Water pump shattered? Need help.
 

I've never seen this before. Went to the track two days ago and had no issues (kept an eye on coolant temps with an actual gauge), then yesterday I come home from work and notice coolant all over the ground. Pop the hood, and it was coming from my waterpump. No big deal, ordered a mazmart for next day shipping. Well today I decided to take my old waterpump off. What the hell happened inside?! I hope it's safe to install my new waterpump on here! I don't see anything sticking out or any reason it should be unsafe, but what would cause this? I was running 75% distilled water 25% coolant and a bottle of royal purple ice.
https://cimg9.ibsrv.net/gimg/www.rx8...1af257f188.jpg


https://cimg8.ibsrv.net/gimg/www.rx8...b83aa308b1.jpg

I'm missing it. What's shattered on it? I see some chatter marks like it was wobbling and hitting the plate.

Chatter marks may be a better word. It just reminded me of something that may have shattered but not completely busted.

That looks like corrosion damage to me. I am not sure I would reuse that front cover and I would have gone with an OEM replacement pump, the Mazmart pump is not worth the extra $$$$. Is the pump shaft really wobbly?

There doesn't seem to be any play in the shaft. I guess sitting around 9k for a total of an hour could have caused extra stress. Hmm. My plan is to just do a complete drain and fill incase anything is floating around, and hope the area it bolts to is ok :/

I track my car a decent amount, so I figured I would upgrade since it needed replaced. Wasn't expecting the damage inside.

Did you find any debris? That looks pitted to me...

skip the fancy colored snake oil additive

pitting from corrosion and/or cavitation

but if it was corrosion the heater coil etc. would have likely gone out well before then

likely not just a casting issue since it's on both the pump and front housing

cavitation seems like the only conclusion given it exists on both parts right where impeller is, but it would have to be really severe for that to happen like someone had an overdrive pulley on it or something

a bit baffling ...

I didn't have a pulley and the last owner was some lady.

At the end of the day I'm just hoping a new pump will be safe for now :(

That's a new one! The pitting you're seeing in the housing is the damage that cavitation can cause. It happens when a liquid in a very tiny location is turned into a vapor bubble for a short period of time by extremely low pressure (usually behind the impeller blade). The vapor bubbles then collapse with such an intense force per unit area to shatter metals into tiny bits.

https://upload.wikimedia.org/wikiped..._implosion.png

The damage to the front cover shouldn't effect the pump's flow too severely since the innermost portion of that inlet ring is still intact, but I wouldn't re-use it in a rebuild if you ever have to do one of those. This is one of the few situations where the Mazmart pump would be beneficial or even necessary, since it significantly reduces cavitation (at the expense of flow). I don't know why it would be cavitating this much other than staying at really high RPMs for minutes at a time, or something as abstract as the coolant mixture having a lower vapor pressure than normal mixtures.

As long as it doesn't progress any further it shouldn't cause issues, and the Mazmart pump should keep that from happening (this is the only time I'll ever suggest that pump).

If you can figure out why its cavitating so much it would be better to solve that and go OEM, but the MM pump would be an ok "catch all" solution in the end.

Well I race my car more often then most. Two days ago I was on the track for an hour and it was 93* out. Sitting at 7-9k that long with those hot days make me wonder if I should have done a MM waterpump sooner. Just glad it went at home and not at the track!

I have access to a lift and will just fill it up at home with the new pump and drain and fill it from the radiator and block the next morning incase there is any metal floating around now.

Have you modified the return from the radiator to the engine? You want to minimize the restriction at the inlet of the pump, and the return line to help prevent cavitation.

I have not. I've don't a few cooling mods; aluminum undertray, larger vents behind the oil coolers, and was running 75ish water 25 coolant with 10w40 RP oil, idemitsu two stroke, RE-Amemiya intake with no undertray, new foam around the radiator, blah blah blah.

Never heard of what you're talking about.

I've never seen cavitation on a car water pump, but on a regular HVAC pump sure. Its usually from too low NPSH (the head pressure required to overcome the inlet fitting of the volute, basically causing the suction to create the vapor in the above diagram. If you haven't restricted your hoses, perhaps one got hot and collapsed on the track but is now back to normal shape. If you want to reduce suction head of the pump trim the impeller down in dia, but I'm not recommending you reduce cooling flow by doing so. I'm not familiar with the MM pump, I'm new to Mazdas.

Hmm maybe it's time to upgrade my hoses? I always hear bad about aftermarket pulleys for street driven Rx8s, but do you guys think it would help with my case?

Could you explain what you're talking about? And decreasing the inlet restriction won't help much because on this type of impelller cavitation occurs in a very localized area at the edges of the trailing side of the impeller, and given enough time it will occur no-matter the inlet/outlet pressure differential.

I suppose somebody could be dumb enough to put acid or some other kind of chemical in there trying to 'clean' the system

I can't see factory components having that severe of cavitation under any circumstance

We'll likely never know why ...

You don't need special anything. OE or OE replacement is fine.



.

I suffered with cavitation on the stock Mazda pump on my race engine - I bolted the S2 pump on and slowed it down with a bigger pulley (as well as enlarging the size of the radiator outlet) to get rid of it, started at about 6500-7000rpm upwards.

Did you suffer from similar damage as I?

Nowhere near that bad, no, but then our car gets stripped every few hundred miles :yelrotflm
It showed up on the pressure gauges on the pump inlet when we were trying to get to the bottom of a cooling issue though, we had a bit of pitting just starting so it was obvious what was causing the cooling issue then.

Ah thank you very much for your input!

Are you using the stock water pump in your race car, or?

Dude, this is a non issue. Whatever happened on your engine is very unique and unusual. Stop fretting over needing special parts. I's your money to burn if you want. Just hate to see you get caught up in needless BS.

All I bought was a MM waterpump lol. I'm just asking if it's normal, and if it can be prevented.