XK8 / XKR ( X100 ) 1996 - 2006

easi(er) partial coolant removal

Old 06-02-2019, 06:19 PM
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Default easi(er) partial coolant removal

Partial Coolant Removal:

My goal was to just remove enough coolant to lower the mix from 50/50 to closer to a mix of 75% distilled water / 25% antifreeze + a 12 oz bottle of RedLine Water Wetter. The existing coolant was fairly new, and in excellent condition, I just wanted to improve the heat transfer properties of the coolant and get a modest reduction in coolant temperature. This is fairly easy to accomplish with adding some water wetter and reducing the percentage of antifreeze. RedLine advises not to lower the percentage of antifreeze below 20% in cars with air conditioning to avoid freeze-ups when blowing cold air thru the heater core.

Without being too much of a shill for Water Wetter, here are some numbers from RedLine. For the most part they mirror my own experiences when using Water Wetter plus water, or Water Wetter with 25% antifreeze :

Cooling System Fluid : Stabilized Temperature :

50% Glycol/ 50% Water.. .......... 228°F
50/50 with WaterWetter®.......... 220°F
Water......................................... 220°F
Water with WaterWetter® ......... 202°F


before attempting a radiator drain, on my 2002 XKR, I read all I could find on the subject here on the X-100 forum. All postings were in agreement that removing the plastic drain plug was going to be a risky operation due to the plug material being old, brittle, and heat-cycle compromised. So without a spare plug, and/or spare radiator, I decided to leave well enough alone as far as the radiator plug was concerned.

Next up for consideration was removing the lower radiator hose from the radiator attachment point. Although many here have accomplished that without access issues, some folks have reported a lack of access preventing them from getting the hose clamp loosened, even with the proper tool. So in those cases various parts had to be removed or at least partially loosened and moved aside in order to access the lower radiator hose clamp at the radiator lower stub. I wasn't too keen on spending a sweltering afternoon pulling parts if I could avoid it.

So with a large plastic syringe I removed the fluid from the expansion tank, which turned out to be about exactly one liter. Then I removed the top end of the lower radiator hose clamp without needing to remove any other parts in order to gain access. About 250 ml, more or less, of coolant spilled out there and I caught all of it with pans placed under the motor.

Then I attached a 3/8" ID plastic hose to my large plastic syringe and inserted the hose down inside the lower radiator hose until it bottomed out where the hose met the lower radiator connection. In short order, about 10 minutes, I had sucked an additional 3 liters of 50/50 coolant from the system. Removing a total of approximately 4 liters of 50/50 coolant. Which I replaced with 4 liters of distilled de-ionized water plus 12 oz. of the Water Wetter product. Now my coolant ratio is approximately 66% water / 33% antifreeze. Pretty close to my goal of 75% H2O / 25% antifreeze. At this point, just TWICE replacing the liter of fluid in the expansion tank will give me a theoretical 73% water / 27% antifreeze, without needing to remove even just a hose clamp.

But I'll probably just see what change I have in coolant temperature before doing any more "adjustments". This winter I'll likely up the antifreeze content to 40%, at the most. 40% antifreeze would provide a substantial safety margin for my winter climate.

After I've put a few hundred miles on the car I'll post a detailed report. so far a short 50 mile jaunt gave me coolant temperatures of 191-195, down slightly from my normal of 199-204 under similar conditions. I continuously monitor the coolant temperature and the engine oil temperature via my X-60 multi-gauge:

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Last edited by zray; 06-02-2019 at 08:14 PM.
The following 2 users liked this post by zray:
DavidYau (06-02-2019), volkris (06-03-2019)
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