PDA

View Full Version : Oil pressure. 3 little questions.



Lowboy55
22-01-2008, 02:06 AM
Hi all. I have 3 basic questions that may be pretty dumb. Please forgive me if this is stupid, but I'm not an engine technician. (Flimsy excuse, I know. I just want to keep my Sterling alive.)
Well, some background: I have an 1835cc VW "mail order motor" as I call it. (I bought it pre built, and shipped home) It has 2- 40mm Kadrons, a "mild" cam, and the snazzy aluminum fan shroud. :laugh:
I've had it for quite a few years, not so much mileage though.
Lately I've noticed the oil pressure staying low at idle, but only after the engine warms up. Seems normal pressure while it is still cold. (20 to 30?lbs) But sitting at a stop light idling, or any idling really, the idiot light either flickers, or comes on completely. The gauge is hardly "accurate", but needle travel is diminished. I'm guessing it shows 5 lbs psi at idle at operating temperature. Then when I rev up and drive the pressure comes up to say 15 to 20 I'm guessing. Sorry I can't remember. It's been a couple of months since I drove it last. And since this problem arose, I've been driving it even less. So my first question. Am I doing any harm by driving it at all?

Now, I also have an external 8 pass oil cooler, but I recently relocated it and added a fan & thermostat and mounted it horizontally where as before it was vertical.
The most recent addition is a small mini-sump. It adds about a pint more capacity and also sports a washable/reusable mesh filter.
Which leads to me to my next question:
Could there be something about the setup I'm overlooking? Pickup tube? Too much oil?

Which leads to my final(and possibly stupidest) question. Since my oil cooler sits flat, and there's a couple of feet worth of hose, I have to presume the oil might not all drain back to the case and sump. I'm confused now. Just how much oil is there.
I thought I read somewhere a long time ago that you should check your oil level with the engine running if you're using a setup like mine. I can't believe that, that's not what I was raised to believe. :annoyed:
So, how do I check my oil?

letterman7
22-01-2008, 03:16 AM
Well, short answer to the first question: possibly. Even at idle, the oil pressure shouldn't be below 15 lb. Anything lower is starving the bearings. Since it comes up under load, it may be getting enough.
Two: mini-sump. Standard fair under the engine or something else? I've not heard of sumps with built-in filters, but I've never looked, either. If the pickup tube is anywhere near the filter, there is a real good chance that the pickup is getting blocked by the mesh. Best idea: get rid of the internal filter, and put a "regular" automotive spin-on type before the oil cooler.
Three: oil cooler. Flat shouldn't be too much of an issue, so long as it's reasonably close to the block. "A couple feet" of hose is somewhat vague - if it's four combined feet going in and out of the cooler at anything over 5/8" ID, then you'll definately lose some pressure, especially with an 8-pass cooler.

I think I covered some of this in a previous post. Your engine, being a mail order, may contain some used parts or remanufactured parts that you're not aware of. Oil pumps are really common to find since they are the hardest to check easily (well, cranks too, but I digress). My first instinct is telling me the oil pump is worn and loosing pressure. They are easy enough to replace if you have the time and a couple tools - you just need to be able to pull the crank pulley to get it out. And all the necessary tools are readily and inexpensively available.

Replace the pump, and get at least another 50,000 miles out of the motor!

R

Lowboy55
22-01-2008, 04:13 AM
Three: oil cooler. Flat shouldn't be too much of an issue, so long as it's reasonably close to the block. "A couple feet" of hose is somewhat vague - if it's four combined feet going in and out of the cooler at anything over 5/8" ID, then you'll definately lose some pressure, especially with an 8-pass cooler.



Aha. So I will lose pressure in the hoses. Yes there's 4 foot combined. Easily. But I had that before I moved the cooler from in front of the fan shroud intake to the side of the engine bay.

Lowboy55
22-01-2008, 04:16 AM
The Mini sump in question.
http://www.cbperformance.com/catalog.asp?ProductID=202

Lowboy55
22-01-2008, 04:34 AM
Yeah. The easiest part to replace. In the second hardest to reach location.

OK. Assuming I get to the pump area. Do I need to just replace it or can I get away cheaper with just a new cover?
What about the bore the pump sits in? If that's bad, aren't I throwing good money at bad?

Spacenut
22-01-2008, 09:01 AM
Chances are that Rick is right with the diagnosis, but there may be a couple of other things to check.

First off, is the guage accurate? If it's a capillary type guage, with a little oil line going all the way to the guage head, it's probably reading right (unless the capillary tube springs a leak somewhere - it has happened to a friend of mine, dumped hot oil on his girlfriend's legs, so he got dumped :D).

If the guage is electric, the sender unit could be suspect. I had a sender fail on the Barracuda, the guage said I had zero pressure at idle and maybe 20 psi at speed. No oil pressure warning light on the Rallye dash, so I had to get a proper screw-in guage to measure the actual oil pressure, which turned out to be 50 psi at idle!

The other thing to check is the grade of oil you are using. Air-cooled engines use the oil as an engine coolant and the more modern multigrade mineral and synthetic oils are too low in viscosity. I've heard that monograde SAE 30 oil works well in VW's, but it may be another thing to check.

My friend's 390 AMC Javelin (not reknown for high oil pressure at the best of times) was running with the oil pressure warning light on most of the time (he has a competition-spec 18 psi switch), until he changed the oil filter (AMC parts aren't easily available in the UK :( ), whereupon the pressure went back up to 60 psi at speed, 20 psi idle. We suspect the internal filter relief valve may have been faulty!

Lauren

letterman7
22-01-2008, 01:42 PM
Good points, Lauren. Senders are easy enough to check by substituting the sender for a direct read gauge, sometime available for rent through your local NAPA store. Or, cheap capillary style gauges are easy enough to come by at the local FLAPS. Just cut the sending tube short, and hook it up. That should give you an idea if your sender or gauge on the dash is suspect.
And oil viscosity is always an issue. I've run nothing but either straight 30 weight or Shell's Rotella 10W-30 in my motors. Synthetics really aren't the best thing for aircooled engines.
As for the bore of the pump - makes no difference. The pump itself is essentially a hollow tube with a set of gears. The gear spacing between the gear face and the pump cover is what's critical. As they age together, the gears wear a groove in the cover, and the oil slips by the gears in this groove, loosing pressure.
Depending on the pump you have, you may be able to re-face the cover. If the pump is a bypass pump - with the oil outlets coming off the face of the pump - those are the ones you can reface. Four bolts, and you're good to go. Refacing is nothing more than putting some wet/dry sandpaper (400 grit or better) on a piece of glass, wet with some oil, and slide the face plate around until the grooves are gone. Use progressively higher (finer) grades of sandpaper as you finish up - you want a really smooth surface.
When you re-install the faceplate, use the thinnest gasket possible. Before you put the gasket in, get a piece of paper, fold it in half, and put it between the gears and the faceplate - hold the faceplate in place - and see if you can easily slip the paper back out. There should be some resistance. If you can't get it out at all (and you're not pressing hard), then the tolerances of the pump are gone (gears hitting the faceplate) and you'll need a new unit anyway.

Rick

MicksRedNova
22-01-2008, 10:08 PM
I vaguely recall reading somewhere that the pressure sensor point is after the filter so a blocked filter could lead to a low reading. If you've had your system in bits recently you may have introduced a small amount of debris causing a blockage.

Mick

jimcub
22-01-2008, 11:33 PM
What is the correct oil to use in a standard beetle engine, there are so many people with there opinion but just who is right even books argue.

Lowboy55
23-01-2008, 01:23 AM
The other thing to check is the grade of oil you are using. Air-cooled engines use the oil as an engine coolant and the more modern multigrade mineral and synthetic oils are too low in viscosity. I've heard that monograde SAE 30 oil works well in VW's, but it may be another thing to check.


Interesting. I've heard this from an old timer friend of mine as well. Currently I'm using dino oil, SAE 30. So apparently this isn't helping. Looks like I need to get at that pump. Oh, and the sender is electric, on a T fitting shared by the idiot light sender. They're reporting the same issue. Maybe I should check the T fitting to make sure it's not dirty. No matter what I do, oil will be spilt.

Lowboy55
23-01-2008, 01:38 AM
What is the correct oil to use in a standard beetle engine, there are so many people with there opinion but just who is right even books argue.


I have the book right here. It says for 40Deg F to 86deg. F use SAE 30 (MS)
And above 68 deg. F use SAE 40. (MS)
Capacity= 5.3 pts.

I wonder what that (MS) stands for?
So it looks as though I should be using SAE 40 since I only drive mine in warmer weather.

My take is this: Most experts disagree with each other in all fields, and that's to be expected. But to my mind, who would know better than the originators of the species? So I would consider VW themselves to be the most reliable source of information. They did the most testing so that they could sell vehicles and keep their owners happy. And buy more vehicles. Since they were successful, they must've done something right IMHO.

letterman7
23-01-2008, 03:21 AM
M=detergent type oil S=spark ignition (versus compression ignition for diesel). Dino oil really is the best to run, and just about every VW group, forum and person that I've talked to or overheard states that. Now, with that, the "new" thing to run since Dino oil is getting harder to come by in single weights is oils for diesel engines (MC). Apparently those contain a hefty amount of zinc for extra lubrication, and work perfectly for an aircooled motor. Some guys even run motorcycle oil (aircooled only) in their VW's, but that can get expensive fast - and there really isn't a difference when you read the labels.

R

Lowboy55
23-01-2008, 05:38 AM
OK, I have some things to look at. Thanks.
So how much extra oil do you think I need to figure into the equation?
5.3 pts stock cap.
1~ish pts for minisump.
Thats around about 6.3 pts.
How much do you think the 8 pass cooler and 2 sections of 3 foot hose would take? Say 5/8"ID hose.
Coupla pints?

letterman7
23-01-2008, 01:41 PM
Sounds about right. I wouldn't worry about what's in the lines too much, and whatever is in the cooler won't drain back, so figure 8 pints or a little over. Fill it, run it, then check the level. If it shows at or a little over the level, you're good to go. Overfilling might lead to other issues like excess pressure at seals that aren't leaking - yet. If it's slightly under the line, but between the two hash marks - leave it. The rest of the oil is hanging in the cooler and lines.

R