Technical No Oil Pressure - Gauge Or Pump?

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Technical No Oil Pressure - Gauge Or Pump?

Muzzie

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Well, not quite true, it has oil pressure.

I start it on the morning, light goes out straight away. Idles at 2bar, at 100 its got 3.5bar.

Now 50% of the time after it's warmed up slightly, my oil pressure at idle goes down to just under 1 bar, and at 100 its 2bar at most.

The other 50% is idles at 2 bar and has 3.5bar at 100.

Why the differences? Is it gauge or pump? Is it alright to just ignore the gauge and use the light as an indicator or do I have some serious problems?

Thanks
 
Oil gets thinner as it warms up, so a slight drop in oil pressure is quite normal. But are you saying that when its warmed up it drops 50% of the time, and the other 50% it doesn't (even though its warmed up)?

The Haynes manual states that the 1301cc i.e. turbo has the same specification for the lubrication system as the non turbo. :confused: There's no details of the lubrication system in the turbo engine specs, but it says 'see 1301 non turbo details in chapter 1 for all other specifications'.

Anyway, 1301cc engine has following specs:

Oil pressure at normal operating temperature and average road/ engine speeds = 3.34 - 4.9 Bar (50 - 71 lbf/in2) - (that's inch squared, not a typo!)

So though yours seems to be a bit low, as it runs at about 3 bar under normal driving then I wouldn't worry. Also, as long as the low oil pressure warning light doesn't come on then all should be ok.

But the best person to ask is AlexGS, as he has a turbo and he knows what he's talking about! Alex, have you anything to add from your own experience with a turbo? Any other turbo owners know what the oil pressure gauge should be showing?

Chas
 
Its easy to hook up an aftermarket gague to check. The gagues always read very low, my mk1 was less than 1 bar when warn at idle. I've never been worried about it, the engine would of expired long ago if it was accurate.
 
Well,
My Turbo performs according to the handbook - the gauge may drop slightly below the 2 bar mark (literally, the second line on the gauge) with the engine hot and idling. At other times, the gauge stays around the centre.

Knowing how these oil pressure senders work (or, more to the point, how they don't work) I would say that you have a 'tired' sender, like my Alfa 164 has. They are quite capable of reading fine with the engine cold, but very low once the engine has warmed up - the actual pressure does drop somewhat (as Chas says) but nowhere near as much as your gauge would suggest.

This is probably the reason why you have an oil temperature gauge kindly provided by FIAT - so you can see if the oil is hot, and therefore if it's fair to expect a pressure drop. During a track day with my Uno Turbo, the oil temperature is frequently over 140 degrees (C, of course!) It would be nothing unusual to expect a pressure drop at these temperatures. If, though, you have the pressure drop with the temperature gauge hardly registering, it's more likely to be just the sender.

I recall that a common fault is that a seal inside the sender leaks, causing the housing to fill with oil. Since oil isn't compressible, this leads to the gauge under-reading because the diaphragm can't move properly.

To fix this problem, you can try drilling a small hole in the top of the housing, to let the excess oil out. This may either fix the problem with no noticeable oil leak, or, at the worst, you'll have a small oil leak from this new hole. It has to be worth a try, but what I can't tell you is where to drill the hole: the senders have several different designs. I'd try on the end surface, opposite to the electrical terminal.

Steve is right in that, if there was a problem, you would have known about it by now. :)

One other thing: oil flow is just as important as oil pressure, and it follows that if the oil pressure is low, the flow may be still strong. If the oil pressure was over-high, that would probably be worse because it would suggest that the flow has become restricted!

But perhaps, next time you change the oil, you might like to use a 15W50 like I use: now that it's summer over here and the daytime temperatures are unlikely to fall below 24 degrees...

-Alex
 
Last edited:
alexGS said:
Well,
My Turbo performs according to the handbook - the gauge may drop slightly below the 2 bar mark (literally, the second line on the gauge) with the engine hot and idling. At other times, the gauge stays around the centre.

Knowing how these oil pressure senders work (or, more to the point, how they don't work) I would say that you have a 'tired' sender, like my Alfa 164 has. They are quite capable of reading fine with the engine cold, but very low once the engine has warmed up - the actual pressure does drop somewhat (as Chas says) but nowhere near as much as your gauge would suggest.

This is probably the reason why you have an oil temperature gauge kindly provided by FIAT - so you can see if the oil is hot, and therefore if it's fair to expect a pressure drop. During a track day with my Uno Turbo, the oil temperature is frequently over 140 degrees (C, of course!) It would be nothing unusual to expect a pressure drop at these temperatures. If, though, you have the pressure drop with the temperature gauge hardly registering, it's more likely to be just the sender.

I recall that a common fault is that a seal inside the sender leaks, causing the housing to fill with oil. Since oil isn't compressible, this leads to the gauge under-reading because the diaphragm can't move properly.

To fix this problem, you can try drilling a small hole in the top of the housing, to let the excess oil out. This may either fix the problem with no noticeable oil leak, or, at the worst, you'll have a small oil leak from this new hole. It has to be worth a try, but what I can't tell you is where to drill the hole: the senders have several different designs. I'd try on the end surface, opposite to the electrical terminal.

Steve is right in that, if there was a problem, you would have known about it by now. :)

One other thing: oil flow is just as important as oil pressure, and it follows that if the oil pressure is low, the flow may be still strong. If the oil pressure was over-high, that would probably be worse because it would suggest that the flow has become restricted!

But perhaps, next time you change the oil, you might like to use a 15W50 like I use: now that it's summer over here and the daytime temperatures are unlikely to fall below 24 degrees...

-Alex

I'll give that a shot, or try and borrow a replacement sender from IAC up here to test the gauge.

And I use Penrite 15w60 :)
 
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