1999 996 Coolant Leak Question

I am new and apologize no picture as yet. I recently purchased a 1999 996 cab. No PPI (I realize now this was a mistake). Drove fine for a month, then the low coolant light came on (in driveway) so I shut down and found a coolant puddle left rear. Couldn't detect source of leak, most seemed to be dripping off of the lowest pulley on the motor. Flatbedded to 911 Enterprises. Diagnosis: Water pump. Price: Water Pump, coolant, belt hose $1,700. Seems a bit high but the shop has a good reputation. Concern: Barry at the shop told me that the coolant temp gauge on 996's is not accurate and that I could have been driving around fat dumb and happy while the motor was toasting itself. The low coolant light never came on before and there was no sign of leaks/dripping under the car prior to. I've searched through the forums and can't find any mention of this particular issue (poor gauge accuracy). Now of course I am waiting for diagnosis around engine damage. Has anyone heard of this? Is seems a bit odd that the coolant gauge would miss a chronic overheating condition.

Well, live and learn. Barry at the shop is wrong...the coolant gauge is accurate. You need to do a little bit more research on your car. The low coolant light came on because the level in the coolant tank dropped below the minimum mark, because your water pump was leaking coolant. It did exactly what is was supposed to, warn you and then you stop and check for problems. Fortunately the low coolant warning light came on before any real damage occurred. I would venture a solid guess that the engine is okay because the car warned you of something wrong before anything bad could happen. Now, before you take off and start driving again, just like any other vehicle on the road and ever made, learn how to perform the basic maintenance and check everything visually (oil level, coolant level, etc.) and so on about once a week. Why? Because you are maintaining a $15,000 engine not some Honda motor you can replace for $600. Finally, Water Pump - about $260, Porsche coolant about $30 per container, serpentine belt - $65. If you have any mechanical skills at all there are some really great threads on here on how to do it yourself. With some patience and advice, you might be able to tackle this one on your own and learn some great stuff about your car in the meanwhile. Also, RennTech.org has threads on how to do this as well. Good luck!

$1700 is waaaay too high for a water pump replace with a coolant flush. Call the dealer and see what they quote -- when mine went out, the local Indy was around $800 to replace, and dealer was around $900-$1000. I did it on my own, took a few hours (probably around 5 all told), but saved quite a bit of money.

water pump, under 1K for sure.

Other items to check are a cracked coolant expansion tank, leaking coolant cap and cracked/leaky hoses. If the part # on your coolant cap ends in 00 or 01 then it is the old style. Updated caps should end in 03 or 04. Like other have said $1700 is way over priced.

Thank you all for the feedback. Regarding regular inspection, point well taken and thank you. Regarding DIY on this item, I have the background and skills to have done the work, but truth be known, I love the car so much I allowed emotion to dictate my initial response...(rush it to the experts). Regarding cost, do me once your fault, do me twice, my fault...I will consult the forum next time. Too bad, I don't mind spending money fairly but 2X standard cost doesn't really set me up as a repeat customer.

Quotes source post: 10532432

The gage is not a real accurate indicator of temperature. It is dampened and not linearly either is my observation monitoring coolant temperature in real time using an OBD2 code reader/data viewer. (As an aside, I was running a special monitoring/tracking device in my car during this device's development. For testing purposes a really high coolant temperature level was used to trigger some debug output. This was used for bench testing using a vehicle ECU simulator in which I could crank up the temp by turning a small ****. I left this debug code in when I moved the device to my car for in vehicle testing. When driving my Boxster around occasionally this debugging output was generated. I tracked this down to a loose connector, more a marginal connection, that causes the signal from the coolant sensor to read very high (215C) under high speed, hard cornering on rough roads. The temp gage never reacted to this spike in temperature and doesn't still since I have never bothered to worry about the sensor connector.) Anyhow, what you were told about the engine suffering from overheating due to the gage not informing you is right, as far as it goes. Briefly, if there is a low coolant condition or a pressure leak hot coolant can flash to steam. This steam blocks coolant flow either over an area (where the steam is) or perhaps even through a passage. The area/region gets hot, too hot, but because the coolant is not picking up this heat the over temp condition doesn't register at the gage. Because of the above it is important, very very important, to ensure the car's cooling system is in perfect working order and if it is not to get into perfect working order pronto. Any leak, however small can allow pressure to not build up and it is the pressure that raises the boiling point of the coolant. I have seen my 02 Boxster's coolant reach and stay at 226F sometimes for it seems like hours. (Driving through 116F heat in southern AZ one damn hot July.) Only because the cooling system was in good working order did the engine not suffer one tiny bit of harm from this. Since it has been that hot -- I can't seem to get the coolant any hotter than 226F -- and yet the engine is just fine. I might add still fine after nearly 268K miles. Next to keeping up on the oil/filter keeping that cooling system in tip top shape is the 2nd most vital service you can do for your car. As for the cost of the water pump service, it does seem a bit high, but I note you having several things attended to at the same time, and your car is a 996. My water pump experience, such as it is, is with my 02 Boxster. I had my 02 Boxster's water pump done at a dealer some few years ago (before 2006) and it cost around $1100 but this included along with a new factory water pump (the original one lasted 172K miles) a new t-stat and all fresh coolant along with an oil/filter service too. The hoses then were fine and have remained fine since. (Keeping that coolant "fresh" helps the hoses. I have the coolant drained/replaced with fresh every 4 or 5 years.)

Macster- Thanks for the detail. The bad news is, I still have to worry that there may have been some damage to the engine. The good news is that even though the shop didn't provide me with the cause/effect information, the info they provided was/is valid, at least in theory. If I am going to pay a premium, at least I can trust the source now. Best regards.

EdTexas - sounds like you're going to have the shop do the work. There are good articles about the topic here on Rennlist and in addition we have an article about water pump replacement for the DIYer but it's a great technical read for the knowledge itself. Would not sweat it about your engine, sounds like you shut it down well-in-advance of damage. Water Pump and Thermostat Replacement 996 Mark/Pelican Parts

I did have the shop do the work. No long term damage. The car is a daily driver and I travel a great deal, so Adam Smith would likely opine that both parties maximized. That said I will exercise due diligence going forward in terms of both research and involvement. Regards to all.

I would be remiss if I didn't mention the professionalism that both Randy and Barry displayed. Time will tell if the repair holds up, but my guess is that will not be an issue. Again, thanks to all of you.

I would want them to buy me dinner and give a weekend vacation at a nice getaway for two with what they charged to replace a water pump.