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On Thursday, in the rain, I stepped out of my car at work to the smell of coolant. A quick look at the back of my car and the steam cloud coming from the engine cover told me I was screwed. I'm very happy to report that here, Monday AM, I'm all back together and riding cooler. 

Two signs your water pump is going: bearing squeal on start  up/ while running & the accessory belt had "walked" to the rear of the idler pulley nearest the water pump.

The failure was the water pump bearing. I was  very surprised the pump had not leaked earlier and that I had not smelled coolant. The bearing was completely toast, having more than 3mm play all around. When I pulled the pump, the plastic impeller fins had all the corners broken off, and you could see on the block where it had been "polished" by the impeller. A metal impeller would have been disastrous!!

I replaced the pump with a Peirburg sourced from eBay @ $234 shipped w/ gasket. While I was at it, I also replaced the T-stat  with a MotoRad  160 degree unit (also eBay, $60). This AM on the 1-hr drive to work temps never got above 185, and stayed at 178 on the highway. Outside  temps were mid 50's. On the old t-stat temps were typically 6-10 degrees warmer. I'll report later about how she does in traffic.

Coolant police, please read no further!!

 I  replaced the coolant with Prestone Dex-Cool 50/50 and a  bottle of  water wetter. This was done after 4 flushes with distilled water, run and drained under pressure from my air compressor. About 5 years ago I had to replace the pump on my Boxster and I used the same mix & procedure. She's still running fine. 

Thanks to all who have posted water pump DIY's. The job went as described, with only one bolt being a real PITA. Honestly, all of the flushing/burping took longer than replacing the pump and t-stat. 

  

 

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Why a Peirburg pump? Should have used OE Porsche ($299 with gasket). And you don't need Water Wetter in a street car, especially a street car with coolant. Water Wetter is for track cars (for easier clean-up by track personnel after dropping fluids on the track and safer for your track buddies) that run straight distilled water, no coolant.

 

Good job on the DIY!

Edited by White987S
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Make sure that all of the broken impeller blades are accounted for, because they can get lodged in the coolant passageways and create cracked heads if you're not careful

 

Not entirely sure, but shouldn't one flush the entire cooling system by two different directions just to maximize the chances that all foreign parts come out from those small cooling channels? This is actually quite easy to do as the big coolant tubes are easily accessible underneath the car.

 

Would hate to see myself that much later some cyl is running a lot hotter than the others.

 

Perhaps more experienced persons should comment to this.

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Make sure that all of the broken impeller blades are accounted for, because they can get lodged in the coolant passageways and create cracked heads if you're not careful

 

Not entirely sure, but shouldn't one flush the entire cooling system by two different directions just to maximize the chances that all foreign parts come out from those small cooling channels? This is actually quite easy to do as the big coolant tubes are easily accessible underneath the car.

 

Would hate to see myself that much later some cyl is running a lot hotter than the others.

 

Perhaps more experienced persons should comment to this.

 

 

I would suggest flushing it backwards to normal flow to try and dislodge any bits that have found a home.  You should be able to recover a lot of the impeller bits, but you will never get all of them.

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I flushed the system 4 times with distilled water, and by the fourth it was running clear. I've got an old coolant tank cap that I drilled a hole in, and I use this to plumb in my air compressor to push the last of the fluid out of the system. It's surprising how much can be pushed out after the system seems to be finished draining.

 

Anyway, here's how things look after a couple  of driving days. On the interstate @ 71mph, temps stay between 178-180. Outside temps have been anywhere between 38-75. Before, highway coolant temps were 185-195. In traffic, temps have climbed as high as 213, but that's it. Before, temps were going as high as 223. Now, it also seems that temps fall more rapidly once the car gets moving and out of traffic. From 213, the temp falls pretty quickly down to 200, then continues at a slower pace down to the 178-180 range. 

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I flushed the system 4 times with distilled water, and by the fourth it was running clear. I've got an old coolant tank cap that I drilled a hole in, and I use this to plumb in my air compressor to push the last of the fluid out of the system. It's surprising how much can be pushed out after the system seems to be finished draining.

 

Be careful using air pressure, these systems are only designed to operate at pressure just below 20 PSIG, and it is very easy to go way over that using compressed air.  We have had customer's blow the side tanks off the front radiators doing this.

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 When I pulled the pump, the plastic impeller fins had all the corners broken off, and you could see on the block where it had been "polished" by the impeller. A metal impeller would have been disastrous!!

 

See my nearby story on oil - coolant intermix. The culprit that was found lodged near my cracked head was a piece of plastic water pump impeller. Evidently, the plastic impellers are no less a threat than the metal ones.

 

Jake Raby says he strongly advises changing these water pumps prospectively ... every 2 - 3 years rather than waiting for one to fail and taking the chance of this exact scenario occurring. I know I certainly will from this time forward.

 

(update on my repair) Engine running strong. Still flushing due to difficulty of breaking oil loose from cooling system due to cold wx preventing engine from reaching the higher end of its operating temp range. Tomorrow they will put it on they dyno and try for 200 deg. Jake says its like trying to wash greasy dishes with cold water.

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Thanks for all of the input. How do you go about backflushing the system? I can see using a hose and tap water, but do you follow that with a couple of "regular" flushes with distiller water?? If you are using a hose, where's the best place to open the system and what becomes the drain point?

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Thanks for all of the input. How do you go about backflushing the system? I can see using a hose and tap water, but do you follow that with a couple of "regular" flushes with distiller water?? If you are using a hose, where's the best place to open the system and what becomes the drain point?

 

You are going have to fabricate some bits to do this; on a Porsche, the water normally flows from the radiators towards the engine thermostat housing, so you want to disconnect the hose coming off the thermostat housing and make up some fittings to connect a hose into the car's hose.  Then remove the thermostat and housing assembly.  Now run the water into the hose, thru the front radiators, back to the water  pump and engine, and out the thermostat housing.  You want to be able to "throttle' the water pressure (house systems can have as much as 90 PSIG water pressure, the car is only rated for 20 PSIG and you can damage some very expensive parts if you over pressure the car).  We do this with a system we built that uses a pump to push water from a heated reservoir into the car at 20 PSIG, thru the system and back into the reservoir thru a stainless filtering screen to catch the bits.  You don't need to be that fancy, but I think you get an idea what is involved.

 

coolant_flow.png

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  • 4 weeks later...

Since I was scared to death that some little piece of impeller was stuck in my engine, I cobbled together a tool for backflushing the coolant system:post-6798-0-80854600-1417032253_thumb.jppost-6798-0-74674900-1417032275_thumb.jp

After draining the coolant and backflushing until the water ran clear and tasted great, I am happy to report that no impeller pieces showed up in the drainage. Better safe than sorry. Thanks for the advice and information.

Edited by jaekormtb
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