Water pump impeller blades
 

Seems to be a rash of water pump failures these days...

OK, got the failed pump removed (along with the engine mount, for replacement) and was hoping the impeller blades would be intact. They were...sort of:

http://i213.photobucket.com/albums/c...IMG_8445-1.jpg

http://i213.photobucket.com/albums/c...IMG_8446-1.jpg

The obvious question (with, it seems, not so obvious answers) is: How many people would worry about the small amount of the blades that's missing? I don't yet have the replacement (it's ordered), so I can't tell exactly how much is missing. Is it big enough to meet Jake's "pencil eraser" cut-off? Dunno.

How many people (especially those with specific experience in this area) would

1) disassemble the entire cooling system looking for pieces
2) figure out some way to back flush the system
3) not worry about it, and slap the new one on

Jake, I suspect you'll hit me with your well-noted 'doom and gloom' response (no offense!), but level with me here...As a former Marine, you're obviously something of a gambling man...how much of a gamble we lookin' at here, going with Option 3?

If the consensus is to do Option 1 or 2, is this something a novice mechanic (but getting more experienced all the time :) ) working in a garage, with jack stands and a decent set of tools could hope to pull off?

Hi Doug - looks like your preventative maintenance is keeping you busy.
As to the damaged impeller, does the damage look like an actual breakage or erosion of the plastic - difficult to see from here. How many miles /years has the pump done? I bet you were losing 25% of your coolant flow looking at the impeller vanes......

If its erosion, there shouldn't be a problem, but if bits have actually snapped off, then the debris could still be in the system. The first place I would look ('cos its easy) is in the thermostat housing to see if the thermostat has stopped the damaged bits from circulating. I think Jeff (JFP in PA) has suggested in the past to "back flush" the system to make sure any loose bits are flushed out before bolting back together - how difficult this is I'm not sure but its probably easier and cheaper than having a coolant blockage in the cylinder heads.

I'm sure one of the professionals with more experience than me will chime in with some good advice...

Try doing a reverse flush and see if any of the pieces come floating out. The thermostat will have to come out and then use (if possible) a flush nozzle. Good chance is you'll recover your missing plastic. :cheers:

FWIF when I replaced mine a couple of weekends ago, my faile pump looked similar to yours, maybe just a little bit less impeller damage. Mine started to leak and then I got some slight chirping noise before i shut it down after about a 2 mile drive home.

I didn't even take a close look at the impeller until after I got the new one back in. No bits in the old coolant and I didn't back flush.

If I had to do it again, I would back flush, espacially the the engine a couple of times. But I don't know what the procedure is.

As to your question, How would you distinguish between "actual breakage or erosion"? The exposed edges (where the small amount of plastic has disappeared) are roughened---don't know if that tells us anything. The optimist in me says that erosion would do that, that if the pieces suddenly were snapped of they'd leave an irregular but smooth edge. Does that make sense?

I did take off the thermostat, and saw no parts in or around it, or the pump.

I'm not really sure about how to go about back-flushing the system. If anybody knows of (or wants to create---your good deed for the week!) a DIY, I'd be all ears.

I assume it's the original pump. I'm the second owner. Car has 57K miles; got it in 2005 with 19K miles.

quick cooling system primer:

water is ALWAYS circulating through the engine, regardless of whether the thermostat is open. to properly flush the block, remove the water pump and force fluid into the CENTER hole behind the water pump. this reverse flow fluid through the block first, then the heads, & then back out through the OUTER two holes behind the water pump.

when the thermostat does open, flow is FROM the block TO the radiators THROUGH the thermostat (true on all cars). water returns from the radiators to the engine & enters the engine on the left hand side of the car through the oil pump housing.

OK, sorry to be so dense, but I need to get specific here...

To begin with, I currently have both the water pump and the thermostat off the car. This is what it looks like:

http://i213.photobucket.com/albums/c...MG_84531-1.jpg


I've labeled the openings into the chamber where the thermostat lives.

A: The big opening over which the thermostat housing is bolted, with its gasket. One of the big hoses (either going to or returning from the radiators) attaches to it.

B: Follow the arrow; this opening goes up to the center opening of the water pump (where the impeller blades reside).

C: This is the opening over which the bottom part of the water pump unit attaches; it's got a small hose coming off it that I believe goes to the heater core and the bleeder valve.

D: This is the opening seen at the back of Opening C. It travels off to the right somewhere, I think communicating with the other big hose that makes up the circuit through the radiators. Don't know if it goes anywhere else.

As far as I can figure, the thermostat opening and closing affects only one thing: movement through the big opening A. Movement through B, C and D are not affected by the thermostat, right?

OK, to your suggestion specifically, ie to send water through the center hole of the water pump. So you're talking about fitting a hose (somehow--I have gotten some suggestions) onto Opening 1 here?:

http://i213.photobucket.com/albums/c...MG_84521-1.jpg

I'm assuming you mean do this with the thermostat on, otherwise water simply runs down through B all over my garage floor. (As far as I can tell, Opening 1 goes only that one direction...wish I had one of the flexible endoscope videos!) So, if I put my t'stat on, do I do it with the t'stat itself in the housing? Being cold, it would be closed and prevent water movement out through the big opening A. [[ And since the water pump won't be turning, I guess little/no water will be going up through B. IGNORE that previous sentence---I wasn't thinking when I wrote it: the water pump isn't installed at all while we're flushing :rolleyes: ]] So that leaves Cand D. Is that where we want water to flow, in order to flush out the block and the heads?

you want the water to go in through 1. to make this work, you will want the thermostat housing on the engine WITH the thermostat installed. you will also need to plug C/D. it would also be best if you clamp the big hose on the other side of the engine as well (goes to the radiators).

the idea is to isolate the engine itself from the radiators & heater bypasses. when you get it right, water forced into 1 will come out of 2/3 after having fully circulated through the block and heads. FYI you will need a VERY good seal, as the engine really holds a lot of water. not even sure a common garden hose will supply enough volume/pressure to shake any sediment loose.

if you have trouble sealing off a hose into 1, i think as a (slightly less effective) alternative, you could re-install the water pump & unclamp/remove the big hose from the other side of the engine. attatch a hose to the water pump (pumping into C/D in your diagram) & pump the water out the other side of the motor. you will miss some passages this way.......

Nice thread...and great pictures keep it up

OK, Insite, I'm still confused...Suppose I'm a cockroach crawling around inside that chamber we're talkin about, all warm and fuzzy about my choice of hangouts---after all, I'm kind of hidden but I've got escape routes through A, B, C and/or D. Now---you said I should bolt on the thermostat housing with the t'stat included, AND also block off both C & D. With the thermostat cold (ie closed), I, the cockroach, am not going to be able to crawl out through A, and additionally C/D have also both been blocked. That leaves B as the only way out, and that's where you want me to put the hose (actually 1, but that goes only one place: down through B). Once that's done, and the water turned on, there's no escape for either me or the water---it's a locked box with no exits. What am I missing? :confused:

frodo -

you can't see it in your photos, but there is an 'E'.......

hang on; i'll go take a photo of one.

re-reading your post, you had it labeled as D.

basically, when the thermostat is closed, water gets sucked from C & D into the wather pump inlet (1). it is then forced through 2/3 into the heads, then the block, then back through D. you want to reverse this by flowing water into D.

You da man, Kev.

How'd you get that photo???

Extra engine. :)

you know, i'm looking at these pictures now & something concerns me. when i spoke earlier about coolant flow bing from the engine to the radiator over the thermostat, it was a general comment; cars are engineered that way for a reason. FYI, a centrifugal pump like the boxster's water pump is designed to suck from the center and blow to the edge, so we can deduce direction this way.

looking at our photos, two things strike me as very odd:

1. the thermostat opens to the low pressure side of the water pump. this means that the pump IS sucking water from radiators across the thermostat. this is not common, and strikes me as incredibly stupid. the cooler water from the radiators would cause the thermostat to start to close again almost immediately. the temp the thermostat is 'seeing' is the cooler radiator water combined with some engine recirculated water. this would imply our 190deg thermostat is actually running the engine at MUCH higher temperatures.....by design. essentially, the thermostat would try to achieve a 190deg exit temp from the radiators. hmm.....

2. the second thing is that our thermostat looks like it may be two thermostats in one. it looks like the bottom of the thermostat covers 'D' in the photo & like a second spring/actuator rod opens this second 'stopper'. my GUESS is that this is an attempt to heat up the heater core / passenger cabin before any other concern. i want to drop one into a water bath to see if this is the case.....

raby's point w/ the low temp thermostat is that when they measure engine temp at multiple points on test motors, they see some areas that get really hot WAY before the OEM thermostat starts to open. this design could be a reason why.

anyone else have thoughts on this?

insite,
I think we are missing something here. I need to look at a complete cooling system diagram to get clear on this. I can hardly believe Porsche set it up so coolant water flows from rads to t-stat to motor. It makes no sense.

JFP - good diagram; pretty much sums it up.

Topless - I poked around my spare motor today; the water pump DEFINITELY pulls water past the thermostat. The TStat is downstream from the radiator. Seems a bit of a mistake to me.

Checked a vette lt1 diagram and it's the same; thermostat downstream of radiator. WTF? Makes no sense to me. What am I missing?

Btw frodo, this doesnt change the direction you want to flush the motor at the pump

Nice to have a spare, eh?


OK, I was half way through typing that question when I realized you had already anticipated it and responded (with the answer I expected!)

The other question I had was one of PRESSURE. I've been told (thank you, JFP) that too high a pressure, including that produced by a garden hose, could be a problem when flushing, especially with the radiator, heater core and oil cooler. Per suggestions from more than one source, I plan to back flush the engine and the rest of the system separately. With regard to the engine flush, the first two (radiator, heater core) wouldn't be involved I guess (though I'm wondering if I'd need to clamp off the other big hose---the one not shown in my pics, the one NOT going through the t'stat---to be sure that's the case.) That may be all moot, though, since back flushing the engine (ie through D) will still include the oil cooler.

The conclusion would then have to be that, if too high a pressure can be a problem, that would still be true regardless of whether you're doing the engine circuit or the rest of the system (radiators, etc). True?

For those who have done back flushes, have you worried about (or even known about) any potential problems with too much pressure? If so, how have you worked it so as to not exceed a "safe" pressure? If you didn't worry about it, have you had any problems?

I ask, because I had considered (considered!) using this:

http://i213.photobucket.com/albums/c...IMG_8459-1.jpg

It's a plumbing tool, for unplugging stuck drains. The attractive feature is that, when attached to a hose and water turned on, the black rubber part expands, filling whatever hole it's in. It creates a pretty tight seal. Then the water that flows actually pulses somewhat (maybe helping to stir up missing impeller blade pieces!). Without being able to measure the pressure it creates, I'm a little hesitant to use it. OTOH, unless I can incorporate some sort of pressure gauge into the system, I'm not really sure how to monitor the pressure anyway (with or without the plumber's tool).

Thoughts?

Here's some pictures of the original pump in a 2000 2.7 with 40K miles. Looks pretty good, but I'm replacing as many problem parts as possible.

This indicates that the pump is original since the gasket had to be cut:

http://i33.photobucket.com/albums/d6...t/P7020540.jpg

All blades intact and no slop in the bushing:

http://i33.photobucket.com/albums/d6...t/P7020543.jpg

Ok I gave this some thought and I think I understand why the motor is on the pressure side of the pump. It creates a higher pressure zone when picking up heat in the water passages which raises the boiling point. A few psi makes a pretty big difference (Boyle's law). Now the T-stat simply acts like an automated valve. When it opens coolant is sent to the radiators and when closed coolant returns to the water pump for recirculation through the motor.

Frodo,
I like the water jet idea a lot. The pulsing action should help to free anything that got lodged internally. As to pressure, you can get a drip system pressure regulator that will bring your hose pressure down to 15-30psi at any garden center or hardware store. Also use a ball valve so you can control the water flow and ramp it up slowly. I might put a catch screen at the other end and take inventory of everything that comes out. You can count the pieces and see if you got everything.

Is the water pump able to be swapped without lowering the engine at all?

Is it a one-man job? I always get pretty paranoid when attempting a job that requires the car to be on jack stands.

I did mine yesterday with the rear wheels on ramps, no engine lowering. But the back of the car does need to be up in the air.

I didn't need to remove the thermostat hose either. The pump can come out through the bulkhead access door. I also didn't replace all my coolant, it was only a couple of years old so I just replaced the 2 gallons that drained from the pump.

There are alot of jobs that require the car to be on jack stands. Limiting yourself to jobs with the wheels on keeps you from doing alot of fairly easy jobs.

I know... working on acquiring a lift, but the shipping/hauling home aspect is quite a hurdle.

I had an "experience" once when lowering my Blazer way back when... car on jack stands, lowering rear axle, and *SNAP* whole thing lowered on me... scary.

I'm also nervous because the jack stand area is like a donut, but the top of the jackstands is a "claw"... (they need some kind of standard here). where do y'all put the floor jack so as not to take up the jack stand spot?

EDIT: I have had the rear on ramps before and have had been able to "one tire at a time" a few jobs (spark plugs, brake rotors/pads), but thinking of tackling the motor mount / water pump combo as preventative maintenance.

Still seems weird to me. As Insite points out, why would you want a system where, when the water (coolant) circulating around the engine gets hot enough to need the radiator action for removing some heat, you then start pulling relatively cool water from the radiator part of the system across the t'stat, presumably causing it to close back down? Sorta defies logic.

Not familiar with your 'drip system pressure regulator' but sounds like it might be worth looking into. As to the valve, you don't think that could be controlled well enough with an assistant slowly opening the spigot the hose is attached to? I'm no engineer---probably already abundantly clear---so I don't really know much about characteristics of the various different kinds of valves.

I had already planned on doing the catch screen thing.


Quote:

Is the water pump able to be swapped without lowering the engine at all?

Originally Posted by stateofidleness.

I agree with blue, it is doable as a job on its own. Since I was doing the motor mounts at the same time, I think I did raise/lower the engine some when trying to get to the bolts holding the water pump in place. Made it a little easier, but I'm pretty sure I could have done it without doing that. I also worked from inside the car through the access panel behind the seats to get the top bolts. How old is your motor mount? As Pedro (and others) have pointed out, these jobs kind of go hand-in-hand. Doing one kinda makes the other easier.



QUOTE:

Is it a one-man job? I always get pretty paranoid when attempting a job that requires the car to be on jack stands.

Originally Posted by stateofidleness.

Geez, I know what you mean. I was helping my kid replace a fuel pump in a 1999 Mercury Marquis (his gf's car---I call it 'the starship'), and we had to remove the fuel tank (since that's where the fuel pump lives). I was nervous as hell gettin' underneath this beast of a car sitting on jack stands. I've got lots of lumber layin' around that I'll stack up under strategic support points in case something gives way. If you're removing a wheel, you can also slide that underneath the car. The trick is to make it safe without getting so much stuff under there that you have limited access to get you under there.

As far as the 'one man job' question: I've done everything (so far) by myself.


QUOTE:

I'm also nervous because the jack stand area is like a donut, but the top of the jackstands is a "claw"... (they need some kind of standard here). where do y'all put the floor jack so as not to take up the jack stand spot?

Originally Posted by stateofidleness

Do a Search on "jack stands"---there's all kinds of recommendations and good advice out there. This is how I do mine...

http://986forum.com/forums/boxster-general-discussions/22250-jacking-boxster.html?highlight=jack+stand

...but there's lots of other techniques that can be used. With my system, BTW, note that I don't get under the car with just the jack/4x4 holding it up. One, because there's a small chance the hunk of 4x4 could suddenly crack and, two, I just don't trust a jack that much. I think others would agree with that.

topless -

you're definitely correct that the pumps are designed to apply pressure into the engine; this is normal. it's still possible (and usual) to do this, but to put the thermostat on the other side of the engine at the large outlet. this way, pressure is into the engine, but the thermostat is placed in hot flow rather than cool flow. bottom line: the thermostat is usually (i thought ALWAYS) at the coolant EXIT of the engine, not the entrance.

frodo -

don't worry about pressure unless you have an actual means of pressurizing your system. the pressure in your engine can't get above the water pressure from your hose, which is not very high.

you asked what COULD happen if the pressure got too high. the answer is that you would pop a freeze plug out of the water jacket. these are pressure relief plugs designed to pop out if the coolant/water freezes & starts to expand.

What is the nature of the rear motor mounts? Can and damage occur by lowering the engine at the front? How much rotation is allowable so as not to damage the read mounts if any at all. Its hard to see in there without a hoist

Don't really know for sure, but judging by the lack of any mention of such a problem in the 2 or 3 DIYs I've read on this, apparently not. I never raised or lowered the engine more than 2-3" either way...wouldn't think that would be a problem.

Well, finally got an opportunity to do some flushing. Don't know if this was the ideal set-up, but this is how I did it:

http://i213.photobucket.com/albums/c...IMG_8522-1.jpg

This was to flush the engine half of the system. When I first flushed, I left the pressure gauge off, and just let some water come out of that opening. After a minute or two, turned off the water and put the pressure gauge where you see it here. (It was just this little cheapo made in China thing---all I could find locally. Got some rubber stoppers, drilled a hole through one and screwed the gauge into it.)

To flush the radiator part of the circuit, I put the hose (with the plumber attachment) into the big hose that normally would attach where the t'stat is.

Ran MANY gallons of water through both circuits and you know what? I got squat. I sieved every ounce of water and saw, essentially, nothing. (Did see two tiny pieces of something---much smaller than the head of a match---that might have been miniscule pieces of impeller blade. It was hard to tell, they were so small.) Funny thing is, I never got the pressure gauge to register anything above zero---pointer seemed pegged there, never moving once.

Don't really remember much fluid dynamics, but I wondered if, with the water moving past the gauge with a certain amount of speed, it created a relative low-pressure area. Like air moving over the top of a wing, or like when someone's smoking in a car and opens the window---the smoke rushes out towards the low pressure zone (ie outside). Dunno. I crudely tested the gauge at one point: held the hose directly against the opening in the stopper and turned it on. Lots of leakage, but I could get the gauge up to about 30-35 psi doing this.

So I don't know. Maybe I wimped out on how much water pressure I was putting through? Seemed like it was a fair amount, but with the gauge telling me NOTHING, I wasn't sure how far I should push it.

Emailed a guy that I've worked with before, works at this big shop that specializes in pcars. I've seen EVERYTHING imaginable there, Porsche-wise, including many track vehicles...they always have at least 6-8 Porsches at any given time. Anyway, he emailed back about their experiences with water pumps. Some excerpts:

We have done probobly 25-30 water pumps on Boxsters and a few 996's. I have yet to see one come out with the impellers intact, the bearings fail and the the impeller hits the block and breaks

The very first one we did (had to be 6 years ago) the impeller was gone, all of it!. We pulled the radiators, all the hoses, back flushed the system. Never found any of it! Put it all back together and sent it down the road, he still has the car with no problems.

We dont even bother flushing them now, it is never an issue.

I would...say you have nothing to worry about.

I've had several other knowledgeable sources give me the same advice.

So, while it's clear that some people have seen problems with this (JR), it seems to be relatively rare. In a perfect world I'd have a 3 car garage with a lift, two reliable back-up vehicles (instead of one---a '96 Camry with 195k miles), and lots of time on my hands. As it is, I really don't see me tearin' into this, looking in every nook and cranny trying to find 1/4 gram of plastic. Sooooo, unless I come up with any other ideas, I'm puttin' it back together and goin' with it. Mine will be the test case car, eh? Life...it's a crap shoot, right? You get lucky or you don't. Time will tell....

If you have missing impeller blades and they were not found during the flush, then you still have missing impeller blades- they do not disappear.

When the blades become lodged into capillaries within the head is when we see issues and it takes more than water pressure to remove them as heat and engine vibration helped to get them there.

This is why changing the pump electively before any failure is experienced is so beneficial. That means changing the pump every 3 years, no matter the mileage.

If you have missing impeller blades the only way to remove them may be while the head is on our milling machine having a crack repaired.. Digging these out during crack repairs is common practice, its what taught us the true reason for most unexplained head cracks from engines that never had overheated.

Thanks, Jake. I knew that.