Does anyone know why GM put the thermostat on the water entering the engine, as opposed to the outlet, as it would be on most other cars.

I have a C6 and have no issues, but I am building a factory five GTM which is based on a C5 and I am having some issues with cooling.
Namely, at idle:

On my kit car at least, the thermostat never opens if the car is just idling:
a) the heads heat up first
b) this turns on the fans
c) by the time water gets back to the engine, it's cool, so the thermostat stays closed
d) not enough water flows thru thermostat, and back to a) again

Under this condition, the head reaches 250, but the block stays cool.
My kit is using a LS376 engine. I am trying to understand how the corvette system is supposed to work to try to figure out my problem.

I saw some mention of a bypass line to the intake manifold, but this may have been on older vettes, in any case the GTM doesn't have such a thing. Any help understanding would be appreciated.

Ian

 

Aren't the LSx based motors reversed flow because of the serpentine belt system and cross flow radiators?

 

What have you got hooked to the ports that normally feed (and return) the Heater Core.

 

Nope.....you are thinking Gen II LT1

 

It sounds like you have a misunderstanding of how the cooling system on the LS engines works. Here is from the service manual.

"Cooling Cycle

Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Some coolant will then be pumped from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.

Coolant is also pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.

The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.

Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body. During normal operating temperatures, the coolant assists in keeping the throttle body cool.

From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or it will flow through the thermostat and into the radiator where it is cooled and the coolant cycle is completed."

 

From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or it will flow through the thermostat and into the radiator where it is cooled and the coolant cycle is completed."
-----------------------------------------------------
Wrong!

 

Service manual is wrong?

 

Thanks, I wasn't sure. I knew my former '96 Impala SS was reversed.

 

I think it is. Let's see what others think. I could be wrong, it wouldn't be the first time. But, if the Service Manual is wrong, it wouldn't be the first time for it either. I think we'll hear other opinions, ok?

 

 

do you have the t-stat in upside down? The copper capulary tube may not heat up right then? just a thot, good luck with it

 

I don't think the thermostat will fit in the housing upside down. On the early models it comes in the housing and on the later models the bottom (engine) side is square and I don't think will clear the rounded housing.

 

Lucky, what does that mean? What are your thoughts? The bottom of the radiator feeds directly to the Thermostat Housing. You think I'm off my rocker?

 

Don't disappoint me now.......are you right?

 

Having just my heads off theway i read it is:

Don't care what the manual says this is how it works. I also have a Dewitts radiator (last year) and I forgot what temp thermostat I put in it a few years ago, 187 degree I think. She runs cold, in traffic rarely above 190, and in cold weather I really have to let it warm up.

With the engine cold and thermostat closed the water pump cycles coolant through the block, heater core and heads.

Because of the head gaskets the water goes up to the heads at the rear of the block and flows to the front of the engine where it returns to the pump through the block. Hence the temp sensor in the head by Cyl #1. This is not the only path back to the pump it also flows through the block. With the left bank and Cyl #7 thought to run leaner and hotter this would make sense as the temp sensor would be located in the path of highest temp coolant.

When the temp rises and the thermostat opens the coolant flows/pumped/sucked from the bottom of the radiator through the pump to the block, heads etc. The thermostat does not just go open and stay open until the entire system including the radiator is up to temp. The thermostat in this mode is managing coolant temp by constantly opening and closing. This is also why you should not set your fan turn on temps below your thermostat rating.

Because the coolant flows through the thermostat housing on it's way to the heater core, it controls the opening of the thermostat. Also because the path through the heater core is much smaller than the path through the radiator when the thermostat opens there is less restriction through the radiator and the majority of the coolant will use that path.

The little bypass tube from the heads to the radiator is just to bleed any air in the system back to the radiator. on 97 and 98 models this tube was at the front and rear of the heads (4 places) on later models and Z06s it is just on the front of the heads (2). Hence, if you go to a Zo6 intake, you either have to grind the bottom of the manifold fins or get a later model bypass and plug the rears. I plugged mine and went with a late model system.

 

From Blue Dragon's post-------When the temp rises and the thermostat opens the coolant flows/pumped/sucked from the bottom of the radiator through the pump to the block, heads etc.
--------------------------------------------------
Thank You!!!!!!!!!!!!!!!!!!!!!

 

Blue Dragon says I am.

 

hehehe........do you feel vindicated? Honestly, I've never noticed that in the service manual....

It's a pretty good manual, but that part is poorly written....

 

I have the two small ports next to the thermostat going to the heater core, but I think they get blocked off by a solenoid valve when the heater is off. Could that be the issue?


The water must flow into the thermostat 1st, as this the the last place to heat up when I fast idle the engine. (3k rpm).

 

Nope, not correct!