Technical Oil presure problem

[Leo500]

Hi guys!
I'm new in this forum and i have a problem!

When i drive the car everything looks ok, after about 20-30 min driving, when the car heats, oil lamp turns red but just when i stop or driving to slow, but when i speed up, the light does not come on...
Today i have mesured oil presure, and when the engine is cold when i start it, presure is at 3 bar, after 30min idling presure drops to 0.6-0.7.
When engine revs are raised, oil presure goes to 1bar
Is this a cause to concern?

 

[lazylobster]

Hi and welcome, and no, the oil light can come on when hot at idle.
Saying that, I have oil pressure gauge in my car (594cc) and when cold and starts, it's 4.4 bar and when hot at idle around 1.4 bar. so maybe a bit low, which engine do you have? I'm sure others can advise on what they get from their engines.

 

[Leo500]

Hi and welcome, and no, the oil light can come on when hot at idle.
Saying that, I have oil pressure gauge in my car (594cc) and when cold and starts, it's 4.4 bar and when hot at idle around 1.4 bar. so maybe a bit low, which engine do you have? I'm sure others can advise on what they get from their engines.

Thanks for reply!
I have 499cc engine

 

[fiat500]

Thanks for reply!
I have 499cc engine

What grade of engine oil are you using?

 

[Leo500]

What grade of engine oil are you using?

20W-50

 

[fiat500]

20W-50

That's good; but you could try one of the multigrades that has a higher top end in the range.
You could increase the tickover speed a little; that might just be enough to stop the light flickering and it will push a bit more cooling air over the engine.
You probably have some wear in the engine; I wouldn't expect the light to come on, even though it's only when driving slowly.
I would change the oil for something like a 10W60 after giving the oil filter a good clean.

 

[the hobbler]

That's good; but you could try one of the multigrades that has a higher top end in the range.
You could increase the tickover speed a little; that might just be enough to stop the light flickering and it will push a bit more cooling air over the engine.
You probably have some wear in the engine; I wouldn't expect the light to come on, even though it's only when driving slowly.
I would change the oil for something like a 10W60 after giving the oil filter a good clean.

As has been pointed out by Peter, Fiat says in the workshop-manual that it is OK for the low-oil-pressure light to come on when the engine idling HOT, but MUST go out as soon as the engine is revved above idle speed (about 800/900 rpm). Using a good 20/50 oil in a standard 500 engine should give no lubrication problems. When did you last clean out the filter? Your engine has a centrifugal filter that is built into the alloy front-piece of your crankshaft pulley---6 x 10mm bolts, and it will come off. Cleaning it with the rear cross-member in place is a bit of 'faff', but can be done; make sure that you also clean out the crud from the pulley. It will look like rubber, but it is the muck in the oil that has been spun out to the edges of the pulley and front cover. Before you remove the front cover, mark it at the timing marks---although the cover-retention bolts will only fit in one place, it will just make it a bit easier to put it back in the correct place.
Secondly, have you replaced the oil-pump? I have seen the oil-pumps sold as suitable for both 500 AND 126 engines----this is incorrect! Although the 126 oil-pump will fit into the timing-chain cover from a 500, the 126 oil-pump is slightly deeper than the 500's pump, so the oil-pressure-relief-valve (built into the pump) will possibly 'lift' when the engine gets hot, which will reduce oil pressure.

 

[Leo500]

As has been pointed out by Peter, Fiat says in the workshop-manual that it is OK for the low-oil-pressure light to come on when the engine idling HOT, but MUST go out as soon as the engine is revved above idle speed (about 800/900 rpm). Using a good 20/50 oil in a standard 500 engine should give no lubrication problems. When did you last clean out the filter? Your engine has a centrifugal filter that is built into the alloy front-piece of your crankshaft pulley---6 x 10mm bolts, and it will come off. Cleaning it with the rear cross-member in place is a bit of 'faff', but can be done; make sure that you also clean out the crud from the pulley. It will look like rubber, but it is the muck in the oil that has been spun out to the edges of the pulley and front cover. Before you remove the front cover, mark it at the timing marks---although the cover-retention bolts will only fit in one place, it will just make it a bit easier to put it back in the correct place.
Secondly, have you replaced the oil-pump? I have seen the oil-pumps sold as suitable for both 500 AND 126 engines----this is incorrect! Although the 126 oil-pump will fit into the timing-chain cover from a 500, the 126 oil-pump is slightly deeper than the 500's pump, so the oil-pressure-relief-valve (built into the pump) will possibly 'lift' when the engine gets hot, which will reduce oil pressure.

Thanks for advice!

I bought a car 4 months ago and I cleaned a filter.
New chain, timing belt, new carb, new fuel pump, ignition coil, condenser, oil pressure sender...
I haven't changed oil pump not sure how old it is and what partucular pump is on the car now.

 

[the hobbler]

Thanks for advice!

I bought a car 4 months ago and I cleaned a filter.
New chain, timing belt, new carb, new fuel pump, ignition coil, condenser, oil pressure sender...
I haven't changed oil pump not sure how old it is and what partucular pump is on the car now.

The important thing to remember about oil-pumps is that you cannot "mix-and-match"---if it is a 500 engine (engine type 110) you must ONLY fit a 500 pump. If it is a 126 engine (engine number 126) than you must fit a 126 pump. A 126 timing-chain cover will fit onto a 110 engine--if this has been done, than a 126 pump must be used. As I mentioned before, I have seen them advertised as a "500/126 oil-pump" THIS IS INCORRRECT. Have you had the problem ever since you bought the car? Another cause of low oil pressure are the core-plugs on the side of the crankshaft coming loose and weeping---as the oil heats up and becomes thinner, the loss of oil pressure through the cor-plugs becomes more apparent.