Possile knocking in engine?
02-13-2016, 02:35 AM
#1
Melting Slicks
Thread Starter
Possile knocking in engine?
Today I started up my 82 to move to the other side of the garage so I pulled it out into the drive to warm up. She was idling great but noticed as she was warming up I was hearing a knock coming from the engine. I also noticed a slight knock in the fall before I put her up but ignored it. So the noise is noticeable when warm but not cold so does that corresponds with a knock? Two years ago I pulled the engine and replaced the cam, heads, timing chain and intake and wanted to do the short block but did not have the funds but are now regretting it. My oil pressure is above 40 when cold and below 40 when hot more like 25 when hot and in "D". How can I pin point this and what to do about it?? Car has 96 or 98K on it.
02-13-2016, 06:30 AM
#2
Le Mans Master
The Gen 1 V8's are notorious for piston Slap or rod knock when cold but usually goes away when hot...your situation is the opposite so may be more serious. I am suspicious of the oil pressure being 25 when hot at idle...that seems to me to be a little low. You may be able to isolate the knock to a certain cylinder by pulling the spark plug boots one at time while the car is running...the knock will stop once you have pulled the boot on the offending cylinder. You may be able to reduce or eliminate the knock with a different grade oil...if you are running a 10W-30 for example, going to a 15W-50 should increase the oil pressure and help with the knock if that truly is the issue. Lastly, you are correct that its too bad you did not do the bottom end since these engines usually require some bottom end work once north of 100K miles....
02-13-2016, 12:34 PM
#4
Le Mans Master
Connecting rod bearing noise is a knock. You could try a cheap fix if funds don't allow a better one.
That would be taking the oil pan off and removing each cap, one at a time, and replacing the bearing shell halves (two per rod). They are pretty cheap and it could be done in an afternoon. It's not a long term or high powered engine solution, but will get you buy for the time being.
You may find your problem is worse or better than you think as you remove each bearing.
What wt oil are you running. Running thicker oil can extend the life a little, but only if you are easy on it.
That would be taking the oil pan off and removing each cap, one at a time, and replacing the bearing shell halves (two per rod). They are pretty cheap and it could be done in an afternoon. It's not a long term or high powered engine solution, but will get you buy for the time being.
You may find your problem is worse or better than you think as you remove each bearing.
What wt oil are you running. Running thicker oil can extend the life a little, but only if you are easy on it.
Last edited by REELAV8R; 02-13-2016 at 12:36 PM.
02-13-2016, 02:34 PM
#5
Burning Brakes
Connecting rod bearing noise is a knock. You could try a cheap fix if funds don't allow a better one.
That would be taking the oil pan off and removing each cap, one at a time, and replacing the bearing shell halves (two per rod). They are pretty cheap and it could be done in an afternoon. It's not a long term or high powered engine solution, but will get you buy for the time being.
You may find your problem is worse or better than you think as you remove each bearing.
What wt oil are you running. Running thicker oil can extend the life a little, but only if you are easy on it.
That would be taking the oil pan off and removing each cap, one at a time, and replacing the bearing shell halves (two per rod). They are pretty cheap and it could be done in an afternoon. It's not a long term or high powered engine solution, but will get you buy for the time being.
You may find your problem is worse or better than you think as you remove each bearing.
What wt oil are you running. Running thicker oil can extend the life a little, but only if you are easy on it.
Is it audible when driving? Rod bearings usually go quiet when accelerating, then get noisy on decel. If it's doing that, you'll need to drop the pan for sure.
02-13-2016, 03:17 PM
#6
Melting Slicks
Thread Starter
I haven't driven it as the roads are full of salt just idling in the driveway. Will it do what you describe by just revving the engine then make the noise when the idle comes back down or do you have to have a load on it?
02-13-2016, 03:57 PM
#7
Burning Brakes
The knocking on decel only is a classic symptom of a worn rod bearing. It happened to my 396 C2, but that was many years ago. I don't remember if it did it in the driveway.
Last edited by 454Luvr; 02-13-2016 at 03:58 PM.
02-20-2016, 10:58 PM
#8
Melting Slicks
Thread Starter
Well I took the car out for a drive today just to see and my noise eventually went away so could I possibly be getting this mixed up with a lifter noise? It seems to be coming from the front driver's area and not really under the valve cover but the water pump area?? I have had to adjust the lash a couple times since I installed the cam so maybe one is loose. I will pull the VC when I get time to check but it's the location in the front of the motor the confuses me...
02-21-2016, 12:50 AM
#9
Melting Slicks
Last edited by mikem350; 02-21-2016 at 12:51 AM.
02-21-2016, 08:43 AM
#10
Le Mans Master
front of the motor could be harmonic balancer loose or coming un-bonded from the inner ring. It could be just a loose crank pulley as well.
Start trying to wiggle things and take a close look with a good light.
If you've ever heard lifter noise vs rod knock the two sound completely different.
One is a knock consistent with RPM, lifter is more of a clacking or clickity-clack noise.
Start trying to wiggle things and take a close look with a good light.
If you've ever heard lifter noise vs rod knock the two sound completely different.
One is a knock consistent with RPM, lifter is more of a clacking or clickity-clack noise.
Last edited by REELAV8R; 02-21-2016 at 08:45 AM.
02-21-2016, 11:36 AM
#11
Melting Slicks
Thread Starter
front of the motor could be harmonic balancer loose or coming un-bonded from the inner ring. It could be just a loose crank pulley as well.
Start trying to wiggle things and take a close look with a good light.
If you've ever heard lifter noise vs rod knock the two sound completely different.
One is a knock consistent with RPM, lifter is more of a clacking or clickity-clack noise.
Start trying to wiggle things and take a close look with a good light.
If you've ever heard lifter noise vs rod knock the two sound completely different.
One is a knock consistent with RPM, lifter is more of a clacking or clickity-clack noise.
02-21-2016, 12:35 PM
#12
Burning Brakes
If the noise went away, it's extremely unlikely to be any of the things being discussed except possibly lifter clearance. You need to determine why the lash isn't stable.
02-21-2016, 02:35 PM
#13
Instructor
Years ago I was chasing a knock at the front of an engine, sounded like rod knock for sure. But for some reason the belts seemed suspect. I squirted a small amount of WD 40 on each one, knock went away and never came back. One of the belts was doing a slip and grab on each revolution and being amplified by the pulleys and water pump. Weird. Just a thought.
Jim
Jim
02-21-2016, 03:22 PM
#14
Safety Car
One other item at the front of the engine is the fuel pump push rod. It can sound like a tapping lifter when cold or all the time if the push rod or fuel pump arm are badly worn.
02-21-2016, 10:21 PM
#15
Melting Slicks
Thread Starter