Hi,
I'm new in here as a registered user but I know this forum from quite a few years

The car is 91 Firebird with LT1 and 4l60e.
The problem I have at the moment are fxxxxx air bubbles in my cooling system. So far I tried:
With engine running I closed the radiator cap when the coolant was on the top of radiator. Also I was trying to remove the air with bleeding screw on the thermostat housing.
When engine is cold usually water is below "cold level". With the engine running level is geeting higher up to "hot level" and then even exceding this one. After a few minutes of running I can see some air bubbles in the reservoir... With every minute more and more. I can see the water pump is working OK so it shouldn't be an issue. I checked the thermostat 2 months ago - it does work fine (160 degrees). All hoses looks fine, no leaks at all.
I have manual switch for dual fans and once they are working bubbling stops as well... With fans on, the level is going really low I would say the reservoir bottle is almost empty. I tried to use bleeding screw.After 1-2 turns, mostly there was no coolant dropping or sometimes just a bit. I noticed that when I'm loosening the screw there are some more bubbles in reservoir bottle. When the bottle is 3/4 full of coolant I stop the engine and after a while radiator is sucking almost the whole coolant from the bottle into radiator. I have no idea how to sort that out. I've spent a few hours on forums but no luck.
I'm quite sure there are no coolant leaks, there is no white smog from the exhaust, there is no oil in the coolant and there is no coolant in oil - so I hope it's not a head gasket issue.
I have a throttle body bypass. I'm not so sure if the coolant going from steam pipes on the back of heads through the t-piece to the radiator is in the right place - it is connected to the pipe between reservoir bottle and radiator as per picture.
Here is the diagram:
http://picasaweb.google.com/10129897...87282428902290

http://picasaweb.google.com/10129897...80035839734690

I've tried to add these as pictures but doesn't work somehow.

 

You've still got air in the system and how the steam line is connected into the overflow bottle line, it cannot create pressure it needs in the system. Any pressure thats built up is vented through the steam ports into the overflow so you see bubbles

Lets simplify the system

Cap the small heater core hose on the radiator and the single on the drivers side of the WP. The two on the pass side are feed and return for the heater core, leave those alone, mostly. The cyl head steam line is supposed to be plumbed into the highest point in the cooling system thats still pressurized. The capped heater core port on the radiator is ideal, but requires several adapters to scale down the 1.75" port to the 3/8" tube. An easier method is to Tee into a heater core line. For my swap, I used a short section of 1.75" steel tube and a piece of fuel line (also steel) welded together into a Tee. MrGasket sells several similar pieces for around $40. These are usually aluminum with a threaded barb fitting inserted

Once you get all that squared away, modify your T-stat by drilling a 1/8" hole in it to prevent air locking the system. It will help immensely when bleeding the system later. The small hole will prevent an air tight seal and since the hole is so small it will not allow enough extra coolant by to upset the 160* setting

The best way Ive found to properly fill LTx/LSx engines with coolant is to unhook the upper radiator hose from the rad and pour coolant through the engine first. Once it's full it will begin to fill the radiator. After it's full, reconnect the hose and bring the engine up to operating temp. Once the T-stat pops open shut it down and let it cool. Repeat the fill procedure to top the system off. Ive never needed more than 2 cycles to fill one completely

 

That sounds way more complicated than how i bleed my LT1.

I just crack the bleeder on t-stat housing, fill it up with as much as it will take, then start the engine and let it bleed until the t-stat opens, all the while adding coolant when needed. Eventually it maxes out and there is no more air from the t-stat bleeder. Close the bleeder, put the cap on and off you go.

I don't know why so many people have trouble bleeding it, it seems simple enough.

 

Thanks for explanation.
Just to make it clear. I should dismount the t-piece I have (the one connecting reservoir bottle, radiator and steam pipe). The very top hose (just under the radiator cap) should be going now directly to reservoir bottle.
Hose from steam pipe should be connected using custom T-piece with the one below small hose going to reservoir bottle. The steam line hose is app. 13mm(0.51") inside/17mm(0.67") outside and the second one is app. 17mm(0.67") inside/27(1.06") outside in my system.
I'm gonna sort out the t-piece if i have it right - pls correct me if I'm wrong).

Many thanks

 

I went throught this exact same problem. The passenger side hose is too close to the top of the radiator and is going to continue to suck in air. You will never be able to keep the radiator full of water with the outlet that high. I ended up having a custom radiator built with the outlet mimicking the 4th gen radiator. Try the bypass option first and hopefully it works.

 

Hmm...maybe that's why I don't have a problem then, i'm using a 4th gen LT1 radiator. Wouldn't have thought of that.

 

Yup, I used an LT1 radiator/fan setup, it has all the correct ports to hook everything up like it came from the factory.

 

I'm not saying you can't use a 3rd gen radiator. I am saying that it is going to be very difficult, to nearly impossible, to get all the air out of the system. This is why so many people use the 4th gen rads with the LT1. Instead of paying for a custom radiator, check the scrap yards and ebay for a good LT1 rad with fans.

Instead of using a custom, try and get ahold of a 4th gen at a junkyard and just swap the tanks. Carefully pry the tabs up and the plastic tank comes right off. Then, clean the area really good and place a small amount of silicone along the edge and reseal the tank with the tabs. Make sure the tabs are tight. I did this on my dad's car and it hasn't leaked in 5 years.

 

Thanks guys for information. I've put new t-piece and removed the old one as per my description and looks like the problem is gone now
During 10-15 minutes idling (with fans on and off) I saw air bubble just once in my reservoir bottle. I'm going to put LT1 radiator but have to wait for a second hand one. It's not as easy as you think In here you won't find LT1's on junkyard unfortunately.
I've found t-piece in local diy market and paid 2.5GB. Cheap :-D
Now it's time for a speedo and ECM wiring to laptop. Looks like I'm getting there.