Flickering oil light....( a little long ) :)

[RevelationX]

Hello folks...I have been lurking for awhile and have decided I need some tech help..I recently bought an 84' Rabbit diesel..The P/O had been running Castrol 20/50w oil and as far as I could see it was not C/D rated..
So shortly after I bought the car I changed to Shell Rottel 15/40w with 1 quart Lucas oil treatment ,now when when the car is warm after a sustained highway run when I come to a a stop the oil light will quit often flash on and buzz then settle down to a flicker..It did not do this when it was cooler out.. and it is idle dependant..I can give it the least bit of throttle and it is fine..I check the oil and it seems kinda thin. But the temp gauge never exceeds the mid point on the gauge ..Even when stuck in shipyard traffic ( you would have to live around the Hampton Roads area of Va. to know about it...think 10k people trying to exit one place via 2 3 lane roads..) ...Do I need to think about pump? an oil cooler? senders? different oil?
Other than this the car runs fine..no unusual noises after I tightend the alt. belt, runs strong..This is not my first VW but it is my first diesel..BTW I do have the Bentley book  Anyone with an idea please feel free to chime in..the Car itself has 278K miles..supposedly the motor has 80k and it suposedly has a new tranny..I know it is really clean under hood except for  what apears to be an oil leak around the head front side of the block..

[DieselsRcool]

Put a gauge on it. I have seen weak senders cause this on aircooled VWs. You need to be sure you have an oil pressure problem before you start fixing it.  

[fspGTD]

The '84 also has a complicated "dynamic" oil pressure light.  There is an oil pressure light control unit (looks like a relay), which takes signals from 2 oil pressure sensors (set for different pressures) as well as an RPM signal from the "W" terminal off the alternator.  In theory, it uses the RPM signal to determine which switch is supposed to be switched.  It is supposed to change logic used for operating the light at 2000 rpm or something like that.  Problem is it's complicated and not very trustworthy on a 20 year old car.  You could hook a multimeter up directly to your oil pressure switches and maybe figure out that way what's happening with the oil pressures more directly.

[RevelationX]

Thanks for the replies folks   ...I went ahad and changed out the oil today and went to a semi synthetic 20/50w oil (only desiel oil in that grade I could find for less than $7.++ a quart)...I made a short run of about 15 min and it seems to be a little better, I am hopeing that it is just a goofy sender... It seems so strange that this all started after I changed the oil and it started to warm up .. I want it to be simple as this is my DD for a 60+ mile run to work and I have only had the car since march :evil: .I will be hooking up a mech oil press. gauge ASAP...

Thank you again, And I will post a fallow up/s as thing progress..

Keith

[VWRacer]

Keep your chin up, Keith. I've had this happen so many times on engines with electric senders that I not longer trust them at all. Buy a $10 mechanical oil pressure gauge at "CheckZoneBoyz" and live happily ever after! :wink:

[RevelationX]

Keep your chin up, Keith. I've had this happen so many times on engines with electric senders that I not longer trust them at all. Buy a $10 mechanical oil pressure gauge at "CheckZoneBoyz" and live happily ever after! :wink:

Update.....I installed a Sunpro mechanical gauge...and I'm thinking it is the sender at the oil filter...as I installed the oil gauge at the head...and it still flickers and comes on...was scarry this am on the way to work..it was on constantly at idle...anyway..I got plenty!!! of oil press....which brings me to a new ?...how much is too much...27-ish psi at idle...nearly 75psi at 60-ish mph..and nearly 100psi on hard acceleration...20/50w Valvoline cl/cd semi-synthetic oil,Normal op. temp..no additive (Lucas)...Am I spazing the other way now...too little, now too much ??

Do I need to change the sender and go to a thinner oil ??

Thanks folks for you help and ideas...

Keith

[fspGTD]

The installation instructions that came with a german-made febi/bilstein 30mm gear depth VW oil pump I just bought have the following information for checking the oil pressure after installation:
* After switching on the ignition the oil pressure light should go out by an oil pressure of between 0.15 and 0.45 bar (that's 2.2-6.6 psi).  At a minimum of 2000 rpm and an oil temperature of 80 deg. C the oil pressure should be at least 2.0 bar (that's 30 psi).

It isn't that unusual, I don't think for cold oil pressures to come up towards or beyond 100psi.

Sounds like you have no problems to me.  I also see about 1.8 bar (26.5 psi) of oil pressure at a hot idle.  The standard "all-season" weight of oil for these motors is 15w40 for a non-synthetic.  If you can afford a full synthetic, 5w40 weight works really well especially in cold temperatures.

[fspGTD]

FYI: here are the specs from the ETKA Parts database for the '84 Rabbit oil pressure senders:

at the cylinder head:
* 1 pin, brown, .25 bar

at the oil filter bracket:
* 1 pin, white, 1.8 bar


Information in the "dynamic oil pressure system, US produced cars" From the Volkswagen Introductory Service training information manual:

"System operation
* When the ignition is switched on the LED will glow and will continue to glow until the engine has started.  This checks the operation of the LED and the oil pressure switches. (Note: the LED may flash once or twice and then glow continuously.  This is normal.)
* If oil pressure is below 0.30 bar (4 psi) and if engine speed it below 2000rpm, the oil pressure switch on the cylinder head, will close.  The LED for oil pressure warning will then glow.
* If oil pressure is below about 1.8 bar (26 psi) and if engine speed is above 2000 rpm, the oil pressure switch on the oil filter flange will open.  The LED for oil pressure warning will glow and a buzzer will sound.

Checking system
* Pull the wire off the oil pressure switch on the oil filter flange.
* Start the engine
* Increase engine speed to at least 2000 rpm
The LED should glow continuously and the buzzer should operate
* Return engine to idle
* Reinstall wire on oil pressure switch
* Pull the wire off of the oil pressure swith on the cylinder hea and connect the wire to ground
The LED should glow continuously
* Reinstall wire"

Hope this helps!

[RevelationX]

FYI: here are the specs from the ETKA Parts database for the '84 Rabbit oil pressure senders:

at the cylinder head:
* 1 pin, brown, .25 bar

at the oil filter bracket:
* 1 pin, white, 1.8 bar


Information in the "dynamic oil pressure system, US produced cars" From the Volkswagen Introductory Service training information manual:

"System operation

<SNIPAGE>


* Reinstall wire"

Hope this helps!

Thanks....Alot of that was in the Bentley book also...I am thinking the sender at the filter bracket is/was the problem or some small gremlin..as the pressure is right at 25psi when the buzzer/light comes on..I'm thinking that the sender went kaput and doesn't know how fast the motor is running..I have done away with the cylinder head sensor and will prolly either get the upper sensor and place it in the oil filter bracket and jumper the wire from the head so it will read super low oil press. or just get a plug and trust the gauge..

Thanks guys..I really do mean it. I wish I wasn't sch a novice to these motors so I could give back something...

[Rat407]

I too have the low oil light problem. But when I hooked up a Sunpro oil gage it reads 0 at idle and any other RPM when warmed up. The light buzzer only comes on at idle. I took a reading at the oil filter and I get 60 psi there. There is plenty of oil at the head. When I pulled the valve cover gasket the cam is soaked with oil and all over the rest of the head. I'm running 20w-50 and even went as far as to pull the rod bearings and installed new ones. Even though the old ones were good. I even installed a new oil pump. The main bearings looked great as well. The engine has 157k on it and has had the oil changed every 5k by the previous owner. That isn't the greatest but at least it was changed.  
I pulled the head due to a coolant overflow pressureization problem and there doesn't seem to be any evidence of head gasket problems. So off to the machine shop to get the head checked. My luck just isn't with me on this vehicle.  

Any suggestions?

Thanks.

[RevelationX]

I too have the low oil light problem. But when I hooked up a Sunpro oil gage it reads 0 at idle and any other RPM when warmed up. The light buzzer only comes on at idle. I took a reading at the oil filter and I get 60 psi there. There is plenty of oil at the head. When I pulled the valve cover gasket the cam is soaked with oil and all over the rest of the head. I'm running 20w-50 and even went as far as to pull the rod bearings and installed new ones. Even though the old ones were good. I even installed a new oil pump. The main bearings looked great as well. The engine has 157k on it and has had the oil changed every 5k by the previous owner. That isn't the greatest but at least it was changed.  
I pulled the head due to a coolant overflow pressureization problem and there doesn't seem to be any evidence of head gasket problems. So off to the machine shop to get the head checked. My luck just isn't with me on this vehicle.  

Any suggestions?

Thanks.

Beats me..Was that a mech or elec. sunpro? just curious..as we do from time to time get bad electronic parts at work right out of the box..

BTW..what part of N.C. are you from..I'm originally from the Wilmington/Rocky Point area...

[Rat407]

I bought a mechanical gage.  I hooked it up to the oil port at the oil filter and got 70 psi down there.  I just pulled the head and the machine shop said that the head is getting oil. The cam saddles looked great. If it wasn't getting oil or had true zero oil pressure then the cam saddles would be trashed. Also the whole area up in and around the cam is soaked with oil. So the head is getting oil.  Just weird. On a cold start up oil pressure at the head reading is 10 to 15 psi then goes to zero at operating temp.  I should be getting the head back tomorrow. They were going to go through it 100%. He even said that the cam it's self looked great.

I'm in the Goldsboro area. I actually live close to I-40. I'm right in the middle of Wilmington and Raleigh. An hours drive and I'm in either city.  I really like the Wilmington area.  Maybe some day when I get out of the Air Force I will move down there.

[RevelationX]

I bought a mechanical gage.  I hooked it up to the oil port at the oil filter and got 70 psi down there.  <Snipage>.  Just weird. On a cold start up oil pressure at the head reading is 10 to 15 psi then goes to zero at operating temp.  I should be getting the head back tomorrow. They were going to go through it 100%. He even said that the cam it's self looked great.


I'm in the Goldsboro area. I actually live close to I-40. I'm right in the middle of Wilmington and Raleigh. An hours drive and I'm in either city.  I really like the Wilmington area.  Maybe some day when I get out of the Air Force I will move down there.

I'm pulling my readings from the head I did think about going to the oil filter but decided to leave well enough alone..

I know exactly where you are. Go right by every few months when I road trip to see the folks..I jump on 701 to cut the corner on the 40/95 junction, right through Newton Grove.

Good luck on the oil press. problem I hope you get it worked out..with the way fuel keeps going I expect we will see a few more oil burners on the road...

Keith