PAwelder Posted March 9, 2014 Report Share Posted March 9, 2014 Hello i am new to posting on this site, however i have frequented it before as a non member and have found the dialogue very informative and helpful to my past problems. anyway my current problem has got me stumped. about a week ago making my commute to college (about 80 miles) i noticed my oil pressure warning light was coming on at about 1300 rpm towards the end of the drive. i assumed the oil pump had worn out and i was due for an oil change anyway so i got a melling 111 pump, which i thought was bigger than stock, and 10-30 oil and a k and n oil filter. after much trouble installing the pump (the timing rod lost its place) i got her running again but the problem was still there with little to no effect on the oil pressure. today i was researching once again the problem and realized 10-30 was a pretty lightweight oil, so i replaced it with chevron delo 400 15-40. i went for a spirited drive to warm up the oil and although it helped, the oil light still comes on at 1000 rpm or so, but crusing along at 16-1700 rpm the gauge shows 40 psi. so i guess my question is where can i look next. in my head the only things i can think would be the tolerances in the engine are loose, the sump screen is partially clogged, the sump tube has an air leak, or there is a leak in the engine above the pump. oh yeah and the truck has about 140,000 miles and there is no oil in antifreeze and no anti freeze in the oil. sorry for the long story and any help would be greatly appreciated. Quote Link to comment
datzenmike Posted March 9, 2014 Report Share Posted March 9, 2014 If you have a gauge then what does it read when the light comes on? Datsun oil pressure senders as set to come on between 5-8 PSI. My tired 300,000Km L20B read 17 PSI at hot idle and was fine doing so. Maybe the oil light sender is crap. BTW it hard to wear an oil pump out as it's very well lubricated. :lol: :lol: Quote Link to comment
ggzilla Posted March 9, 2014 Report Share Posted March 9, 2014 15W-40 is lighter than 10w-30. New oil always makes a difference. 15W-40 is as thin as 15w when cold, and no thinner than 40W when hot. Quote Link to comment
PAwelder Posted March 9, 2014 Author Report Share Posted March 9, 2014 If you have a gauge then what does it read when the light comes on? Datsun oil pressure senders as set to come on between 5-8 PSI. My tired 300,000Km L20B read 17 PSI at hot idle and was fine doing so. Maybe the oil light sender is crap. BTW it hard to wear an oil pump out as it's very well lubricated. :lol: :lol: i got my idle set around 800 and the gauge reads on the zero mark or below when hot idling with the light on, and please correct me if i am wrong but i thought the gauge and the light run off different senders. I cant see both going bad at once, but i guess stranger things have happened. any other thoughts Quote Link to comment
datzenmike Posted March 9, 2014 Report Share Posted March 9, 2014 The stock one is a single sender with two outputs, one for gauge and one for the red light. As you have changed the oil, the level will be correct, the pump change eliminates that and a new filter. That leaves only the sender or a bad internal oil leak. I guess for about $15 you can replace the sender as a hail Mary. Quote Link to comment
ggzilla Posted March 9, 2014 Report Share Posted March 9, 2014 Low oil pressure can have many causes. The least common perhaps is a worn oil pump. The sender is a combo sender for gauge and light. A loose/leaking connection can cause a low reading. Worn bearings is the traditional cause for low.pressure. Quote Link to comment
ggzilla Posted March 9, 2014 Report Share Posted March 9, 2014 Two FRAM oil filters in a row can cause it. A weak oil pressure spring can cause it. Quote Link to comment
datzenmike Posted March 9, 2014 Report Share Posted March 9, 2014 New K&N filter, new oil pump, new oil. A blocked filter would simply push the by pass ball behind the filter and unfiltered oil would circulate. You can easily push the by pass ball with your finger. As you say the oil bleeding past worn bearings faster than the pump can supply at idle speed is the most likely. Replace the sender as a last effort. X fingers. Quote Link to comment
ggzilla Posted March 9, 2014 Report Share Posted March 9, 2014 I would check the oil pressure spring first. Just unbolt the spring and inspect. Easier then removing the engine to check the bearing clearances. Quote Link to comment
datzenmike Posted March 9, 2014 Report Share Posted March 9, 2014 The thing is ... he has replaced the oil pump with no change. Plus it reads 40 pounds when revved up so the spring can't be weak at idle and good for 40 PSI when revved. Quote Link to comment
PAwelder Posted March 9, 2014 Author Report Share Posted March 9, 2014 thanks for all the replys, i am learning alot. ill replace the sender probably today or tomorrow, while crossing my fingers. watch it be that simple of a fix all along Quote Link to comment
datzenmike Posted March 9, 2014 Report Share Posted March 9, 2014 Have a read through this for wrench size to use and where and how to get at it... http://community.ratsun.net/topic/60742-heavy-leak-from-oil-pressure-sensor/. This is about the last think you can do on the outside of the motor to correct this. If it works then there never was a pressure problem, if not.... Quote Link to comment
Robert Posted March 13, 2014 Report Share Posted March 13, 2014 Try the easiest fixes first like Mike says. I would bet its the pressure sender. Mine worked fine until the engine was warmed up and it lost its signal and dropped the oil pressure guage. Another easy check is to look at your oil pan and see if you have dented it somehow from hitting bottom...if you have a large dent in the oil pan you can restrict the oil pick-up. These guages are common...ALL nissans have the same resistor bias and will all work in your truck. There is an access port on your oil filter pedistal....put a guage on it and see whats actually happening. 10W30 or 10w40 are both fine. Your problem is not oil weight. Quote Link to comment
Robert Posted March 13, 2014 Report Share Posted March 13, 2014 15W-40 is lighter than 10w-30. New oil always makes a difference. 15W-40 is as thin as 15w when cold, and no thinner than 40W when hot. 15w-40 is heavier than 10w-30 at both 0 and 100 deg C. 10w-40 and 10w-30 are the same wieght at 0 deg C but 40 is heavier at 100 deg C. Measurement is done by the amount of oil that can pass through a standardized orifice and standardized pressure and temperature. The W nember is always lower because it is tested through a much larger orifice even though it is tested at 0 deg C. I cannot remember the actual diameter of these orifices of the top of my head, but I know is unit of measure is Centistokes....I know this because I did a research paper on oil viscocity in college. Also did one on Octane and Octane ratings. Just to add, the first number is the winter designation...not weight. Therefore you cannot say 40W when hot....just saying. Correction...its 40 deg C for the W number. I forgot and just looked it up. ISO meathod 3448. Quote Link to comment
ggzilla Posted March 14, 2014 Report Share Posted March 14, 2014 thanks for the info. The W means winter. Oil formulation numbers are related to temp. This is what Nissan used to recommend Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.