Head or Lower Intake Gasket?

[floater]

On my 98 Tahoe 5.7 litre I started getting the P3000 code last week. I put in new wires, cap, rotor and plugs and issue was still there. After a 40 km drive I got home and decided to check the oil. Took off the cap and steam was coming out and I notice a bunch of white goo on the cap!!! Now is there an easy way to tell if this is the lower intake or a head gasket gone? Thanks

 

[SUBURBIAN]

Compression and leakdown tests, as well as coolant pressure testing should provide accurate diagnosis.

 

[floater]

I was afraid of that. So the steam and goo isn't indicative of one or the other? No white smoke coming from exhaust and no major leaks on block but it does drink coolant.

 

[drakon543]

It wont have any white smoke in either case until it gets so bad your adding significant coolant daily. Both intake and head can start leaking just right so its only contaminating the oil. I wouldn't wait till that starts tho the coolant will thin the oil. Follow suburban's advice and have it diagnosed

 

[floater]

Ok thanks guys. I've called around and it's 3000 to 3500 Canadian for a full rebuild.This motor has 333 000 km on it. At this price I'm going to take the intake and the heads off myself and see about replacing both gaskets myself! If it goes easy enough I will also replace the Spider with that new style one and hope to get more years out of this motor. THAnks

 

[SunlitComet]

have you run a compression test and read the plugs at least?

 

[floater]

Ok I just did the Compression test on this motor. Cyl 1--185, cyl 2--155, cyl 3--185,
cyl 4--195,cyl 5--200, cyl 6--190, cyl 7--185, cyl 8--195.

I squirted some oil into Cylinder 2 and got a 185.

There is white milky oil on the bottom of both valve covers but nothing on the lifters or rockers.

I tried to do a leak down by connecting shop air to each cylinder at TDC but they all hissed through the intake so couldn't really tell anything from that.

So it looks like I have worn or stuck rings on Cylinder 2? This doesn't explain the P3000 and P3006 code though. Any ideas anyone? I'm going to open up the top plenum and check out the Spider injector tomorrow. thanks

 

[floater]

I took the intake off today and I had a stroke!! There was two inches of sludge in the lifter valley and about an inch under the valve covers!! Factory gasket was broken in 3 places but all leaks were internal. Front bolts for intake are pitted but rest are good. Took three hours to scrape out all the gooo. I poured some kerosene into the lifter valley and scrubbed away. After I dried it all I poured in a jug of 10w30 and made sure to hit all the lifters. I got parts coming soon and I will put it all together and then take it to a re-builder if it still runs rough.

 

[Gordo1728]

Word of advice for the future,

If you have a misfire on cold start only, and smooths out as it warms up suspect the head gasket, and take it to the shop and have them check it and confirm.

If the miss is constant and plugs don't take care of it, take a can of carb cleaner, let the truck idle, and spray around the edges of the lower intake, and upper, listen for a change in idle, it may bog down and possibly stall out, but the change may be slight as well.

Did the intake gasket solve the issue? It's fairly common on these trucks.

 

[floater]

Parts arrive today. When I was removing the intake I noticed the rubber 'elbow' fitting that connects the PCV valve to the top of the intake was ripped. I'm wondering if that could have caused the problems? After I did the compression test I did the Combustion gasses (?) test with that blue fluid. It didn't change colour after five minutes on the radiator opening so I moved the tester over to the oil filler cap tube and retested there and still got no colour change. I'm hoping this means the heads are in good shape.