Low Oil Pressure and Knock

[Polsonator2]

I was going down the highway today and noticed my oil pressure started dropping off.  Pulled over and checked oil level and it looked like it was way down.  Filled it up then got it going, oil pressure stayed low.  I also started noticing what appeared to be a faint knock or rattle.  Would this be from a bad oil pump or bearings all of a sudden going out?  Noise comes on when revving up to about 20 - 30 mph.  I have always had good oil pressure at idle and at speed so not sure if something just failed.

[YukonJack]

Old timers used to say that if you pull the dipstick while the engine is running and the oil level shows normal, then the pump isn't pumping. I don't know if this still holds true or not. 

[Polsonator2]

If it was just the oil pump causing low pressure and if it was replaced is it possible the knock goes away?  The pressure is down to 20 at 20- 40 mph.  Its not zero but low

[Sniper]

Doesn't sound good.  Last time i had that happen it was a rod bearing gone south on me.  But that was on an 89 Plymouth adn I know what cause that problem, too much boost from teh turbo rattle the engine an started the rod bearing;s demise.   I'd drop the pan and inspect the bearings myself.

[Ulu]

I think a sticky or weak oil pressure relief valve can cause this low oil pressure condition. I think it typically affects cyl #5 wrist pin first, then that rod brg.

[Los_Control]

3 hours ago, Polsonator2 said:

  I have always had good oil pressure at idle and at speed so not sure if something just failed.

 

To me it sounds like, which came first ... chicken or the egg.

If the oil pump failed it would not provide lube to the bearings.

If the bearings failed, would require more effort from the oil pump to keep up with the slop?

 

Either way, I wish you the best of luck, sounds like you were on top of it and the repair may not be so bad.

[pflaming]

I have a very good stethoscope, come get it anytime.  That’s how my truck started to go bad. If I had had the stethoscope I could have found the problem much sooner, now I’m in deep dodo. Bummer. 

[John Reddie]

I had a '49 Chrysler Windsor with the 6 cylinder engine. I noticed a sudden drop in oil pressure (from 40 lbs to around 18 lbs at cruising speed). Luckily it happened right near my service guy so the next day he pulled the pan and found the pickup screen was plugged with sludge. Back then I used non-detergent oil. He was able to clean the pickup screen and tube and everything was okay after that. I remember he also said that if the oil pump had failed, most likely I would have had no pressure. Good luck to you. 

John R

[Sniper]

The knock part is what worries me

[Dodgeb4ya]

If the oil level was way down and you said you "filled" it up ....seems to me you ran it too long not watching the

oil level/oil gauge often enough.

I say the engine is done...some bearings got a little too dry.

[Ulu]

 

On 4/12/2020 at 3:21 PM, Polsonator2 said:

If it was just the oil pump causing low pressure and if it was replaced is it possible the knock goes away?  The pressure is down to 20 at 20- 40 mph.  Its not zero but low

If you have a really light knock, the sound can come and go.

The damage doesn't go. Just the sound.

 

I ran an old noisy Edsel with oil just silly-thick with Motor Honey.

Maybe 25% Honey to 75% 10w40. It wouldn't have started in freezing weather.

You couldn't do that in Minnesota, but in the desert it worked.

All the noise went away and I drove that engine another year.

 

In your case, first I'd just drain some oil out in a glass and look thru it in the sun.

If you see gold and silver glitter in it, then you'll know the score.

 

Edited April 14, 2020 by Ulu

[dpollo]

pull the connecting rod caps and have a look at the shells before you ruin the crankshaft,   It is not unheard of for the Babbit material to flake off the bearing.

 

  clean the screen while you have it apart.

Edited April 18, 2020 by dpollo
spelling

[kencombs]

On 4/12/2020 at 5:06 PM, Polsonator2 said:

I was going down the highway today and noticed my oil pressure started dropping off.  Pulled over and checked oil level and it looked like it was way down.  Filled it up then got it going, oil pressure stayed low.  I also started noticing what appeared to be a faint knock or rattle.  Would this be from a bad oil pump or bearings all of a sudden going out?  Noise comes on when revving up to about 20 - 30 mph.  I have always had good oil pressure at idle and at speed so not sure if something just failed.

Generally speaking, oil pumps don't suddenly fail, other than broken drive components in which case they don't work at all.  They wear over time, but very gradually.  I think the key question here is:  How much oil did you add?  Was it low enough to starve the bearings?  If so, the rods and mains are likely damaged.  If it were mine, it would not be run again until the pan was off and the bearings and crank examined.

[Polsonator2]

Put a new oil pump in today, oil pressure seems fine at idle.  When I said low on oil, I had left my home with a full 5 quarts plus 1 in the filter so I was full.  I ran at high rpms for 36 miles and then 21 miles back before the low pressure came on.  I always top off a half quart after 60 miles of driving and it has been consistent like this for 4 years and 34,000 miles of 3000 rpm driving.  I also never leave the house without checking the dip stick first to make sure she is full after each trip I take and before I go anywhere.  She has always dripped a little oil at highway speeds and occasionally leaves an oil puff of smoke when flooring it at a stop light.  She does not leak a drop of oil at stand still. Compression is good and so is vacuum.  I have a PCV that may suck a little oil and I think I burn oil from worn valve guides and probably worn rings.  Does not constantly smoke. This was the first time where I had an issue and I ended up filling it with maybe a quart or 2 of oil.  I was pushing her a little hard up the mountain pass as I had finished rebuilding my stock 3 speed tranny a couple days before. She also heated up to 200 degrees and has a 170 degree thermostat. Was only at 200 degrees because I was going 65 - 70 up a mountain pass grade for a couple miles.  When going back to more level surface or downgrades she cooled back to her typical temp of 180 - 195 degrees at highway speeds of 60 - 70. 

 

I visually saw the oil pressure go from 40 to 20 at 65 mph.  I immediately slowed down and my pressure never went to zero.  It went from 40 to 20 and then dropped with rpm drop.  It never went back up above 20 and this is where I thought I was hearing a knock or maybe even pinging when I tried bringing her up to 20- 30 mph.  If I ran it dry I would imagine I would have zero oil pressure at 65 mph and not 20.  Took no chance driving it and car was towed home.

 

Car ran like a brand new top the whole way before the issue and seemed to rev faster and decelerate faster with the new input shaft bearings.  Input bearing was bad and had noise in 1st and 2nd. Replaced this and worn thrust washers.  Tranny noise completely gone.  Also jetted up my primary jet on my weber one jet size as plugs were looking lean.  These were the only changes I made. 

 

I fired her up today after getting the new oil pump figured out and hear a slight knock or rattle at idle with when cold and it gets a little quieter once warmed up at idle but I can still hear it. Using a stethoscope I can hear the rattle low in the oil pan.  When revving it seems to hide it.  I drained the oil and saw no metal pieces, flakes, or glitter.  I will pull the pan tomorrow and take a look at the main bearings and the rod bearings.  My exhaust valves were set at .014 and .09 for intake about a year ago.  I leave my exhaust valves loose per the manual for high rpm driving so my valves have always been a little ticky at idle but quiet at speed.  

 

Had a little trouble getting my new oil pump and distributor aligned the 1st time.  Had it all lined up correctly at 7 o clock but most have moved somehow when inserting the pump.  Wouldnt start, got carb backfire.  Took out spark plug 1, felt for compression, lined up tdc and rotor at 7 o clock. Still wouldnt start and got carb backfire.  Flipped it 180 degrees and it works fine now and rotor is at plug 1 firing position at 7 o clock and timing mark on pulley is tdc.  Now though, when using my timing gun, it shows I have like 20 degrees advance.  I have distributor turned as retarded as it can and just up a hair or it won't start.  I also have vacuum advance plugged.  Last time I checked my timing when I set it a year ago it was at 4-7 degrees advance.  Not sure why it reads  so high. Any thoughts anyone?  Fun times!  Appreciate all the input!

Edited April 15, 2020 by Polsonator2

[Dartgame]

My guess is the oil pump gear is indexed slightly different than the old one, or the gear was worn on the old one to the point of changing the static timing when the new one was installed. The distributor has more timing adjustment than it appears. There are two adjustment bolts, one easily seen and another on the bottom, hex head down threads point up thru a plate. The plate on the underside of the distributor is adjustable, it may just be a matter of loosening the bolt on the underside and reset with the timing where needed and lock it down.

 

For the knocking sound - my guess is you will find a rod bearing or bearings that are worn.

Edited April 15, 2020 by Dartgame

[Merle Coggins]

I have to wonder if you have a broken advance spring in your distributor and it is advancing way too early. I've seen this happen before. A quick check is to pop off the distributor cap and give the rotor a twist. You can usually twist the rotor slightly, in one direction only, and it'll spring back when you let go. If you can twist it back and forth several degrees and there's no resistance, or spring tension, you have a faulty advance mechanism under the breaker plate and it'll want to go to full advance all the time. This could attribute to the pinging/knocking you heard. Of course the noise could also be a bearing failure, which would attribute to the oil pressure loss. And, if the advance failed to full advance and caused detonation that could have lead to a rod bearing failure.  

Edited April 15, 2020 by Merle Coggins

[Polsonator2]

Got the oil pan off and inspected rod bearings for piston #3 and #4.  #3 looked fair but look at #4.  The scoring on the crank looks pretty bad.  I haven't looked at the other bearings as this looks like the crank is going to have to come out.  Is this something a machine shop can fix?  Or will I need a new crank?    Here is a picture of #4 rod journal

[Polsonator2]

Here is #3 rod journal

[keithb7]

Looking at your #4 rod contact area. I see a straight vertical line. Is that not the bearing halves butting together ? Did your rod bearing spin in its bore? Are we looking at a scored damaged, spun bearing here, and not your actual crank shaft rod surface?

 

Edited April 15, 2020 by keithb7

[61spit]

I agree with keithb7. It looks like the bearing shells have spun. You are looking at the bearing insert not the crank shaft.

[Polsonator2]

Here is the bearing caps. #4 is on top

[DJ194950]

Tap that #4 rod up in the bore and remove the bearing halves by rotating them and check crank condition of  #4. It May be OK but the rod will will have to removed and resized after the bearing spun inside it. Certainly could be worse?

 

 

 

DJ

[Ulu]

Yep. #4 is badly spun.

 

Your previous oil consumption seems extremely high leading me to believe that this thing should’ve been producing a trail of blue smoke behind it down the road.

 

Also,is there a constant drip of oil coming from the road draft tube?

[Polsonator2]

This is my first time ever dealing with engine bearings so appreciate everyone's help!

[Polsonator2]

Never had a trail of blue smoke. Only smoke at intersection on take off occassionally or if I had an extreme rapid deceleration.  No road draft tube, have pcv setup in place of road draft. It does suck a little oil.

Edited April 15, 2020 by Polsonator2