Bad engine water pump?

[TomW]

Last week I got O'Reilly's Auto Parts to order me a new, heavy duty water pump:

Originally Posted by O'Reilly's web site

MASTER PARTS DIVISION - New Water Pump
Limited lifetime warranty
HEAVY DUTY WATER PUMP
INCREASED COOLING CAPACITY/HEAVY DUTY COMPONENTS

It came in on Friday, and the Store Manager laid it out on the counter beside a regular duty water pump for my inspection. Without taking the backing plate off (did you catch that, Terry ), I couldn't see any difference between the two pumps. I was hoping the super-duper pump would at least have a glitzy paint job.

The manager, who appeared to have turned a few wrenches in his life, could not shed any additional light on the subject and admitted this was the first one of these pumps he had seen. Hoping that the pump might help, I went ahead and bought it.

Here is a picture of the old water pump with the backing plate removed:



There does not appear to be anything wrong with it. The impeller neither loose on the shaft nor rotted away. Several threads from another forum drove me to look at the impellor clearance, which was measured to be [about] 0.070":



Pulling the backing plate off of the super-duper water pump, there was one immediate, noticable difference - a round plate riveted to the impeller:



With my limited knowledge of hydrodynamics, I can see that plate making a difference in the pump's efficiency. Since the plate is there at all AND it is riveted on, I must assume this was the manufacturer's concession for "increased cooling capacity". My reasoning here is that nowadays, manufacturers don't add parts that are not essential to operation or to back up a claim.

Everything on the HD pump I could measure was the same size on the regular pump.

I also flushed the system and went back to green coolant.

Although the Overlander's next trip is still a week-and-a-half away, I will drive the Suburban to work this week to get all the bubbles out of the cooling system and gauge the truck's "unloaded" performance.

Thanks for everyone's help,
Tom

[tomjunw]

Check for either plugged tubes inside the radiator, or the cooling fins coming loose from the tubes. The other thing it could be is dirt plugging the fins.

[overlander63]

Tom, the plate on the back of the impeller is to reduce cavitation, and increase coolant flow.
For those who don't know, but do care, cavitation is caused by extremely low pressure allowing water to boil at very low temperatures, hence the bubbles (boiling water). That is one of the reasons submarines travel in very deep water, the higher pressure from the water decreases the tendency to cavitate behind the propeller (boiling water is noisy). The boiling cold water can cause damage to metal parts as well as noise, and cause a loss in efficiency of the device moving the water.

[TomW]

Although the Overlander's next trip is still a week-and-a-half away

It's onward ho to Jackson MS with all the replacements/improvements. We're staying at a new Camp Jellystone near the area while attending my Uncle Bill's 70th birthday party (read: family reunion).

Wish us luck,

Tom