Coolant leak 1997 Suburban

[dangerousD]

I have what I believe may be a manifold or head gasket leak on my '97 sub 4x4 5.7L w/ 100K miles. For the past couple years I have noticed a very slight ping, but it's only noticable once in a while. The local dealer checked it over and said nothing came up on the scanner and recommended some injector cleaner. I tried this and even running different fuel grades just to see if it went away, but it still pings. For a while now I have been noticing a coolant smell outside the vehicle only, but never any drips on the pavement. Seems like the smell is from under the hood. I haven't got down and smelled the exhaust yet. I replaced the nipple/adapter that threads into the manifold that connects to the hose from the heater core because it was obvious there was a very slight leak at this connection. That seemed to fix that. I also just replaced the water pump because it sounded funny and I thought maybe the bearings were shot and leaking around it. That took care of that sound, but I still smell coolant. The amount of coolant I lose is probably about a quart every 1000 miles.

Also, when I start it up when it's cold (especially during winter) it knocks or basically has a sound like a bad lifter, but it goes away shortly after I pull out of the driveway. After replacing all those things, I'm now leaning towards the ping being a result of coolant leaking into a cylinder through a manifold or head gasket. I have not yet pulled the plugs to inspect each one. I'm thinking maybe the knock at startup is coolant that has entered a cylinder(s) after the vehicle was last shut off.

Do you think I'm on the right track? Any thoughts are appreciated!!

Dave

[2000CAYukon]

Have the intake gaskets ever been replaced on this vehicle? This is a pretty common issue with this engine and the gasket has been redesigned.

Look for the sticky post on DIY Intake Gaskets by GMMerlin.

//2000CAYukon

[777stickman]

Welcom to the forum Dave. As the Yukon says the intake gaskets are always suspect. Definately pull the plugs and see what they look like. There's a world of info on them. Make sure you note where each plug comes from. Please post back what you find on the plugs.............Steve

[dangerousD]

Thanks for the info guys!! To my knowledge the intake manifold gaskets have not been replaced. I bought it about 4 years ago w/ 60K miles so I'm guessing they are original. I'll check out that post by GMMerlin and look at the plugs and report back.

Thanks again,

Dave

[GMMerlin]

Since you are not seeing any coolant on the outside of the vehicle and you are getting a lifter tick, I would guess that the intake gaskets are leaking internally and coolant is mixing with the oil.
At this point, minimum repair would be gasket replace and possible lifters also.
Don't let this go any longer, the coolant will wipe out the bearings..next step..NEW ENGINE