So I have read about a thousand and one plenum threads and was getting horrible gas mileage and losing coolant. I took the throttle body off, and when I checked the gasket, it seemed fine. (Maybe it wasn't I can post a pic in a bit if anyone needs to see it) The problem, however, is there is still a bunch of gunk in the kegger, so if it wasn't the gasket, then what could it be?

Thanks

 

maybe I am confused by your question but the gasket issue is the one under the kegger not the throttle body, and the gunk should be burnt oil.

 

Loss of coolant is usually a bad head gasket, bad intake manifold gasket, cracked head or a cracked cylinder.

To check your plenum. Simple remove the PCV and the air breather element and place your hands over both holes while running. IF you feel vac at the PCV- your plenum gasket is shot.

If that checks out ok. Check the heads by pressurizing the system. Remove the radiator cap, remove the plugs one at a time and note if there's signs of coolant on the bottom of the plug. If so, using shop air, connect the correct adapter to the suspect cylinders plug hole and apply pressure to the cylinder. If nothing happens at the radiator level, hit the key slightly or, rotate the engine by hand at the crank. If there's an issue, coolant will exit the radiator.

After that, it's time to remove and inspect the head gasket and the head and block for cracks as it could also can be a cracked cylinder at which point you will have to remove the engine and send it out to a machine shop and have it sleeved.

You may have a blown plenum gasket and an external coolant leak vs. internal. Have you seen / smelled any coolant at the exhaust level? Any white smoke? How about in the cab - do the windows fog up or any sweet smell inside?

 

Do you mean the crankcase breather(w/ hose connected to air box) on driver side or the PCV valve on the passenger side?

 

if theres gunk on the inside of the manifold the plenum is shot. they should be clean only air is supposed to travel through. if its black around the inside of the manifold, the plenum is gone.

 

Yes, that is the one.

 

It looked like there was a leak at the gasket between the intake manifold, not sure what the leak was, coolant? oil? I had no idea... Turns out there was vacuum on the PCV valve... In addition, the gasket behind the water pump was bad and coolant was leaking, but I guess only when I was driving since there was no puddle under the truck but obvious signs of leaking.

All in all, got thrown off by all the issues going bad at the same time. Maybe they were linked or maybe it was all just random. Thanks for the help, sorry for the confusion I was in a hurry to post because it was getting dark outside and I was in a hurry, but I got it back together and pulled drove it to a friend's garage to look at it again.

 

Well that's good news my friend. It's sounding better already. Looks like all that's needed is a new water pump and a new intake gasket and plenum gasket and your on your way! Really, it's miles better than having a cracked cyl and having to pull it and send it out to have it sleeved.

If your intake is leaking at the intake / head interface, I would get on that ASAP as it's most likely a water port leak. When this happens, water gets in the combustion chamber through the intake valve on the intake stroke. This is very bad as water is not a compressible medium and can do some major damage to the connecting rods.

Oil; highly unlikely unless you have a gross major leaker and, at that point, you would have real problems if it were allowing oil to flow up through. Water would be everywhere and it would smoke like an SOB at the intake while running.

After tear down, check for signs of coolant in the lifter valley and in and around the intake ports.

Any knocking or thumping in the low end? Overall, does it run fine otherwise?

 

^ this is off topic, but i cant help myself

CMCKENNA, where did you get those fuel rails?

 

^^^ yay I knew someone would ask . Im dieing to know too.