Oil pressure light and buzzing intermittently

[erisaaka]

After driving my 1987 vanagon for a little bit the oil pressure will buzz when the rpms drop lower than 2000 rpms. If I rev it back up again the buzzing will stop. I know that the oil pressure is fine I just think the electrical system is going bad...I think....

How do I diagnose and replace?

[E1]

We just had a thread about this in the past week or two.

Best of Luck, hope it's nothing. We installed a VDO oil pressure gauge and couldn't live without one now. Peace of Mind lives there.
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‘84 Westy, 2.1L with Digijet, 5.43 R+P, GT Gears
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[Tobias Duncan]

Good chance your pressure switch is going out. Order a new one from one of the vanagon vendors because FLAPS will often give you the wrong one and really cause confusion.
That is where I would start.

[Paulbeard]

[SyncroHead]

First, it's very helpful to know how this systems is intended to function when very part is working correctly.

I wrote the original version this many years ago (in the last century actually) and it's in the archives of the Vanagon email list-server.

The following describes the operation of the 1986-1991 Vanagon Dynamic Oil Pressure Monitoring System:

The system utilizes two oil pressure switches, a "high" pressure switch and a "low" pressure switch. While there is a "high" pressure switch and a "low" pressure switch, they both cause warnings when the oil pressure drops too LOW.

Since "too low" is a bit of a subjective thing in an engine, VW decided to implement two standards. The higher the engine RPM, the higher the oil pressure should be. If you have just one oil pressure switch with a setpoint low enough (say 4.4PSI, 0.3 bar) to not engage at idle, that leaves way too much slack for when the engine is at high RPMs when the engine should have at least 13.2 PSI (0.9 bar) . The "low" pressure switch is used to alert the driver if the oils pressure dips too LOW while the engine is running at less than 2000 RPM and the "high" pressure switch is used to alert the driver if the oils pressure dips too LOW while the engine is running at more than 2000 RPM.

More specifically it works like this:
The dynamic oil pressure monitoring system gets inputs from two pressure switches. One switch is closed with no oil pressure and opens when oil pressure rises to about 0.3 bar, called the 0.3 bar switch. The 0.3 bar switch is located between the left (driver's side) two cylinders. The other switch is open with no oil pressure and closes when oil pressure rises to about 0.9 bar, thus called the 0.9 bar switch. The 0.9 bar switch is located below the water pump & crank pulley, near the oil pump.

The monitoring system watches the 0.3 bar switch below 2000 RPM and ignores the 0.9 bar switch. Above 2000 RPM the active switch is the 0.9 bar switch while the 0.3 bar switch is ignored. Below I've described a properly operating monitoring system. Note that I say "monitoring system" because some of the conditions describe an abnormally low oil pressure condition.

There is no indication, monitoring, or alert of engine oil LEVEL. Oil level is only determined by looking at the dipstick.

A. Ignition ON, engine NOT running -- or -- engine running at LESS than 2000RPM
0.9 bar switch is ignored

1. Low oil pressure exists (below 0.3 bar, about 4 psi), keeping 0.3 bar switch closed
Oil light: Flashes
Buzzer: Silent

2. Normal oil pressure exists (above 0.3 bar, about 4 psi), opening 0.3 bar switch
Oil light: Off
Buzzer: Silent


B. Engine running at MORE than 2000RPM
0.3 bar switch is ignored

1. Low oil pressure exists (below 0.9 bar, about 13 psi), keeping .9 bar switch open
Oil light: Flashes
Buzzer: Sounds (Really pretty frightening when it happens!)

2. Normal oil pressure exists (above 0.9 bar, about 13 psi), closing 0.9 bar switch
Oil light: Off
Buzzer: Silent

There does not appear to be any condition in a normally operating monitoring system when the light should be on steady.

I hope this is helpful.

Regards,
Jim Davis
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[dobryan]

How do you know the oil
pressure
is fine?
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'87 Westy w/ 2002 Subaru EJ25 and Peloquin TBD

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MD>Canada>AK>WA>OR>CA>AZ>UT>WY>SD
https://www.thesamba.com/vw/forum/viewtopic.php?t=620646

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[danfromsyr]

FIX YOUR OVERHEATING ISSUE 1st
https://www.thesamba.com/vw/forum/viewtopic.php?t=703265


and while fixing that change your oil.
use a proper MANN/MAHL filter

from the vanagon owners manual

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[AndyBees]

Bringing this one up to the top as it is short and contains pertinent info.

Back story first.

89 2.1 that I purchased 1/2016. Early on, I did a lot of maintenance and preventative maintenance, including changing both oil pressure sensors/switches. No problems, just changed them.

Then several months later, I noticed that the oil light did not come ON when I turned the ignition ON. No oil consumption, engine sounds good, no rattling lifters, etc., so I never bothered to change that sensor/switch.

Now, fast forward to this past weekend, as I was driving down the drive-way, the Oil Light and Buzzer began communicating to me. I shut-down the engine and restarted, everything is fine until the engine hit that magic RPM, 2000-2100. So, I went ahead with the 22 mile round trip we'd planned (go hiking).

Then, today, I installed two new sensors. The low pressure sensor is China made. The high pressure switch is Made in Germany.

Now, the oil light comes on for about 1.5 seconds when the ignition is turned On, then it goes out. Also, at the magic RPM, the oil light and buzzer begin cussing me..........

This engine is fine..... starts good, idles good, runs good, no oil consumption, head gaskets don't weep coolant, etc. I'm running 10w-40 Castrol brand oil. The oil filter is a VW filter than come with the Van. There were 8 or 10 of them in Van when I purchased it.

So, what's up?
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[crazyvwvanman]

The .3 bar low pressure switch goes down between the pushrod tubes. The wire from it needs to connect to a blue/black in the vehicle harness.

The .9 bar high pressure switch goes by the waterpump pulley.
The wire from it needs to connect to a yellow wire in the vehicle harness.

When you turn on the key the oil led should start blinking and keep blinking forever until the engine is started.

Mark

[AndyBees]

Mark, I have the two switches installed in their correct location as you referenced.

The engine had 142k when I got the Van. It now has well above 150k miles. The high RPM Buzzer and Light never, ever gave a problem until this past weekend. As I stated, the low pressure switch quit turning on the light about five or six months after it was installed. And, yes, I do remember, when it worked properly, it did flash until the engine was started.

And, as stated, two new switches, and the issue is not solved!

I did inspect the wires back to the connector(s). The wiring harness has never been hacked on this Van..... looks all original!
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[crazyvwvanman]

If both wires were disconnected somewhere between the swiitches and the instrument cluster it would do what you say it is now doing. Follow the wires.

Mark

[Steve M.]

without meaning to be offensive...quit screwing around and get an oil pressure gauge on your engine.
It is the only way you will know what is happening inside your engine.
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[AndyBees]

Steve thanks for not being offensive.

I think the issue is electrical and likely in or at the cluster. I'm quite familiar with VW air-cool engines and somewhat with the 1.9 & 2.1 WBXers. I'm also very familiar with the BS oil pressure warning system on the early VW in-line 4 bangers.

This engine has never given any indication that it has an oil pressure issue. The first time the high pressure buzzer and light come on was after the Van had been sitting for about 10 days. Started fine, idled fine, no lifter rattle and drove fine until the RPMs went about that magic number, 2000. The oil was changed back in the summer, not sure exactly when, but very few miles on it. This engine has never had a lifter rattle even after sitting for weeks on end without being started.

Anyway, as you suggested and what I had planned to do anyway, I did do oil pressure tests.

Here are the results (comments above photos)

Below is a pressure reading with cold engine with ambient temp at 70f. This is a made in USA VDO gauge with 1 psi increments.

Below is a pressure reading using a different gauge. The engine had only idled for about 3 minutes (brand new old stock VDO gauge)

Below is a pressure reading with both gauges after the engine was fully warmed-up and rad fan cycled one time, this is at 2300 RPMs

Below is a pressure reading about 30 seconds after the 2300 RPM run.

Below is a pressure reading about 40 seconds after the 2300 RPM run comparing the two gauges

So, finding the electrical culprit is the challenge!
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[Steve M.]

What is your oil pressure at 3000 rpm and 2000 rpm?
Glad to see you do have the gauges! These oil threads can go for pages while the guessing at the problem without definitely knowing what the oil pressure is.

If I remember correctly at 2000rpm - 176°F you should be getting 2 bar or 28psi of oil pressure.
It's in there in the Bentley what the pressure should be at 2000 or 3000 rpm.
I haven't got the manual in front of me to give you the exact pressure.

If you do not have what the bible says then you might have a problem in the making.
I'd rather see at least 9psi at idle myself, but it does drop down low after a coming off the gas when it's hot.

Since you have the VDO in your hand I would run a new wire from the sensor to the gauge and see if the reading improves. resistance in old wiring can slow the speed of the smoke down as it travels through the wires from the sensor to the gauge.
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[AndyBees]

I'll dig into the Bentley and study-up on Oil pressure. However, I'm leaning heavily on the culprit being an electrical issue as I stated previously.

When the engine is cold, the pressure is very high at idle (above 50 psi as can been seen in the first pic). So, when cold at 2000 RPMs, the buzzer and light go off.... no way is that associated with low pressure.
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[AndyBees]

To be clear, both of the VDO oil pressure gauges are mechanical and screwed into a T that was connected to the engine between the push rod tubes.

Okay, I've read-up on the Dynamic Oil Pressure System. I found a pretty good write-up on the topic. I also dusted off my Bentley and followed the circuits from the switches to the cluster. They both go to the Engine Oil Pressure Control Unit (J114) inside the cluster. J114 also has a circuit to it from the Tachometer. Thus, the J114 uses data from all three that determines if we see a flashing light and hear a buzzer if pressure is below a set threshold/limit.

You could say the systems function on pressure and RPMs. I could not find any connection or association with engine temperature.

So, as can be seen in the first pic above, the oil pressure was above 50 PSI when the engine was first started (cold engine). But, when I revved the cold engine above the magic 2000 RPM, the flashing light come on and the buzzer sounded based on those pre-set pressures and RPMs as set forth in a previous post in this thread.

So, what's the problem?

1. Bad switch, even though it is new and made in Germany

2. Circuit issue of some sort

3. Engine Oil Pressure Control Unit malfunctioning

Keep in mind, the Van had never done this previously. It has a fairly fresh oil change (10w-40). It has 162k original miles (I'm 3rd owner). Lastly, when the issue appeared, the engine had not been started in about 10 or more days...

Lastly, as I stated previously, the oil light quit coming ON several months ago when the ignition is first turned on. Now, with the two new switches, the light comes on for less than a second. This would seem to indicate there is something going on other than oil pressures..

Hopefully, I can get back to it and run some ohm tests on circuits from the back to the front, check connectors, check the big cluster connector, etc.
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[Steve M.]

The only connection between the oil temp and pressure is at high temps, 220°+, you loose viscosity and you will loose oil pressure.

What VW is saying or my interpreting of it is if the bearing tolerance is worn so much that if at 2000rpm it cannot keep oil pressure at 29psi and the oil temp is at 176° then they are saying the bearings are worn too much and it's time to rebuild.

If your oil temps are high and you lost the "normal" 176° viscosity then even if your bearings are good the high oil pressure sensor is going to see it is not 29psi at 2000rpm and alarm because you do not have the pressure to float the crankshaft away from the bearing surfaces at high rpm.

Unless your sensors or the dynamic oil pressure/rpm monitor mounted inside the speedometer are bad and causing the alarm. It could also be burned wiring where the wire from the high pressure sensor is routed along the top of the engine. It gets hot enough to melt the insulation along there. Over time that wire insulation is going to become hardened and crack letting the wire inside the insulation get corroded or maybe short out as insulation is melted away.
It could be any connection in that wire circuit being corroded to cause resistance to weaken the signal and the Dynamic pcb inside the speedometer is not seeing a good enough signal at 2000rpm and alarms.

This is where having the oil pressure gauge installed pays off to tell you what your oil pressure really is when the alarm goes off.
It's why these oil threads go on for pages because until the driver knows without any doubt what the oil pressure is it is just a guessing game causing some mental stress and a P.I.T.A. if you need the Vanagon to get to work and you are afraid to drive it.

You know your oil pressure is good so you know you can drive it even if the alarm goes off. You have time to fix it properly while while being able to use the Vanagon.

[/b]
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This free advice is worth exactly what you paid for it.

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[AndyBees]

Well, I get it as to why there is a dynamic oil pressure sensing system and how it works. No problem there. But, considering that both the light and buzzer can be prompted to go off at 2000 RPMS with a cold engine having a known oil pressure in excess of 50 PSI at idle tells me there is something else amiss.

I did check the two sensor wires up to that first connector. They are both in good order.

Not a daily driver by any means. That's why it had been sitting and not started in over 10 days.

I'll report back after more investigating...
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'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.

[crazyvwvanman]

You know, it is only 2 switches and 2 wires.
If you reverse the 2 switch wires it will always do exactly what you just described.
If both wires are unplugged at any point between the switches and cluster it will always do exactly what you just described.

The 2 switches work OPPOSITE from each other.
The low switch OPENS when it sees pressure.
The high switch CLOSES when it sees pressure.

The "high pressure" switch is supposed to be .9 bar, around 13 psi (some parts books and even some places in the Bentley wrongly say 1.8 bar, WRONG)
The "high pressure" switch goes by the water pump.
The "high pressure" switch must connect to a yellow wire in the main vehicle harness going to the dash and then pin 12 of the cluster 14 pin connector. (sometimes starts out green at the engine harness, then connects to yellow inside the engine compartment wiring box)

The low pressure switch is supposed to be .3 bar or close to that like .25 bar, around 4 psi.
The low pressure switch goes down by the pushrods on left side.
The low pressure switch must connect to a blue/black wire in the main vehicle harness.
The low pressure blue/black wire goes up to the dash and then pin 13 of the cluster 14 pin.

In about 5 minutes you can test the switches and wires with a test light or ohm meter.

If you are comfortable working with the cluster, start at that end.
Unplug the 14 pin connector from the cluster. Find the blue/black wire (not the blue)
Turn on the key but leave engine off.
Test the blue/black wire for the presence of GROUND
Start the engine, verify that ground is now GONE
Are both things are true? They must be for the oil warning to work properly.

Move on to the yellow wire.

With key on but engine off.
Test the yellow wire for the presence of GROUND, should NOT have it!
Start engine and slowly rev to 2500+, verify that the yellow wire NOW has GROUND
Are both things true? They must be for the cluster oil warning to work properly.

Of course the oil pressure changes as the oil gets hotter so the rpm needed to trigger the high pressure will also change. VW expects the high switch to trigger at 2000+ even with hot oil. With cold oil it can trigger at idle rpm.



Mark

[MarkWard]

When I worked at Audi in the mid 80s, we had some 4000s that would have intermittent oil warning and buzzer problems. When we were not able to pin point a problem, we would ground the hi pressure switch lead and send the customer on their way with the idea they would report back if this solved the problem or not. If it did, we knew the problem was related to the sender or the actual oil pressure. If the warning was still going off, we knew the problem was related to the wiring or the control unit. The vanagon system could be tested this way.

Also, the WBX high pressure oil switch actually works at a much lower pressure compared to the inline 4 cylinders vw audi had. Make sure you have the correct range switch for the vanagon. Another note, but slightly unrelated. The 1.6 TD also had a high pressure switch that worked at lower pressure to take away some of the sensitivity of the system.

I worked for VW in the early inline years. Despite some of the info above, the dynamic warning system, was not engineered to tell you the engine was worn out. If you think of the era, self serve gas stations were taking the place of full serve stations. Oil levels were just not getting checked at each fill up. VW bought a lot of short blocks in the late 70s under warranty because the oil pan only held 4 qts and customers were consuming enough oil between the 7500 mile interval that the engines were seizing up.

VW Audi came up with two simple solutions. They added a larger oil pan to extend the range and the dynamic oil warning system. If the engine managed to run low on oil, the system could hopefully warn you. This was before the engineers figured out how to have an electronic oil level sender.
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