Ape Man

Car : 2001 Z28
Motor : Fully rebuilt LQ4 with LS1 heads
Waterpump : Stock LS waterpump, new gaskets

Problem :
Car doesnt overheat, runs good. If I check coolant when warm, shows near top of rad, after car has sat for 2-3 hours, level is maybe 2-3" down into rad. No leaks underneath.

Car is had about 1000km since motor build, Im assuming air is out of system bu now.

Any suggestions?

Mercier

iTrader: (15)

Depending on your steam pipe setup, you could still have pockets in the engine/tops of heads. How is yours connected? Have you tried filling the radiator when cold then warming the car up to see what happens?

MaroonMonsterLS1

Is your overflow tank empty? Sounds like the rad should pull from the resivoir when it cools to keep it full to the top, then puke some out back into the tank when it gets hot.

In an f body, the coolant reservoir is located under the battery box.

Ape Man

Its in a 01 Z28, at this point the overflow is over the full mark. I suspect the rad cap isnt allowing flow back into rad when cold. I just put a new one on and we'll see.

I have the x pattern factory LS steam pipe style. How would I check for air, how to bleed these?

Mercier

iTrader: (15)

IMO, if you've got a 4-corner pipe setup and the engine isn't mounted tilted forward(unlikely), then you likely don't have steam pockets in there.

What I did was hold the top water pump--> radiator hose up all the way(connected to water pump; not to rad) and filled through there and had the steam pipe output disconnected. when steam pipe is full, connect it, then continue filling and connect radiator. Then heat cycle and top off. But with all 4 corners hooked up and connected properly, that system is literally designed to evacuate the steam pockets in the tops of the heads. (Do you have this hooked up properly?)

It sounds like you are on the right track trying the cap. Usually the simplest explanation wins. Check the rad-->overflow hose for blockages as well. It could be slightly clogged up or kinked and hot, pressurized coolant could flow out but it would be more of a battle for the vacuum to pull cooler coolant back in.

Ape Man

Let it run with cap off, coolant comes in (no air) from steam pipe inlet. Let it get hot, no bubbles seen, put cap on, drove it. Letting it cool now, so we will see if it drops again with new cap.

I blew air through line from rad to over full tank, flows good and hear bubbling in tank when I do so, so I assume shes not blocked.

Mercier

iTrader: (15)

Does the overflow in those vehicles feed into the bottom of the tank, or is it top with a straw going to bottom? If the latter, straw could be broken, cap not sealing, hole in tank, etc. preventing vacuum from sucking coolant in. If it feeds into the bottom it can't really pull anything but coolant until the overflow is empty.

joecar

Did you try a new rad cap...?

Darth_V8r

iTrader: (4)

I just had similar issue as OP, and the overflow would bubble if I blew through it. Finally decided to rip the tank out and a **** ton of scale came out. **** would settle and block the hose, but if you blew on itbyoudvthink it was free