[never satisfied]

my chevy 350 long water pump is not leaking or showing signs of wear but seem to have flow issues keep overheating .. pulled apart and noticed impeller is about a 1/16 away from housing is that to far away to pump good never rebuilt one?

[327NUT]

Not too far away but personally I wouldn't waste my time rebuilding (??) one. Just buy a the appropriate Stewart stage 1 or 2 and never look back.

[bigdog7373]

It's not always the water pump's fault for an engine over heating. How old is the radiator? It may be clogged up or it may be too small. What kind of fan are you running?

[never satisfied]

rad is not very old it is a griffan aluminum little bigger than stock, i have a 18 inch flex fan and 16 in electric fan for back up. been threw 2 t stats, 2 gauges, flushed block and rad with hose seems to flow fine pump is the only thing left . no sign of head gasket damage they are new no water in oil and no smoke while running ....

[bigdog7373]

Wait, you have an electric fan? By "for backup" do you mean it's mounted but not on?

[never satisfied]

it is pre set for 185 and goes off at 165

[bigdog7373]

There's your problem. Take off the elec fan and run just the mech fan with a shroud. The electric fan is just restricting airflow through the rad.

[never satisfied]

its worth a shot , water pump is off so i ordered a new one.. thanks for the reply

[techinspector1]

Never had a flex fan that worked. Sling it over the fence and install an 18", 7-blade OEM steel fan and full shroud. Sling that backup fan over the fence too.

Sorry for the bad attitude, but I just never had an electric fan that was worth bringin' home. Never, ever had any trouble with a properly sized radiator, mechanical water pump, 18", 7-blade OEM steel fan, full shroud, thermostatically-controlled fan clutch and high-flow 180 thermostat. BULLETPROOF. Oops, almost forgot, put a spring in the lower radiator hose to prevent collapse.

[never satisfied]

i am up for any good ideas , my question is the distance from the back of the impeller to the housing inside the water pump is greater then it should be, as i compared it to a old pump a rebuild guy said it should be around .010-.0135 gap in there .. so would that cause water not to flow out of engine threw rad?

[oldbogie]

Originally Posted by never satisfied

my chevy 350 long water pump is not leaking or showing signs of wear but seem to have flow issues keep overheating .. pulled apart and noticed impeller is about a 1/16 away from housing is that to far away to pump good never rebuilt one?

Pumps are seldom the cause of overheating, they leak and beaings fail, but otherwise if they once pumped adaquatly, they will continue to do so.

Most over-heating issues are found to be with the fan, shroud, thermostat, senders and gauges, radiator, and hoses.

While there are exceptions; usually cooling problems at idle and extended stops with the engine running are related to a lack of air flow thru the radiator which leads mostly to fan and shroud issues.

All the time cooling tends to be thermostat failure, inlet hose collapse, or bypass issues

High speed problems usually point to coolant flow problems within the radiator.

The SBC is also sensitive to the bypass, it is designed to take a certain amount of coolant from the engine side of the thermostat and recycle that back to the inlet side of the pump. The fitting usually being on the top of the pump but also found in the radiator's suction side tank or Tee'd into the pump suction hose. Models without air conditioning simply route coolant thru the heater core using the bypass system and just shut off the heat by closing an air door to the cab. Air conditioned models intercept the coolant with a 3 way valve to shut off flow to the heater core when the AC is switched on while re-routing the bypass flow inside the valve back to the suction side of the pump. The purpose of the bypass is to provide movement of coolant inside the block and heads when the thermostat is closed to prevent the formation of seam pockets around the exhaust valve seats and spark plugs, also, to prevent cavitation at the pump impeller.

To id the possibilities further, I need some specifics as to how and when it overheats, and what parts are on the engine and what the vehicle is.

Bogie

[never satisfied]

let me start from the begining car ran good but motor was stock with mild cam, it always cooled nice, put a set of trickflow heads on car 61 cc , comp xtream energy roller cam and solid lifters air gap intake, 650 holley, new 180 stat , ran car and noticed temp would jump up rapid and come back down rapid, so i though i would put a flex fan and shroud on it to aid in cooling since i only had a griffin rad and electric on it , also put a new 180 mr gasket t stat in it and new fan control for the electric. ran it a little coolant droped figured i got the air out. toped off and took for a ride , temp started to climb to 240 shut car off and it max out like stat was not open. no steam or nothing car started fine and sounded fine , let cool and got it home ,, checked gauge reads correct , and put t stat in a pot and it opened and closed fine. water pump is the last part to change out very frustrated oil has no sign of water and no smoke from exhuast