7.4 MPI Milky oil now a noise, listen

NJMatt50

NJMatt50

Member
Apr 28, 2009
225
Jersey Shore
Boat Info
2005 Sundancer 420. Sea lift platform, Axiom Pro, FLIR.
Engines
Cummins 480ce
Just had heads redone and all new exhaust and risers on my 7.4 MPI. Ran the motor for about 2-3 hrs. Started to hear this noise below. Found that the oil is milky. Maybe the oil cooler is leaking? Did not narrow down why the oil is milky. My next move is changing the oil. Wondering if changing the oil will cure this noise problem? Can this be lifter noise because of the water in oil or collapsed? If not out goes the motor, hoping this is not a bearing. Also the plugs look fine, compression is fine. I removed the plug wires while running the motor 1 by and the noise is still present. Oil pressure is good on the stock gauge. Any ideas?


 
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No mechanic but that sounds like an awful hard knock to be lifters. Ya, not what you wanna hear though.
 
My first question is why are you running it with the milky oil? If it isn't a rod bearing it soon will be.

I agree it doesn't sound like just lifters. The oil pressure can still be normal with a spun bearing if the bearing sealed off the feed hole in the crank. It won't be for long though.

Change that oil then see what you have from there. If you spun a bearing already it won't make much differance.

Good luck.
 
Second thing I noticed is you don't seem to have much oil going to the rockers.
 
Is it running rough? I cant determine by video...

Did you change yur distributor cap? If you did, put back the old one and see if noise goes away...

Oh YES!!! Change the oil ASAP.
 
I got saltwater in one engine by a failed oil heat exchanger. The oil turned milky as soon as I shut the engine down. I changed the oil 4 times in a couple of hours and it was still slightly milky. I ran it for 8 hours and changed the oil again. When I changed the oil after 8 hours there was no milky colour in it. That was 500 hours ago. Your noise problem might be your entire engine not getting enough lubrication due to water in your oil. Figured a few quarts of oil were cheaper than new engine I think I went through 36 quarts and I replaced the oil filters each time.
Perhaps some one knows of a product that will absorbe water in oil or different oil filter that will take out water? I thought of puting in a gas filter at first but did not as I did not know how it would work or if it would fail and cause more damage.
 
Well After further troubleshooting I changed the oil with 7 new quarts. The noise comes and goes. At one point I thought I had it gone. Will a bottom end noise come and go? Seems unlikely. The motor will run fine unless I mess with the rocker bolts and it will stumble. Weird thing is when it runs rough noise goes away. I just ordered a set of lifters so thats my next move. Head gaskets have 2 hrs on them so I don't think that they are blown. I think where I have a leak is from the intake water jacket to the head. I will report back later in the week as to what the new lifters do. I don't think I diluted the oil too much because it really was not up high on the dipstick and you really could not tell from the dipstick. I am keeping my fingers crossed. Thanks.
 
Update - replaced the lifters, no change. It really sounds like its coming from the front of the motor right under the intake. Putting my head low near the pan and block level makes it harder to hear. I am stumped at this point. I have to take a closer look by the exhaust manifold gaskets. One of the heads had a valve seat replaced, I wonder if that can make a noise?
 
If the seat falls out it can definitely make a noise...usually an expensive noise. Does one valve look like it is stuck open? It sounds like the knock is at the same frequency as the valve gear IE (1/2 speed). What were the valve clearances like before you changed the lifters?
 
It looks like the noise is exactly in rhythm with the valve opening and closing. The rockers are bolt down and there is not and play on the rockers...
 
Another Update, loosened the rocker that had a valve seat replaced and the noise goes away, tightened back and noise comes again also it seems if I loosten any exhaust valve the noise goes away..WTF? Valve seat issue? Crooked? Coming out?
 
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Ummm.. Could try that but I am using a week old Craftsman.. If I dick with the valves on the rear cylinders it noise goes away as I am tightining them... Urggg this is driving me crazy...
 
If a seat had come out of the head you would see the valve spring would stay more compressed than the others.
It seems like the lifters aren't pumping up to take up the lash when i watch the video or there is to much lash for the lifters to take up. If you hold a steady 2000rpm does the noise go away?
 
I might be missing something in your responses. It looks like in one you say that the noise goes away when you loosen a rocker and in the next you say it goes away when you tighten. Which is it ? If it goes away when you tighten I would question if you set the initial lash as indicated
in the manual. I believe one of the setting options is when the engine is running. Something like tighten until quiet and then another 1-1/4 turns. (verify my 1-1/4 turn, bad memory). I have found that mine work best with only a 1/4 turn tighter than quiet. You could tighten each valve slowly until it is quiet as possible. Then starting with the first one loosen until noisy, then tighten as above. If there is still noise you can turn each rocker one at a time until you identify the culprit. Might just be a lifter not pumping up.

If the noise goes away when you loosen then I would check the rocker arm assembly for any kind of excessive wear.

one other possibility is a bad/bent pushrod or two. My 7.4s used to suffer from water reversion. A valve would eventually stick from the rust
(usually an exhaust valve). Fortunately the pushrods would fail before any other major damage other than a need for a valve job.

The problem with all this is, as a previous reply stated, running the engine till you find out what and why may continue to damage the lower end if the problem is an oil supply issue. Then again the damage, if any, is probably already done.
 
Ok, Here is another thing I found. The 3 & 5 spark plugs are wet. Seems that the riser is leaking into the motor. All new Osco risers and Mercruiser gaskets... Oil is milky as can be..
 
As far as the valvetrain noise is concerned, that motor seems to have a "non adjustable" valvetrain. You said you had the heads done - most shops that redo a set of chevy heads probably do no account for this - grinding the valves pushes them deeper in the heads (and the tips higher) Decking the heads will "lower" the valves and tips. Also, different head gaskets have different thicknesses. Any changes like this to a motor with a non adjustible valvetrain (without taking these measurements into account) creates a problem. I would suggest you get screw in studs and convert the valvetrain to adjustible (like 99% of small block and big block chevys have) and properly lash the valves. As for the water problem........somthing was reassembled wrong or has failed.
 
Ya, I have the fresh water part of the motor pumped with the pressure tester. Holds well only drops a pound after 15 minutes so I don't think that is an issue. Something with the Osco Risers or manifolds? Also have the 3 inch spacer, and used the good quicksilver gaskets. I guess my next move is to get the oil cleaned up and put the exhaust back on?
 
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