Calling all mechanics!!
 

I have a 2012 Malibu MXZ with about 150 hours on the Indmar 6.0. Last summer at the beginning of the season I switch to synthetic oil.I heard a light tapping coming from the engine. I quickly switched to a thicker synthetic oil. When it continued, I went back to conventional oil. The noise revs up with the engine and doesn’t go away with higher rpm’s. I know it’s not a rod knock ( i’ve felt that pit in my stomach before) But it seem to be coming from the valvetrain. I took the boat to boat masters in Livermore, a “ certified Malibu service shop”. They remove the valve cover and valvetrain from one side and said everything looked good and they had no idea what was wrong with it. I paid them $350 for the tear down and put it back together myself changing the needle bearing rocker arms to Bronz bushing trunnions. I took it out last night and I still have the noise. Has anyone had any experience with something like this? I’ve been reading that a bad lifter will sound like this, but my engine is so new. Oil has been changed at least once if not twice a year and is very clean. I’ve never seen any metallic flakes in my oil and it’s been doing it since the beginning of last summer. I’ve been out every weekend last summer running it at 4500 rpm all day and it still runs great. Any advice, recommendations, or suggestions would be appreciated. I’ll try to upload a video..

Here’s a link to a video. Thanks again!
https://www.youtube.com/watch?v=vTQi-ws7RgI&sns=em

Did you replace the lifters?

No.. you have to pull the intake and heads to check the lifters.

Well there is your issue.

You need a different shop with real mechanics. The fact that they removed a valve cover and only inspected then put it back together tells me they don't know what they are doing. The 350.00 charge without a clue of whats wrong is just short of criminal.

Sounds lifter to me as well...

You don't have to pull the heads to replace the lifters.

Also if you use too thick of an oil the lifter won't pump up. I would try a 5w30 and see if the noise goes away. Otherwise you may have a lifter leaking down.

Thats a LS based GM engine right ? If so even for as reliable as they are every now and then they have lifter failures . The problem is if you keep running it with out fixing it you might need a lot more then a lifter .

I checked the pushrods last night and they are perfect. When I torqued on the rocker arms the lifter is so stiff , it actually preloads the valve instead of pushing the plunger down on the lifter. I think it might be the ls “piston slap”.. I think that if it was a lifter something would’ve happened by now. There is less than 150 hrs. On this boat. If the lifters weren’t under the heads, I would’ve checked in already.. I sent the video to indmar. Hopefully somebody there can point me in the right direction.

Pretty sure you do on an LS......

LS1 you don’t have to pull heads, newer LS2 and up, you do

The 6.0 requires pulling the heads... I’ve seen plenty that act tight according to the push rod but the rotating motor puts a lot of load on them. Is the noise louder when first cold started and then get better 5 seconds in to oil pressure?

Not really. It’s the same consistent sound hot or cold. The noise revs up with the motor and doesn’t go away but becomes faster and eventually the engine noise drowns it out. Would there be any difference in speed to determine if it was Valvetrain or piston slap? I’ve pretty much decided I’m gonna just run it. Ive been reading those engines have a huge problem with the pistons being loose in the cylinders but it sounds way worse than it is. If I’m wrong and it WAS the cam, I had to pull the engine to swap out the cam/ lifters our anyway. I’ll just throw another short block in it in a weekend.. Thanks for all of your replies!

This is a far fetched idea, but worth a look... I've noticed newer engines have really loud injectors... GM seem to be some of the loudest. Now the video you posted sounds much more solid and louder than any injector I've personally heard, and I'm pretty sure I hear a quieter tick of the injectors, but maybe there is one that is much louder than the rest??? It would explain the valve train seeming to be okay, no metal in the oil, and the sound speeding up with the engine speed as well.

Did any one to check compression in cylinders?

Could be an exhaust leak! They sound pretty similar.

I'd replace the gaskets for the headers first.

Piston skirt

Calling all mechanics!!
 

As crazy as it sounds, Bam might have a point. I chased a valve train noise for quite some time on an old Ford engine just to find out it was the header gasket.

Stethoscope. It will be very apparent if you have a exhaust leak.

I’ve had the header off a couple of times with no change. I’m using some reusable aluminum gaskets

i know that Malibu states to use 15W40 and the Malibu Dealer heres Mechanic told me all they use is 20W50 in their service department for ALL Malibu's..

is there still a warranty on engine? you'd hope they would pay for this as it sounds like just a coincidence it happened after you switched oils..each time you switched oils after the knock you changed the filter again, correct?