Water Pump

I have had a few mes­sages regard­ing the LS3 water pump, so I have repos­ted a page from  Pirate4x4.com I have referred to this site a num­ber of occa­sions ;

A = Water pump out­let to heat­er core, 58″.

B = Water pump inlet from heat­er core, 34″.

C = Water pump inlet / ther­mo­stat hous­ing (in to engine from radi­at­or), 1−1÷2″.

N = Water pump out­let (out to radi­at­or, from engine), 1−1÷4″.




Generic LS coolant flow








Start­ing at the water pump and fol­low­ing the num­bers in sequence, here’s the flow of the sys­tem :

  1. The water pump pumps coolant out of the lower two ports on its back side and into the block.
  2. Coolant cir­cu­lates through the engine block…
  3. … and through the cyl­in­der heads.
  4. Spe­cial LS-spe­cif­ic “steam tubes” or “engine vent lines” are installed on top of the cyl­in­der heads. As vapour or steam will always seek the highest point, any steam pock­ets cre­ated by loc­al hot spots, par­tic­u­larly in the cyl­in­der head exhaust valve area, will migrate up and into the steam tubes which will carry them and a small amount of coolant away and either into a port loc­ated at the top of the rad (as shown here) and from there to the surge tank, or dir­ectly to the surge tank (depend­ing on applic­a­tion) where the steam is sep­ar­ated from the coolant.
  5. Coolant return­ing from the cyl­in­der heads enters the two upper round ports on the left and right back sides of the pump
  6. Some coolant cir­cu­lates through the water pump’s bypass cir­cuit and is again pumped back through the engine. This keeps the cir­cuit flow­ing when the ther­mo­stat is closed.
  7. Hot coolant exits the smal­ler, rear “heat­er out” port of the ther­mo­stat hous­ing on the water pump. This takes it to the heat­er core. The port is 58″ “.
  8. After exit­ing the heat­er core, coolant return­ing from the heat­er passes through the surge tank to keep coolant cir­cu­lat­ing through that tank.
  9. After passing through the heat­er core and then the surge tank, coolant re-enters the engine via the lar­ger, front 34″ “heat­er in” port of the ther­mo­stat hous­ing on the water pump.
  10. Hot coolant exit­ing from the engine that doesn’t fol­low the pump’s intern­al bypass cir­cuit exits the water pump via the top 1−1÷4″ port and enters the top of the radi­at­or.
  11. Hot coolant flows across and down through the radi­at­or, cool­ing as it goes.
  12. Cooled coolant exits the radi­at­or via the lower 1−1÷2″ out­let and returns to the inlet side of the water pump.
  13. Return­ing coolant is blocked from re-enter­ing the water pump inlet if the ther­mo­stat is closed. When the coolant on the inside (engine side) of the ther­mo­stat reaches the tem­per­at­ure of the ther­mo­stat (e.g. 190° F) the ther­mo­stat opens and the cool coolant enters the water pump inlet to be cir­cu­lated through the engine again, start­ing over at #1.
  14. A radi­at­or bleed or vent port loc­ated at the top of the radi­at­or con­nects to the surge tank. Any air or steam in the sys­tem, espe­cially that com­ing from the engine’s steam tubes, will nat­ur­ally seek the highest point and will there­fore exit the radi­at­or via this port and travel to the surge tank. At the surge tank, coolant and steam enter and the steam or air is sep­ar­ated from the coolant. The light­er steam / air col­lects and remains in the surge tank at the highest point, just below the rad cap, to be elim­in­ated first in the event the rad cap purges. The cool­er, dens­er coolant goes to the bot­tom of the surge tank where it is col­lec­ted by the flow return­ing from the heat­er core and cir­cu­lated back through the sys­tem.
  15. In the event of a sys­tem over-pres­sure con­di­tion, the rad cap opens and burps excess coolant and steam out of the sys­tem to be col­lec­ted by the over­flow tank.

As can be seen, the surge tank is an import­ant and very use­ful com­pon­ent of the sys­tem. Fol­low­ing are a few more details on the use of a surge tank :

One of the prime reas­ons for mount­ing a pres­sur­ized surge tank in the cool­ing sys­tem is the flex­ib­il­ity it gives in the mount­ing loc­a­tion of the rad cap. Because it is the pres­sure relief valve of the sys­tem, the rad cap :

  1. Must always be loc­ated at the highest point of the cool­ing sys­tem – oth­er­wise it will be impossible to get a com­plete fill of coolant and air will be trapped in the sys­tem. Also, when the rad cap is the highest point in the sys­tem, steam and air will nat­ur­ally migrate to the area just below the cap. In the event the cap vents due to excess­ive pres­sure, the steam and air will be purged first.
  2. Should be on the low pres­sure side of the sys­tem – oth­er­wise the high pres­sure cre­ated by the water pump run­ning at high RPM can tend to unseat the cap and blow coolant out, lead­ing to over­heat­ing.
  3. Should be loc­ated in an area of low coolant velo­city so that the any steam or air can sep­ar­ate from the coolant, even at high RPM.

The surge tank provides the ideal envir­on­ment for sat­is­fy­ing all three of these require­ments, and provides a low velo­city, low-pres­sure envir­on­ment for de-aer­a­tion of the coolant.







Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.