Mrecruiser 4.3 Intake vales #3 and #5 leaking after replacing valve seals

easyloader

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I just finished up replacing valve seals in a 4.3 mercruiser with balancing shaft and efi. (first time)
When replacing the seals I would bring the cylinder I was working on to top dead center then put 50psi of compressed air. The problem I'm having is with #5 and #3 cylinder intake vales.When finished replacing the seals the cylinder valves are aren't leaking however when I start tightening down the rocker arm it slightly compress's the spring and air comes out the throttle body. To verify the issue I started at no 1 cylinder tdc added compress air to it to check for leakage and then rotated motor 120 degrees and check #6 and so on down the firing order. I did this three times to verify the issue is in #5 and #3. I also made double checked the push rods and shot air down the push rod hole in case something got in the top of the lifter.
A couple of weeks ago I performed a leakdown test and only had 12 percent leakage and no air coming from throttle body.

I learning to the hydraulic lifters but don't want to tear stuff apart to get at the lifter unless I need to.

If anyone has any ideas it would be great.
 

Volphin

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If you did a valve job at the same time, then there will be a little leakage unless the valves were lapped into their seats. This is rarely done anymore, because the valves will do it on their own after a few hours of operation. Set the valves and crank her up.
 

alldodge

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I just finished up replacing valve seals in a 4.3 mercruiser with balancing shaft and efi. (first time)
When replacing the seals I would bring the cylinder I was working on to top dead center then put 50psi of compressed air. The problem I'm having is with #5 and #3 cylinder intake vales.When finished replacing the seals the cylinder valves are aren't leaking however when I start tightening down the rocker arm it slightly compress's the spring and air comes out the throttle body. To verify the issue I started at no 1 cylinder tdc added compress air to it to check for leakage and then rotated motor 120 degrees and check #6 and so on down the firing order. I did this three times to verify the issue is in #5 and #3. I also made double checked the push rods and shot air down the push rod hole in case something got in the top of the lifter.
A couple of weeks ago I performed a leakdown test and only had 12 percent leakage and no air coming from throttle body.

I learning to the hydraulic lifters but don't want to tear stuff apart to get at the lifter unless I need to.

If anyone has any ideas it would be great.

What is the serial number of your engine?
 

easyloader

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Apr 25, 2014
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I didn't do a valve job. Since the motor has a balancing shaft you have to torque the rocker nuts. when I do this air comes out the throttle body. The serial number is OL622296
 

tpenfield

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Self-adjusting lifters ??? Are you tightening the rocker arms per the procedure outlined in the manual ( As stated the serial number of the engine would help)

You could check for valve lash and leakage once the engine has been run a bit.
 

easyloader

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Serial number is OL622296.

I'm going to try to turn turn motor over with starter. If hard turning, I'll loosen up lifters and then snug them down, start motor and slowly torque tighten lifter to motor stutters, then let it smooth out and repeat until lifter is torqued down to 30nm.

I am open to ideas and don't want to start motor if I'm going to screw something up. What's bothering me is why only 2 intakes have this issue and not the other 4 and why only intakes?


I'm very frustrated and any help would be great.
 

easyloader

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Better news. I did more testing today and now #3 and #5 are sealed and #6 is leaking. When I was at TDC of a cylinder I tightened the rocker to zero lash and on the all the cylinders but #6 I had about 1/2 turn before tight and almost at torque specs which is 30NM. On the leaky cylinder I had at least a full turn.
I'm not very versed on how hydraulic lifters work but this is telling e that the oil isn't releasing from the lifter. I've also roatating the engine at least thirty revolution by hand if that akes any diffence for the lifters. On Wednesday I'll loosen up #6 intake and start motor and work on the lifter.

Does this makes sense to anyone?
 

Volphin

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Lifters require oil pressure to operate properly. Turning the engine by hand will not build enough to "charge" them.
 

Bondo

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Thanks,
Do you think I have corectly diagnosed the problem?

Ayuh,..... It sounds like ya bled off the lifters, Yes,....

As noted, the motor's gotta Run to repump 'em,....
 
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