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

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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 :D  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:

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