Oil Pressure -- what to do next???
Thread Starter
|
Registered User
Joined: Sep 2020
Posts: 2
Likes: 0
Oil Pressure -- what to do next???
So, I bought a virtually new looking (for its age) 2001 Ram 1500 (5.9 liter gas) with 155K miles. CarFax was clean -- no accidents/major mechanical. BUT, the oil pressure gauge dropped to zero when RPM' dropped below about 2K. Thinking it was a sensor or oil pump, I bought it anyway -- given that there were no odd engine noises, blue smoke, or other tale-tell signs of eminent doom. I changed out the oil pump with a high volume version, replaced the suction tube, the oil pan gasket (no metal in the pan) , and (of course) gave her a complete oil/filter change (synthetic Castrol 10w30/high mileage). BEHOLD! IT WAS BETTER. But, the oil pressure gauge still dropped to zero but now only at about 1200 RPM's. I expected that I would be changing the sensor so I did just that. BEHOLD! Now it only drops to zero when I come to a stop. What the hell?!?!?!
The good advice I read here tells me to test it with a mechanical pressure gauge. I suppose that if I confirm that I have good oil pressure when the gauge reads zero, I should just disconnect the chime/sound and accept this as a quirk of an old truck. But I have to wonder if it may be something else. I have read that main bearings, timing chains, valves and pistons can also cause to these symptoms, but as I said, I have none of the other symptoms associated with these serious problems (has good compression, no blue smoke, no leaking or burning ridiculous amounts of oil, or knocking/ticking engine sounds). WHAT GIVES?!?!?! Could there be a problem with the sensor wiring? The instrument panel gauge itself? I sure would appreciate some sound advice -- or informed guesses!
I should add that the truck runs GREAT even when oil pressure reads zero.
Thanks!
The good advice I read here tells me to test it with a mechanical pressure gauge. I suppose that if I confirm that I have good oil pressure when the gauge reads zero, I should just disconnect the chime/sound and accept this as a quirk of an old truck. But I have to wonder if it may be something else. I have read that main bearings, timing chains, valves and pistons can also cause to these symptoms, but as I said, I have none of the other symptoms associated with these serious problems (has good compression, no blue smoke, no leaking or burning ridiculous amounts of oil, or knocking/ticking engine sounds). WHAT GIVES?!?!?! Could there be a problem with the sensor wiring? The instrument panel gauge itself? I sure would appreciate some sound advice -- or informed guesses!
I should add that the truck runs GREAT even when oil pressure reads zero.
Thanks!
Last edited by brandall; Sep 7, 2020 at 08:37 PM.
They are not all created equal. Getting one from the dealer should solve the issue.
Captain
Joined: Sep 2018
Posts: 553
Likes: 64
Please note I don’t know the exact details of the lubrication system on your truck - this info is generic. I’d recommend buying a service manual or finding an oil flow diagram to better diagnose the issue.
That said, you should definitely get a mechanical gauge to verify the actual oil pressure. The rule of thumb is 10 PSI per 1,000 RPM; though some manufacturers say as low as 7 PSI is acceptable.
Assuming the pump and related seals are functional, oil pressure is primarily dependent on bearing clearances on the crank and cam main journals. Without the restrictions created by the bearings, plenty of oil (volume) can be reaching the bearings but the pump isn’t able to build adequate pressure because the oil is freely draining from the bearings.
If the mechanical gauge verifies a loss of pressure at low RPM, the easiest way to test for bearing clearance as the the problem is to run a heavier oil (15w40 is a good start). Just drain and fill the pan.
There could also be a restriction in the supply passage leading to the pressure sensor. This will most likely be verified as the cause if the mechanical gauge reads adequate pressure at low RPM. Brake parts cleaner, a pick, piece of wire, etc are all ways to clean it. A couple of times, I’ve cleared them by disabling the ignition or injectors and cranking the engine for about 5 seconds. It’s messy but it works.
Good luck.
That said, you should definitely get a mechanical gauge to verify the actual oil pressure. The rule of thumb is 10 PSI per 1,000 RPM; though some manufacturers say as low as 7 PSI is acceptable.
Assuming the pump and related seals are functional, oil pressure is primarily dependent on bearing clearances on the crank and cam main journals. Without the restrictions created by the bearings, plenty of oil (volume) can be reaching the bearings but the pump isn’t able to build adequate pressure because the oil is freely draining from the bearings.
If the mechanical gauge verifies a loss of pressure at low RPM, the easiest way to test for bearing clearance as the the problem is to run a heavier oil (15w40 is a good start). Just drain and fill the pan.
There could also be a restriction in the supply passage leading to the pressure sensor. This will most likely be verified as the cause if the mechanical gauge reads adequate pressure at low RPM. Brake parts cleaner, a pick, piece of wire, etc are all ways to clean it. A couple of times, I’ve cleared them by disabling the ignition or injectors and cranking the engine for about 5 seconds. It’s messy but it works.
Good luck.