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I'm in the process of installing my engine back in the car and have a few things I'm not sure about. Any help is appreciated!
1. Is there supposed to be a coolant crossover hose/tube on the rear? When I disassembled everything, there was no tube, just blocks that screwed down in the ports to close them off. However, I found what appears to be an air tube behind the engine that wasn't connected to anything. It connects perfectly to a coolant crossover tube (tested with the one on the front of my engine) and is located in the correct spot. Currently I only have a coolant crossover tube on the front of my engine that is connected to a radiator hose.
(testing coolant crossover tube on rear of engine below with hose connected)
2. I have a hose connection on the passenger side of my throttle body and I'm not sure what it connects to. Any idea? I've already connected all my radiator hoses and none go to it. Is this part of the AIR system?
I would install one of these https://www.summitracing.com/parts/tfs-306sb601 I would bypass the throttle body coolant lines, run the steam line kit from the right front of engine to the radiator !! PS the blocked off steam plugs cause air pockets and make #7 cyl. run hot, makes for a better coolant flow !!
Technically called the coolant air bleed system, 2001 and later C5's did not have the rear head ports connected because there is not enough room under the later LS 6 intake manifold for the earlier coolant air bleed lines to fit from the rear head ports. Many of us have added rear coolant air bleed lines as Pounder has suggested. There has been some belief that GM's deletion of the rear coolant air bleed system on 2001 and later C5's has been the cause of No. 7 cylinder overheating and failure.
The small hose connections ( 1/4" +-) on the throttle body are to allow coolant to circulate through the throttle body keeping it warm and guarding from potential icing. Many of us think this circulation is totally unnecessary and bypass the throttle body.
I added rear coolant air bleed lines and throttle body bypass over three years ago, no issues have come up.
After reviewing your post, here are some answers to your questions;
However, I found what appears to be an air tube behind the engine that wasn't connected to anything. That air line I believe that you have circled is for the HVAC (VAC Line) and is supposed to be connected to the back of the intake, see below pic of a LS6 Engine. Note as previously stated by other CF Members posting to this thread, the steam ports on the heads were blocked off on 2001 cars which you can see in the below pic.
. I have a hose connection on the passenger side of my throttle body and I'm not sure what it connects to. Any idea? I've already connected all my radiator hoses and none go to it. Is this part of the AIR system?
That hose connection is to connect the throttle body via coolant line directly to the radiator, see pic below.
that small plastic hose goes to the vacuum accumulator canister. looks to be enough tubing to get to the connector. you can connect after the engine is in. just pull the inner fender and pull the pcm, the accumulator is behind the pcm.
regarding the steam lines, the reason you don’t need them at the back of the heads is because the engine tilts downward ever so slightly, so the front crossover is your high point steam vent for the engine. If you bypass the line under the TB, the crossover still needs to connect to the radiator.
Connecting to the radiator gives you a steam (vapor) path back to the reservoir.
Finally, save yourself some grief later on getting air (vapor) out of the heads. Don’t overfill the reservoir. Never fill above the “full cold” mark. the mark is embossed on the front. Filling to the black top of the reservoir cold is too full. Filling too full will cause overheating sometimes mis-interpreted as steam bubbles in the heads.
In some respects, the reservoir acts like a DA tank on a boiler. the vapor space helps control boiling
Thanks for all the feedback. I'll look into the steam line kit to unblock the rear ports. I don't recall seeing a port where the HVAC hose can connect to the backside of the intake. Hopefully I just overlooked it. I'll leave my throttle body coolant lines bypassed and cap them off.
Reassembly Questions
