RB25 Water pump failure, seen before?

[joshg123]

Hi all

I carried out a timing belt/water pump on a RB25 s1 in a C35 laurel today, everything went well, no hiccups and genuine parts were used. We were doing this because the old water pump was leaking, and the owner did not have a t-belt history so logic is to put a new belt on. Genuine nissan belt, and Nissan N1 w/pump were used.

Put it all back together, filled with coolant and bled cooling system. Got owner to take it for a drive as we had some boost control issues to work out, went up and down the street and around the block (approx 2k), on 0.8 bar was all good. Pulled it in, rechecked and bled the cooling system again. Replumbed some vaccumm hoses to get correct boost. And sent him for another road test.

Got it warm, and went down my road, gated 2nd gear at 1.5 bar ( which is straight to limiter with wheelspin). And upon decceleration the water pump completley sheared off. Sending the viscous hub fan through the radiator and sending fan blades flying.

Rolled it back into my workshop, first thing i checked was to see if the viscous hub fan had locked solid, nope, resistance but not locked. The way it should be for the conditions. Fan wasnt hitting anything as i would have heard it before sending him on the road test. And Belt was correctly tensioned.

Has anyone else seen this, and if so what did you determine the cause? I dont really want to start claiming warranty if its a vehicle issue, or an issue when running big turbos and the accelleration rates of the pump are a common problem. Vehicle is running Apexi RX6 highmount and all the neccecary bolt ons and plug ins to make it work. Is rather fast.

All i can put it down to is a poor casting.

Here are some photos of what im trying to explain, note the water pump impeller blades were damaged when the pump cracked, we can see big witness marks on the outside of the pump housing.


http://i6.photobucket.com/albums/y220/joshg123/IMG_0022.jpg

http://i6.photobucket.com/albums/y220/joshg123/IMG_0024.jpg

http://i6.photobucket.com/albums/y220/joshg123/IMG_0025.jpg

http://i6.photobucket.com/albums/y220/joshg123/IMG_0023.jpg
Cheers

Josh

[Joe]

FARKKKKK!

That would have made a crazy ass noise... did the water pump shaft seize up maybe, grabbing on the housing and smashing it straight off like that?

[joshg123]

No noises untill it happened, all that was heard was a loud clunk then it obviously threw the belt off, so no noises after that.

[31-EVO]

How tight was the belt :P
I've seen something similiar, but on a Commodore without the viscous fan, sheered the front of the pump off completely.

[phil_drift]

yep crazy stuff, oh its a series 2 RB25 too Josh, not that should make much of a difference i guess

[Alt_F4]

Damn... decent effort!

[joshg123]

How tight was the belt :P
I've seen something similiar, but on a Commodore without the viscous fan, sheered the front of the pump off completely.

Early commodores had a habit of their viscous hub fan locking and ripping their water pumps out. Hence the first thing i checked.

[Shauno]

WHAT THE!?!?!?!?!? Man ive done some WP warranties but nothing like that! I'd say try and claim it but chances are they will say it were an overtightening issue...

[SimonR32]

why a n1 water pump?!?

not needed for a street rb25

[joshg123]

Not a street rb25, not going to see low revs to often.

Overtightening a belt would result in premature bearing failure, not this.

[Scradly]

Possible that the viscous hub is out of balance causing massive vibration making the pump shit itself.
Had one on do it a ca18.

[Milhouse]

would the shaved fins on the fan cause an imbalance ?

then again ive seen loads of skylines with the fins chopped down to accomodate cooler pipes....

[AD4M]

intercooler pipe cross over the top of the fan?

[mitchy]

i assume it was all bolted together with nothing between pump/pulley/fan, ie running true?

all i can think of is massive balance issues as she came hard on boost like others have said

[Milhouse]

yeah adam, his pipe has 3-4cm of clearance tho, unlikely the motor moved enough to push the pipe into the fan

had 5-10 minutes of warming up with revving up and down of the engine with no issue mitch, even drove it around the block to check and came back

it was the 2nd drive with the boost controller hooked up when the damage occured.

[phil_drift]

car has cross over cooler pipes, and the fan had no blades missing when it was running fine. there was no clearance issues with the fan and the cooler pipe when we put it all back together. on the first test drive the car was only boosting to 0.8bar but still taken close to the rev limiter. came in, double checked everything, raised to 1.5bar and bang, off she goes

[AD4M]

I would check engine mounts

[Brockas]

Pics have stopped working.

Rehost?

[mitchy]

work fine for me, even with a forced refresh?

[Brockas]

My bad, better now :)

[Lump]

I would check engine mounts
+1

[Milhouse]

engine mount bolts are tight, and motor has very little movement

[AD4M]

they shear in the rubber, easiest way to check is get a engine crane and lift the motor while its still bolted to the mounts and chasis.

I've had both mounts seperate, couldnt tell by free reving the motor but once you've got load on the driveline on the street its a tottaly different story

[Lump]

going by what i can see in the fotos, the casting quality looks fine.
put a new pump on without a fan (temporarliy) & see what happens
i still rekon its mount related

[joshg123]

Yeh im doubting its a casting failure also, but its all that makes sense.

Just got the fan out of the boot and double checked, W/P bearing is free and spins smooth, viscous hub fan is still smooth.

Adam, the amount the motor would have had to move is a bit large, there is a good 3 inches between cooler pipe and fan blades, youd feel the engine mounts when driving and engaging drive as it wants to tilt. And it would have to rise to hit the pipe, tilting side to side there is plenty of clearance.

Im changing my tune to viscous unit out of balance, it had yellow paint marks and i lined them back up though. It was tricky to get the fan from the old water pump, i just cleaned the rust out of the viscous unit and refitted.

[Lump]

if there was a flaw or porosity in the castng it would be pretty obvious, so i rekon you can discount that straight away.

one thing that confuses me a bit is you said it went bang on decel?
which means fan/motor would have been going away from top cooler pipe (ie, down)

viscous coupling out of balance, nah. that damage is way too severe & sudden for that imo
how much clearance did the fan have if it did move down on decel?

[e30_power]

damn... that went KA-BOOM!

[joshg123]

I went back over everything today and i did find something.

I was checking for anything that could cause it to be out of balance or allignment. Its a interferance fit for the viscous unit onto the water pump, so up and down (like a wheel) out of balance i could discount as the problem.

I did find a tiny little scratch on the water pump pulley, that when i put it together i didnt think would be a problem, checked it still assembled and the fan unit, allthough tight i could get a 10thou feeler gauge between the fan and water pump pulley. Couldnt get 15thou, only 10 and i couldnt see daylight through it. And it was only in a 2cm section where this scratch was. Dont know if this was the cause, i buffed the scratch out and it sits dead flat now.

Perhaps a stupid oversight on my part, but as the pump went down and felt it tighten up by hand, and could see the viscous unit and the pump pulley had met solid, didnt even take it into consideration..

Dunno, 10 thou on a 2cm patch enough to cause this much damage?

[SLEEKA]

+1 on physical collison

Big revs, big load, sudden change to decel, engine will move a shit load (especially with dodgy/soft mounts), something got in its way and stop the fan immediately resulting in it snapping the pump off.

The only thing i dont get is why didnt it do it to the last pump?

EDIT: or it could be as above ^^^ :D

[reNEGade]

Yeh, a tiny crack/scratch is enough to snap something brittle like a cast water pump.

[Lump]

lol, alloy is not known to be brittle dude.
also the tiny scratch, causing slight misalignment (if im reading it right) would have sfa effect. Maybe it could cause fatigue, but not in the time frame stated here imo

[ovaxitd]

i doubt it could have moved enough for it to smash normally the fan will take a fair bit against it and make a wicked noise b4 it did something like that.... i would be speakin to nissan for warranty..... how the fuck can someone stuff up a water pump install... even graylands nut case would get it right... parts prob imo...