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Engine Specific Info and Questions => IDI Engine => Topic started by: wjdzl on December 08, 2014, 11:59:06 am
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Slowly but surely getting sucked into the diesel world, having bought a Vanagon with AAZ.
Something that's been bothering me is how long it takes for the oil pressure light to go out when starting. If it's a warm start [the light] goes out pretty quickly, if it is a cold start, sometimes it takes 4-5 seconds? Is that normal or should I look into switching oil weight (not sure what the PO has in there, think it's Mobil 1 Syn) During those 4-5 seconds I feel like I can hear more valvetrain noise as it's building pressure.
Cheers!
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I see the same behavior with my AHU, currently running 15w40. Interested to see other responses here.
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1992 1.6 na. After an oil change about 5 sec. After a cold start. Maybe at most 2 sec
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I've got a digital gauge attached to the head (that's the switch that flashes the oil pressure light at under 2000 engine RPM). The head switch triggers at about 0.1 bar. I do usually see that much within a couple of seconds at current temperatures but it takes more like 15 seconds for oil pressure to completely stabilize.
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I have both the stock system and an autometer electric gauge. I get my light to go out while it is cranking or less than 1 second. I also see with cold 10w-30 around 15lbs before it lights. I did have the crank machined and new KS bearings when I rebuilt it.
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Are you measuring at the head or at the filter flange?
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Newly built 1.6d with hydro head and matching mk2 oil pump, turns off after just a couple seconds of cranking.
.:Sent by pneumatic tubes
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Fwiw there are a variey of different oil pressure switches. Since i converted from mech to hydro head, i did some research and put an 0.25 bar in the head and a 1.4 bar in the filter flange.
Iirc 0.1 bar is the spec for mech heads.
.:Sent by pneumatic tubes
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Are you measuring at the head or at the filter flange?
I measure from the cylinder head.
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having bought a Vanagon with AAZ.
Something that's been bothering me is how long it takes for the oil pressure light to go out when starting. If it's a warm start [the light] goes out pretty quickly, if it is a cold start, sometimes it takes 4-5 seconds? Is that normal or should I look into switching oil weight (not sure what the PO has in there, think it's Mobil 1 Syn) During those 4-5 seconds I feel like I can hear more valvetrain noise as it's building pressure.
my ahu the oil light goes right out. on my older (mk2) it takes a second or just a little longer.
in an older engine/used car changing oil can be a problem in its self, if po had one thing (oil) in car use only that oil; changing brand can be a problem. weight can too i believe.
sounds like you have a problem there though. if po used 5w-40 mobile1 change back to this; if you still have a late light, next you likely test sensors.
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Are you measuring at the head or at the filter flange?
I measure from the cylinder head.
How long do you have to crank to have it start? Mine usually lights off on the second bump of the starter - nowhere near enough time to build up any pressure if it's been sitting overnight say. I get your results if I come out of the grocery store or something like that where it has been sitting for less than an hour.
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Are you measuring at the head or at the filter flange?
I measure from the cylinder head.
How long do you have to crank to have it start? Mine usually lights off on the second bump of the starter - nowhere near enough time to build up any pressure if it's been sitting overnight say. I get your results if I come out of the grocery store or something like that where it has been sitting for less than an hour.
I am running around 17:1 compression, if it is cold maybe 5 turns of the starter, but the oil is cold so it shoots pressure right up. If it is warm it will light first turn and have oil pressure right about then...maybe a thousand one count.
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I have a AAZ powered Caravelle (euro vanagon). Running on mobil 5w50 currently. If i glow a long time, it fires up at first crank, then the light stays on 1-1,5 seconds.
If its cranking 2-3 times before start i never see the oil light... hot starts i never see the light...
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I installed a mechanical gauge (using a metric T-fitting like this one http://www.jegs.com/i/VDO/918/240-850/10002/-1?CAWELAID=1710621319&CAGPSPN=pla&catargetid=230006180000848799&cadevice=c&gclid=CKnboP7Du8ICFfPm7AodOhEAOg) and have the light as well
note: my mechanical gauge (sunpro) is 1/8NPT but it went into the metric fitting without much trouble
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Yeah 1/8 NPT and m10x1 are almost the same thread. Almost.
.:Sent by pneumatic tubes
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note: my mechanical gauge (sunpro) is 1/8NPT but it went into the metric fitting without much trouble
Yeah 1/8 NPT and m10x1 are almost the same thread. Almost.
always err on the side of being exact/esp. with npt threads.
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I would not thread an NPT fitting into the head as it will distort the threads in the head and very possibly make the head unable to accept a stock sender without leaking. I would have no qualms at all about threading an NPT into a bronze 8mm fitting or threading 8mm into a bronze 1/8"npt. I have done so several times without issue and if I did ever happen to have an issue it would be very easy to replace the fitting and sender.
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So, with almost 25 miles logged on my build, I am comfortable with the fact that with a pressure sender in the filter flange, I see around or in excess of 80psi (per fake vdo sender and real vdo gauge) when the oil is cold, and after the oil is uniformly heated it will drop to 35 or so when idling and surge back around 80psi under power.
and it's boring. And I'm pretty sure the idiot switch on the flange does a plenty fine job of letting me know that i have completely lost oil pressure. I have tested it twice now and the local streets are still oily.
I love metrics. I respect and admire metrics. My life is dedicated to quality assurance so I'm all about measuring and verifying. I feel like my oil pressure metrics in the coupe aren't really telling me something i am interested in knowing.
Is there a downside to simply replacing the oil pressure switch in the head with a (real VDO) oil pressure sender and letting that side of the warning system go hang?
or should i install a tee. which might have to be a tee and a bushing.
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Slim, If you really like metrics and like them to be close to what they are then why depend on electric senders to tell you fake values. They do sell mechanical gauges and if you pay more than 17.99 for them you might have faith in what they are tell ya.
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I disconnected my head switch years ago to install a gauge but I've kept the high pressure switch at the flange. That way I still have a working alarm system plus a gauge without having to deal with a tee. The head switch is only so valuable really - it doesn't really come in to play under normal driving, just at idle or if you happen to be lugging your engine.
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I just don't really like the idea of plumbing oil through the firewall. I also doubt that the difference in accuracy is that great.
.:Sent by pneumatic tubes
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I'd tend to agree, I don't see electronic sensors as being all that bad, as long as you use good quality ones. Same is true for any gauge though - quality matters huge with measuring instruments.
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I just haven't convinced myself that electronic senders are all that good. You have to convert a pressure ( something physical) to an electronic signal, then send that signal to a gauge that converts it either back to a mechanical or digital readout. Can you really trust that to be accurate? If you pay enough for the parts to be good enough to be accurate but time goes by and stuff gets out of spec. To me the more inbetween conversions you have going the less dependable it will be.
I never worried about fuel or oil in the cab. That is what grommets are for and that line is tough if you don't kink it. Besides we are driving diesels, you is really going to notice the smell?
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There's a certain leap of faith that the gauge printing is precisely relative to the motion of the mechanical needle as well.
the linearity of a transducer is relatively easy to establish. assuring correct relative motion of the needle to the dial isn't a hard engineering problem, but we really don't need a lot more than a rough measurement.
I have more faith in my ability to maintain perfect electrical connections than my ability to maintain perfect hydraulic connections. to each his own.
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I use a mechanical oil and coolant gauge. The oil pressure is from the side of the head, and the coolant temp is from the front of the head.
I could not be happier with its reaction times and accuracy. I can see the coolant temps drop on the gauge from turning on the heater fan.
I use a 0w40 Rotella T6 (AHU) and I get oil pressure at the head right after the engine fires, unless it is WELL below freezing (like -4f) and then it has taken the longest of 3 seconds to start moving the needle from 0. By 4 or 5 seconds I am at full cold start oil psi at the head.
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I have been using the auber gages/senders for a while now on my 2 chasis.
I don't have anything bad to say about them. Egt, coolant and oil pressure.
I have an aircraft alarm that pierces your ears when my set alarms go off.
On my fresh 1.6td at the flange I get 100+ psi on startup. At stock hot idle it stays around 27psi. Pressure rises right after startup. Thats with a windage tray and 36mm oil pump.
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I see the same behavior with my AHU, currently running 15w40. Interested to see other responses here.
15... isnt that much? i mean it has turbo... i have a 1.9 m-tdi afn i run on 10w40
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Yeah my plan is to run 5w40 Rotella T6, I'm about due for the second oil change on a fresh engine.