Water pump impeller blades

[Frodo]

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?

[insite]

frodo -

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

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

[insite]

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.

[Frodo]

You da man, Kev.

How'd you get that photo???

[insite]

Extra engine.

[insite]

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?

[JFP in PA]

[Topless]

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.

[Frodo]

Originally Posted by insite

Extra engine.

Nice to have a spare, eh?

Originally Posted by insite

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

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:



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?

[Paul]

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:



All blades intact and no slop in the bushing: