98' 5.7 vortec

kylebigbucks · May 31, 2003

I have a 98 GMC Sierra with the 350 vortec in it. It uses roughly 1 quart per 1000 miles or a little less. I bought it with 111,000 on it now it has 118,000.

It does not leak any externally to speak of, however, the two middle cylinders ( I think #s 4 and 6) on the passenger side seems to be where all the oil is going. There is a lot of buildup on those two spark plugs even after 1000 miles.

The engine seems to runs good when I put new spark plugs in those two cylinders.

What could be the likely possble problem? Does this sound like a consistent problem with these engines?

I am wondering if it could be a fairly easy fix or am I going to need a whole new engine to fix this problem. Hoping maybe its the headgasket or something that is bad in that area.

Any thoughts, experience, or suggestions would appreciated. I am going to bring the truck into a mechanic to get the transmission replaced (details on another post) and I am thinkg of having them dig into the engine a little to see if the can find the problem.

97C1500&84Z28 · June 2, 2003

sounds like valve guides to me.

CanadianZ71 · June 2, 2003

Check your PCV valve.

kylebigbucks · June 2, 2003

hmmm, valve guides, I would assume if that is the problem it would warrant a rebuild to fix it?

I am going to have a compression check done on the cylinders when I get my tranny done.

I should also mention that it does not seem to smoke out the exhuast, maybe a very little on start up.

New PCV valve was put in when I bought it.

Keep the replies coming if you think you might be able to help me out and thanks for the replies already posted.

Kyle

97C1500&84Z28 · June 3, 2003

if the compression check shows good compression, then you can get away with just having a valve job done. otherwise a complete engine overhaul would be needed. if the 118k are easy miles, you can be pretty confident that all it needs is the valve job. good luck

kylebigbucks · June 9, 2003

Okay, had a compressoin check done on it, all cylinders are +/- 2psi so the rings are not bad.

The only thing the the mechanic could come up with was leaky valve guides becuase you would not notice it in a compression check becuase the valvles would be closed.

Looks like you were right 97c1500!

Both the leaky vlave guides are on one side, I should be able to get away with doing just one head, right? It is still around 800 for just one side.

americanmuscleman · June 11, 2003

Before you go through all the hassle of fixing enlarged valve guides, I would try replacing your valve seals first. You can do that with the head still bolted on the engine. If that doesn't solve your problem, then go ahead and pull them off.

If you need it fixed ASAP, then I would say pull the heads, have new valve guides pressed in, and put new valve seals in. I would change your valvesprings at 118k miles while your in there too.

Good luck!

redchev · June 11, 2003

I had a 1993 k2500 with the 350 and the same problems. It actually sucked in the intake gasket on those cylinders in the lifter valley. Be sure to check before major head work.

brauchle · April 7, 2007

I have a 98 GMC Sierra with the 350 vortec in it. It uses roughly 1 quart per 1000 miles or a little less. I bought it with 111,000 on it now it has 118,000.

It does not leak any externally to speak of, however, the two middle cylinders ( I think #s 4 and 6) on the passenger side seems to be where all the oil is going. There is a lot of buildup on those two spark plugs even after 1000 miles.

The engine seems to runs good when I put new spark plugs in those two cylinders.

What could be the likely possble problem? Does this sound like a consistent problem with these engines?

I am wondering if it could be a fairly easy fix or am I going to need a whole new engine to fix this problem. Hoping maybe its the headgasket or something that is bad in that area.

Any thoughts, experience, or suggestions would appreciated. I am going to bring the truck into a mechanic to get the transmission replaced (details on another post) and I am thinkg of having them dig into the engine a little to see if the can find the problem.