Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner

Coolant flow direction?

36K views 46 replies 14 participants last post by  Thetonymartin 
#1 ·
Can someone verify which way the coolant flows. I assume it flows from the thermostat(bottom hose) to the bottom of the radiator. The spring on the thermostat is in the engine, therefore in contact with coolant at different temperatures, it opens, sending coolant to the radiator. :undecided
 
#7 ·
It runs backwards as compared to other GM vehicles. Typically the T-stat is on top, with the spring inside the block, so it runs into the rad via the top hose. But this runs into the rad via the bottom hose. Just wanted to make sure I was not over thinking it. :weird:
 
#12 · (Edited)
The last time I looked ( I need to add, looking from the front) the coolant flows from the bottom of the left side tank of the radiator through the lower hose to the water pump. The water pump pumps the coolant through the block and heads and the heater hoses. The coolant absorbs the heat from the engine that heats the thermostat that is mounted in a housing near the top of the engine. There is a cover over the thermostat that holds the thermostat to the housing (or manifold) that the upper radiator hose is connected to. The heat sensing "pellet" is under the thermostat and when the engine heats the coolant to the operating temperature the pellet expands, pushes the thermostat open, releasing hot coolant to the upper hose and right side tank top to the radiator . The coolant flows across and down in the radiator and air flowing through the fins on the radiator removes the heat. The cooled coolant then flows back into the engine.
 
#13 ·
The last time I looked ( I need to add, looking from the front) the coolant flows from the bottom of the left side tank of the radiator through the lower hose to the water pump. The water pump pumps the coolant through the block and heads and the heater hoses. The coolant absorbs the heat from the engine that heats the thermostat that is mounted in a housing near the top of the engine. There is a cover over the thermostat that holds the thermostat to the housing (or manifold) that the upper radiator hose is connected to. The heat sensing "pellet" is under the thermostat and when the engine heats the coolant to the operating temperature the pellet expands, pushes the thermostat open, releasing hot coolant to the upper hose and right side tank top to the radiator . The coolant flows across and down in the radiator and air flowing through the fins on the radiator removes the heat. The cooled coolant then flows back into the engine.

You haven't changed the thermostat in an I6 engine recently have you?

I just did - the thermostat connects to the LOWER radiator hose which is on the drivers side of the engine. It may look like the short upper hose is where the thermostat is at - but trust me it is not. It would make replacing the thermostat a MUCH easier job if it were on the upper hose. Thank you GM engineers!
 
#16 ·
Ok, all of this reading made by brain bleed,


All i know is that when i changed my t-stat and my hoses, and when i did all my tests for the e-fans, i had to flush and fill my rad quite a few times, what i can tell you is that the top hose, the one on the passenger side is the radiator in from the engine, the hot coolant flows from the engine TO the rad from the top hose and that the bottom hose of the radiator is the colder coolant out to the engine block, i've also verified this with a flash light at the coolant through the opening of the top rad cap,
 
#20 · (Edited)
All i know is that when i changed my t-stat and my hoses, and when i did all my tests for the e-fans, i had to flush and fill my rad quite a few times, what i can tell you is that the top hose, the one on the passenger side is the radiator in from the engine, the hot coolant flows from the engine TO the rad from the top hose and that the bottom hose of the radiator is the colder coolant out to the engine block, i've also verified this with a flash light at the coolant through the opening of the top rad cap,
:iagree: that makes more sense (to me at least)

Here is what the much revered Haynes manual states:


"Coolant is drawn from the radiator by an impeller type water pump mounted at the front of the block. The coolant is then circulated through the engine block where it passes around the individual cylinders. After exiting the cylinder block, the coolant then enters the cylinder head where it quenches the combustion chamber area. The coolant flows out of the cylinder head and into the thermostat where, depending on coolant temperature, it is either blocked until the desired temperature is obtained or allowed to pass through the thermostat into the radiator."

Unless I'm reading it wrong, they are saying the thermostat is in the head.
 
#26 ·
I am so positve that it flows in that position that if you pay the plane ticket i will come....


lol


seriously the reason why i also needed to know is that i i needed to add a temp sensor, and i remember pcmforless using the lower rad hose, but after noticing that one was always cold, i decided to completly empty the rad and see if were to fill up from underneath or from the upper hose on top, well as soon as the t-stat open all the good juices came from the top hose, if uou are unsure, let teh truck idle a bit and remove you rad- cap, of course you will need to drain a bit of coolant so when i fiils up it won't overflow...
 
#24 ·
As to post 19 I did miss that. Actually I was hoping for a chart or diagram from the service manual.

Yes I agree with the thermostat being on the drivers side in the block - especially since I just spend a few hours changing the *** thing last week!

My point in saying "Unless I'm reading it wrong, they are saying the thermostat is in the head" is that the Haynes manual is not always accurate.
 
#28 ·
the coolant flows from the block into the thermostat .....the spring on the tstat is on the block side which adds to the theory that the direction of the coolant flow is from block, through tstat out to the radiator, the themostat is connected to the lower hose where the coolant enters the radiator, is forced up and out of the radiator through the upper hose, back into the block near the water pump which gives it some push through the block again ...........thats my take on it even though this thread seems to have been left with the consensus of the coolant flow in the opposite direction
 
#31 ·
I looked up the thermostat for that engine on O'reilly's web pages and it says lower hose, driver's side for the location. The price they have listed for it seemed extreme, too. I doubt that anybody would forget or mistake the location after they had to change one. :mad: GM seems to be going out of their way making things difficult to fix.
 
#36 ·
Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Coolant will then be 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 the coolant absorbs heat.

Some coolant is also pumped from the water pump to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.

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 the coolant absorbs additional heat.

Coolant is also directed to the throttle body. There the coolant 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 the coolant will flow through the thermostat and into the radiator where the coolant is cooled and the coolant cycle is completed.
fwiw here is alldatas explanation
 
#37 ·
I just placed a clear hose where the top rad hose is, I then ran the TB, watching for flow, making air bubbles move, and holding(separately) both radiator hoses with my hand at operating temperature. The top hose is warm, while the bottom hose is cool, almost cold.

Coolant flow is from top to bottom :woot:
 
#42 ·
OK, here's the story. The I6 engine has a "reverse-flow cooling" design. The thermostat controls two flows in the engine. It directs the flow from the radiator through the coolant pump and to the heads first where the coolant is heated until flow back through the thermostat is hot enough to direct a regulated flow around the cylinders and then back to the coolant pump and then to the radiator. Notice several additional parts in the system. It's for more HP, better engine operation on lower quality fuel, etc.

http://www.procarcare.com/icarumba/...icar_resourcecenter_encyclopedia_cooling1.asp

http://en.allexperts.com/q/Chevrolet-775/350-chevy-turn-key.htm
 
#45 ·
does anyone know how much difference changing your stock thermostat to a after market 160 degree thermostat do to the engine performance?
If you are talking abuot the I6, Yes

frist you get a check engine light, then you happy a serious rich mixture and then you finnish with a clogged cat....


lol

seriously, it can be done, but you need to get the mixture changed with a tuner and have some codes disabled,
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top