Another Oil Pressure Issue! I know...bare with me

[bkendall]

So I did tons of research on here and cabby-info so I have exercised many options. Here is what the problem is:

The car:
1987 Cabriolet - Manual

At idle: no oil pressure light or buzz
2000+ RPM: light and buzz (only when temp is above 80)(low pressure, right?)

Here is everything I have done to try to fix it:

Replaced Oil pressure sender (on crank, pn 035919561)
Replaced Oil pressure sensor (on filter flange, pn 056919081E)
Mobil 1 Oil Filter
20w-50 Castrol Syntec Blended Oil (4.8qts)

Is my next option the oil pump screen? While I'm in there I might as well replace the pump for the 2.0. After I changed the oil and the filter my pressure at idle was showing 4bar with the temp at about 80. Before the oil change it was around 2bar.

I just bought the car on Sunday and the guy rebuilt the top end of the engine so I know the internals are good.

Any insight on this would be great!

Gotta show some pics!

[CalAltaDubber]

First welcome to TRF, Congrats on the purchase of the '87 (I own one too!)

First, you mention that the light is not illuminated at idle, what does the pressure gauge read?

Since you mention the light illuminates (with buzzer) above 2000 RPM, what does the pressure gauge read at that time?

The low pressure sender (the one on top of the oil filter flange) is the one that has the buzzer associated with it, I wonder if there is a slight blockage there? Since the engine was only partially rebuilt it seems possable to me.

Another possability is: there is an oil pan baffle that attaches to the end of the oil pump to keep a supply of oil at the opening. Did the P/O remove it?

If you are going to drop the oil pan to look at the screen, you will see if it is there. It looks like a big plastic plate attached to the end of the oil pump.

For the $100 os so for a new pump, it is only two screws to replace the whole pump.

Just my 2 cents worth.

Keep us informed.

[bkendall]

First, you mention that the light is not illuminated at idle, what does the pressure gauge read?

After the oil change it is at 3.5 bar at temp 90

Since you mention the light illuminates (with buzzer) above 2000 RPM, what does the pressure gauge read at that time?

About 6-7 bar

I'm not sure about the oil pan baffle but I guess I am going to have to drop the oil pan if I have no other options so I will make sure to check that. As far as the blockage at oil filter flange...how would I chack that? Shove something in the hole when I remove the sensor?

[gull]

If you're seeing 6 to 7 bar, you have *plenty* of pressure. The factory minimum spec is something like 1.8 bar at 2000 RPM and 80 degrees C. If the light is coming on at that pressure level, something is wrong with your pressure warning system.

The oil pressure warning system on these cars is complicated. There are two switches.

- One in the head, which *opens* at roughly 0.7 bar. This controls the light at idle.
- One in the filter flange, which *closes* at around 1.8 bar. This controls the light and buzzer above 2,000 RPM.

You can do some troubleshooting of the latter part of the system by disconnecting the wire from the switch on the filter flange. With the wire disconnected, the buzzer should go off when you rev the engine up 2,000 RPM. With the wire grounded, the buzzer should not go off. If it still goes off when the wire is grounded, you have an open circuit somewhere. If this test passes but the light still misbehaves, the sender may be defective.

[bkendall]

You can do some troubleshooting of the latter part of the system by disconnecting the wire from the switch on the filter flange. With the wire disconnected, the buzzer should go off when you rev the engine up 2,000 RPM. With the wire grounded, the buzzer should not go off. If it still goes off when the wire is grounded, you have an open circuit somewhere. If this test passes but the light still misbehaves, the sender may be defective.

I've changed both of the parts you mention but it still worth trying this. What is the best way to ground the wire?

[CalAltaDubber]

You can do some troubleshooting of the latter part of the system by disconnecting the wire from the switch on the filter flange. With the wire disconnected, the buzzer should go off when you rev the engine up 2,000 RPM. With the wire grounded, the buzzer should not go off. If it still goes off when the wire is grounded, you have an open circuit somewhere. If this test passes but the light still misbehaves, the sender may be defective.

I've changed both of the parts you mention but it still worth trying this. What is the best way to ground the wire?

This is a good test, To ground the wire out, disconnect it from the sensor and either have a helper hold the terminal so it is touching the block or use a short piece of wire with an aligator clip on each end to connect the wire to the block. Just remember, there has to be a good connection.

[gull]

If you have the aforementioned alligator clip wire, the valve cover studs make good ground points.

[sixsracing]

Don't know if you have resolved this issue or not. There is a circuit board in the instrument cluster that controls the buzzer. 2,000 rpm is a point at which the control comes into play. My bet is this has gone bad. If you can get a spare instrument panel then swap it out. This was a HUGE bad spot in Vanagons. Good luck.