Need advice, motor knocking

[davidc11291]

Bobby-

It's a loud knock, not a high pitched tap. I'm not mechanically knowledgeable enough to be able to tell much more than that.

I didn't rag the car out at all. I'm trying to start a business with this, and I actually want to be ethical. That's why I can't just get the car up to operating temp before a buyer comes and looks at it, then just dump it on them without them knowing it knocks. I gotta do the right thing, even if it cost me big $.

No oil pressure gauge, just a "low oil" warning light. The light hasn't come on.

As soon as it started knocking, I drove it home, did an engine flush, drained it and put 10w40 in it, so there's no thick Lucas in it anymore. It calls for 5w30, but I figured with 221k miles all the natural engine wear would make the slightly heavier 10w40 a better choice?

 

[mwoolfso]

Id bring it to a local repair station and see if they can hook up and odp1 probe to it and see if it is coding.

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[mbkite]

don't change the oil again find out what noise you have.
use a long screw driver and put your ear at the big end and probe
the other end around the engine when its cold to find the loudest area.
rocker arm lifters rod knock it could even be a loose torque converter.

 

[BobbyG]

Bobby-

It's a loud knock, not a high pitched tap. I'm not mechanically knowledgeable enough to be able to tell much more than that.

I didn't rag the car out at all. I'm trying to start a business with this, and I actually want to be ethical. That's why I can't just get the car up to operating temp before a buyer comes and looks at it, then just dump it on them without them knowing it knocks. I gotta do the right thing, even if it cost me big $.

No oil pressure gauge, just a "low oil" warning light. The light hasn't come on.

As soon as it started knocking, I drove it home, did an engine flush, drained it and put 10w40 in it, so there's no thick Lucas in it anymore. It calls for 5w30, but I figured with 221k miles all the natural engine wear would make the slightly heavier 10w40 a better choice?

All good information and I was just asking....rops:

I'm in your camp. I always use a little heavier oil in high mileage engines due to wear and tolerances opening up.

What's odd is the loud knocking symptom subsides once the engine reaches operating temperature. If it was a spun bearing this wouldn't be the case.

Rod knocks are deep within the engine. These will not go away unless a mechanical repair is made.

A hydraulic lifter can be pretty loud when the engine is cold upon initial start up. Hydraulic lifters are like self adjusting cylinders that take up space or lash between the pushrod and the camshaft. If the lifter goes bad it won't be able to pump up fully leaving some space resulting in a mechanical knock until oil reaches it.

Lifters also wear. Lifter bodies are only case hardened and the base can wear from the cam lobe rubbing against it millions of times.

The bottom line is without actually seeing it, correctly diagnosing it here can be challenging...You may have to take it somewhere and have it looked at.

Another thought. Could the party you bought this from have done something to hide this problem until after you took ownership? Again, I'm just asking questions and not implying anything...

 

[tomsteve]

you could have a pluggered up oil filter. any additive to clean an engine, be it, MMO, seafoam, tranny fluid, or any other, will braek down the sludge. where does it go?? through the filter. what hapens? well, the filter filters it, gettin pluggered up and lowering oil pressure to the engine. i would highly sugest gettin that drain plug out, draining the oil properly( if it wasnt supposed to be drained/changed through a drain plug, then a drain plug wouldnt be there) and putting in a new filter and oil. then go from there. seafoam through the brake booster is a very good way to clean up the top end. do it as it says on the bottle and it'll work. dump a can in a full tank and it will help clean up the fuel system. prolly wont be noticed at once, but a few tanks of gas afterwards difference should be noticeable.

 

[LegacyGT]

you could have a pluggered up oil filter. any additive to clean an engine, be it, MMO, seafoam, tranny fluid, or any other, will braek down the sludge. where does it go?? through the filter. what hapens? well, the filter filters it, gettin pluggered up and lowering oil pressure to the engine.

Oil filters have an internal bypass valve that opens when they clog so oil flow/pressure is not greatly reduced.

 

[ShaunD]

A heavier weight oil in a high mileage engine can put more strain on the motor before it helps it, especially when outside temps are lowering. When the temps are lower you should use the lowest viscosity oil recommended by the manufacturer; lower viscosity helps mostly on start ups and overall strain on the motor. Rely on high mileage additives/oil to help clean out the engine and help rejuvenate the internal parts, not thicker oil.
I would def get the drain plug off/changed especially if you are trying to do things right with selling used cars; and you have changed the oil enough so it wouldn't have been a big deal. With it being rounded off that would make me question/want to see what is going on on the other side of it.
With out knowing if there is oil on the spark plugs or the condition of the top of the pistons, I would guess that the internal wear from the bearings and such are eating/using oil.
If you are doing this to make money then be careful the money you are putting into these cars. Find out from your mechanic or another reputable one in your area if the cost to repair is worth it for the value of the car. Someone would possibly buy it as is and do the work themselves.
You should also get on a model specific forum or a mechanics forum to research troubleshooting the vehicles you purchase. Not to say you can't get help here.

 

[tomsteve]

Oil filters have an internal bypass valve that opens when they clog so oil flow/pressure is not greatly reduced.

yes, they do, and its possible that it got pluggered up,too. its a pretty cheap and easy thing to replace. it could help, but beings how the engine is knocking like it is desribed( any chance its something on or around the engine instead of internal? i've run across that before.) theres prolly some wear that even an oil filter wont help.
now i'm trying to recall how i used to hook up an auxilliary oil pressure gage to check the pressure the pump was puttin out.

 

[davidc11291]

All good information and I was just asking....

Thank you for the help. I didn't mean to come off as curt at all..... just trying to answer all the questions, and I'm very appreciative of your help

 

[opie_7afe]

go to advance auto or autozone and see if you can rent one of those cameras that you can see into engine without taking it apart, might help to see if stuff is clogged ect, can put camera into oil fill hole, oil drain hole(replace the drain plug if its rounded they costs around 3-5$), and stick camera in spark plug holes to inspect cylinder walls and pistons.autozone will loan you tools for free just pay a 100% refundable deposit.also try to drag a magnet through the old oil see if there's any metal bits. i really would see if you can rent a camera to see inside of the engine without removing parts.also since its obd1 im sure you can find a way to pull the codes by jumping wires in the diagnostic box and then the check engine light will flash and you count the flashes giving you an error code worth a shot.

 

[BobbyG]

Thank you for the help. I didn't mean to come off as curt at all..... just trying to answer all the questions, and I'm very appreciative of your help

Dave,

No offense taken. We're all trying to help understand what could possibly be causing the problem...

Hopefully you'll find out the root cause for the knocking. I'm curious to hear what it is....

 

[tomsteve]

any word on the cause?????

 

[davidc]

I remember my Dad Had a 78 (I think) Suburban 454ci. That thing would knock like crazy first thing when cold and then it would go away. I do not remember if it was consistent or not. If I remember right it was piston slap on cold mornings and at the time was a fairly common thing with the 454. He sold the Suburban many years later and it was still running fine.

Dave

 

[BillE]

I remember my Dad Had a 78 (I think) Suburban 454ci. That thing would knock like crazy first thing when cold and then it would go away. I do not remember if it was consistent or not. If I remember right it was piston slap on cold mornings and at the time was a fairly common thing with the 454. He sold the Suburban many years later and it was still running fine.

Dave

You are correct...454's were famous for that, even the early 8.1 (496) had the same situation. When ya have pistons the size of a quart oil can...there's a lot of metal to expand.

Bill

 

[Bigpat]

Heres my guess.... lucas oil is VERY THICK so if you added that to 3 or 4 qts that were left after u were down a qt and the next morning on a cold start you got a knock..i would change oil to get the lucas oil out of the equation, i would warm up engine, drain it by the pan.... (using vice grips to remove rounded plug) pour a qt of oil through to help remove any excess it will catch on its way down, fill it back up with recomended oil and try it again..with new filter and new drain plug

 

[JBL]

I was thinking the same thing. The oil plus the stabilizer might be too thick and on a cold start the old motor might not be able to circulate the weight, hence the knock. Once the oil warms up, thins out and starts to flow better the knock goes away.

Heres my guess.... lucas oil is VERY THICK so if you added that to 3 or 4 qts that were left after u were down a qt and the next morning on a cold start you got a knock.

This was the first thing that I thought of, but I don't remember reading where the poster was from. Have you tried a thinner/winter oil and heard the same thing at start up?

 

[Flash Gordon]

This was the first thing that I thought of, but I don't remember reading where the poster was from. Have you tried a thinner/winter oil and heard the same thing at start up?

It was not that cold when this occured

 

[davidc11291]

Wow! 4 pages of responses. Thank you guys so much for the help!

Problem solved! My mechanic agreed with my suspicion that the oil pathways or the screen covering the oil pickup tube were already clogged up really good, and when I put the super-thick Lucas in it, the Lucas clogged everything up completely. Here's what we did to fix it-

Drained 2 quarts off and replaced them with 2 quarts of transmission fluid. Per my mechanic, the transmission fluid works as a detergent, and will actually flush out a motor better than the flush kits, which are mostly kerosene based products. The transmission fluid acts like a dawn dishwashing detergent.

So I've got 2 quarts of transmission fluid in the oil, I let it idle for 10 min to get up to operating temp, then run the rpm up to 2,000 for 45 min, with the car in park, letting it go back down to idle every 5 min or so, and making sure it doesn't get anywhere close to over-heating.

After 45 min, I cut the car off, and drain the oil immediately, while it's still scalding hot, before the crud that's been cleaned out has a chance to cool down, gel up, and clog up the oil pickup tube screen.

I change the oil filter, and fill it back up with new oil, however, I substitute 1 quart of transmission fluid for 1 quart of oil. My mechanic has a 25 year old Mustang with 350,000 miles, and every time he changes the oil, he puts a quart of transmission fluid in it and drives it that way.

So I've done a motor flush on it with transmission fluid, then drained everything out, replaced the oil filter, and put new oil in it, along with 1 quart of transmission fluid. The next morning, I crank it up from a cold start, and it's still knocking, but noticeably less. That was several days ago, and now that I'm driving it with 1 quart of transmission fluid in it, the knocking gets less and less every day. Currently, it'll knock at start up for right at 1 min, till it's built up oil pressure, then it quiets down perfectly. When all this started, it would knock for about 10 min, till it had gotten up to operating temp. Plus the knocking that it's doing now is MUCH quieter than the knocking it was doing before the transmission fluid engine flush.

 

[mwoolfso]

Glad to hear it. This was similar to a House episode.