Erratic Oil Level Gauge

[7783911]

My oil level needle works just fine one minute, staying steady at a level. But on occaision it starts bouncing up and down and even pegs and sticks to the very top....i tapped on the gauge to see if it was a binding issue but wasnt. A minute later it went back down to steady normal level.

What tests are recommended to narrow down between gauge or oil level sender? Could it be a grounding issue?

All help appreciated

Bob

77 Targa/83 SC engine

[darrin]

Bob - few thoughts --

1) always remember that the oil level gauge will only work when both a) the engine is up to full operating temperature, and b) the car is stopped, with engine running, on a flat surface. If you're observing this erratic behavior while driving, it's probably normal if the gauge "behaves" in the above circumstance.

2) I had a similar issue with my oil level gauge -- bounced around like it was possessed. Fixed it by replacing the gauge. It's nothing more than a float that activates a variable resistor (similar to a dimmer switch) and the gauge reads the resistor's value -- over time/use, the assembly basically wears out -- fortunately, it's easy to replace -- the oil level sensor lives in the oil tank and is accessable by removing the right rear wheel and taking out a few small nuts. Sensor also is (Was?) pretty cheap. This may be one of the few situations where throwing parts at the problem (buying a replacement sensor up front) makes sense, as it'd likely be easier to simply remove and replace your current sensor as step 1 in problem solving -- a grounding issue would generally manifest as either no reading or pegged reading consistently -- be sure to pick up a gasket too, as you'll likely ruin the existing gasket while removing the sensor.

3) keep in mind that you should not rely on the sensor -- always check oil level with the dipstick, with engine fully warmed and running. Once you have a steady reading on your oil level gauge, you can see how it correlates to the dipstick level and, if necessary, bend the sensor's float to remove discrepancies. BUT again, don't rely on the gauge, verify with dipstick.

4) when you remove the old sensor, you might want to fish around in the oil tank a bit, you might find a lost dipstick or 3 while you're in there and you don't want a dropped dipstick to foul the oil level sensor.

[7783911]

interesting observations...the needle when "calm" is in the middle of the dial while driving and while idling at a stop...it may move up down on hard turns but barely. I dont really use it as I only trust the dipstick and my oil pressure gauge..but it just bugs me sometimes...i am fussy that way. i will look into the sensor idea a bit further

thanks

[7783911]

one more thought...i did notice the needle freed up when i hit a bump...maybe the sender is just old and not moving freely?

[darrin]

think of the sensor and oil tank as being analagous to the float valve and water tank in a toilet. Imagine how the toilet float valve would behave if you shook the toilet's water tank around -- sounds like what you're seeing is perfectly normal if the gauge is stable when stopped (and you've given the engine's dry sump system a chance to pump oil out of the sump and into the tank). The bouncing is caused (as I understand it) when the sensor hits the defective/worn wiring on the variable resistor.

Easy to double check the wiring to the sensor -- you could even unplug the wire from the sensor and confirm that it causes the gauge needle to drop to zero (or does it peg while disconnected? -- either way, it should help rule out a wiring issue)

[Tea Tray]

My oil level gauge was jumping all over the place. I decided to pull the sending unit to check it over and found the ground wire really loose. Tightened ‘er up and works like new.

[DRACO A5OG]

Here you go: Oil Level Sending Unit: How to Service / Repair / Maintain

[midnight911]

Originally Posted by DRACO A5OG

Here you go: Oil Level Sending Unit: How to Service / Repair / Maintain

i did this the other day. just purchase a new cork gasket from the host and go to town. simple. my level gauge works as designed now rather than in spasm all the time.