oil switch question

[Marc]

No.

On a single-relief case the pulley-end valve also serves as the overpressure relief, dumping excess pressure to the sump to protect the cooler. On dual-relief cases that function is performed by the flywheel-end valve, leaving the pulley-end one with only one job - when the engine is cold and the oil is thick, the piston moves down against spring pressure to open up a passage which feeds the main oil galleries directly.
In either type of case, the passage to the cooler is ALWAYS open, but when the "direct" passage is uncovered oil will go that route because there's less restriction than going through the cooler.

The pistons are not sealed tightly to their bores (they don't have seals or rings like the combustion pistons) so a small amount of oil inevitably escapes around them. To prevent pressure from equalizing across the piston, which would render the control system inoperable, each bore has a small hole near the bottom which opens to the sump to give an escape path to any oil that makes it past the piston. Lacking that piston, Kevin's engine has been losing oil pressure there since it was assembled - when the oil's cold & thick it won't squeeze through that little hole fast enough to lose ALL pressure, but once the engine's warmed the oil pump can no longer keep up.

As a rule, the external cooler adapter arrangement (typically including an inline filter; sounds as though this is what you have) is actually a BAD idea. Thousands upon thousands of dollars have been made in the last 45 years selling them to people - they're shiny bits of metal and seem as though they'd be an improvement, but that was debunked decades ago...the word hasn't gotten out because the manufacturers have no incentive to admit that they're a mistake. The stock "doghouse" cooler/shroud arrangement is far superior, and even the early-style setup with the cooler inside the shroud is actually preferable to "fool-flow"

[E_bug]

I guess you learn somthing everyday .

I have never heard the fool flow !

What i purchased was called a full flow oil return adapter. It looked as a solution because at the time i had no intention of spliting my case..

After i did i drilled and tapped it too

I have a post why i split the new long block .

[Marc]

My disparaging comments were directed at the old-school setup that goes on top of the engine, in place of the stock cooler. Back in the `60s, before these became ubiquitous, my best VW pal got his dad to turn out some of the flange adapters on his lunch hour (he was a machinist at Boeing) and we fit automatic transmission coolers to our engines. At the time we were just looking to remove the stock cooler from the airflow path to the left side in the pre-doghouse engines of the day, unaware that the resultant disruption in air distribution could actually raise head temperatures. There have been dozens (if not hundreds) of manufacturers marketing these kits to the unaware; they can be used as a source of parts for a better-engineered setup, but unfortunately 99.99% still go to fool-flow installations.



The return-line fitting in your photo is a more recent aberration which eliminates the need for drilling/tapping the case when installing an external-outlet pump for true full-flow filtration...adding an auxiliary cooler in this leg is OK. Because the piston & spring are removed there's no longer any thermostat action - since the fitting occludes the port which feeds the direct passage, all the oil has to go through the cooler all the time which does delay warmup; that can be a "biggie" even in a moderate climate on a cold-morning startup, since if you rev the engine too high it's possible to blow the stock cooler (or at least its seals). The flywheel-end valve will open at ~65 PSI, but the small relief hole in the case may limit its capacity...so long as you are conscious of the situation (a gauge is strongly recommended) there should be no drama. As Piledriver mentioned, the hole can be enlarged; arguably, the advantage outweighs any slight potential liability.

[crvc]

So now I'm paranoid. What if there's no piston in the bore nearest to the flywheel? How might that affect the motor. Like the other bore, I assume I can I unscrew the plug without draining the oil first?

kevin

[Piledriver]

So now I'm paranoid. What if there's no piston in the bore nearest to the flywheel? How might that affect the motor. Like the other bore, I assume I can I unscrew the plug without draining the oil first?

kevin

No issues, there is a bit of oil in the bore and the main gallery, but nothing a small cup or a large rag could not catch.
Have you stuck a mechanical gauge on it to see what the pressure IS now?
If sane, I would not sweat it, just keep an eye on it in case the low pressure caused damage.

I should mention that a "fool flow" block adapter setup (FJCamper coined the term AFAIK) can (and probably should) be modified for use in a true full flow system if you are ONLY using an external cooler and pressure relief... on a late shroud or any T4 conversion.

If you drill one of the holes through it becomes a loop, and you can use it as the oil return port. (plug the second hole)
This effectively eliminates the stock oil cooler setup/primary pressure relief from the circuit unless you use a modified relief piston. (it must sit below the top of the main gallery)
The relief piston blocks the pulley end of the main gallery if fully up, the oil cooler port feeds the main gallery directly.

It essentially replaces the bottom feed screw in bit you have, but leaves the piston/spring in place, and does not require plugging the sump return port. Does the ~same thing but is 100% bolt on.

[crvc]

Couldn't take the pressure. This morning in the garage I jacked the rear enough to crawl under. Then unscrewed the plug nearest the flywheel. The spring came out as oil poured. But no piston. Dammit, I did it again. I found a piston in the spare case. Working blindly because of the oil seeping I put the piston in, then the spring, then started screwing in the plug. But I only got it in about halfway. Uh oh. Grabbed the magnet. It took some jostling but eventually another piston came out. Dammit, I had it right all along. By the time I had the solitary piston, 30mm spring and plug seated I had a pool of oil 3-feet wide, made wider by me crawling back and forth on my back.

So I emptied a can of engine cleaner on the garage floor. I'll let it soak then later today clean the floor before my wife gets home.

kevin

[Piledriver]

Sorry, I figured you would have jammed the rag in the hole...

[Ol'fogasaurus]

Doc, if there isn't one already there is a lot of information here and a couple of other places. I think it would be a good idea to gather it up, for both the upright/pancake engines and T-4 builds and make it a sticky or two to post in the appropriate places.

Lee

Edited to make sense

[helowrench]

A nice writeup on the correct methods for an external cooler would be nice.

[Piledriver]

Out the oil pump cover through filter (with pressure relief, Bergs cover might suffice) to thermostat bypass, and back in the adapter. The oil cooler hooks up to the bypass. If not using a thermo bypass hook cooler up in the same loop.

Old Volvo turbos have a nice bimetal oil cooler tstat thay can be fit to an external cooler adapter with a filter (sandwich style)

There's really no need to drill out the adapter if you are just feeding it in there as long as you connect to the proper hole...

[crvc]

It's always had a leak. Actually there's 3 or 4 small drips on the concrete each morning. The engine is nearly 50 yrs old so I didn't obsess over it. I added the relief valve piston the day before yesterday and since then no drips at all. Coincidence?

kevin

[Marc]

...There's really no need to drill out the adapter if you are just feeding it in there as long as you connect to the proper hole...

If you don't drill it, the only way oil will have to get to the sending unit is the long way 'round through the main gallery and out the passage on the pulley-end control valve (and then only if you've left the piston out of it)...the upper passage between the sender and the original cooler outlet will be a dead leg that traps air and cushions pressure changes to the sender, slowing the response of a warning lamp or gauge using that location. I'd definitely drill it.
The first time I used this plumbing arrangement was back in the early `80s on a race engine that had been involved in a rearend collision which resulted in the block being cracked just below the cooler flange into the "hot" passage. Rather than scrap it or take a chance on welding it, I just tapped the hole in the case and inserted a pipe plug deep enough to get below the crack, then ran the full-flow return line into the "cold" side using one of those bolt-on adapters (with an external cooler added in series). I then put another pipe plug into the bottom of the "hot" side of the adapter so I could cross-connect its passages and use the otherwise-abandoned one for my sending units. Worked like a charm. As you pointed out, this setup mandates the use of a doghouse-style shroud with the air supply to the doghouse blocked off - after skinning the doghouse off the shroud you're left with a slit by the fan that needs to be patched over. A less-elegant (but reversible) way is to fabricate a sheetmetal blockoff plate to mount in the doghouse.

[JW63]

...There's really no need to drill out the adapter if you are just feeding it in there as long as you connect to the proper hole...

If you don't drill it, the only way oil will have to get to the sending unit is the long way 'round through the main gallery and out the passage on the pulley-end control valve (and then only if you've left the piston out of it)...

Hi folks, I realize this thread is getting older, but it has a lot of good info (always learning), thanks. As I read through all the posts, it became clear that a mechanical oil pressure gauge was needed to eliminate the possibility of low pressure issues, and that the pressure relief valves needed to be inspected. It's always good to see an owner get to the bottom of his/her VW problem! My only comment would be re: climbing those hills to a pass and coasting down enroute to Salt Lake City (I think he said Salt Lake). My Bug has had plenty of experience in climbing up to passes in both Utah and AZ. Because we are probably reaching max cyl head and oil temps going up, I'd recommend not coasting and keeping in gear to maintain full cooling airflow coming down.
P.S. a lot of good stuff has been done at Boeing during lunch hours (laugh).