Help..oil pressure/noise in engine

[pmprdldy99]

Yesterday I was driving from Virginia to Delaware, when I noticed white smoke coming out the back end of my Explorer 1991 stock engine. I pulled over lifted the hood and noticed that the oil cap was missing. Jerry-rigged it to put a cover on where the cap is supposed to be and search for the closest parts store. About six miles down the road I pulled into Napa and purchased an oil cap and oil. I filled the oil and put a new cap on it and went down the road. I was still sending some smoke out the back, but figured it was oil on the engine burning off. About 10 miles from my destination, I lost oil pressure completely but the oil light did not come on. Approximately 1 mile from my destination, I heard a loud noise coming from the engine but still no oil light. I milked it the final mile. What should I start checking. I am a female with some automotive experience, and am about 150 miles from home.

 

[trashtruck]

it depends on what "noise" the engine makes. a tapping sound would indicate upper engine while a rapping or banging sound would indicate lower engine. start by checking and watching the oil level. do a compression check to see if there is a mechanical issue.

 

[jmdirk]

The oil pressure gauge in these things is basically an idiot light. There is an oil pressure switch on the front drivers side of the block, kind of tucked back behind the steering linkage, power steering pump and box.

Is it the exhaust smoke that is white? Or is it just smoke coming from the engine bay and blowing out the back? Usually white smoke is coolant, oil smoke is more blueinsh. If it's your exhaust that is blowing smoke, you may have a blown head gasket or something. If you were actually running low on oil, the noise may be something that is sticking on just not moving right due to lack of lubrication.

 

[pmprdldy99]

The oil pressure gauge in these things is basically an idiot light. There is an oil pressure switch on the front drivers side of the block, kind of tucked back behind the steering linkage, power steering pump and box.

Is it the exhaust smoke that is white? Or is it just smoke coming from the engine bay and blowing out the back? Usually white smoke is coolant, oil smoke is more blueinsh. If it's your exhaust that is blowing smoke, you may have a blown head gasket or something. If you were actually running low on oil, the noise may be something that is sticking on just not moving right due to lack of lubrication.

The smoke was coming from the engine bay. When I got to my destination the first thing I checked was to see if there was oil coming from the exhaust pipe or any kind of liquid.

 

[pmprdldy99]

it depends on what "noise" the engine makes. a tapping sound would indicate upper engine while a rapping or banging sound would indicate lower engine. start by checking and watching the oil level. do a compression check to see if there is a mechanical issue.

What is the best way to test this I'm not familiar with it.

 

[trashtruck]

you should be able to buy or rent a tester from the parts store. in simple terms, remove spark plug, insert tester and crank but don't start the engine for all 6 cylinders testing each. compression shouldn't vary much between cylinders. you can add a teaspoon of motor oil to each spark plug hole and repeat the test. if compression increases, it would indicate an issue with piston or rings. if it doesn't you should investigate valves, lifters or heads. a large difference between cylinders usually indicates bad head gasket.

question: does the noise remain constant or does it increase with rpms?

 

[pmprdldy99]

you should be able to buy or rent a tester from the parts store. in simple terms, remove spark plug, insert tester and crank but don't start the engine for all 6 cylinders testing each. compression shouldn't vary much between cylinders. you can add a teaspoon of motor oil to each spark plug hole and repeat the test. if compression increases, it would indicate an issue with piston or rings. if it doesn't you should investigate valves, lifters or heads. a large difference between cylinders usually indicates bad head gasket.

question: does the noise remain constant or does it increase with rpms?

Do I remove all the spark plugs first or just one at a time? I want to say that it increases but can't be sure as I was so nervous about getting to where I was going. I know that I slowed down hoping not to ruin the engine. Needless to say that I was nerve wracked! What is the best/ worse case scenario?

 

[trashtruck]

some say remove them all, some say one at a time. just don't get the firing order mixed up. best case is all cylinders are within 40 psi of each other and you can move on to something else. worst case no compression at all. i asked about the noise earlier to try and rule out stuff like the fan hitting the radiator or a broken steel line somewhere.

 

[natenkiki2004]

As said previously, the oil pressure gauge is basically a "yes/no" gauge. Anything above 5 PSI and it will show smack in the middle of "normal". However, there can be grounding issues that cause the gauge to move slightly. Mine moves around a bit, sometimes between the red and normal area. I've had a mechanical oil pressure gauge on and it's perfectly fine, just crappy stock gauge.

The oil light is similar but is supposed to turn on when you get about 2 quarts low. How much did you have to put in to fill it back up?

With the oil cap removed, the engine would have been running lean. I don't know if the computer can compensate enough. It could be that you heard the engine pinging? That itself isn't a good thing but a bit here and there will not kill the engine instantly.

You can do a compression test as long as you're confident to remove the spark plugs. The typical ones for our engine aren't nickel plated and can stick in place pretty good. The heads are cast iron so you likely won't strip out the plugs but they can be a bugger to remove without a cheater pipe. The one on the passenger side rear will likely have you contorting in all kinds of fun angles to reach it.

My best recommendation would be to take a video of the noise (if it's still occurring) and share it here. There's big differences between clicks, taps, clacks and knocks.

 

[pmprdldy99]

some say remove them all, some say one at a time. just don't get the firing order mixed up. best case is all cylinders are within 40 psi of each other and you can move on to something else. worst case no compression at all. i asked about the noise earlier to try and rule out stuff like the fan hitting the radiator or a broken steel line somewhere.

No, I am somewhat afraid to look...I think it is probably internal.

 

[Turdle]

Is there a lot of oil in the intake tube and throttle body?

You might rev the engine with the dipstick removed, hold your thumb over the dipstick tube and feel for pressure blowing out the tube while revving the engine, as a quick test for excessive blow-by. In fact, I wonder if you didn't have excessive crankcase pressure which blew off the oil cap.

 

[pmprdldy99]

Is there a lot of oil in the intake tube and throttle body?

You might rev the engine with the dipstick removed, hold your thumb over the dipstick tube and feel for pressure blowing out the tube while revving the engine, as a quick test for excessive blow-by. In fact, I wonder if you didn't have excessive crankcase pressure which blew off the oil cap.

What would have caused the excessive pressure?

 

[Turdle]

Honestly, I think a compression check will answer a lot more than we can on the internet. It is all speculation at this point. The test I suggested "may" tell some-

 

[92exp4x4]

What would have caused the excessive pressure?

If the rings or piston fail, then compression can pressurize the crankcase and cause the cap, dipstick, or PCV blow out. Oil can come out of the dipstick as well. Make sure your PCV is not blocked. This can cause similar symptoms.

An accurate compression test is done by removing all the plugs and opening the throttle plate while cranking the engine while having a battery charger attached. Just make sure the cylinder pressures are as the same as they can be. I recommend removing all the plugs so the starter doesn't have to work so hard while testing.

 

[pmprdldy99]

If the rings or piston fail, then compression can pressurize the crankcase and cause the cap, dipstick, or PCV blow out. Oil can come out of the dipstick as well. Make sure your PCV is not blocked. This can cause similar symptoms.

An accurate compression test is done by removing all the plugs and opening the throttle plate while cranking the engine while having a battery charger attached. Just make sure the cylinder pressures are as the same as they can be. I recommend removing all the plugs so the starter doesn't have to work so hard while testing.

I haven't done a pressure test yet. I did check the oil to find nothing on the dip stick. I put oil in, waited about 5 minutes before checking the oil again and starting the engine. At first I had oil pressure on the gauge and it was making a slightly louder noise than before... which I attributed to rocker/push rod noise. It is more a tapping noise and the engine was shaking a bit. After about 3 minutes, I lost the pressure gauge so I shut it down. I rechecked the oil and it looks good. I will recheck the oil again in a couple hours.

 

[trashtruck]

good, a tapping noise is much better than banging or rapping noise. you an use a screwdriver as a stethoscope to try and locate where the noise is coming from, left, right, front, rear.

 

[natenkiki2004]

Does it sound like this:


That's my lifters/valvetrain clattering away on a cold start. Should be fixed, yes, but not detrimental enough to overcome the cost and labor.

 

[92exp4x4]

You will probably need to put an actual gauge in it. It is a common failure for an engine to display oil pressure at cold start and then for it to bleed off and go to nothing when the engine warms up.

The parts inside the engine expand with the heat, the clearances open up and oil pressure drops. Think about internal bleeding of oil, usually cam and main bearings.

More than likely this is what is happening. It could be a pump issue but I doubt it. I am dealing with a customer piece of equipment at work. It displays the exact same symptoms as your engine. We put a pump in it at customers request, and it did not fix the machine. It was an attempt to save a $40k engine. I would not recommend this work for yours. It would be more cost effective to just figure on a rebuild if you see bad oil pressure. At least at this point it's rebuildable.

I hope it's not this bad, but I think this is the way things are heading.

 

[pmprdldy99]

Does it sound like this:


That's my lifters/valvetrain clattering away on a cold start. Should be fixed, yes, but not detrimental enough to overcome the cost and labor.

It does, maybe a bit louder and the engine was shaking a little. I noticed your oil pressure gauge wasn't moving up a lot. Is that the norm?

 

[pmprdldy99]

I kind of agree about the rebuild. Fortunately, my daughter and son in law have come to my rescue...they drove the 200+ miles with a tow dolly to pick me and the truck up. They know a reliable mechanic who has agreed to take a look at it.

I want to thank everyone for their kindness in trying to help me with all of this...you guys are really a great group of people! I am so glad that I joined this forum 5 months ago. I really appreciate knowing that there's a place I can go for help![