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Replacing water pump on Porsche 986 Boxster S

November 28, 2015

One night some weeks ago, my wife called to say that on the way home from work her Porsche Boxster S made a rattling sound, then all the engine lights came on the dash and it was “smoking”.

I told her to immediately pull over and asked where she was.  I drove out to pick up the car in my rollback truck and found it still venting steam and coolant out the right side of the car almost an hour after her call.  The right rear fender was covered with greasy antifreeze residue and the underside of the chassis continued to drip on me as I loaded the car on the truck and secured it to the deck.

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I began work on the project the next day and was glad to see the car still started up and moved about normally as I drove it into the shop.   Up on the lift with the multitude of plastic covers removed, I found what I expected, the serpentine belt derailed and the water pump pulley and shaft flopping about.  Numerous ball and roller bearings fell out as I removed the covers.

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I removed the water pump and found the plastic impeller completely destroyed – only a few pieces remained.  I was concerned that perhaps some of these pieces might have circulated, along with pieces of seal and bearing race and might clog up the radiators, or circulate around and damage the new pump I was getting ready to install.

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I removed the thermostat and found some more pieces behind it.  I recommend this step to others who may find themselves in the same situation.

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I replaced the thermostat and water pump, and accomplished this from under car with a bit of effort.  Note that the bolts are different lengths, so lay them out on your work surface using the old pump or gasket as a keeper for each bolt so you can be to put them back in the correct locations.

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I found some round rubber plugs at the hardware store and bored one out so that a garden hose could be threaded into it and it placed and clamped (with the hose clamp) first into one of the radiator hoses leading to the front of the car, and then the other.  With this process I was able to backflush the system in both directions until clean, clear water flowed out the opposite side.

Flushing water through the heater hose seemed to do the best job of pushing clean water through the block and flushing residual coolant and small parts out of the thermostat and water pump cavities.

To install the new serpentine belt, you need to access the front of the engine through the passenger compartment.

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The instructions call for removal of the passenger seat – no need to do this. Simply slide both seats forward and then fold the seat backs forward.

There are four plastic round retainers that snap onto threaded metal pins that retain the carpet and molded foam on the rear bulkhead.  You get to these by finding the seam in the carpet just below the sliding plastic compartment doors behind the seats.  Reach into the seam and pry it open.  You should be able to see the round black plastic retainers.

After the carpet is removed,  there is an insulated sheet metal cover retained with a number of 10mm bolts around the perimeter.  This is easily removed to access the front of the engine.  This is a good opportunity to check the torque on the upper water pump bolts and install the belt.  Check the bearings in the other pulleys and rollers.

To this point, I had no trouble.  I refilled the system, but noted that I was only able to put in a bit less than 2 gals of the rated 5 gal capacity.  I assumed that running the engine with the coolant tank open would circulate the coolant and free any trapped air.  Not the case!

After running the engine for 5 mins, the radiator hose was hot at the water pump and perhaps warm half way to the front of the car, but the rest of the lines were stone cold.

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The heat was only from convection, not proper circulation.  After a few more mins of engine operation, even though the temp gauge displayed 180 degrees, the over temp red light came on and began to blink.

I tried a number of things to clear out the air block and it was time to consult the great and wise Google.  This revealed a number of threads in Porsche forums on this topic and solutions ranged from a tedious series of drive and refill cycles, to opening an air vent to allow proper filling.

This mysterious air vent was described as being in close proximity to the coolant fill port in the rear compartment.  Here is what I found in our car – no vent evident.

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Was this only on some model years?  Did the location vary?   I tried my same search on google for “Porsche boxster coolant vent”, but selected “images” for the results and then found the vent shown.  Looking carefully, there is a thin plastic cover plate that can be removed by removing all the fill caps for coolant and oil, and prying along the edges.  With this cover removed, the vent is revealed!

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Flip up the metal ring as show below.

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This opens the vent and the coolant level immediately begins to drop in the coolant tank and you can now pour in the full capacity , or nearly so.   Following this procedure, coolant properly circulated and both lines became warm on either side of the car (checking the hoses in the front fenders.   After driving the car one or two miles and letting it cool, I was able to top off the coolant.  One more top off may be required after an extended drive.

Overall, I found the information contained in a particular subscription based mechanic’s reference tool to be somewhat helpful, but incomplete as no clear explanation for the vent procedure was provided.   Some steps, like seat removal are clearly not required.   The value of the collective experience of many people captured in forum discussions, blog posts, and photos, and revealed through Google or other search engines proved more valuable in the end.

 

 

 

 

 

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