Can a water pump be intermittent?

It's *POSSIBLE*, yes - I can think of a scenario or two that would let it happen, but can't say for sure if the one I'm about to offer is true for your vehicle (year, make, and model of which you don't bother to mention, so we're stuck going on ESP to try and help you...)

Consider a water pump whose impeller is, under ideal circumstances, held tight to the shaft by a bolt into the shaft, or a nut onto the shaft. Consider said nut or bolt somehow backing off - not completely, but enough to be loose, perhaps permitting the impeller to spin free of the shaft - but only when it "backs straight away", rather than getting tipped - When it moves to a tipped position, it spins with the shaft, and for the most part, acts as it should - namely, moving water thorugh the system. But when it gets into a "straight" position, instead of turning the impeller, the shaft simply spins inside it, leaving the impeller stationary, and moving no water.

Presto... Intermittent water pump...

Same concept could be happening on the pulley side of things - replace "impeller" with "pulley" everywhere in the paragraph above, and you end up with the same thing happening.

Either way, your junk Autozone pump is a "lifetime" unit, so go get a new one and replace it. Not too difficult, eh?

(And for the record: About the only thing I consider Autozone good for is name-brand oil and brake pads, and I consider the brake pads dodgy, at best. Overall, and in my opinion, Autozone blows syphyllitic goats in almost every other category.)

I once bought a 1966 Plymouth with a 225 slant six. It had an overheating problem that I traced to the water pump impellor slipping on the shaft. It was a press fit. There may have been more slip at different engine temperatures and speeds than others, I can't say for sure. If it were true, though, that water pump could have been considered intermittent. Anyway, the slip was obvious when spinning the impellor by hand - with the water pump off the engine, of course.

I have had that happen a couple years back in my Jeep. The impeller slips on the shaft sometimes and my first symptom was no heat. No fluid flow = no heat instantly. If I still have inside heat, I still have a pump working.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 (More Off Road album links at bottom of the view page)

And of course, don't forget the role of heat expansion in the 'slipping impeller' scenario. ;-)

My only experience with an Autozone WP was helping my dad put one onto my mom's 82 Cutlass. It was a bit of a job, lasting several hours (probably could have been quicker w/o my dad's help, but you know how that is :-D ). We got it on and back together only to find that the flange on the end of the shaft was pressed on crooked. Not enough to notice readily when you take it out of the box, but when you spin the fan on it, it was bad real.

So we got to start over.

-phaeton

P.S... just a fluke thing, i know. Maybe the rebuilder put on one wrong shoe that day?

Never heard of one getting intermittent. That doesn't mean it's impossibe but.... it's not likely.

The 'pumping' part of the pump is an iron impeller pressed onto the waterpump shaft. They don't wear out. The reason pumps get changed is mostly the shaft seals fail and they start leaking. The shaft bushings (or bearings) are place outside the seals so when the pump starts leaking ot can affect the shaft bearings and cause the pump to make noise.

You may have a hose that is collapsing and not letting the water pass thru.

Heater cores will also get stopped up from rust and scale deposits that break loose and travel with the water to the heater core.

Buy a 'quality' thermostat. I tried several of those 'cheap' ones made south of the border (wherever the heck the border is) and they all failed within a years time. They 'look' good and the price is right but I'd rather spend a few dollars more and not have to take the crappy things out and do the job all over again next year.

Never heard of one getting intermittent. That doesn't mean it's impossibe but.... it's not likely.

The 'pumping' part of the pump is an iron impeller pressed onto the waterpump shaft. They don't wear out. The reason pumps get changed is mostly the shaft seals fail and they start leaking. The shaft bushings (or bearings) are place outside the seals so when the pump starts leaking ot can affect the shaft bearings and cause the pump to make noise.

You may have a hose that is collapsing and not letting the water pass thru.

Heater cores will also get stopped up from rust and scale deposits that break loose and travel with the water to the heater core.

Buy a 'quality' thermostat. I tried several of those 'cheap' ones made south of the border (wherever the heck the border is) and they all failed within a years time. They 'look' good and the price is right but I'd rather spend a few dollars more and not have to take the crappy things out and do the job all over again next year.

Much more common: a collapsing lower rad hose. When the water flow speeds up as the pump drives it through the system, the pressure in the lower hose drops (Bernoulli's Theorem) and an old, soft hose can collapse and restrict the flow. My Dad once replaced the pump two or three times before his brother came along, revved the engine and pointed out the lower hose squeezing itself shut. That's why many replacement hoses had springs inside them. Dan