Prius oil system

<div class='quotetop'>QUOTE(LongRun @ Nov 20 2006, 05:57 PM) [snapback]352360[/snapback]</div>

The Prius is just like a conventional auto engine which will drain back thru the pump if there isn't an anti-drain back valve in the filter. Buicks were particualary susceptiable to this condition. If you look at a cutaway of a modern oil filter you can see the drain back valve. Or if you cut apart a filter it's that rubber diaphram at the inlet end of the filter housing.

 

The filter's anti-drainback valve must be workin' because every time I have removed Prius oil filter it has been full of oil.

I would claim that the the novelty of the engine oil system is that the pressure sensor is a two-state device that is "on" above 1 to 3 psi (reports vary) and is "off" below. Means that the oil pressure warning light only comes on if things have already gone south, and that an additional sensor must be installed (somehow) if a person really wanted to observe oil psi. Not my favorite Prius "feature".

It would also follow that the oil warning light is inhibited by some ECU if the engine is not spinning.

 

<div class='quotetop'>QUOTE(tochatihu @ Nov 21 2006, 08:56 AM) [snapback]352535[/snapback]</div>

has anybody put a momentary NC switch in the wire to the pressure switch and while driving with the ICE runnig pushed the switch thereby giving the ECU's an indication of no oil pressure and seen if it eventually tells the ECU to shut off the fuel flow to the injectors? That's what I'd hope would happen and there are some vehicles that do just that. Other than in ACC. mode I've never seen the "check oil light" on my car.

 

I remember two or three 'loss of oil' incidents reported for Prius. The engine was not inhibited from running, apparently in some cases to its own demise. The unfortunate drivers noticed the oil warning lights eventually. It is, admittedly, somewhat subtle.

The oil light bulb is tested (along with others) during startup cycle in NHW11 Prius. Look fast or you'll miss it.

If Toyota won't implement 'ICE-inhibit on low oil' programming, they should make the oil warning *at least* as intrusive as 'low fuel'. Y'know, a ding and some French. I have whined about this in the past.

The simplest version of Frank's test might be to pull off the oil sensor's connector and then boot up. I expect it to start normally except the (stupid little) light will be on.

 

<div class='quotetop'>QUOTE(tochatihu @ Nov 22 2006, 06:57 AM) [snapback]352979[/snapback]</div>

I'm not sure how long it will run with the remaining fuel pressure on the rail but it might be15-20 seconds at idle before the pressure gets low enough to cause it to stop, that was the reason for the driving test as more than a few seconds at 1500-1800 rpm should have the rail pressure so low as to cause it to quit.

 

DH can't think of any toyota engines that cut out when low oil pressure is sensed.

i think everyone should have it strongly reinforced to them that the "oil" light means pull the *&^% over immediately and shut off the car.

 

<div class='quotetop'>QUOTE(galaxee @ Nov 22 2006, 05:27 PM) [snapback]353302[/snapback]</div>

Honda has low oil cut on some of it's engines. As for the "oil" light I can't agree more. Try it on a turbo ICE and see what it costs.

 

<div class='quotetop'>QUOTE(galaxee @ Nov 22 2006, 06:27 PM) [snapback]353302[/snapback]</div>

Right. Make the light/other warning display of a magnitude commensurate with the scale of the problem.

 

<div class='quotetop'>QUOTE(tochatihu @ Nov 23 2006, 06:57 AM) [snapback]353444[/snapback]</div>

you mean DING and a banner on the MFD, "NO OIL! Stop Car NOW" after all the MFD say's "Low Fuel" along with a DING.

 

DH wanted me to share this real quick-

he had a 2g prius with a pretty bad oil leak (filter wasn't on tight) come in the other day, the triangle light came on (assuming the oil banner showed on the mfd but the owner did not notice) and the car shut down with about 3/4 quart of oil in the engine. would not start again. so there may be a cutoff mechanism.

 

Please explain the function of the check valve (anti-drain back valve) in the oil filter. I had been told by someone on Priuschat that the oil filter check valve was to keep oil in the filter when the engine was shut off because in some filter applications the filter was mounted with the open part facing down or to the side. This, of course, would mean that the oil would drain from the filter when the pump stopped so when the engine restarted the pump would need to fill the filter before it delivered oil to the engine. But with the Prius engine this was not a factor because the filter was mounted with the open side up and the oil could not drain out of it anyway.

After reading this topic I see that Frank H. and Tochatihu, both people I tend to listen to, are talking about the oil draining back through the pump with the engine stopped. Please explain, in simple terms, what happens? Is the oil siphoned back through the pump because the filter is higher than the level in oil pan? I have never seen the inside of an automotive oil pump but I always thought they were a positive displacement gear type pump, how does the oil get back through?

 

<div class='quotetop'>QUOTE(tumbleweed @ Dec 21 2006, 08:30 AM) [snapback]365111[/snapback]</div>

your correct in saying that it gets syphoned back thru the pump. All oil pumps with the exception of piston pumps have clearance between the gears and over time, more so while the oil is hot, it can and gets syphoned back into the pan. Only exception is if the filter is below the oil level in the pan.

 

<div class='quotetop'>QUOTE(Frank Hudon @ Dec 21 2006, 08:36 AM) [snapback]365113[/snapback]</div>

OK Frank that explains it, thanks. I would say in the Prius and other HSD hybrids it is more important than in "normal" cars because the engine stops and starts more frequently. Another good reason to use a high quality filter.

 

<div class='quotetop'>QUOTE(galaxee @ Dec 21 2006, 08:55 AM) [snapback]365089[/snapback]</div>

Hmm, interesting. Perhaps a useful test would be to unplug the standard oil pressure sensor and see if the car proceeds normally, albeit with the warning lamp lit. I am not quite ready to volunteer for this.

On DH's unfortunate 2g Prius, it would seem appropriate to take an early sample of the subsequent engine oil fill to confirm that it is not shedding wear metals like crazy, would you agree?

 

<div class='quotetop'>QUOTE(tochatihu @ Dec 22 2006, 07:41 AM) [snapback]365638[/snapback]</div>

I was thinking the same thing but as easy as it is to drop the oil pan, I drop it and pull the rear main cap and the rear rod cap and check the bearings. Next time I have mine up in the air I'll disconnect the oil pressure switch and see what happens.

 

<div class='quotetop'>QUOTE(tochatihu @ Nov 21 2006, 11:56 AM) [snapback]352535[/snapback]</div>

This is not a feature unique to the Prius. The oil pressure sensor set to a ridiculously low pressure is endemic to virtually all new cars.

In fact, the joke is that the 'check engine oil pressure' warning light should be changed to 'buy new engine now' because that's essentially what it means if it illuminates due to an oil pressure related failure.