Hi all,

Would have posted in the diy forum, but can't seem to.

Was wondering what people are doing regarding topping up coolant, flushes, etc. as their 991s age a bit.

My coolant is a bit below min and testing a bit weak on my cheap turkey baster coolant tester. I'm debating topping it up with either concentrate or concentrate and distilled water, or doing a flush. Thoughts?

Not seeing much on rennlist on 991 coolant but pelican has a diy.

Thanks!

 

Get this tool: https://www.homedepot.com/p/Astro-Pn...8585/206859181

Follow these steps:

You need 3 Porsche coolant and 4 bottles of distilled water (make 6 gallons total for total fill, but 1 spare distilled bottle for top off).

 

Thanks! I ended up topping up the coolant/distilled ahead of a trip. It only took about 0.7L to move the indicator from below min to about 2/3 of max on a cool morning. I would have put a little less since it was pushing up on max when around 120f (had cooled off for a few hours after a drive). I'll top up slower when I do do a full replacement in the spring.

I've also learned that topping up the oil slowly is a good practice. It seems that it takes a couple drive cycles for the oil level sensor to stabilize at a reading, regardless of whether it's the in dash reading or my diag tool's read out of how much oil to add to get it to the full line.

 

Timely thread as my dealer wanted me to flush the coolant while I was getting winter tires put on (and new front winter tires mounted). The mornings are getting cold enough that I don't want to drive on the CR-S tires and my upcoming schedule is full of travel. At least I can take another car to avoid driving in summer temps on the winter tires.

I kindly declined the suggestion to flush the coolant (2019 with 20k miles) and it is still at the 'full' marking so have not had to add any yet.

Curious when people are flushing the coolant? if they are flushing the coolant
It isn't listed on the maintenance schedule, and although considered a 'lifetime' fluid I think it should be changed at some point. That being said I have flushed the coolant on other vehicles that are 10 years old with appropriate mileage and have had it come out looking new..

 

Agree with flushing every x years instead of lifetime. Whether X is 5, 7, 10, for each person is up to them. Water pumps are known to fail occasionally on the 996, 997 cars. Not sure about the 991.

 

We will all be replacing when our water pump fail at some point.

 

I jokingly brought this up, but they said with the 2019 that it would be much less likely

 

the bill for my water pump/valve block replacement (warranty) shows a half quart of anti-freeze so I'm thinking that they just re-used the coolant that they drained. I have had to add a cup or so twice as the rest of the air burped out over a couple of weeks. I can't see the need to flush and replace lifetime coolant.

 

I do not believe in "lifetime fluids". And as there is no "Best Before" date on my jugs of new ZEREX G-40 coolant, I believe coolant life is a function of mileage and heat/temperature cycles, sort of like engine oil.

My 2015 991.1 is now 9 years and 4 months old since production, but with only 7822 miles on it. Back in June 2021 at 4251 miles, I replaced the coolant O-ring at the thermostat-black plastic pipe junction. The insides of the castings looked like day one...new...no corrosion at all. Expected with that mileage.

But like I maintain my vehicles well in advance to any recommneded intervals, like the manual transmission, front differential and AWD controller lubes that I changed August 2023 at 6877 miles, long before any Porsche recommendation. Like the aircraft I used to fly, respect your engine and associated components!

 

I do not believe in "lifetime coolant" either. And I support the idea that coolant ( mono-ethylene glycol plus water plus some anti-corrosion additives) will detoriate with temperature and time, thus primarily with operation hours of your engine. What you may expect is the coolant loses its anti-corrosive properties and at the same time it will change from alkaline to acidic, which is caused also by the detoriation of the ethylene glycol itself.
New, undiluted coolant specified for the 991 (BASF Glysantin G40) as per data sheet has a pH value between 8.2 and 8.6, clearly alkaline. Diluted with water 50:50 you may expect a pH of 7.9 - 8,3. If you have a pool, you may happen to have an inexpensive electronic pH tester to verify this.
I have a 2015 991 , 30.000 mls. I recently checked the pH value of the coolant by dipping the tester into the expansion vessel. It indicated pH 7.9, which still seems quite acceptable.
Interestingly enough, the coolant in my wife's car, 7 years old, but with 50.000 miles of mostly commuting, and presumably 3-4 times the operating hours of my mostly long-distance car displayed a pH of 6.98, close to neutral if not acidic. This is a figure where you want to replace the coolant.
I neither have a vacuum device for refilling the coolant, nor did I want to run the risk of air trapped in the cooling system. I thought about a simpler approach, which did not necessarily result in a complete exchange of the coolant.
The expansion vessel of the 991 allows for sucking out about 2.5 l of the total coolant. It is useful to do this when the engine has not cooled down completely after a drive, because the thermal expansion enlarges the amount of coolant in the vessel. You suck the vessel empty, then top-up with the same amount of new coolant mixture, which replaces about 10% of the total volume. If you do this repeatedly and drive the car for at least an hour or two between these suck out/refills, you will gradually replace the coolant. The process becomes less and less effective with each repitition, but after doing this 10 times, you will have replaced about 2/3 of your old coolant, at the price of the some amount of coolant as for a complete exchange with conventional methods.
I did the sucking out using a plastic canister and 2 PVC tubes of 1/4" inner diameter fitting tight through appropriate bores made in the cap of the canister. One tube into the expansion vessel, one into the air. I then (do not laugh) used a vacuum cleaner and carefully applied its nozzle to the end of the free plastic tube. Within a minute you may empty the coolant from the expansion vessel into the canister. Beware not to suck the coolant into the vacuum cleaner, nor use to much vacuum making the canister collapse.
I verified the effectiveness of my method on my wife's car and its quite detoriated coolant with the pH-tester, and its readings are within my expectations. Her car's coolant now reads around pH 8, quite acceptable for many more miles.

 

@IXLR8
So when do you plan on flushing the coolant?

I agree that it is going to be dependent on usage, but am not sure where that # will be understanding it will vary for all users.

 

Well now that I bought a QuickJack 5000 TL as a spare lift, I can do a brake flush and coolant flush in the driveway. The MaxJax in the garage has another Porsche on it, so why make a mess in the garage.

Maybe this year, likely next year. The original brake fluid reads 1.4 and the coolant is fine, but both will get changed. My Porsches are not a daily driver and have never seen rain, besides I keep a dehumidifier in the garage.

As for the coolant flush, I'll get the necessary O-rings for the tubes and do a complete drain. Then do a 60-40 fill with my vacuum filler. The brake flush is easy and a no brainer although not really necessary.