Oil Pressure and External Oil Cooler

[Mitchell]

I recently installed an external oil cooler to aid in keeping the oil temperature cooler on a stock 1600 cc engine. The car is a 1970 convertible. I had tried all of the suggestion from previous posts and searches, but the oil temperature still ran over 212 F. I live in Houston, TX so it does get warm during the summer. The issue I have now is the oil pressure is about 20 psi lower than before the cooler was installed. Before installation on start up the oil pressure was 65 psi. After the engine was at operating temperature the oil pressure was 35 to 40 psi at 65 mph. The head temperature was 340 F, and the oil temperature was between 212 F and 220 F, before I would shut it down. The oil temp was measured using a sender mounted in the pressure relief port. In order to mount the oil cooler I used the oil return adapter that mounts in the oil relief galley and requires removal of the spring and plug. I installed the sender in the oil pressure relief galley, with the spring and plug still inserted. Now upon start up the oil pressure is 40 psi and at operating temperature the oil pressure is 22 psi at 65 psi. The head temperature is 340 F. The oil pump is a new 26 mm pump that was plugged and the adapter plate is new. I did use a thin gasket with a thin layer of sealant. I have read not to do this, but I have always applied sealant and it did not affect the oil pressure. The engine is stock, with all of the seals and tin in place. The timing is set properly. The engine is filled with 30 wt oil, and it has a 1 and ½ quart oil sump. The deck lid has 6 vents and I have tried using the tennis ball to prop the deck lid open to keep the engine cool, this did not help. The system was installed with the high pressure hoses provided. They are rubber and not the braided ones I have seen.
My questions are:
Are the rubber hoses the issue?
Do I replace the gasket without sealant?
Did I possibly install this incorrectly?
Should I consider installing a stiffer spring in the pressure control port?
Should I install a 30 mm oil pump?
I would appreciate any suggestions,
Thanks,
Mitchell

[Marc]

Don't see any errors. You're still running the stock in-shroud cooler too, and it's been confirmed to not have a problem?
The flywheel-end plunger/spring are there just to relieve excess pressure back to the sump, in order to protect the cooler from overpressure when revved up cold - I don't know the design max pressure for the `70, but its spring is only about 5% softer than the `71-up spring so I'd expect to see ~60psi as a maximum when revved up shortly after cold startup, but 65psi should be OK. You said it had 65psi on startup before adding the full-flow cooler; that shouldn't have changed appreciably. The new pump is a large-passage (111 115 107AK) not a 311 115 107AKHD, right?
½" I.D. rubber hoses should be adequate unless they're quite long. Common brass plumbing fittings tend to be a little undersized, and the 45 or 90° elbow style add significant restriction. The pump cover, hoses/fittings, cooler, and return fitting would be the added restrictions in the system; you could temporarily bypass the cooler to see how much difference that makes in the pressure (at comparable temperature). With that return fitting ALL of the oil has to pass through the stock cooler - the "cold" bypass passage directly to the galleries is occluded by the fitting - which brings me back to questioning if it's been the issue all along.

1970 coolers were one-year-only (in the USA), to go on the large-passage/dual-relief cases using 021 117 151A seals. If you have the "wrong" cooler with conversion seals and spacers it's nearly as good, problems don't usually arise unless the incorrect seals are used or the spacers aren't thick enough - either can result in the seals constricting and blocking flow.

I wouldn't expect to need the 30mm pump unless your cooler is mounted far away from the pump, and the extra pressure wouldn't be good with rubber hoses.

Excess gear endplay in the pump (like you have if the cover gasket is too thick) will manifest itself as low oil pressure at hot-idle, without much effect at mid- and high speeds, and as long as it truly is a thin layer of sealant I doubt there's any problem there.

[Mitchell]

Marc thanks for the reply. The pump installed is a 311 115 107 AHD, not the 111 115 107AK. I need to remember to provide all of the information when I purchase something. The engine in the '70 vert is a latter model engine, case number AJ065114. It does have the correct oil cooler and dog house fan. You are correct the oil pressure was fine before I installed the external cooler. I made a change this morning that brought the pressure back up. I changed the oil pressure control spring with one provided with the cooler kit. It is longer than the one that was in the engine. I did this because I remember it was very easy to install the temperature sender unit in the oil control galley. There is a slight issue now with the oil pressure being high when the engine is cold. If I rev the engine up, the pressure will easily hit 70 psi. After driving for about 10 minutes the oil pressure stayed under 60 when accelerating. It appears I have two things to change. First buy the correct oil pump or enlarge the intake passage on the pump I have. Will this work OK. If not I will purchase a new pump, not worth ruining another engine. Then I will replace the oil control spring with a new standard spring. I am not sure the spring I removed is correct. I installed this engine to replace one I had built that locked up after I was sold the incorrect oil pump. I thought I had purchased a pump for a dished cam, but it turns out I was sold one for a flat cam. It did work for several months, then one day is slipped out of the slot, the oil pressure went to zero and two rods locked up.

Thanks,
Mitchell

[helowrench]

You could try changing to a 10W30 multiweight oil.
If you do, please post the results, to give the rest of us data.

[Marc]

..It does have the correct oil cooler and dog house fan...

Correct for a `70, or correct for a doghouse fan? I know you can stuff the wider fan into a SP shroud if you're determined enough, or did you update the whole shroud & cooler setup to doghouse-style?
Nothing wrong with port-matching the pump you have, just be careful that you don't nick the margin on the sump side or it'll leak. I usually wrap a big hoseclamp around the end of the pump to protect it in case I slip. I don't know how much pressure it takes to balloon a SP cooler (doghouse coolers tend to leak first, but the SP will stay intact with the flat tubes expanding out until they block all airflow) but as long as you've got a gauge and are aware of the issue it shouldn't be unsafe to drive for a while with the spring that's in there now. If you don't switch to multi-vis oil before winter you'd better change it though.

It looks like you are already aware of the below info but let me sum it up for the benefit of any future readers.

Small-passage, single-relief cases use the 311 115 107AK (21mm) or 311 115 107AKHD (26mm) pump. Through `67, the oil pump studs were m6x1.0; `68/`69 were m8x1.25. The O.E.M.s quit making the 311 115 107K and 107KHD 6mm-stud versions years ago, but there are repops on the market now. The 8mm pump works fine on a 6mm-stud case, although ideally you should try to stay with the 6mm cover (311 115 141)...if you must use the 8mm cover (311 115 141C) you'll need some little fender washers under the 6mm nuts. The bolt circle is larger on the 8mm cases, so it's not as simple a matter as redrilling a 6mm case or pump housing to 8mm - you must use a jig to enlarge the bolt circle as well. All 311 pumps are intended for three-rivet, flat-faced cams - no stock pump was ever made for a 4-rivet, dished-face cam in a small-passage case.

No factory-equipment pump ever bore an "HD" suffix, that's an aftermarket abberation and therefore it hasn't a specific meaning - it's just a heads-up that the gears are longer than stock for that basic P/N, the seller usually will provide the details. You've also got to be aware that some sellers append a "B", "BR" or "BZ" to the number to denote Brazilian manufacture, so you could see weird numbers like 111 115 107AKHDBR...

Large-passage, dual-relief cases (1970-up) all have 8mm studs and use the 111 115 107AK pump with a 3-rivet cam, and the 111 115 107BK with a 4-rivet. The BK goes deeper into the case so it has longer gears but looks identical from the outside. If you have a 4-rivet cam and don't want more than a 21mm pump, you can use the AK if you press the shaft deeper into the gear so it will engage the slot in the cam properly...same trick works on the 111 115 107AKHD 26mm pump. Similarly, if you had to run a 4-rivet in a small-passage case you could press the shaft on a 311 pump.

Here's the 111 115 107AK, correct for dual-relief case and 3-rivet cam. This is the stock 21mm-gear version, the 26 and 30mm variants with a thicker flange are usually sold as 111 115 107AKHD or 107AKS:


Here's the 111 115 107BK, for a dual-relief case and 4-rivet cam. The pump housing is longer, extending deeper into the case to allow longer gears without protruding any further outside of the case. Again there are thicker-flanged "HD" variants with even longer gears available:



A 311 pump will fit into a large-passage case, but the ports are smaller and don't align properly with the ones in the case. This can be resolved by carefully port-matching the pump out to match the case. Conversely, if you had to run a 111 115 107AK or BK in a small-passage case you could open up the ports in the case to match the pump (or nearly so, mustn't get too thin on the sump side).

AutoStick pumps went through the same changes (except that there are no 6mm-stud, or "HD" versions). One was used for `68/`69, one for large-passage with 3-rivet cam and one for large-passage with 4-rivet cam. They have a different number designation, 113 115 101A, 101B, or 101C.

[Mitchell]

Thanks for the information Marc. The information was very helpful. Even though I have had VW's for a number of years I did not realize all of the differences between the oil pumps. I will be pay a lot more attention to the engine I am building for my Ghia. I don't mind doing the work, I just do not like re-doing it, so now that I am better informed hopefully it will go smoother.

Yes I did update the oil cooler and fan to the larger doghouse fan with the offset oil cooler. All of the tin is installed around the cooler including the Hoover bit.

The engine case is a dual relief case with DP heads.

When I remove the pump to open it up I will do as you suggested. I will also check to see if the spring I removed was not the correct one, although it worked before the external cooler was installed. The issue might be with the new pump that was installed. The pump that was replaced worked fine, I just damaged it when I was plugging the exit port to install the external cooler. I never looked at the inlet port to compare with the new one.

I have never used multi-vis oil in an ACVW. I have always used 30 w. I use multi-vis in my other vehicles. I might give it a try just to see how it works, as straight 30 is sometimes hard to locate. If I make the change I will post the results.

Thanks,
Mitchell

[helowrench]

I run Rotella synthetic 10/30 & 10/40, during the stupid hot season, i have even run 15/40.
Dallas tx temps.
(stupid hot =105+)

[Marc]

...Yes I did update the oil cooler and fan to the larger doghouse fan with the offset oil cooler. All of the tin is installed around the cooler including the Hoover bit.
The engine case is a dual relief case with DP heads....Mitchell

And the case is an "AJ", with a 3-rivet cam. It'd be less confusing if we just called this a `71 motor with AS21 case from now on.

Multi-vis oil is totally legit in an ACVW; the cars predated it when first designed, but that's no reason not to use it. Personally I run 10W-40 in most of my engines for at least half the year, and 20W-50 in hot weather or for racing. The hard part today is to find oil that has a ZDDP additive package that's sufficient for flat tappets (especially important during break-in and/or with stiff valve springs). It shortens catalytic converter life and isn't needed with the roller lifters used in modern engines, so its content has been reduced with each upgrade of the API standard. Even oils compounded for diesel engines have had their ZDDP content reduced lately. You can buy additives, but there are still a few off-the-shelf oils that are safe to run in an ACVW. Valvoline VR-1 and Brad Penn are two that I use; Castrol GTX was good once but nowadays I only use it to save a little money for a high-mileage (and stock valvespring) engine where the cam & lifters have been broken in for many miles and are the least of my worries.

http://www.zddplus.com/TechBrief2%20-%2 ... 20Myth.pdf

[Mitchell]

The case is an "AJ" case. I know the different ID's used are confusing to me, so easier is better. I will try the multi-vis oil next oil change.

Thanks for the link, it was very informative.

Mitchell

[Mitchell]

UPDATE:
The inlet port for the pump was drilled out to match the port in the case. The pump was the re-installed with the original oil pressure relief spring. At start up the oil pressure was 40 psi. After warm up and driving the oil pressure at 60 mph in 4th gear was 22 psi. I changed the spring and installed the longer one that was provided with the oil cooler kit and the start up pressure was 60 to 65 psi at idle. I did not change the plunger. One of the plungers provided with the kit was longer than the stock plunger and was recessed below the top of the plunger. When the engine is revved up the oil pressure pegs the gauge at 70 psi. After the engine was at operating temperature the oil pressure at 60 mph in 4th gear was 30 psi. At 50 mph in 4th gear the oil pressure was 22 psi.

Marc while the pump was out I verified that the cam is a 3 rivet flat cam.

Thanks,
Mitchell

[Marc]

I would not expect the length of the plunger to have any effect on the hot oil pressure, although increasing it has pretty much the same effect as running a longer/stiffer spring - higher maximum pressure as when cold.
The slot serves no function whatsoever in this location; however the plunger may be a little larger in diameter and thus allowing less leakage around it, or there may be a worn spot in the bore wall which was allowing leakage and the longer plunger reaches above it.
The pump outlet port typically requires some enlargement as well, at least on O.E.M. pumps.

Sounds like you're out of the woods, even though it's not a "textbook" solution it should do no harm provided you avoid overpressurizing the cooler on a cold engine. The one combination you haven't tried (a stock spring and new plunger, preferably also stock) may also have done the job.

There's one other potential place where some pressure could be lost but you'd have to pull the aftermarket oil-return fitting out to investigate it. Near the bottom of the bore (but above the threads) there is a small bleed hole, necessary to prevent any oil leaking past the piston from building up pressure under it and preventing its function. Ideally the return fitting should be made to occlude that hole when installed (perhaps with an O-ring positioned above it); if it's not you could lose a little pressure there.

It's getting close to lighter-weight oil season so there's probably no point in futzing with it any longer until you see what effect multi-vis oil has.

VW's recommended viscosity table from a late-model Mexi-Bug owner's manual: http://smg.photobucket.com/user/MarcVel ... 9.jpg.html

...Marc while the pump was out I verified that the cam is a 3 rivet flat cam...l

I never doubted that. As you once learned the hard way, a "short-reach" pump won't engage the slot in a dished-face cam well enough to work for long.

[Mitchell]

Marc I agree with you, leave well enough alone, for now. When I change the oil I had planned to remove the oil return fitting to aid in draining oil from the cooler. That will provide me with the opportunity to check the bleed hole you mentioned. I think I will try the new plunger and spring, as I have one now, before I change the oil so I can compare it with the set up I have now. For now I am tired of being oily and by the way I was never good with text books.

I have learned a lot from this recent experience. Your advice has been great. As has been said before, trust but verify. As I work on the engine for the Karmann Ghia, I will more careful.

For this weekend it will stay in the garage, it's time for a motorcycle ride.

Mitchell

[Steve Arndt]

We have only had one engine in our shop with that relief plug fitting full flow adapter and it had low pressure. That is a sample size of one, but I don't like those things.

[Piledriver]

Are you using a VDO oil pressure sender/gauge or a simple mechanical gauge?

Many of us have gradually developed a deep distrust for the former, and now consider VDO to ~ the same reliability expectations we have for Lucas.

[Max Welton]

I believe each VDO unit ... that I have personally compared to a mechanical.

No need to trust or not trust. Just verify.

Max