Oil pressure

[Farabomb]

I just spent a fair ammount of last night installing a 2" oil pressure gauge. After needing some more parts and having to do some modifications to said parts I got it done somewhere around 11ish.

No leaks so far so I took it for a spin. Is the pressure supoused to swing from damn near 0 all the way up to 75-80psi? When I'm on it it's around 75, when I'm just driving normal it's 50, and when I stop at a light or something it allmost drops to 0. Is it supoused to do that? I know it changes while driving but watching it drop to 0 scared me a little. :eek:

Anyone have a pressure gauge in their car? Does it drop to allmost 0 when you pull up to a stop? :confused:

[dicki]

hummm it didn't use to in my lancia... the only time it did was just before the main barings packed up...

might be different in a scooby though...

dicki

[Player0]

Err...i dont know.

I usually thought this would remain pressurized while running. It does in the cars Ive seen with the guages. Ive never seen it drop to 0. Maybe you have a leak somewhere?

How can it run without any oil pressure?

[Farabomb]

I started it up and noticed a leak on the sender. Fixed it and drove to work and so far I see no leak. It still drops at idle (not to 0psi but damn close) but when driven it's 50-75psi depending on how hard I'm on it.

[Farabomb]

Ok, more info.

I think I took care of the leak but I think I'm still going to tear it down and put teflon tape on the fittings. The destructions told me not to because of the ground issue but it's present mounting is zip-tied to the rear of the block so I think it's getting good ground. It still seems to be seeping from the sender adapter but it's just on the threads. It hasn't leaked enough to drip onto the block. It's clean there so when it does I will see it........ Well I just went and looked and %^&$# it pissed a little onto the block. Have to fix that tonight or tommrow. :(

Seems the scooby likes to swing from 13.5psi to 80psi depending on how warm it is and how hard I'm on it. I was supprised about that. I thought it would be more stable. It's a steady 50psi on the highway so hopefully everything is getting enough oil. :)

Next project: Fix the 12v+ to the gauge (wired it to the stock boost gauge harness only to find out it only works with the lights on ;) ) and install a oil temp gauge. I have space for one more but I don't know what one. Then I have to make the gauge mount. :)

[tripodal]

I would first verify the accuracy of the gauge... after that if your oil pressure is really 0 at idle close, the most likely cause is a spun bearing.. or just partially spun. 80psi is a high but normal figure depending on the motor. old vw's ran that in diesel motors.
but that oil was 15w40.

I would look up the normal spec. for yoru motor in the manufactur's manual. Go from there.


As far as the gauge goes, a small leak isnt likely to cause the gauge to be off much considering the available volume(probably a lot)
I would make sure you have a good solid 12v and a nice ground.
That is critical for the gauges accuracy, assuming its not just lighted and is electically controlled.

The swinging of oil pressure from 40psi - 60psi is something ive seen quite frequently. in fords, on stock gauges ive seen it go as high as 70psi and as low as 20psi but never 0.

[Synthohol]

hey fara, most all cars idle around 15-25 lbs oil pressure, if memory searves, didn't you have a rapping in the engine at one time?also loose main bearings will also lower pressure.
so will a clogged p/u screen.
for a 5.00 diagnostic, get a can of motor honey like stp oil treatment and see if the pressure goes up, if so its main or cap bearings with alot of clearence. tossing that harmonic balancer/drive pully could have caused some damage to the front main bearing from the vibration too.
if winter was not imminent i would suggest 20w50 oil for a couple thousand miles to see if thicker oil does the trick.
is the oil pressure high when the engine is cold and lowers as it heats up? could be worn gears in the oil pump.
imho, if the oil light comes on when the key is first turned on then you know the dummy light works and dont worry about it until the proposed engine swap.
good luck bud:)

[tripodal]

I would reccomend aganst 20w50, if your oil pressure is spiking at 80psi now... who knows what it will be at full thottle. that could be bad.

[krucibus]

All cars have some oil pressure once running, with an average low between 15-25 PSI at idle, increasing with engine RPM. My MOPAR V-8's top off at cruising speed (Highway) at around 60 PSI at 2500-3000 RPM. If you've got a little four-banger, which rev higher, I might expect 10 to 15 extra pounds of pressure, so 80 is not too much of a problem if it's within your cars' specs. As for it dropping to 0, that's the only thing that shouldn't be indicated. If you have a mechanical problem as suggested you would definitely see an increase in engine temps at idle, otherwise it's simply a gage gripe. What you really want is to be able to monitor pressure without having to resort to different grades of oil.
Electrical sending units also need to be matched to the gage (I.e., Autometer with Autometer, brand-wise), since their requirements as far as voltage and resistance vary from brand to brand. Mechanical ones are more precise and you don't have to worry about a sending unit, since they plumb directly into the block by way of a tube connected to the gage, and all pressure is recorded and measured at the gage.
As far as a small leak or seepage at the sending unit, this won't make any difference in its function, all you need to worry about here is your own sense of aesthetics under the hood.
Just some info from a gearhead. Hope this helps:)

[Synthohol]

Originally posted by tripodal
I would reccomend aganst 20w50, if your oil pressure is spiking at 80psi now... who knows what it will be at full thottle. that could be bad. all cars have a high pressure relief valve located in or on the oil filter housing, if the pressure gets too high the oil is redirected back to the pan, its like a spring loaded ball that opens with enough pressure to stop a potential oil filter from exploding.
plus fara pushes his car like its blocking the front door to the sam adams factory, im glad this is all that is wrong with the car:)

[Farabomb]

I use Shell Rotella in the scooby. I think it's 15/40, a lot thicker than the 5/30 scooby recomends. I spun a bearing about a year or two ago so that's the reason I could be seeing low pressure @ idle. It drops to about 13.5 with the clutch in but it never reaches 0 exactly. The needle may swing a bit lower for a second but it comes back. I think it's just the air filled gauge making it's swing.

I don't like the leak on the engine so I will be fixing that. I thought about a mechanical gauge but the thought of having 2 oil lines plumbed into the cabin made me go with the ele ones. I'm not about dead nuts accuracy I just want ballpark figures and see when things are going wrong.

Like Synth says I beat in my car. I drive it quite hard and fast and haven't been all that kind to it, hence the new motor it's getting when I can afford it. I want to limp this one for as long as I can. Seems all the nice parts I want are very, very expensive. :)