Hi,
I have used this forum to find out many things about (and fix) my vehicle, however it has come time when i have to ask a question. (have been through the other posts)
This is about low oil pressure on start-up, and while running the engine. Suspect it is to do with the oil pump.
Engine: 4JB1T, bighorn.
The story:
Firstly, I run waste vegetable oil (WVO), which gets past the rings in my engine and into the sump oil. The effect of this is that the sump oil level rises, and when the engine gets very hot, the sump oil becomes thick & gooey.
I believe the problem started here.
- After having gone 4x4ing with a friend up some long steep hills (about 6 months ago), the engine temp gauge was 3/4 the way up when arriving at the top. When i next used the vehicle, i noticed that the oil pressure stayed around the '4Kg/cm^2' mark, which it doesn't usually do unless the engine is cold. I did about 200km with the engine like this.
- To rectify this problem, i did an oil change with valvoline 20W40 (stuff i usually use with no problems), and replaced the oil filter with a ryco oil filter. The oil taken out of the engine was extreemly thick and gooey (the last of the stuff that came out was like maple syrup - poor engine
).
- After this oil change, I was able to hear a funny faint 'clicking' sound from the front of the engine (if you could imagine, sounds a bit like alternator brushes jamming against a part of the alternator while moving). Audible when the engine was cold, and faded away after 20 seconds of having the engine on. Oil pressure appeared to be lower than normal, however no big noticeable difference on the pressure gauge.
- Another 2,000km, noise was still there. During this time on a trip away, rocker cover came loose, oil went everywhere, used cheap warehouse oil for the rest of trip. Went through 16L of red-stamp oil on trip (time did not permit to fix problem at the time). Fixed rocker cover. cheap oil still in. About another 1,000Km later, noticing oil pressure is lower than normal (i.e. around 2Kg/Cm^2) when driving at normal temperatures. Taking longer for the oil light to go off when engine started (i.e. 3 seconds).
- Got 4x4 stuck on a hill for several days (steep gradient). When i went to start it, the oil light stayed on for about 15seconds (had 3 attempts starting, put more oil in top of engine, 3rd time oil light finally went out after a while)
- Now noticing whenever i start engine cold, oil light stays on for 10 seconds or so, worse when very cold (20-30 sec), so did oil change (to 20W50) & oil filter change to Fram filter, still no difference.
Symptoms:
- When engine is cold, a ticking sound can be heard from front of engine (close to where oil pump is), and continues until oil pressure is there.
- Oil pressure is non-existent for first 20-30 seconds when cold (i.e. red oil press light stays on).
- After first 30 seconds, oil light goes off, pressure stays low (i.e. about 0.25Kg/Cm^2) until oil gets warmer, then when at warm temperature the oil pressure shows about 2Kg/Cm^2.
If i try to rev the engine when cold, oil pressure drops back down and oil light comes on.
If i rev the engine when luke-warm(medium?), pressure will drop to about 1Kg/Cm^2 & no oil light comes on.
When engine is at driving temp (slightly hotter than normal temp, when driving up long hills) the oil pressure will drop back to 1Kg/Cm^2 until engine becomes colder because of driving down long hills (assume because the oil is hotter & thinner).
- when the engine is warm, it takes significantly less time for the oil light to go out (0.5 - 3 sec), unless engine has been left for some time (3 hrs or so)
Conclusions:
- oil pressure gauge and oil light not faulty (as i believe that they are independent sensors, and correlate)
- changing oil makes no difference, filter type (ryco, Fram) makes no difference
- engine temperature changes viscosity of oil, thus changes pressure of oil from oil pump
- abnormal conditions have occurred due to using different fuel type (my fault
)
Would like to know, would it be the oil pump, pressure relief valves, or something else?
I know that replacing the oil pump is a big job/messy (i.e. front diff off, sump off, timing belt off, ...). Are the pressure relief valves behind the oil filter (as i haven't checked these yet)?
Thanks for reading my short novel, any help or suggestions would be appreciated,
Nick