b0b

iTrader: (1)

I've had this problem for a while. It was worse before due to a leaking water pump. When I made a track pass it would push coolant clear out the top of the overflow and get everywhere. I replaced my pump, tstat, and also radiator cap about a month ago. I also tested the system for leaks with a pressure tester I rented. No leaks, it held 18lbs for 30 mins or so without budging. I'm confident it's not a BHG. It acted fine for a while and I thought the problems were over. Well I went to the track this weekend and made 4-5 passes without issue. After the last pass of the day it got hot coming back on the return road. I shut it off and checked everything. Fans were blowing cold air meaning no circilation. Overflow was almost plum full and radiator was low. I'm guessing it pushed a little coolant every time til it eventually got low enough in the radiator to stop circulating. What is causing this. I know it's not my WP, tstat, cap, or a leak in the system. I have already been through all of that once. I have also replaced my coolant temp sensor FWIW.. I've also tried bleeding using the common various different ways.. I'm at a loss at this point

superskaterxes

why are you confident its not a BHG? clearly theres excess pressure coming from somewhere in the system causing it to overflow which usually means one thing..........

b0b

iTrader: (1)

I tested the system under 18 psi and it held for 30+ mins without leaking off. How would a BHG allow this if it was leaking combustion into the coolant system causing it to push coolant to the overflow. I have also done a dye test to the coolant to look for exhaust gases in it and there were none. Oil is clean, no smell or water in exhaust.. The car has cometic HGs and arp head bolts torqued properly to spec. Car has always been NA

joecar

Did you test the rad cap to see what psi it opens...?

b0b

iTrader: (1)

Bump.

No I tested the cap to see that it wasn't leaking. How do you test to see when it opens?

joecar

The test kit you use for pressure testing cooling system at radiator also comes with an adapter for testing only the cap...

see the shiny short tube-like thing at the right in the attached pic.

ramairetransam

iTrader: (18)

i had this issue but im procharged . I would never push coolant when driving easy just for a night two or three gear pull . So i did the aster bracket and since i needed a new waterpump i did that , new v6 radiator which is lt1 thickness but ls1 outlets only, new 160 stat and new hoses. I havent had an issue since . But i opened the coolant overflow and it smelled like exhaust a little . So i assume a bad headgasket . But being at 13 lbs this winter i will do new headgaskets and headstuds.

b0b

iTrader: (1)

That's the same kit I used to test evrything. The system held about 18lbs for over 30 mins without leaking off any. That's why I'm confident it's not a BHG. My old cfactory cap had a slight leak so I bought a new one and iirc it held 16-18 psi also. I think I'm going to try a 20+ psi stant cap and see if that makes any difference. The new cap I bought is a cheap generic looking one from auto zone so I'm hoping it's spring is too weak and that's the problem.

IDriveChevy

iTrader: (5)

You're probably lifting the heads under boost and pushing exhaust through the coolant passages. Good idea to do studs lol

RockinWs6

18lbs is nothing compared to the pressure in the cylinders @WOT.

b0b

iTrader: (1)

Bump.

Question regarding the steam line coming from the heads. With the system full of coolant and functioning properly, when you start it up (even cold) there should instantly be coolant coming from the steam tube at the fill neck. Correct? Any sputtering of coolant or absence of flow from the steam line until it warms up means you have air in the system? Correct? My steam line does this.

joecar

[QUOTE=b0b;19019223]Bump.

Question regarding the steam line coming from the heads. With the system full of coolant and functioning properly, when you start it up (even cold) there should instantly be coolant coming from the steam tube at the fill neck. Correct?[quote]Yes, coolant only, no air.

Yes...

but it should still have only coolant even when hot, unless you're driving the engine pretty hard...

i.e. hot idle and moderate engine speed at moderate load will still produce coolant only.

which, air or no-air...?

b0b

iTrader: (1)

When you start it cold.. nothing at first. Then gradually starts sputtering coolant. Then as it gets up to temp and starts circulating it will steadily start flowing constantly

joecar

This indicates there's a leak into the block as the block cools.

Pushing thru a new rad cap tested to 18 psi indicates a combustion leak, what was said above re lifting heads... there's a $20 block test kit that tests for presence of combustion gases in coolant in radiator.

b0b

iTrader: (1)

I have arp bolts That were torqued properly and cometic gaskets. The car has always been NA. I don't see how it could be leaking. Plus when I did a leak down on the cooling system it didn't leak off any for over 30 mins it was on there

IDriveChevy

iTrader: (5)

So you did them in a 3 step sequence of 25,50,75ft/lbs? The ARP bolts use a different spec than OEM. Maybe try retorquing the bolts?

b0b

iTrader: (1)

Yes I did it in the 3 step torque sequence just as directed. Used the pattern from ls1howto

joecar

For example: http://www.tooltopia.com/lisle-75500.aspx