The oil pressure gauge on my '97 Explorer starting fluctuating between a low reading and the middle of the gauge approx. 6 months ago. I was told that the oil pump was bad and that if I replaced the pump I should just replace the engine (140k miles). Another shop said that I should put in heavier oil to see what happens. I starting using 20W-50 and the reading stayed normal until my most recent oil change. Now sometimes the guage is erratic and sometimes it is fine. Could there be another cause that doesn't require the oil pump change, like a faulty oil pressure swtich for example?
Ever think of hooking a pressure gauge up to where the sender is piped in to get a indipendent reading, sender might also be defective
A broken spring in the oil pressure relief valve in the pump could cause it too
Any filings on the drain plug indicating extyreme wear
On some motors you caan get a high output pump to help overcome pressure loss ( done it with a 440 cryco)
January, 10, 2006 AT 2:17 PM
Thanks for the reply. I'm not a mechanic so I am just trying to find out if I can get around replacing the engine. Is there anything I can request my mechanic to do first?
January, 11, 2006 AT 1:04 AM
Normally if a engine is worn out their are several indications
1/ using a quart of oil or more between oil changes
2/spark plug electrode sooty black
3/compression low or more than 25% different between cylinders
4/ oil pressure low as compared to specs
5/lack of power under load
If you dont have any of the above and you get a sudden pressure fluctuation it souds like the sender unit or the the oil pump pressure relief valve
One of the cheapest ways to get a long life from a engine is to change oil & filter every 2000 miles or 5000 km and do it like a religion
January, 11, 2006 AT 1:24 AM
To the best of my knowledge I have none of the problems that you listed. I am familiar with the oil pressure relief valve but could you explain about the sender. Also, are the two parts difficult to replace and do you know and approximate costs and hours needed? Thanks.
January, 11, 2006 AT 5:58 AM
On most vehicles there are 2 senders, one for the water temp usually in the aarea of the thermostat which is at the start of the hose going to the rad
the other is normally in the block near the front of the engine
They look like a broken off spark plug with a wire attached
check with a autoparts store for price, also get correct sealent for threads or you will not get a correct reading on gauge (install time 30 minutes max)
January, 11, 2006 AT 12:26 PM
First I want to thank you for your time. I really appreciate it. Finally, the oil pressure relief valve is a separate job from replacing the sender, right? If so, is that a difficult time consuming job?
January, 12, 2006 AT 8:04 AM
The sender is on the outside of the motor
The relief valve is inside the oil pump bottom of motor inside the oil pan
Not a job for amatures usually, however if your determined get a Haynes repair manual for your paaarticular vehicle and it will tell you how
January, 16, 2006 AT 9:50 PM
Hello: The easiest way to watch oil pressure is like one post said, purchase a mechanical gauge and install it, they work WAY better than a gauge and a sender. The sending unit is nothing more than a volume control on your radio. Have you ever had a volume control that had a scratchy spot, well a sending unit for a gauge is almost the same, so it could be shot, just put a new one in, or install a mechanical pressure gauge kit. Either way its easy and pretty cheap
January, 17, 2006 AT 9:53 PM
I'm gonna sume that this is a 4.0L engine in your exploder. If it is a 4.0L motor, then the sending unit is on the driver side of the engine under the power steering pump, really close to the front crank pulley, they are pretty common for having troubles. IF you have a 3.0L motor then the sending unit is even more common to go. This one is placed on the passenger side of the block at the back of the right side cylinder head. Almost in the center of the engine, just above the bell housing.
Now if this doesn't fix your truck. Get it to a technician that can test your oil pressure correctly AND make sure the actual dash guage is ok too!