Oil consumption after head rebuild merc 5.7 2002 (maxum 2500 scr)

[Grub54891]

Well,sometimes stuff gets missed by the machine shop. What may be in spec is just enough out it causes problems. Or just as simple as a bad valve from their supplier. Good luck! And let us know how it turns out.

 

[300sflyer]

Being a 2002, I assume this is a vortec engine? [8 intake bolts] Is it a 2 or 4 barrel carb? Is it just the #1 cilinder spark plug that is caked in oil, or do the rest of them have oil on them too?

 

[Forbes210]

2 bbl carb. All of the spark plugs got baked oil on them and all of them had a tread covered in oil as well. One of the cylinders had a lower compression which after doing leak down test came out was an intake valve although I think thats not related to the oil consumption.

 

[300sflyer]

You may have two separate issues going on at the same time.

With low compression on just the #1 cylinder, it may be a bad valve job on that cylinder. With regards to the oil consumption on all cylinders, you may have the same issue I had... that being a non sealing intake gasket. Who put the engine back together after the heads were redone? Which intake manifold gasket was used?

I would say its time to remove the intake manifold, and check that gasket. Sounds like the head has to come off anyway, to redo the valves on the #1 cylinder.

 

[300sflyer]

Another thought... Who reassembled the engine after the valve job? Was the valve lash set correctly? Perhaps the intake valve is leaking because the valve lash is too tight? You might try removing the valve cover, and backing the intake valve nut off a 1/4 or 1/2 turn. Then recheck the compression on that cylinder.

 

[bruceb58]

I would say its time to remove the intake manifold, and check that gasket. Sounds like the head has to come off anyway, to redo the valves on the #1 cylinder.

Since there are no oil passages in the intake manifold, why would you suggest removing it?

 

[Bt Doctur]

the vortec gaskets come with different port sizes and do not seal the intake port in the valley
see this post by him http://forums.iboats.com/forum/engi...es/8893708-1998-vortec-5-7-intake-gasket-help

 

[bruceb58]

the vortec gaskets come with different port sizes and do not seal the intake port in the valley
see this post by him http://forums.iboats.com/forum/engi...es/8893708-1998-vortec-5-7-intake-gasket-help

Interesting read!

 

[alldodge]

I would suggest pulling the valve cover off and check to see it the valve seals were left off.

 

[Forbes210]

I removed the valve covers and was able to see blue valve seals so it looks like they are in place. Also rocker on cylinder #1 seams to be set correctly.

Like 300sflyer said most likely I got two separate issues. Mechanic who I left the boat with remove the heads and brought new heads from the head guy and install them. They will need to come of anyway to fix valve on cyl #1. Maybe since the heads are new and they could be slightly different then original the seal which they used doesn't work well. Also I've noticed that theres a lot of suction from the hose between valve cover and flame arrestor to the point that the hose was whistling. If I'm correct that could be caused by bad seal between intake and head.

 

[300sflyer]

I think you nailed the reason for your oil consumption exactly. A leaking intake gasket... Removing the intake will confirm.

When you checked the valve lash, was the number # 1 cylinder at TDC on the compression stroke? You should be able to easily rotate the push rods with your fingers, but have no movement up and down, then another 1/2 turn on the nut. Sometimes it bit of fiddling, to get them just right.