Heater core is always hot! Look at the coolant tank, it is in the heater core circuit!

 

Interesting. My bypass tubes are not connected to the radiator but simply run from one head to the other. They were that way with the LS1 intake tubes and the LS6 tubes when I changed to the LS6 intake.

Also, with the coolant reservoir tank being mounted higher than the top of the radiator, I don't believe there is any air space in the radiator. If you connected the tubes to the radiator it would seem you would flow coolant through them and back into the heads?

 

Personally I'll go with the service manual.

And the service manual says:

 

Interesting? Mine stock ran from the back of the heads to the front, through the Throttle body and back to the Rad. I bypassed the TB a long time ago and when I went to the LS6 intake I eliminated the rears, and used the ZO6 part numbers to order the plugs and the single tube setup on the front of the heads. You just have to be carefull to eliminate air bubbles in the system when refilling it.

 

The coolant air bleed pipe you are speaking of was used through 2000. Since the intake manifold changed in 2001 (ls1 and ls6 the same), there are two block offs used for the rear bleeds.

I have a feeling you guys will be at this all night......enjoy

 

Interesting, but in the radiator section it also tells me there is a radiator cap.

I think they may have copied from another manual. When was the last time you saw a cooling system take coolant from the top of the radiator?

I think they are talking theory here.

I have a set of manuals, and they are gospel but the cooling section is wrong, or at least very vague!

 

It's nothing new to find mistakes in the Service Manuals.

 

Funny I don't see that. It does mention a pressure cap on the surge tank.

Radiator
The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a crossflow tube and fin design. This is a series of tubes that extend side to side from the inlet tank to the outlet tank.
Fins are placed around the outside of the tubes to improve heat transfer from the coolant to the atmosphere. The inlet and outlet tanks are molded with a high temperature, nylon reinforced plastic. A
high temperature rubber gasket seals the tank flange edge. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core. The radiator also has a drain **** which is located in the bottom of the left hand tank. The drain **** includes the drain **** and drain **** seal.

The radiator removes heat from the coolant passing through it. The fins on the core absorb heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.

During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling
system. Coolant without bubbles absorbs heat much better than coolant with bubbles.

Pressure Cap
The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring of predetermined strength, which protects the radiator by relieving pressure if it exceeds 15 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator to collapse.

The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature much
higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler, passing air. The pressure in the cooling system can get
too high, however. When the pressure exceeds the strength of the spring, it raises the pressure valve so that the excess pressure can escape. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator from collapsing.

Surge Tank
The surge tank is a plastic tank with a pressure cap mounted to it. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system. The air space
allows the coolant to expand and contract. The surge tank also provides a coolant fill point and a central air bleed location.

During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling
system. Coolant without bubbles absorbs heat much better than coolant with bubbles.

 

Oops sorry don't mean to confuse you. My car is a very early 98, pre Z06 days.

If your car is 2000 or newer it will be different. Having said that and if your car is stock you should find a coolant tube connected to your throttlebody actually two tubes one in and one out, chase them back to see where they go and come from.

 

Sorry, I mis read gthe cap description to be in the radiator description.

Allow me to temper my response, this section does not say where or how the coolant flows in reality, it is a description of the components. The pressure cap is on the purge tank. So far as to how the system actually works I am accurate and the manual is vague. If you can find something in the manual that disagrees with what I have said, Have at it!

 

I believe the system is reverse flow. The thermostat has to be in the hot water flow for it to open and to properly control that flow. If it was blocking cold water flow into the engine then it would heat up until it opened and the cold water coming in from the radiator would cause it to close almost immediately. This would cause a rapid cycling of the thermostat. So it makes sense for the hot coolant to flow into the passenger side bottom of the radiator with the outlet at the upper drivers side of the radiator.

Bill

 

I agree however the manual states the right side of the radiator is the outlet side, and that hose connects to the thermostat housing. that is also the side that contains the tranny oil cooler on automatics. I suspect that the thermostat does rapid cycle until the entire system is up to temprature. If the coolant is going the other way there would be a chance of taking air off the top of the left side.

I just went through my manual, and it does not read like the PDF that was posted so I suspect there are different manuals, Mine is 98-Y3.

Wish I had a scanner, I would post it.

Actually when I think about it, it would keep the temprature more stable in the engine with the faster cycle. Also don't forget these thermostats don't act at light speed, they are pretty slow.

 

The coolant flow is in my attachment and is posted above as well. To me, it matches with what you have posted.

 

Parts Manual list Right Side radiator End Tank as the Outlet side. The colant exits the botom and goes directly to the thermostat. The flow through the Heater Core circuit is a nessary thing. That's the reason for my first post.

 

My manual goes into talking about a slant type radiator and a bunch of other stuff. They are all vague about direction of coolant flow. More to what Bill was stating I thought that one of then earlier year cars was the only reverse flow??

All our cars run at tempratures above what the thermostat is rated at, so when up to temprature it will be open when fully warmed up. The only way to reduce running temprature that I have found is to install a bigger radiator and reprogram the fans. I went to the lower temp thermostat a long time ago and while it helped lower the operating tempature, I did not see a significant change until I went to the Dewitts radiator. I like to have the car running in the 185 to 190 range going down the road without the fans.

 

We know the LT1 is reverse flow with that being defined (from what I've read) as the flow into the heads first then the block.

The DVD version of the C5 manual, where my info is from, says the coolant flows though the block first (along with heater core and thottle body) then the heads. To me that says it isn't reverse flow as described for the LT1.

Haven't had a reason to do anything to the cooling system in my C5.

In my 92 LT1 the combination of a lower temperature thermostat, modified fan settings and keeping the radiator free of road trash made a big difference in operating temperatures. It rarely goes over 190 in bumper to bumper traffic where before it would easily run up to about 230 before the fans kicked on.

 

I may be wrong about it being blocked off, I'll have to map all the pipes.


yep, with the heater set to off, the heater core lines are blocks by a solenoid... that definatley must be a contributing factor to my problem.

 

Pull the upper radiator hose and start the engine and see whether the coolant comes out of the hose. A little messy but not too bad. If it comes out of the hose then the hose fitting on the lower right side of the radiator is the outlet. Then you would know and be able to post for the rest of us.

Bill

 

It feeds in at the top left of the rad (the pipe is hot), and comes out of the lower right port (pipe is much cooler with the fans running).
It the fans stop, the lower right port pipe warms up

 

If the heater core flow is blocked that is your problem. The coolant running through the heater core is what provides the thermostat with the heated coolant and causes it to open. Otherwise there is no significant coolant flow past the thermostat.

Guys, coolant flows into the engine from the lower radiator hose. It goes in through the thermostat, into the block and up. That's why there is the air bleed tube that connects to the top of the radiator from the crossover between the heads. It is the highest point on the engine and the steam/air is vented to the upper part of the radiator to prevent air pockets. Coolant flows out of the engine from the upper radiator hose opening and into the top of the radiator. Until it warms up and the thermostat opens, there is not free flow through the radiator and the thermostat gets it's water flow thanks to the heater core hoses.