Uh, oh oil troubles

[Guest slowpoke]

The oil light is coming on nearly the whole trip back home tonight. At first,(a few trips to work ago) it would come on only after riding for a while-when coming to a stop at idle. Now it is on the whole time. Is there a good way to check for oil pressure assuming the switch is not working? Should I pull the valve cover and start the motor and see if oil is coming to the rocker arm assembly? Has anyone out there had to repair the oil pump? Oil pumps usually don't fail so I'm thinking it might just be the switch. Maybe I was just hallucinating but it was making a noise (metallic) from the heads. Just in case you guys might think I was hallucinating the bike does have fresh oil in the crankcase. Any info would be greatly appreciated.

[Martin Barrett]

It was my switch that failed, dealer fixed under warranty.

If Mr Roper (i'm one of the people that are allowed to call him that and it's not through associating with his daughters) is right, and he surely will be. If the pressure dropped enough to cause the light to come on your mains would be toast. To have run it all the way back home would surely have cause a catastropic failure and you'd know it. There fore by default that you can't see your con rod through the side of the engine it must be the switch.

[mike wilson]

Seconded. If it doesn't sound like somebody is using the engine for sealclubbing practice, it will be the sender. Either disconnect it or replace it. A pressure gauge would be much more useful.

 

m

[twhitaker]

One other possibility, also remote for the above reasons, is the oil filter has come loose allowing some of the flow to go across the filter gasket.

[Guest ratchethack]

A friend of mine also has a 2000 Sport. Last summer he didn't like the way his oil light was flickering at idle when leaving a parking lot on a ride. He had just checked his oil level, so that wasn't the problem. I suspected the oil pressure sender because it's historically had a relatively high failure rate, as Martin and Mike pointed out. He wouldn't ride it though, and left it there, came back later with a truck to pick it up and took it to his dealer. Turns out to have been a wise move on his part. It saved his engine.

 

Seems the oil pressure relief valve had stuck open. This is a potentially catastrophic condition, as would have been a loose oil filter as twhitaker pointed out.

 

In the aftermath of this little excursion, the lessons learned for both of us were:

 

1. Assuming the sender is working properly, by the time the oil light is on steadily, the main bearings are already torched. There are very, very few exceptions.

 

2. It's possible to avoid severe engine damage by immediately STOPPING THE ENGINE AND NOT RE-STARTING IT as soon as the oil light begins flickering at idle.

 

3. Under NO CIRCUMSTANCES should the engine EVER be run - even for a nanosecond - with a steady "on" oil light. The only 2 possible exceptions to this last are: The sender is known to be defective - OR - you would prefer to ride your Guzzi as far as it will go this way (not far ) and witness the destruction of your engine as the crank mains and big-end bearings are rooted by your decision and under your control.

[jrt]

I have to agree with Ratchet here. Conservativism is the better part of valor in this case. The sender unit is the most likely culprit, but the cost of that being a wrong guess is too high. Pop off the valve covers and turn the motor over to see if oil is pumped up to the heads. Alternatively, remove the sender unit and turn the bike over. A "pencil thin" geyser of oil should come out.

[Guest ratchethack]

It might be helpful to emphasize an important distinction here.

 

Seems to me that many riders use the Guzzi oil light the same as they would the oil light on a car.

 

As far as "idiot lights" for oil go, there's a critical difference that IMHO every Guzzi rider should fully understand and never forget.

 

Many car oil idiot lights indicate when the oil level is low. This generally gives the driver plenty of time and distance to get to a convenient place to add oil -- or, as the case may be, to inform Hubby so he can ask the inevitable question that is certain to have no answer: "And just HOW LONG has the oil light been ON, Dearest?!?!" Generally speaking, with a car, potential engine damage can be avoided when attention is given well after the onset of a "steady on" oil light. The oil can be topped up, having never experienced loss of oil pressure.

 

The Guzzi oil idiot light, on the other hand, is an oil pressure indicator, and on top of this, it comes on only at VERY LOW oil pressure. As noted above, regardless of oil level, once you've lost oil pressure for any reason - whether it be low oil level, loose filter, stuck pressure relief valve, plugged pickup, etc., for all intents and purposes, the engine is already running DRY - that is, there is bare metal-to-metal contact in places where it's absolutely mandatory for the continued health of the engine that there be a continuous supply of oil under pressure. Plain bearing shells will cook, gall, and spin, crankshaft journals will be roasted and scored, and bearing shell carriers will also roast and score, and even worse can (and does) happen. Any of this generally calls for a major engine rebuild.

 

It might have been more useful in real-world operation for Guzzi to have designed an oil level idiot light, or at least a sender that comes on at higher pressure, but as the ol' man always said, "If wishes were horses, beggars would ride...."

 

Just a thought.....

[Guest MotoMessiah]

I beg to differ. Cars rely on the same principle - oil pressure, not level. The fact that they may have more oil in the pan when the light comes on is the difference. As well they're designed to activate when the pressure is at a relatively managable amount. As in enough time for the average idiot to find a nice spot to pull over two miles down the road.

[Guest ratchethack]

I beg to differ. Cars rely on the same principle - low oil pressure, not level. The fact that they may have more oil in the pan when the light comes on is the difference.

90288[/snapback]

Hmmmmmmm........I'm more'n happy to be corrected here if I'm wrong, but does it depend on the car, then? I've added oil pressure gauges to many cars, including the 2 I'm now driving. The oil idiot lights come on when the level is low but the gauges still read full pressure.

[Guest MotoMessiah]

Hmmmmmmm........I'm more'n happy to be corrected here, but does it depend on the car, then?  I've added oil pressure gauges to many cars, including the 2 I'm now driving.  The oil idiot lights come on when the level is low but the gauges still read full pressure.

90289[/snapback]

Sorry I just corrected my original post. They're designed to come on when the pressure is low, but not low enough to cause immediate damage. I have never heard of an oil level sending unit. The idiot light works off an oil ""pressure" sending unit.

[Guest ratchethack]

Sorry I just corrected my original post. They're designed to come on when the pressure is low, but not low enough to cause immediate damage. I have never heard of an oil level sending unit. The idiot light works off an oil ""pressure" sending unit.

90290[/snapback]

The Guzzi oil pressure switch comes on at I think when the pressure drops to just a few lbs.. This would seem to have limited - though still very useful - value. It seems to me it'd be much more useful to know when it reaches, say, half pressure - before the mayhem begins????

 

I'd still like to understand more about the operation of automotive oil idiot lights relative to the Guzzi, (if it's not by oil level) since they seem to operate entirely differently - and much more safely in the case of a car. It may well be that as you've suggested, it's the pressure that the senders are designed to close contacts. The motors are both wet-sump, so I can't imagine why there'd have to be such a dramatic difference in the way the Guzzi sender is designed?!?!

 

Many's the Aunt Matilda who drove in from Albequerque in the old Ford with the oil light on the whole time before Uncle Fred found out about it and had his aneurism, only to discover after Fred got back from Intensive Care that there was no engine damage after all?!

 

This begs the question, "Is there a more sensitive (and reliable) oil pressure sensor available than what we got from Mandello?"

[Guest MotoMessiah]

The difference is the amount of pressure required to activate the idiot light. The goose's oil system is most likely low pressure to begin with. Any drop in pressure is dangerous. Most cars, and some bikes for that matter, run at a higher level. A small drop in pressure is less troublesome immediately. You simply really can't have a low oil level (as in dangerously low) and high pressure unless there's a block in the system or you're running 90 weight.

[Guest ratchethack]

You simply really can't have a low oil level (as in dangerously low) and high pressure unless there's a block in the system or you're running 90 weight.

Well, not trying to be argumentative here - honest, though I've entirely rebuilt a pile of both wet and dry sump motors and I should know this stuff, I obviously have a thing or 2 to learn (or re-remember ) here - but the dry sump system in my thumper works just fine, as I presume is the same with a Porsche or any other dry-sump design.

 

Exposing the pickup in any wet-sump motor would obviously result in low oil pressure. Speculating now, it may well be that car sumps are better designed to avoid exposing the pickup. The Guzzi pickup, however, is easily exposed by something as simple as hard acceleration. This is undoubtedly a contributing factor to "the problem" with the Guzzi.

 

In other words, at rest or smooth and level running, a low oil level in the Guzzi wouldn't affect oil pressure unless it got very low. On the other hand, on the road, as the oil level gets closer to the bottom of the sump, the pickup will be exposed on an increasing frequency as the oil sloshes around.

[Dan M]

Hmmmmmmm........I'm more'n happy to be corrected here if I'm wrong, but does it depend on the car, then?  I've added oil pressure gauges to many cars, including the 2 I'm now driving.  The oil idiot lights come on when the level is low but the gauges still read full pressure.

90289[/snapback]

 

 

Here's the deal. Cars have several different systems depending on model:

 

Single oil light. Comes on with loss of pressure. Usually the switch closes with very low pressure, I'd guess most are calibrated between 5 & 10psi.

 

Two oil lights. One for pressure as above and one that is connected to a level sensor in the pan. (two sending units)

 

Gauge only. Pressure only

 

Gauge and light. Gauge for pressue & Light is for level only. (again, two senders)

 

I agree with everything you stated, if that light is coming on, expect the worst.

So far as the bike in question goes, it probably is just the sender. If he rode it for several miles with no pressure, he'd have done damage already.

[Guest MotoMessiah]

Regardless of the sump type low oil level equals low oil pressure. Pressure is based on the amount flowing (viscosity + speed) in the system. Not in the tank - dry or wet. If the feed tube doesn't sit low enough (this is an issue when racing aircooled v-dubs in Baja) then you'll be pulling air when cornering, or as you said, when accelerating. It would appear that the issue could really be that the feed tube does not sit low enough in the oil.