How does the raw water cooling system on the 4.5L dump water when the tstat is closed?

[void7910]

I've been trying to understand the cooling system on my new-to-me 4.5L. Instead of a traditional thermostat housing that has 4 hose returns to both the elbows (when tstat closed) and to both manifolds (when tstat open) the 4.5L has a "crossover" assembly that houses the tstat and only has returns to the manifolds. I am curious, when the tstat is closed how is raw water actually exiting the system? My only thought is that the excess raw water pressure opens the poppet and bleeds out the water through the elbows that way?

 

[alldodge]

This may help

 

[tpenfield]

As AD's picture shows there is a more direct path for water to go to the exhaust, which most of it does until the engine reaches temperature and opens the t-stat. The poppet valve controls a secondary feed to the exhaust in higher engine speed situations.

 

[void7910]

That diagram is amazing. Where did that come from? Service manual?

I am still not seeing where the water exits when tstat is closed The "n" path would only be activated when the tstat is open. Unless you're talking about the top pair of hoses on the poppet assembly "p"?

 

[alldodge]

Came from the service manual and another posted it, I just saved it

The n path is always flowing for the most part. The crossover and thermostat are not 100% sealed off from each other, always very small passage. Also the n path does flow but is restricted a bit. Don't look at the crossover as a complete hollow with a Stat on one end

 

[void7910]

Came from the service manual and another posted it, I just saved it

The n path is always flowing for the most part. The crossover and thermostat are not 100% sealed off from each other, always very small passage. Also the n path does flow but is restricted a bit. Don't look at the crossover as a complete hollow with a Stat on one end

Great info. So when the tstat opens it just dumps the heated water from the block down the n-path as well then?

I am curious about the design of the crossover, for instance the blue drain plug does that connect to a passage that is open to the block or the manifolds. Any ideas?

 

[alldodge]

As I understand it
The flow arrows are not 100% full time.

The hose which goes from bottom of Stat to Y below is moving up even though the arrows show down. The raw water pump is pushing water to the circulating pump and circulating pump trys to push water thru block but cannot because Stat is closed.

The bottom of the stat also connects to n hoses. When stat opens the circulating pump is able to move more raw water into the block and back out the Stat. With Stat open hot water is expelled thru the n hoses

 

[Scott Danforth]

Google mixing valves

Thermostats on raw water cooled motors operate as mixing valves to keep the block and heads at the desired temp