Water pump - opinions please

[Northern Bongolow]

my guess on the pitting would be the little scale/rust particles suspended in a badly maintained system,they could be battered around the pump.
question--------does coolant/antifreeze reduce the effects of cavitation.im of the opinion that it does.
there was a story on here a while back of a fleet of ambulances that were running on the wrong strength of antifreeze,they all suffered waterpump failure due to the impellors being eaten away.

[mikexgough]

my guess on the pitting would be the little scale/rust particles suspended in a badly maintained system,they could be battered around the pump.
question--------does coolant/antifreeze reduce the effects of cavitation.im of the opinion that it does.
there was a story on here a while back of a fleet of ambulances that were running on the wrong strength of antifreeze,they all suffered waterpump failure due to the impellors being eaten away.

As I am slowly getting to grips with who makes components for Mazda so they can buy in and package with their name................ so far... I am dealing with Thermostats(when time allows) but obviously this links other items too....like FL-22 coolant, hoses etc.....and ALL the makers of 'stats in Japan recommend you change the Water pump when you change the 'stat .
Now before we get the "yeah they would just to make money" folks giving opinions... ...they use Long Life Coolant (LLC) that is free of sulphates/phosphates etc....reducing pump cavitation...so why change the pump....Japanese ways...they replace linked components so they do their best to make sure NOTHING else fails...
Back to LLC....it is 5 yr life so a 'stat and water pump every 5 yrs is not a big deal really....but to UK owners and UK thinking...it probably is....
Back to the pump concerned....we know it leaks and poor shaft seals will weep and can allow air into the system.....which could have been the issue in this case
........NOT a Bongo pump but a cross section.......... which shows the main shaft and seals....to try and get some perspective of what's inside a water pump

So IMHO.and prepared to face the firing squad.....if your not using a coolant of the Factory variety or one of the similar chemistry, then you could and I say could... be damaging your Water pump, via seal leaks or impeller damage......as for changing 'stats and water pumps together....it's up to the wallet...

[Northern Bongolow]

makes perfect sense to me

[waycar8]

just thinking steve that the rattle was in fact the pump spinning in a dry state,as in an air lock situation, the water in the pump would normally dull the sound. as we have seen, it was sucking air in at this point and leaking coolant.

Could explain the noise and IF there was something "floating" about in the coolant pipes such as a small piece of metal fragment ect or stone, as soon as the coolant dropped out of the pump, the pump would batter the fragment around in the pump.

they might not have noticed anything as it may have dropped out when the pump was taken off or when the pipes had been taken off previously or it could be lurking still!

The reason I say this is when I bled my bongo after replaceing the top hose due to a swelling in the area , drained the system and flushed it as I decided to put in the 5 year pink stuff as the older stuff was 2 year blue stuff, but it had only been flushed and had the blue stuff in along with a mazda stat around 12 months ago Ady you helped me do it , and my system was very clean at the time, So once I had flushed it this time I dropped the rear hose to the rear heater matrix and found a stone about the size of a 5 pence coin , dont ask me how it got in there but hate to think if it had wedged in a thinner coolant hose or ended up in the pump ect.

[widdowson2008]

Waycar
'stone about the size of a 5 pence coin'. That would create the markings I'm seeing and it IS possible I suppose to accidentally pour one in with on coolant refill.
This particular Bongo has now performed OK for the last few days during relatively short runs. No apparent coolant losses and heaters performing as they should. Today is the crunch day. It's being taken for a long run. Let's hope things are still OK this evening.

[waycar8]

Waycar
'stone about the size of a 5 pence coin'. That would create the markings I'm seeing and it IS possible I suppose to accidentally pour one in with on coolant refill.
This particular Bongo has now performed OK for the last few days during relatively short runs. No apparent coolant losses and heaters performing as they should. Today is the crunch day. It's being taken for a long run. Let's hope things are still OK this evening.

Good luck with your outing , hope you have come to the end of the episode .

only thing I can think of how it got in there, is that we were under the van layed on the floor changing the stat and taking off a coolant pipe and re attaching not forgetting the rear hose also, so presuming we might have had the said stone stuck to our clothes ie our sleeve ect and it fell in whilst re fill ect.

[widdowson2008]

Waycar
'stone about the size of a 5 pence coin'. That would create the markings I'm seeing and it IS possible I suppose to accidentally pour one in with on coolant refill.
This particular Bongo has now performed OK for the last few days during relatively short runs. No apparent coolant losses and heaters performing as they should. Today is the crunch day. It's being taken for a long run. Let's hope things are still OK this evening.

Good luck with your outing , hope you have come to the end of the episode .

only thing I can think of how it got in there, is that we were under the van layed on the floor changing the stat and taking off a coolant pipe and re attaching not forgetting the rear hose also, so presuming we might have had the said stone stuck to our clothes ie our sleeve ect and it fell in whilst re fill ect.

Stone stuck to sleeve scenario sounds a very likely culprit, and quite easily done.
Not my van. No control over test whatsoever. Just helping out a bloke. ....and yes, it would be good to draw a line under this but I suspect not, mainly for the following reason. On initial inspection, the end of the steel pipe to the bottom hose (about 40mm) was perforated. We overcame this by pushing the hose further onto the steel onto sound pipe. However, this is one that we actually could see. How many more are in a similar state that we CAN'T see. Unfortunately, the only way to find out is strip the whole system out for inspection, and I don't think that is going to happen.

[waycar8]

Waycar
'stone about the size of a 5 pence coin'. That would create the markings I'm seeing and it IS possible I suppose to accidentally pour one in with on coolant refill.
This particular Bongo has now performed OK for the last few days during relatively short runs. No apparent coolant losses and heaters performing as they should. Today is the crunch day. It's being taken for a long run. Let's hope things are still OK this evening.

Good luck with your outing , hope you have come to the end of the episode .

only thing I can think of how it got in there, is that we were under the van layed on the floor changing the stat and taking off a coolant pipe and re attaching not forgetting the rear hose also, so presuming we might have had the said stone stuck to our clothes ie our sleeve ect and it fell in whilst re fill ect.

Stone stuck to sleeve scenario sounds a very likely culprit, and quite easily done.
Not my van. No control over test whatsoever. Just helping out a bloke. ....and yes, it would be good to draw a line under this but I suspect not, mainly for the following reason. On initial inspection, the end of the steel pipe to the bottom hose (about 40mm) was perforated. We overcame this by pushing the hose further onto the steel onto sound pipe. However, this is one that we actually could see. How many more are in a similar state that we CAN'T see. Unfortunately, the only way to find out is strip the whole system out for inspection, and I don't think that is going to happen.

I did this with my rear hose for the heater, had a pin hole where the hose attached to the metal pipe, so cut back to where there was good metal to get rid of internal rust in the pipe only to find that the hose only just fitted and I wasnt confident that it would be a sufficient grip so bought a section of hose from motor factors which did the job, only to check a couple of weeks later to find the hose had started to crack where it was bent to create the loop up to the heater matrix, so went to the local scrappers to try and scource a hose with a loop already formed, got one which did the job perfectly and that was about 12 months ago and havent had a problem with the said area since

[g8dhe]

Given that any solid object would be flung outwards it would do as much damage to the outer case as it did to the blades surely ?

I can't see any damage to the outer casing, the coating looks perfect, the only thing that is damaged are the surfaces of the blades which are rotating and the damage is in the form of very small pits - this is just the type of damage that cavitation causes.
Very interesting article here especially about "air ingestion" now if there was an air in the system it strikes me that it likely might make it to the pump, also vaporisation could be a factor given that if the pressure in the cooling system dropped (boiled over and opened the 1.1 Bar vent) then the water would vaporise!

[widdowson2008]

Given that any solid object would be flung outwards it would do as much damage to the outer case as it did to the blades surely ?

I can't see any damage to the outer casing, the coating looks perfect, the only thing that is damaged are the surfaces of the blades which are rotating and the damage is in the form of very small pits - this is just the type of damage that cavitation causes.
Very interesting article here especially about "air ingestion" now if there was an air in the system it strikes me that it likely might make it to the pump, also vaporisation could be a factor given that if the pressure in the cooling system dropped (boiled over and opened the 1.1 Bar vent) then the water would vaporise!

Good read that link Geoff. Think it is talking about industrial pumps of far greater capacity, but the principle must be the same Surely.
With regard to the casing being marked, it does have a small area (at the 12o'clock position - out of sight) which has a few marks, but nothing like on the blades. The damage seems to be mainly on the leading edges and the face of the blades.
Air ingestion - I think you are right here. The article does say that damage can be caused this way and can also be responsible for the noise, and because this particular pump had a leak, this may possibly be the way air was getting in. Sucked in??? Dunno.

[g8dhe]

Yes the principle is identical as soon as the blades exceed the speed of sound in the fluid then cavitation can start to occur, it can happen in tiny pumps as well as larger ones its just easier to see in larger ones as there is more energy around and its easy to photograph! Here is a link for a motorbike engine http://crfsonly.com/forum/viewtopic.php ... cavitation drilling the pump to equalise the pressure.

[widdowson2008]

Very interesting article here especially about "air ingestion" now if there was an air in the system it strikes me that it likely might make it to the pump, also vaporisation could be a factor given that if the pressure in the cooling system dropped (boiled over and opened the 1.1 Bar vent) then the water would vaporise!

Going back to Geoffs link (above), one line in the article is (and I quote):
Cavitation means that cavities or bubbles are forming in the liquid that we're pumping. These cavities form at the low pressure or suction side of the pump, causing several things to happen all at once:

The cavities or bubbles will collapse when they pass into the higher regions of pressure, causing noise, vibration, and damage to many of the components.

Applying this to what we know of the history of this particular pump, can we say this is a possible (probable) scenario?
HISTORY OF EVENTS
Driving along when suddenly there is a rattling noise which lasts for about 30 seconds, then stops. During the rattle, the temperature gauge shoots up, then shortly after the rattling stops returns to normal.
We know this Bongo was leaking coolant, so what would happen if the pump were to 'be temporarily starved of coolant' for 30 seconds? Would it rattle? and then, when the flow is returned, things go back to normal.
Also, because there is a temporary disruption to coolant flow, heat is NOT being removed from the head, hence the temperature rise, and subsequently drops back to normal when the flow is returned.

Sorry about the verbal D. Just trying to piece it all together and make some sense of it.

[g8dhe]

That makes a lot of sense to me, I reckon a pocket of air grew/accumulated which then passed around the system, as it passed around the "rattling" noise occurred either from boiling water itself or its presence in the pump, once it had reached the expansion chamber then it all settled down again for a while.

[widdowson2008]

Daft question. What is the purpose of this hole? There is also another one on the opposite side.
Gonna keep asking these daft questions 'till I ubderstand things.

[g8dhe]

Does it lead into the bearing bore? Perhaps its between the packing washer and the support bearing to allow any water that gets past the packing washer to exit before it gets into the actual support bearing and causes problems ?