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From time to time, my oil pressure will drop to zero and then after a bit come up again. I thought it was happening at a constant speed but maybe not.

I have an oil pressure gauge and I can watch it drop down and when it gets to zero the light comes on.

I have an external filter and external cooler and a CB Thinline sump.

I checked the oil level when this happened and it was a bit over the add oil level. I have read that this is a good level when using the add-on sump. One other reason I didn't fill it to the full line is that I have been having oil come out behind the crank pulley, even after I added a sand seal.

I have a Mocal thermostatic sandwich plate between the filter and the mount to control flow to the cooler. Oil enters the cooler at the bottom and leaves the cooler at the top. I put the outlet at the top to prevent air from getting trapped in the cooler. The cooler is higher than the sump.

Does the Mocal stop oil from draining out of the cooler?

If not, the oil level I am reading may include oil that has drained out of the cooler and after filling the cooler my oil level may be too low.

1957 CMC (Speedster) in Ann Arbor, MI

Original Post


Michael McKelvey posted:

...From time to time, my oil pressure will drop to zero and then after a bit come up again...


This is not at all normal.

Many of us are running external filters, coolers, mocal sandwiches and all manner of wacky plumbing. None of that stuff should cause zero oil pressure, which is generally considered a very bad thing and one of the leading causes of dead engines.

Is there any pattern to 'from time to time' ? Completely at random or after hard cornering, maybe? That would support Stan's hypothesis that the oil pickup is seeing air when it should be seeing oil. The main reason for an extended sump is not to add more oil to the system, but to supply a deeper well of oil, so the pickup doesn't go dry under hard cornering or braking. BUT, the pickup needs to be altered when an extended sump is added to take advantage of that deeper well. Maybe, on your engine, it never was, or it was but broke somehow?


Michael McKelvey posted:

...the oil level when this happened...was a bit over the add oil level. I have read that this is a good level when using the add-on sump...


I have never read that.

But, I'm not the most well-read dude on such matters. Or even the second most well-read dude. I HAVE been lead to believe that the oil should be filled CLOSE to the 'full' mark, but just a bit short thereof. The story goes that if you fill all the way up, the oil can get churned up by the crank and turned into the same stuff that Starbucks uses to make cappuccinos.


Last edited by Sacto Mitch
Stan Galat posted:

You are exposing your oil pick-up to air. Either the tube is cracked/loose/otherwise compromised, or you need more oil (which will doubtlessly get flung around by the idiotic seal-less pulley).

Alternately, you could dry-sump it like some overzealous idiots.

Yup, guilty, just like you @Stan Galat!

Oil pressure is now absolutely NEVER a concern. Although the long oil pump makes pulling the motor more difficult. But who cares, I'll take the compromise!

I'll concur with Stan's diagnosis as well. I would submit this is also what happened with Drake's type4.

@Sacto Mitch: when adding the oil sump extension, whatever the brand, AND extending the pickup tube via a longer one piece tube or a slip-on extension, you can drop the oil level on the dipstick. But you'll still have MORE oil in the engine(1.5 quarts or more). I found that I lost the least due to slosh when I ran a 1/2 quart to a full quart lower on the dipstick, keeping the oil in the sump extension rather than the case.

When I had the CB thinline on there, I extended the tube with a kit from Dune Buggy warehouse. I cleaned everything well, then JB welded the extension to the tube(to prevent air leaks), and clamped the hose clamp on. Then I safety wired the clamp set-screw. Then I added a tubular spacer(with lots of holes!) and a big spring pushing the extension upwards. This is all to prevent ANY possibility of the extension coming off.

I removed all this when I went dry sump. The JB welded extension came right off and left no residue on the oil pickup. I never had any oil pressure variation with the extension. The dry sump system is an attempt to keep the oil IN the engine, as I was losing more to blow-by and breather than anything else. Hence new pistons and cylinders are going in to replace the 43K ovaled ones in there now.

I had a Beck Spyder losing oil pressure briefly on the Type 1 engine during hard fast corners at the track. All the oil was flowing through the pushrod tubes into the rocker area of the head. I needed to go to a dry sump or run baffles on the ends of the pushrod tubes. I did the later and it worked for my track use. If you are losing oil pressure intermittently with no external reason you have a problem that is going to cost you your engine if not diagnosed and repaired.  Good luck finding the issue. Are you using an electrical oil pressure gauge or mechanical ?  The sending unit on your electrical gauge may be defective or have a lose wire or ground.

Since you just examined your oil pickup tube, you have a good idea of its location and where it points inside the sump, i.e., in the middle, pointing left, right, front, or rear. I suggest that you keep track of when you lose oil pressure, and analyze conditions when it occurs, like left/right turns, under acceleration, compression, braking, etc.  You may also want to check if any other electrical function stops momentarily at the same time, which may indicate a bad ground.  Additional ground wires are cheap and easy to run.  Since it happens so fast, a right-seater may help with observation by looking at any other electric gauges.

If you can't find the fault quickly, you may want to consider pulling the oil pan next.  I installed a welded/gusseted after-market oil pickup tube in mine, since Subis had some problems with cracking tubes.  Since you have 2 independent sensors with separate gauges, and both are in agreement, the gauges are likely not the fault.  Oil pumps themselves are reliable and long-lasting, so that may be the last thing to check.

Just a couple of thoughts.  First the easy one:

Does your oil pump have a pressure regulating or relief valve in the cover?  If so, the pressure spring might have weakened or broken and is doing that to your pressure.  The fix is a new spring or a spring and valve if there is a rebuild kit for your particular cover.

Then, Mike wrote: "I took the plate off the bottom of the sump yesterday and the extension seems to still be solidly in place."

That could be the case, but what about where the top of the sump tube goes into the case?  That's usually a press fit and could have a leak there.  The common assembly technique is to install the sump tube into the case and tightly press it in.  If it isn't real tight in there then you use a small punch and peen the case material around the tube to make it tight.  There is also a 10mm bolt holding the sump assembly in place and screwed into the inside of the case.  Depending on what was used on your engine, it may or may not have an umbrella swaged onto the sump tube (above where you attached your extension) that acts as an oil splash manager for the pickup.  That umbrella has a tab on one side with the bolt into the case to hold it in place.  If it does not have that umbrella there is a long-ish tab welded to the pickup tube and you might just see the anchor bolt up in there and can check to see that it's tight.  If the umbrella is in place I don't know if you can see the bolt.

A leak in the pickup can certainly give you the pressure problem you have, but usually that type of failure is a constant and not intermittent, unless the pickup tube is loose and flopping around a little (it doesn't take much movement to allow air in).

That's all I've got for now....   Gordon

Thank you all for continuing this discussion.

Now that I am pretty sure that my oil cooler is draining back into the sump and after it drains I am setting the dipstick level to just above add oil, it looks like I may have been running 2 to 2 1/2 quarts low.

I am a little disturbed that the Accusump allowed the pressure to drop to zero.

I am going to put the plate back on and fill it to the top mark on the dipstick or a little higher and see what happens.

My Accusump is 1 quart.  When the oil pressure is high more oil goes into the Accusump and as the oil pressure drops, oil flows from it back into the engine.

I typically rev the engine as I shut it off to push oil into the Accusump so it will discharge into the engine next time I start the car.

I put the sump plate back on this afternoon and put in 5 quarts - 4 for both sumps and 1 for the oil cooler.  The level in the sump will drop as oil goes into the Accusump.

I added a switch to the Accusump valve so I can turn it off to retain the oil in the Accusump when I am working on the car and want to turn on the ignition.

Mike, can I recommend that you check the oil immediately after shutdown, before the cooler has had a chance to drain back? I used to do that in mine when it was wet sump, there is almost 2 quarts in my cooler and lines.

Gordon: you can see the nut in the case behind the "umbrella" of the pickup tube. But you can't tighten it with the case halves together unless you dent it(yes I dented mine). I did this last summer when I went dry sump. I had to replace the sump studs with longer ones, so they all had to come out. The longer studs were to affix the dry sump suction cover to the bottom of the case.

Some guys put bolts up through the case(bolt heads on the inside) so "studs" can't unscrew or strip the soft case. These studs require VERY little torque to seal with NEW copper sealing washers, and use cap nuts for no leaks. I got mine from our favorite Bug City.

You get what you pay for!

I just called Gene Berg Ent. today. Now, I'm not saying I'm drinking the Gene Koolaid as some of his ideas are out there. But they have QUALITY parts.

Ordered their sand seal cutter and a double lip seal. Cause, well, I'm done messing around with inferior Chinese garbage(Scat). This seal WILL work with my Jaycee billet steel pullet hub! 

Cry once, as my friend Stan says. Believe him, as I already spent the bad money. Now I'm spending it well, like I should have in the first place.

Michael: If you have a 1.5 quart thinline sump, you'll have 4 quarts including the 2.5 in the case. You'll have a quart in the filter, plus about another quart in your lines and cooler. So about 6 total. I had longish lines and ended up running a half-quart down on the dipstick and it was perfect. This was my old configuration: type1 motor, full flow, external Ford-style filter, thinline CB sump, 96 plate cooler, thermostat, AN-8 lines.

You can run lower on the dipstick IF you have an extended pickup tube that is SEALED!

I think that pickup tube may be your problem. In the case where the pickup tube seats.

I have 4 quarts in the sump and case.  I confirmed that the oil cooler itself only holds .22 qt.  I have a Canton cartridge oil filter that I fill before screwing it on.  So, now after draining a quart, I have 4 quarts plus whatever is in the filter.  It seems like that should bring it up right to the full line.  It is about 1/4" above the line.  With the 5th quart, it was about an inch above the line.

I have quite short lines to the cooler.  It is directly above the filter mount with the Mocal sandwich.

I attached my extended pickup tube with JB Weld and I assume it is sealed.

With the 4 quarts, after subtracting what is in the cooler and lines and what gets pushed into the Accusump, that is probably the same as running a bit below full.

On Saturday I drove it for about 5 hours with the 4 quarts and the oil pressure didn't do anything weird.  I am still wondering why the oil is above the line on the dipstick.  I am going to have to look for the original dipstick I replaced with the chrome one.

Michael McKelvey posted:

@ALB thanks for your reply.  My tube seems to be about 1/4" lower.  I wonder why and what it is on other people's cars.

It is nice you used inches instead of mm for us metrically challenged folks to the south.

Just trying to be helpful, Michael. Did you get around to messing with the shifter position at all?

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