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Towed my car back to house last night.....will tow to mechanic Monday...but I was out driving and last time I drove (2 weeks ago) oil pressure went down to 0 at idle...once I revved it some it came up to "normal" at warm....at start it was full pressure as always...thought I had gotten low on oil so yesterday I checked it was down to half ,so I topped off...started up, full pressure...after about 3 , 4 miles , once warm pressure went to 0 at idle again , I revved it at red lights and it was ok....another mile or so ,it went to 0 while driving....just as it did I felt the car shuddering a bit but could have been the bad road surface...I drove another mile to where I was going....met with friends...started it up , had some pressure ,but it went away , called wrecker.
history (which I am not 100% sure about , only hearsay) engine had 500 miles on it when I bought it , p o rebuilt it....I have put 1500- 2000 miles on it since with 2 oil changes first after my initial 500, = 1000 on rebuilt.
Called my buddy (Volvo mechanic, who has moved to Panama) he said it sounded like a bad gauge (but it did move some) or oil pump gone bad...Any thoughts on what this could be otherwise?
 

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This may be perfectly normal. The Alfa gauge reads very low with warm oil when the engine is at idle. But if you check it with a mechanical gauge the pressure is fine.

Look at the needle when the engine is off - it goes way below the '0' on the face of the gauge.
 

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More likely a bad sender rather than gauge, the senders are not the most reliable.

you could remove the wire to the oil pressure sender (on intake side of engine, near starter) and ground it.....pressure gauge (ign. on) should go smoothly right up to max. If it doesn't, then more likely a gauge fault. Check the small connector on the oil pressure sender is not corroded, resistance here would send a wrong signal.

I presume the low oil pressure light didn't come on whilst driving? That sender (exhaust side) is a lot more reliable and should def. not be ignored.
 

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Most accurate verification. Remove the sender (I know this is easier said than done) and hook up a mechanical oil pressure gauge with a fluid line from the engine to the new mechanical gauge. Most inexpensive mechanical gauges have a plastic fluid line and the hooked up gauge can be held in your hand or the line can be run through the vent window and you can lay the gauge on the console for testing purposes. Then start up and drive as normal. I am betting you will find that you have no real problem. A new electrical sender (about $50) will probably resolve your problem.

Oil pumps rarely go suddenly bad. A catistropic oil pressure failure is most unlikely. Don't assume you have real problems until you do diognostic testing.

Robert
 

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I'm a fan of installing a mechanical gauge, even if temporarily. My suggestion is to install it on the driver's side where the low oil pressure sending unit resides. It's way easier than trying to remove the sending unit on the passenger side. And, if you want to make it permanent, just get a Tee fitting so you still have the low pressure light.
 

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Discussion Starter #6
thanks guys.....$50 for a sender would be great vs $1000s for a re build...Will print this out and take to mechanic...I don't have many tools and very cramped garage quarters , hence almost nothing gets done at home...
 

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71 Berlina 74 GTV 17 Giulia Q4
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Has the low oil pressure light come on? Is it lit when the ignition is switched on? I cringe when a po says the motor has been rebuilt, most of the time the term "rebuilt" has a loose interpretation. Of course as said verify the actual pressure. Is this something that has just appeared if so what readings were you getting before? How many miles are on the car? If the readings are correct your gague is telling you the bottom end is reaching the end and the bearings are worn out.
 

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Discussion Starter #9
Has the low oil pressure light come on? Is it lit when the ignition is switched on? I cringe when a po says the motor has been rebuilt, most of the time the term "rebuilt" has a loose interpretation. Of course as said verify the actual pressure. Is this something that has just appeared if so what readings were you getting before? How many miles are on the car? If the readings are correct your gague is telling you the bottom end is reaching the end and the bearings are worn out.
no light came on ,BUT I don't know if bulb is out...I don't recall it being lit ever....."supposedly" it was totally re built and he was 'running it in' , he had done 500 miles and told me not to go over 4.5k RPM for te next 500..thats when I did oil change...the gauges readings were 'acceptable' to me before 3/4 up or more at start up and for many minutes ,then it would be varying by speed....at idle it would show just around 5 ..total miles on car is now at 113k +, and supposedly rebuilt at 110k...seemed fine ,had plenty of power...tomorrow I`ll tow it to mechanic , then we`ll see...I m hoping for a bad sending unit
 

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71 Berlina 74 GTV 17 Giulia Q4
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The low op sender is in the middle of the block on the exhaust side. It should come on when the ignition is switched on. If it doesn't take the wire off that sender and ground it to the block, with the ignition on. If it doesn't come on it's probably the bulb. Pressure readings vary quite a bit between cold and really hot oil temp so that could be what your seeing.
With new bearings and the original oil pump the pressure on Average should be at the mark between 0 and 55 at idle with hot oil and between 55 and the mark to the right of 55. If you still have contact with him ask if they replaced the bearings. New rings require break in, bearings not so much. Don't freak out just yet, if the low pressure light is working and doesn't come on your safe but I would for sure verify the actual pressure.
 

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Discussion Starter #11
Mechanic just called , I do have pressure.....no wire connecting warning light to sender...the sender to pressure gauge seems to be faulty...we`ll replace both senders and connect with wire the oil light...hoping that's it
 
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