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Hi,

I recently managed to fix my very-fast idle in my 1981 spider after a long game of cat-and-mouse with vacuum leaks. After fixing those, my idle dropped to about 2000 (cold) to 1000 (warm). With the lower idle I found my oil pressure drops dramatically at warm idle (to 1/4 to 1/2 what it is supposed to be while driving). This is my first Alfa, I don't know how much pressure drop is to be expected when at idle. I put in a few quarts of 10w-30 I had in the garage one morning when I had low oil level and was in a hurry around the same time as I fixed the idle. Is my oil pressure drop normal for an Alfa, or an urgent cause to change to a thicker oil?

Thanks,
Ian
 

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Does the low oil pressure light come on?

Its not uncommon at all to see the gauge indicate warm oil pressures at idle way down around 10~14psi. Some of the manuals actually say to expect it.

57~70 warm at cruise, way, way down at idle. (light comes on at like 7psi IIRC)
No low oil light is a good thing, and if you're really freaked out by it you can hook up a mechanical gauge to confirm pressures. It won't make the pressure go up of course, but will confirm if the gauge is relatively close or not.

Use caution when just throwing oil at it to top up.
It's a 7+qt system, but overfilling will still screw things up just like any other engine out there.
20/50 is the flavor of choice.
 

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The oil low pressure warning light is set at 5 psi. The gauge is probably not accurate that low. Alfa says as long as the oil low pressure warning light is not on at idle, pressure is sufficient. Off idle at speed you should see the pressure up around 50-70 psi.
 

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Similar but different...

My oil pressure light comes on (flickers) as soon as my gauge reads below 57 while driving. It does go low while at idle but comes back when driving, the light concerns me. Thoughts?
 

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Similar but different...

My oil pressure light comes on (flickers) as soon as my gauge reads below 57 while driving. It does go low while at idle but comes back when driving, the light concerns me. Thoughts?

The gauge isn't all that accurate but you should chage the oil light sender if it different from the gauge sender.
 

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Since I bought my '81, the gauge has shown about 55 at speed and very low at idle...hard to say, but 10-15?

Then I noticed that pressure readings dropped as the car warmed up...even at speed it would get up to only 40'ish. Barely above 0 at idle. Warning light never came on...so I was pretty confident I had pressure.

This spring, it gave a little tick starting it up, barely getting above 0 at any engine speed. Diagnosed as a bad sending unit...whcih is on order. Probably been suspect for a long time.

This is running 20-50.

Update: Picked the car up from my wrench today (wanted someone to actually verify pressure and the new sending unit). Started the car up at the shop...woaa, I've never seen readings that high. Friendly wrench replies, "well, that's right on with my gauges." So yes, the sending unit was failing when I bought the car...
 

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Mechanical is the only way to really know. I have a bad sender on our 944 that gave my daughter a stroke when it came on (at night of course) and had to do the mechanical check on the side of the road before she would drive it home. A real PIA!!!

Might be worth the time to check.
 

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I had a similiar experience with a 88 Veloce. Turned out that the gauge was correct. I have a mechanical failure in the main bearings. One of the main caps was falling off and letting the oil pressure escape through the loose main bearing cap. This is NOT common but happen when a previous mechanic does not do his work correctly. The lock nuts on the cap and one of the primary cap nuts were in the bottom of the oil pan. The main cap stud was so loose it came off with just a pull with the fingers. I had read on the BB that low oil pressure was common on Alfas and not to be concerned about it. The engine was a strong runner so I accepted the statements that low oil pressure after warm-up was common to Alfas.

Don't assume the gauge is just incorrect. You need to double check the gauge with another hooked up to the pressure gauge sender fitting. Another cause is the loss of a crank drilling plug. You can see one of these drilling plugs on the rod throw just below the failing main bearing cap. This will also show up in the bottom of the oil pan. Unfortunately the oil pan is a double bottom pan and draining the oil will not allow you to find such foreign objets in the drained oil. You have to pull the complete pan assembly to find such objects. This bad experience just for what it may be worth.

Robert Hill in Memhis, TN
 

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