as I didn't understand how a little extra oil would cause it to blow out. The pressure really is the thing.

Aeromech and SGKent - Thanks for these opinions on oil weight. I really didn't know that a new engine needed lighter weight. I understand the relationship between viscosity and temp but what about a new engine, specifically, needs lighter weight? Does thicker oil prevent the rings from seating properly because they never contact the piston walls? Thanks for any more explanation of this.

Brian
_________________
1982 2.0L Aircooled Country Homes Camper

[aeromech]

You want the oil to flow. Viscosity is a measure of resistance to flow. When bearings and clearances get loose, thicker oil is required. Many modern cars require 0w-20 oil for different reasons. Some even thinner than that.
_________________
Lead Mechanic: San Diego Air and Space Museum
Licensed Airframe and Powerplant Mechanic
Licensed Pilot (Single engine Land)
Boeing 727,737-200-300-400,757,767
Airbus A319,320,321
DC9/MD80
BAe146
Fokker F28/F100
VW type 1 1962,63,65,69,72
VW Type 2 1971 (3 ea.) 1978, 1969
VW Jetta
VW Passat
Capable of leaping tall buildings in a single bound

[metahacker]

this may be helpful
https://lnengineering.com/products/driven-racing-oils/driven-break-in-oils.html

and yeah a backwards PCV ("PRV") will definitely do that
good thing it's something dumb like that and not a bum rebuild with no ring seal

[Wildthings]