Coolant leak, waterpump? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Chasing down the coolant leak. A little recap for those who haven't followed: Last winter I replaced the metal coolant pipes from the back to the front (base to S version) as well as all pipes and hoses on the front of the car. Filled the car etc, now it has a leak. Funny part, not on any of the parts I replaced; The drips mainly hang where the green circle is, sometimes a few drips from the T-junction on the hose. You can't see on this pictures, but this elbow is angled down slightly, so I guess it is the gasket of this elbow and not the connection of the hose (which would drip the other direction). The hose you see is the one coming from the heater core and the expansion tank. It remained in place during my work, but the big hose towards the radiators might have pushed and jiggled it a bit. As far as I can tell now, this elbow is actually part of the waterpump, correct? I have no reason to assume an issue with the waterpump itself, no play on the shaft, spins smoothly etc. So what to do? Replace the gasket and call it a day? I don't intend to run the engine for more than another few k miles, so not in the mood to throw money on it with the future in mind haha.

I’m going to make a suggestion here, which would be to have a water pump on hand when you do so. The shaft seal is much more likely to fail than the gasket itself.

Thanks! I received the gaskets today (these were cheap) and intend to have a further look in the weekend. Fingers crossed it is not the pump...

Quotes source post: 670312

Marc, you should be able to find the leak if you pressurize the cooling system. .

Pressurizing didn't really show increased drip speed, so not sure what to make of that. I did see a drop of coolant under the waterpump pulley, so I guess the pump itself is becoming likely. The car will go for annual inspection coming Friday, I'll ask them to have a look as well. Otherwise, next step is to get the access panel open and look at it from the front of the engine. It is really hard to see from the bottom.

So why not swapping the pump + thermostat (71°C opening) in one step. This is a recommended preventive maintenance, parts are not really expensive and a classic DIY.

The funny part about the waterpumps is that I can find one (good) brand for $60 while the others are all around $160. That is quite a price difference... But indeed $60 would be fine. Thermostat is not really on my list, but cheaper than the pump. Why would I go to 71C (I think OEM is 88C)? The only thing holding me back on spending money on this engine is that I'll probably won't run much more than another few thousand miles on this thing. Rather spend my money on the engine upgraden haha.

By opening the thermostat earlier, the full water circuit becomes available sooner at a lower temperature, and peak loads are absorbed more quickly. I’ve noticed a temperature that’s about 10K cooler; the oil is now running at 80°C rather than just under 90°C. Cooler oil = less aging = better protection. The new thermostat only makes a difference under partial load; under prolonged full load, it wouldn’t make any difference, of course. I should add that I’ve also retrofitted a third radiator, which has helped me maintain very stable oil temperatures. This is essential for the later M96 and generally advisable for the 986, though it may not be absolutely necessary depending on the weather conditions. I know it's a hotly debated issue, but the figures, data and facts speak for themselves, so I will not reflect any flames ;-) Btw, Pierburg 7.31081.02.0 is the OEM product. Take care of *not* using aftermarket pumps with metal impeller if you want to do the swap.

Inspection was done last Friday. The mechanic took a look and also pointed to the waterpump as likely suspect. Looked up the price and we decided it is worth a further look. Today I removed the access cover so I could take a front look. All dry above the waterpump, little coolant drop on the pulley. That can't really come from anywhere else than the pump itself. So I ordered a new pump (Magenetti Marelli, should be good enough) with new (slightly longer) belt and a brake light switch (reason it failed inspection initially). The only plastic impeller pumps are very expensive (more than 5 times the price), so I did go for the metal one. I understand the whole reasoning for plastic, but am sure it will live the few thousand miles I will put on this engine. Funny part is I actually did break an early model plastic impeller pump on the BMW I had at the time. The impeller let go of the shaft, so was no longer spinning. Things overheat quickly at 150 MPH... Still the engine survived for the next 60k till I sold it...

Other piece of advice, there is a 10mm bolt for the water pump that is really in a corner. Its easy enough to see but you're going to want low profile sockets, I used an old 10mm socket and shoved a 10mm alan L key through it to break it loose. Look for write ups first, its a pain the first time. You'll see when you're in there, aside from that its not really a hard job.

Thanks for all the tips. I see what you mean with the corner one, it took a bit of puzzling to get the right parts together to loosen it (I used a socket, one of those angle things, a short extension and the ratchet, all 1/4"). For others, be aware that there are two different lengths of bolts used. I didn't notice on removal so could only try long one first for each hole and replace with short when too long. Also, cutting the gasket in-situ wasn't that easy. I ended up cutting the gasket in smaller pieces first so I could use the good old metal fatigue to 'cut' it. New one was easy. Also, the pump came with two foamy gaskets (one for the main pump, the other for the elbow). I couldn't really see how to get that to fit together, trying to put the small gasket in place while finding the hole positions etc. So I was happy to have a steel one which I ordered before. Still, it took me two hours from starting to drain the car to having everything bolted together. The belt is not on yet, system not filled, covers not put back. So probably another hour to go. The pump which came out is busted indeed. Significant movement in the shaft (wobble), so I am confident this was the source of the leak and happy that it did leak as it was on its last leg. Also happy that I didn't want to run the car anymore even if the leak was small. Last year I checked all pulleys and found the waterpump to be ok, so I guess it was the short belt that put too much strain on it (it might be tighter in other spots than then one I put it on). The longer belt should help here and if I feel this one to be a bit short as well, I'll be sure to get it right before putting miles on it.