Water Pump and back flush questions

[gdotcvg]

Water pump - 1998, 2.5L, well maintained. I know I should have replaced proactively. But what is done is done. Time to move forward. My water pump is original and failed without warning at ~50M miles. There was no previous noise, no leakage, it just failed. There is no wobble in the bearing but there is moderate vane damage. Now, how to back flush using best approach and then replace water pump and T-stat. Current state: hoses disconnected and drained, water pump and thermostat removed. Looking for advice on best method to back flush and mitigate debris issue without disassembling the engine. I've searched the forums in detail, but there is a lot of conflicting and incomplete info. I've tried to layout a plan of action below and with expert input/corrections, will hopefully help others in the future.

My current plan
• Ordered Pierburg pump, LN 160 T-stat, gaskets, serpentine belt, oil cooler o-rings, and Porsche coolant.
• Remove oil cooler (known area of possible accumulation) and check for debris then reinstall
• Remove (if possible with engine installed) the “2-bolt” access panel on engine bank-2 transmission side (known area of possible accumulation) and reinstall. Is this possible?
• Please reference photo from Pelican Parts: Isolate and back flush the radiators by adapting hose fitting to “Orange arrow” coolant hose and flow backwards through the radiators and then out the “Green arrow” hose into bucket
• Isolate and back flush the engine by adapting hose fitting to “Green arrow” coolant inlet to engine and then out near the “Orange arrow” coolant outlet. Key questions here are: Do I need to replace the water pump and/or t-stat housing to get effective back flush or keep all open?
• How to back flush the heater core… Do I flow water in the “Red arrow” tube and then out the “Purple arrow” tubing or vise versa?
• Note: water flow will be from a low pressure, high volume centrifugal sump or pool cover type pump and all return water will be captured and filtered.

I’d appreciate any knowledgeable guidance that you can provide. Hopefully JFP will input.

[JFP in PA]

The objective should be to flush each section of the cooling loop backwards to its normal direction (below) of flow:

[Frodo]

I had the same issue in 2011. IIRC, maybe 40% of my impeller blade material disappeared downstream.

I flushed and flushed, straining every drop that came out. Never collected a single bit of the lost impeller though, other than flushing, I didn't do all the other steps that you're planning on doing. By all means, do that stuff, recover what you can. I'm sure the Jake Raby tales of 'hotspots' caused by bits of unrecovered impeller blade and the potential disasters that can occur do sometimes in fact occur.

But consider this: I talked with a tech at a local place (Steinels Autowerks in Twinsburg, OH—they do a ton of Porsche work). He told me they used to flush in such instances but rarely if ever got anything back by doing so. And they'd end up having to send the customer on their way with new pump/thermostat/coolant and the caution that problems might occur. He said they never did. To the point where, according to him, they stopped even bothering to do the flush. He said it just hadn't shown signs of being a problem.

Again, by all means, do what you're planning on doing. If nothing else, you'll know you did what you could. But Steinel's approach—while arguably cavalier—does at least indicate that in a significant number of these cases it just doesn't end up being problematic. What percentage? No idea, but it sounded like they had employed this course of action (inaction?) many times without issue. And in my case? It's been 10 years and 50k miles. I stopped losing sleep over it long ago!

[Novas1but74]

I have the same issue with my 01S; previous owner believed engine had IMS issue but turned out to my luck only being the water pump and the vain(s) lost…… car has sat since changed pump, 73,000 and change for miles…… have driven it maybe 5 miles and have not gotten around to “chasing” those elusive bits….. have searched posts too…. And have spoken to specialists in San Rafael…. They said they don’t bother chasing those bits either as “who’s going to pay for all that work for a car that does not have the value making it worth it for them”….. so they say change the pump and t-stat and move on….. no issues of customers returning to squawk they say……. Plan to doing all the things stated in this post but do believe / kind figure for piece of mind will attempt!!! Funny as the oil cooler is either the easiest place to ck or is most common to find any of those bits……. Happy to hear other experiences!!! If I could post from my phone have some great water pump pics……

[dghii]

Helped a buddy with an absolutely destroyed WP afew years ago. Impeller basically destroyed. Bearing wobbly like crazy.
We replaced its and flushed with distilled water three times. To date, All still ppgood.

[gdotcvg]

Thanks for all of the advice to date.

Progress update (slow but thorough)

• There was zero debris in examination of the oil cooler or its path or 2-bolt access panel on the back side of engine bank 2.
• Reinstalled oil cooler and rear access panel and reversed flushed through normal engine coolant outlet port (green arrow in ref. photo) without and then with t-stat installed. Water flowed out of the uninstalled water pump ports and other opening. Partial success: one significant piece and several slivers found.
• I plan one more engine flush path after I source a few more rubber plugs. This will be through the center port of the water pump cavity, with t-stat installed, bottom port in water pump cavity plugged and normal engine coolant outlet port plugged. This will force water out on the two rectangular water pump cavity openings. That will be all that I can do with the engine.
• Reversed flushed radiators extensively with zero debris
• I have a question regarding back flush of the heater core. Referencing the Pelicanparts photo. Is the coolant line near the red arrow the normal in-flow to the heater core and the purple arrow line the return?
• Found 2 new projects to tackle before I get if off of ramps.
1. Front engine mount. I ordered the insert and pads from Pelican and will press into the existing support structure. This looks to be relatively easy with the water pump and hoses disconnected.
2. I have a very slight weep from the return fuel line quick connect. I’d like to disconnect and replace the o-ring in the connector but no parts are listed or identified in the PET. Any advice on o-ring specifics; size, material (assume viton), or part number?

[gdotcvg]

All back together but having issues with getting too hot. Did final flush w/ distilled, drained all hoses, and then filled w/ Porsche mix following Bentley instructions. Drove several cycles with bleed open close to home to manage temperature but it was heading hot. Closed the bleed and again drove several cycles close to home and still getting hot but does not lose coolant.

I'm suspecting a bad new t-stat. Or could it be trapped air?

I still have the under body panel removed for access and I reached under after it cooled for ~30min and the large hose exiting the block is warm and the large hose entering the water pump is almost room temperature. Any ideas? I plan the get it warm again and then on ramps to check the large hoses again while still very warm. Once again thanks for any advice.

[JFP in PA]

Air pockets.

[gdotcvg]

Originally Posted by JFP in PA

Air pockets.

JFP. I appreciate you assistance. How would I clear air pockets? Drive cycles with bleed open or closed? Note: coolant level is not dropping in tank with bleed closed.

[pilot4fn]

Originally Posted by gdotcvg

JFP. I appreciate you assistance. How would I clear air pockets? Drive cycles with bleed open or closed? Note: coolant level is not dropping in tank with bleed closed.

Did you keep the heater on full hot setting (the fan do not need to be running full speed) to allow the coolant to fill the heater core as well?
Sounds like airpockes someplace as JFP mentioned.

[gdotcvg]

Originally Posted by pilot4fn

Did you keep the heater on full hot setting (the fan do not need to be running full speed) to allow the coolant to fill the heater core as well?
Sounds like airpockes someplace as JFP mentioned.

Yes, heat was on.

[JFP in PA]

Originally Posted by gdotcvg

JFP. I appreciate you assistance. How would I clear air pockets? Drive cycles with bleed open or closed? Note: coolant level is not dropping in tank with bleed closed.

While an atmospheric bleed can often clear the system, the correct way to get them out is to fill the system while it is under vacuum. The vacuum tool can also get air out of already manually filled systems.

[Gilles]

Originally Posted by JFP in PA

While an atmospheric bleed can often clear the system, the correct way to get them out is to fill the system while it is under vacuum. The vacuum tool can also get air out of already manually filled systems.

JFP, if you have a small air pocket can you remove it with the Airlift without having to evacuate the entire system?
Or you have to remove the entire coolant and start all over again? Thanks in advance!
.

[JFP in PA]

Originally Posted by Gilles

JFP, if you have a small air pocket can you remove it with the Airlift without having to evacuate the entire system?
Or you have to remove the entire coolant and start all over again? Thanks in advance!
.

The Airlift system does not come into contact with the coolant in the surge tank while evacuating the system; as such, you can apply vacuum slowly and allow the air pockets to bleed out of the system. Takes more time than simply filling it under vacuum, but most correction methods take longer than doing it right in the first place.

[mikeinmass]

Have I done this myself, no. But I've seen posts and what the condition of various hoses looked like after removal to drain. IMO, I'd plan on replacing all (most) of the coolant lines you'll be removing, especially given these are probably original hoses.