Oil Pressure Problems
Oil Pressure Problems
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Oil Pressure Problems: diagnosis and treatment
You're happily cruising along in your Vanagon, music playing, engine humming,sweetheart smiling, dog with his head out the window and ears flapping."Bliss," you think, "does it get any better than this?"
Then it happens: the oil pressure idiot light starts blinking and the buzzer goes off. Your heart leaps to your throat. Did you just throw a rod? Burn a main bearing? Hit a big rock that punched a hole in the case?
Moving faster than your credit card balance at a VW dealer's parts counter, you stomp the clutch to the floor and kill the engine, coasting to the shoulder of the road. Your dog looks puzzled, as you mutter a blue streak of profanities that would make a trucker blush. What just happened?
This scenario is all too common among Vanagon owners, and in this article, I hope to clarify some of the problems frequently experienced in the Wasserboxer (WBX)engine.
There are many things that can cause low oil pressure in an engine: worn main bearings, faulty or worn oil pump, worn pressure relief springs, obstructions in the lubrication system, to name a few.
In addition, there are several things that can cause an artificial low oil pressure reading: bad or incorrect oil pressure senders, oil viscosity, and soon.
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Lubrication: how it works
Essentially,oil in the case is picked up by a sump, and gets pumped under pressure through a filter, and then through the various engine components, after which it goes back into the case. That means we have three distinct parts: pumping, filtering and engine parts. For a rough diagram, take a look in your Bentley manual on page 17.7.
If the pump is worn, it will be unable to deliver enough pressure to the engine.In this scenario, damage to engine parts will occur very rapidly, though it is unlikely that a newly rebuilt engine (with a new oil pump) will have this problem.
If the filter is clogged, it can reduce pressure as well. Oil filters typically have a pressure relief valve, so if pressure is too great on the intake side,the valve will open and oil pressure will not be compromised. However, the oil will now be passing unfiltered and go straight to the engine components that the filter is supposed to be protecting. You will have no indication that this is happening, so keeping the filter clean (by regular replacement) is essential. Also, the definition of when the valve should open varies by manufacturer, which means you can't rely on this as a way to protect against a clogged filter. The only reliable solution is to change oil and filters regularly.
Finally,we have the engine parts themselves. As the engine wears, tolerances between parts loosen, which allows more space for oil to sneak out, thereby reducing pressure throughout the engine. Think of the bottom of your blender at home.Since the blade has to somehow connect to the base/motor, there is a small bearing that passes through the bottom of the blender. When you first bought your blender, you could mix drinks for hours on end and never have a leak through the bottom of the blender (spilling due to inebriation doesn't count). But after a couple of years' use (HARD use, in your case), the bearing just isn't what it used to be, and now every time you mix a drink, you lose some out the bottom. If, however, you were to pour honey into the blender, it's likely that none would run out. Why? Because honey is more viscous (thicker) than the average margarita, and can't quite fit through the leaky bearing like a watery margarita.
This brings us to the first diagnostic tool: oils of different viscosity. Let's say you have an older engine with, say, 125,000 miles on it. It runs pretty well,but hasn't had the easiest life-it was used to deliver pizzas for five years,and you live in a colder climate. Your idiot light goes off, so you start investigating. One of the first things you do is change the oil. No change. You then put in the next higher viscosity (thicker) oil, and lo and behold, the idiot light goes off. What does that tell you? Well, the thicker oil can't fit through the looser tolerances in your engine as easily as the thinner oil did,so it holds pressure and the problem seems to be solved. However, remember that part about the cold climate you live in? That also means that your new,molasses-like oil is just that first thing in the morning. You fire up the engine, and all that thick oil also has a tougher time getting through the engine in the first place, so you incur additional wear on your bearings and soon. So, moral of the story is, use the thicker oil as a diagnostic tool, and then either fix the problem, or be sure not to operate the engine outside of the temperature recommendations for that particular oil. There is a chart with oil viscosities and temperature ranges on page 17.8 of the Bentley manual.
Now then, let's say you have put in the higher viscosity oil, or maybe you've gone so far as to go two steps up in viscosity. There is still no change, and the idiot light keeps blinking merrily away. What this tells you is that some thing in the system will not hold pressure. The two primary suspects here are the oil pump and the pressure relief valves. If the oil pump is worn to the point that it's not holding pressure in normal operation, you have probably done significant damage to the engine already, and may have other indicators that are build is due (low compression, blue exhaust smoke when shifting, etc.). The oil pressure relief valves are another story. They work just like the pressure relief valve in an oil filter-if pressure in the lubrication system is too great, the valve opens, allowing some pressure to escape. As the pressure drops again, the valve closes, and holds proper pressure. But guess what? The valve is operated by a spring-and that spring is pre-set to a specific pressure when it is new. Over time, like all things, the spring wears, and softens. As a result, it may open at a pressure that is too low, and cause the oil pressure to drop below the allowable limit. In other words, the idiot light mocks you once again. So how do you diagnose the oil pump or pressure relief spring?Unfortunately, these are not easily diagnosed without removing them from the van. For the pump, a visual inspection will usually suffice. For the spring, it needs to be tested to determine how strong it is, and whether it has softened.In the event testing facilities are unavailable, the spring can simply be replaced with a new or known-good one.
Common causes for oil pressure warnings in Vanagons
Note that I said "causes for oil pressure WARNINGS", not "oil pressure PROBLEMS". That is because there are several things that commonly happen in Vanagons which cause the driver (unnecessary) cardiac acceleration.
It has been well established on the Vanagon and Syncro lists that Fram oil filters tend to cause mischief with the WBX. While no one has a definitive answer on why this is, several theories exist, including: tight weave of the filter element, lack of back flow valve in the filter, and others. The back flow issue is not a problem in the WBX, since the filter sits at a 45-degree angle, and there fore does not empty when the engine is shut off. The tight weave theory seems to hold the most possibility, stating that oil can't get through the filter fast enough (similar to a clogged filter) to hold pressure, but is not constricted enough to allow the filter's pressure relief valve to kick in. The simple solution to this problem is to use Mann, Mahle or Autobahn brand oil filters. Van Cafe carries Mann, and offers a discount on the purchase of four filters. Be sure to get new crush washers for your drain plug at the same time.
Faulty/incorrect oil pressure sending units:
It is quite common for WBX (and other) engines to be fitted with the incorrect oil pressure sending switches. These are the switches that detect low oil pressure,and cause the idiot light and buzzer to activate. On the WBX (1986 and later),there are two sending units, one for lower RPMs (below 2,000), and one for higher RPMs (above 2,000).
The lower RPM switch is located on the driver's side of the engine, between the push rod tubes for cylinders 3 and 4. To access this one, you will need to remove the engine tin, which means a couple of exhaust nuts as well. Which means you'll probably strip at least one of them,so proceed carefully. The sender should be 0.3 bar/4.4 psi, and is light brown in color. If the incorrect sender (a higher pressure unit) is fitted to the engine, it will give a false warning when pressure drops below its allowed range. Note that the sender will state a range of pressures, not an exact pressure. The range should include the numbers stated above.
The higher RPM switch is located near the crankshaft pulley. This one is a little trickier to get to, but if you remove a couple of belts, and push the exhaust shield out of the way, you should be able to get a socket on it. It helps to use a reducer on your ratchet to make a 1"extension. This sender should be 0.9 bar/13.1 psi, and grey in color. On my most recent Vanagon, I had a Canadian VW factory rebuilt engine, and this sender was the blue one, rated for roughly double the pressure of the grey one.No wonder I was getting a light and buzzer!!
Improper viscosity oil:
Going back to my earlier blender analogy, it is important to use the proper thickness of oil for the climate in which you live. Multi-viscosity oils (20W50, 10W30,etc.) cover a wider range of temperatures, but don't do as well at the extremes as a single grade oil would (SAE 30, SAE 40, etc.). Castrol 20W50 is a popular choice among list members, and it is usable from about 15 degrees F to 85degrees F. When I moved to Colorado last spring, I found that the daytime temperatures (over 100) and the altitude were too much for my 20W50, and the light/buzzer warnings increased dramatically. After switching to SAE 40, they went away almost completely (once I installed the correct sender, they were eliminated altogether, but this still demonstrates the effect temperature has on pressure). REMEMBER, it gets cold in Colorado, so I had to be sure to switchback to an oil that would handle the cold once summer was over. SAE 40 is only rated down to about 70 degrees F-after that, it becomes the proverbial molasses on a cold winter day.
Nirvana: Installing an oil pressure gauge in your Vanagon
With all the possibilities for false oil pressure readings, many Vanagon owners opt to install an oil pressure gauge. This is a simple procedure, and gives a great deal of insight into what is happening in the engine at a given moment. This discussion will address installation of the Van Cafe Oil Pressure Gauge kit, which utilizes the VDO80 PSI electrical oil pressure gauge, VDO sender, and a stock sender.
Essentially,the gauge installation involves three main tasks: 1) replace the sender; 2) route wiring from that sender up to the instrument area, and; 3) Connect and mount the gauge.
Going back to the discussion of the oil pressure senders, one sender was located between the push rod tubes of cylinders 3 and 4. This is the sender that will need to be replaced.
NOTE:The hose and elbow provided in our kit exactly match the thread of the VDO sender extension hose. In both cases, the thread is standard, even though the sender and the engine case are metric. When tightening the hose into the engine, it is important to get a good seal, but without stripping out the case.You can get a good feel for the tightness by attaching the sender to the elbow while it's out of the van.
In the kit, there is a short (6") hose with a tee fitting that holds a VDO sender and stock sender. This hose will be used to attach the senders to the engine. In order for the hose to clear, the engine tin will need to be notched. By notching the tin, you will provide clearance for the hose, and allow the tin to be removed in the future without needing to remove the sender from the hose. So, remove the two bolts that hold the lower (arched) portion of the tin to the engine, and then remove the lower exhaust nut and bolt from cylinders 3 and 4. As you remove the tin, mark it to indicate the location (front to rear) of the existing sender. This will become the center line for your notch. You will be able to remove the tin by rotating it and working it through the exhaust pipes-be patient-when you find the right method, it will come out with no force at all. Next cut a notch in the tin (Photo1 gives a good detail of the notch with sender and hose installed-looking from driver's side, front of van to the left) to accommodate the hose. I chose to make my notch wide enough so the hose would not come into contact with the tin at all. If you opt for a narrower notch, be sure to line the sharp edges somehow so they don't wear through the hose.(PLEASE NOT PICTURE BELOW DOESN'T SHOW UPDATED TEE FITTING AND STOCK SENDER)
Next,you need to attach the hose to the engine. The hose will have a protective cover on one end, be sure to remove it before the installation-it is essential that the hose remain totally free of any and all debris. Attach the hose to the engine, and tighten it down. Be careful not to strip the engine case! Once the hose is tight, position the elbow so it points to the rear of the engine, and tighten it down as well. Leave the protective cap on the elbow for now. Next you will need to replace the engine tin and attach it loosely with the two bolts on the engine (patience,grasshopper, you will be very good at this by the time you finish this project!). Slip the p-strap over the new sending unit and screw the new sending unit into the elbow. Be sure the engine tin is in its installed position, and mark the tin through the holes in the p-strap mounting tabs. Remove the sender and p-strap again, and remove the engine tin. Drill a 1/4" hole (slightly over sized is ok) in the tin where you marked it, and test fit the p-strap bolt for clearance.
The p-strap is the ground for the sender. Clean up the area around the hole you just drilled, and use some light emery paper to remove paint if necessary. The p-strap must make a clean ground to the tin.
At this point, the sender is ready to mount, but it is easier to run wiring with the sender and tin out of the vehicle, so set all this aside for now, and move on to the next section.
The stock oil pressure sending unit wire will connect to the brown stock sender on one side of the tee. The VDO sender on the other side of the tee has two posts, marked WK and G. The post that is marked WK will not be used for this application.The post marked G will be attached to the single blue wire that runs up to the gauge itself. If you open the engine hatch from above, you will see where the existing wire runs, and it is helpful to run the new wire in the same manner. Above all, be sure the new wire doesn't run next to exhaust parts, as it will melt very quickly. Once you have the wire in place at the engine (be sure it reaches the sender!!), you can begin running the remainder of that wire up to the cockpit. There is a large bundle of wiring that runs down the left (driver's)side of the van, and is zip-tied every foot or so. I found it very easy to run the wire on top of this bundle, and simply slid it under the existing zip ties.Once you get to the front of the vehicle, you need to bring the wire into the instrument cluster area. I have found the grommet that surrounds the speedometer cable to be a good entry point. Remove the front grill and left headlight assembly, and access is very easy. Inside the vehicle, remove the hood over the instrument cluster and the cluster itself, and you can fish the wire through the grommet using a coat hanger or similar method.
Now that the wire is in place, you can button up the back end: replace the engine tin, but do not bolt it in place yet; insert the p-strap bolt with one washer through the hole you drilled from the top of the tin; using Teflon tape, attach the sender to the elbow (be sure to support the elbow with a wrench as you tighten), and then tighten the p-strap to the tin using the second washer and the self-locking nut provided in the kit. If you have measured well, the tin should be sitting in place with no tension against the hose, tin or sender. Ift here is a minor discrepancy, loosen the p-strap nut and allow the p-strap to move a bit, then re tighten. If you haven't already done so, attach the wires to the proper posts on the new sender. Finally, re-attach the two bolts to the engine and the nut/bolt to the exhaust. See Photo 2 for the finished product with a detail of the p-strap bolt (looking up, front of van to the left).(PLEASE NOT PICTURE BELOW DOESN'T SHOW UPDATED TEE FITTING AND STOCK SENDER)
Connecting and mounting the gauge:
The back of the oil pressure gauge has five terminals. Two of them (top of the gauge, in black plastic) are for the gauge light, and the other three (bottom of the gauge, with a bolt/nut in the middle) are for the gauge itself. The kit includes three female spade connectors and two wire splices-you can cut off the extra wire and attach these as needed.
To get a really professional installation, I would recommend that you connect the light in the gauge to the dash light dimmer in your headlight switch. To do this, turn on your running lights, and turn the dimmer to its brightest setting. Using a voltage meter, check the wires emerging from both sides of the dimmer mechanism. Then, turn the dimmer to a lower setting and check both wires again. Whichever one gives a lower voltage (i.e. below 12V) reading the second time is the one you want. Using one of the wire splices, connect a red wire to that dimmer wire. This red wire will go to one of the light terminals on the gauge. Next, add a black wire to the other light terminal and run it to the ground block above the fuse panel.
The three terminals for the gauge itself are pretty self-explanatory, as they are labeled: +, - and S. For the + terminal, run a red wire to a switched 12Vsource. To check this, turn the key on, and use your voltage meter to find a wire that reads 12V. Now turn the key off, and check the wire again-it should read 0V. Keep looking until you find one. Using a wire splice, tap into that wire and attach a red wire to it. Be sure you're not overloading a circuit when you do this. Run the other end to the + terminal on the gauge. Next, add a black wire to the - terminal on the gauge and run it to the ground block above the fuse panel. If your ground block is running low on terminals, you can crimp both black wires (from the light and from the gauge) into a single female spade connector and save one terminal on the ground block. Note, however, that there are three ground blocks, and there are probably enough spare terminals.Finally, connect your sender wire (that you pulled from the engine compartment)to the terminal marked "S".
There are several mounting options for the gauge. When considering a mounting location and method, there are several factors to consider: visibility,permanence and safety. Obviously, the gauge needs to sit in a location and a tan angle where it is easily seen and read by the driver. Additionally, you need to decide whether you are willing to drill holes in the dash or other location to accommodate the installation, or if you'd prefer to maintain a "stock"vehicle in this respect. Finally, you need to ensure that the gauge in no way impedes the safe operation of the van (blocking driver's sight, interfering with controls/defroster, etc.), and that it is secure enough that it won't become a projectile in the event of an accident.
With these things in mind, some of the more popular mounting options are: mounting cups, either plain or adjustable; mini consoles; mounting brackets; and a-pillar mounts. Mounting cups sit on top of the dash, and require screw holes to be drilled in the dash. Mini consoles have a sleek look, and also sit on the dash, requiring a large hole (the size of the gauge) to be cut out of the dash.Mounting brackets hang down on one side of the steering column, and require small screw holes. A-pillar mounts attach to the a-pillar (the frame piece around the windshield where it meets the door), and also require screw holes.We carry the adjustable mounting cups in stock, which allow for a wide range of installation locations and positions. We can special order other types of mounts as well.
We wish you all the best with your new oil pressure gauge kit, and please direct any questions or comments about installation or this article to firstname.lastname@example.org.
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