therewolf

There is a service bulletin pertaining to Vortec V8 water pump replacements

which probably pertains to the issue here. It points out that when the system is

being refilled, it takes a while to "burp" all the air out of the system. Apparently,

overheating has actually occurred in improperly filled systems.

As previously stated, keep your overflow tank half full, and watch it carefully till

it stays level for a few days.

Do you only make short daily trips, such as to and from work?

tinbender59

compression check, COMPRESSION CHECK COMPRESSION CHECK
oH DID i SAY COMPRESSION CHECK


You are urinating into the wind until you get some cold hard facts. either the antifreeze is leaking outside the motor, into the oil system "oil would be some shade of caramel" , or it is leaking into the combustion chamber - or rather the compression is leaking into the water system forcing the antifreeze out of the motor. the TBI and Vortec motors have a notorious history of leaking intake gaskets, especially after 100k. take your thermostat housing off, fill the block up with water, start the motor if you see a steady stream of bubbles you probably have a head gasket issue.

RacerX

dont DO THAT if you live n the NORTH. You fail to remove all that water and overnight YOU WILL have a problem. It was 35 degrees this morning, 24 with the wind chill in NYC.
Better to just pressurize the system and hope its a hose to the heater core leaking.

jcwastrel

Yes, Cone up for sure on the stat. No white foam in the oil cap or dipstick and I was sure to connect all the lines again. I had a friend suggest that maybe it just doesn't need to be filled all the way up. I think that sounds a little crazy, but on the other hand, I do put the same amount in the radiator everyday no matter how much I drive it. I even checked the line to the overflow bottle just to be sure it could go back and forth. If I take the cap off the radiator I can see down about 2-3 inches from the top of the cap to where the fluid is. Everything seems to run just fine though.

jcwastrel

now I'm getting some leakage on the driveway. Just yesterday I saw a drip. It looks like it is leaking out of the top oil line that goes in there (top right when looking at it from the front of the truck). It seems that it leaks down to that point and then stops. When I would take off the radiator cap it would be down to about that level. It is coolant for sure leaking out, not oil. The oil seems fine. No carmel color or foamy gook. I think that I'll try putting some thread ribbon on the oil line and see if that stops it. If not, then I guess I'll take it in for a compression check after the holiday. No time or money until after that.

DoubleO7

Must be an engine oil cooler in that tank.
My tranny cooler is in the left tank on my 99 Tahoe.
Might have a pin hole or a fitting leak there.
Fill up the rad again, get it up to temp and open hood to see if there is a leak when it is hot and pressurized.
2 or 3 inches down is only a quart or so of water.
Could easily be pissed out in a five mile trip.

therewolf

Be sure to verify the leak source. Vortec V8s are famous for having poor seals at the waterpump gaskets.

An inexpensive, but annoying problem.

DoubleO7

I think a 1990 is too old to be a Vortec.