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Uview Airlift, Smallish Particles in Coolant, Electrolysis Test

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I've got a MY99 996 C2 with 72k on the clock and the original coolant (11 years old).

1.) I recently had the thermostat off the car and drained about 3 gal of anti freeze. It looked in decent condition, but there were about a dozen or so 1/4 of a dime or smaller black flakes in the bottom of the bucket after putting it back in the car (yes the bucket was clean prior). A couple flakes were floating. It almost looked like deteriorating rubber. It was a very small amount though. In that amount of fluid I wasn't immediately concerned about that amount of residue (though I don't want to see any in the coolant). The flakes didn't look or feel gelatenous at all, and they disintegrated just by touching them (and also broke apart when pouring it back into the tank).

Unsure of the history of the coolant from previous owners other than knowing it is largely still original, whether they had added incompatible fluids - since the "lifetime" coolant is certainly beyond it's "lifetime" - I'm going to replace it.

Given the fact that there is a small amount of residue in the system, should I worry about flushing the system in between drain and refill? Or just drain it out and immediately replace? Or remove and inspect parts to see if there is anything else going on.

I remember with some of my old beater cars I would pour some cleaner in the radiator, fill with a garden hose, and warm it up, drain, fill with antifreeze

Of course, the 911 demands a a little more care than that. Has anyone used any cleaners with success or do you just stick to distilled water when you flush prior to filling?

2.) I purchased a uview air lift 550000000 and have been reading up on it's use. A couple points I have not seen from other threads or posts here and could use some guidance.

I've seen conflicting reports on the correct PSI for your compressor, some say don't exceed 20psi for fear of damaging seals/etc. Others say set it to 90PSI.

Also, while I haven't read it here, some say elsewhere that after you drain the fluid and then create the initial vaccum prior to filling. STOP. Don't fill. Instead, release the pressure, then drain AGAIN. Apparently the vaccum created can draw some fluid trapped in some nooks and crannies and allow it to be drained further. Then proceed to fill according to instructions.

3.) I performed a simple electrolysis test with a multimeter. With the positive probe in the coolant expansion tank, I read negative 0.10 volts with the car off. With the car running it was negative 0.20 volts. I've read it should be BELOW 0.10 volts. Well, it is - negative... am I reading this right here or am I looking at a grounding problem somewhere?


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Any debris in the coolant is reason for some concern; contamination can lead to a premature death of the coolant. Normally, there should be no sealant or other crud in the system as none is used in the original assembly, or should be used if the thermostat or pump is changed out.

One potential source for black flakes in the system is from the pump itself, which uses a black plastic impeller that is well known for breaking up in use. Impeller failure has led to other issues as the debris can block water passages and cause hot spots to form, which can lead to issues like cracked cylinder heads. If you want to flush it, Prestone makes a flush that works well in getting out crud like intermix residues.

As for the pressure on the Airlift unit, use 90 PSIG per the manufacturer's instructions. As there are no seals in the Uview unit, pressure will not harm it; and the unit will get to full vacuum quicker.

As for draining the system; if you have removed the drain plug and pulled the hoses, and then allowed the system to drain, you should not get anything more by evacuating the system as pulling a vacuum does not move the liquid, only the air.

As for measuring the electrical properties of the coolant mix, we have never done that, preferring to test it for visual clarity, pH and freeze levels, which have always been dependable indicators of its condition.

Edited by JFP in PA
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Thanks for the advice. The car has had 0 cooling problems to date but I certainly agree I don't like any unknown crud floating around in there...

When I have the coolant drained, I might take the time to remove the water pump and inspect it, and then reinstall with new gasket. Or if it looks like the plastic is on it's way out that's $250 I hadn't planned on spending but I suppose it would be better safe than sorry as I do undestand they can fail pre-maturely.

When I had the thermostat off a while back everything looked 100% normal as well, no pitting anywhere, and no debris to speak of.

One time when I replaced the impeller on my boat it only had one two fins left and the rest of it was caught up in the plumbing, it was amazing the thing was still pumping water through!!!

Oh and the electrolysis test was not for the coolant properties, but a check to see if the cooling system was being used as a cathode, potentially eating away at the anode (aluminum block, heat core, radiator, etc) by pitting/damaging the metals.... My confusion there is that I actually have a negative reading??? I suppose which is a good thing? I'm not familiar with this test, but did read that anything over 0.10 volts (positive?) is bad for your coolant system and the block, radiator, heater core, etc. is being used as a "sacraficial" anode which could lead to other really bad problems...

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Pulling the pump and putting it back is often false economy; considering the effort and parts costs involved, and the fact these pump go south without much warning, it simply does not make sense. That is also why we never reuse coolant, even when it looks good. Do it right and you generally only do it once……….

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Water pump, gasket, crush ring ordered.

Now to find some coolant (i'm not paying porsche's price @ $40 gallon (incl shipping + tax) when I can get it for $10 a gallon).

AND it's my car and I do the work on it, so it's not like someone will accidentally put an incompatible coolant in there.

As many have said, plenty of alternatives out there, VW G12, or any phosphate and silicate-free formula (non dexcool) will work. Examples...

Zerex Extreme Life 5/150

Texaco Extended Life

Shell Rotella® ELC Extended Life Coolant UNI-GARD 5/150

Mercury Extended Life Coolant Anti-Freeze

Heck, since I'm replacing nearly all the coolant anyways I could change to just about anything... prestone or peak even.

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Does this look like the right stuff for a flush, prior to re-filling?


Prestone®Super Radiator Flush

A premium Prestone® antifreeze/coolant change begins with Prestone® Super Radiator Flush. Helps remove rust deposits and oily residue in an easy, one-step process. Premium formulation helps maximize cooling system efficiency.

1.With engine off and cool, remove radiator cap.* Drain radiator then close draincock.

2.Pour entire contents of Prestone® Super Radiator Flush into radiator and fill with water. For systems larger that 12 quarts, use two bottles.

3.Run engine with heater on highest temperature setting for 10 minutes after reaching normal operating temperature.

4.With engine off and cool, remove radiator cap, drain radiator, and close draincock. Refill with water and replace radiator cap to fully closed position. Repeat step #3.

5.Stop engine and allow to cool. Remove radiator cap, drain system and close draincock. Add enough recommended coolant to achieve a 50-70% concentration. Top off radiator with water. Replace radiator cap to fully closed position. Run engine for 20 minutes to mix coolant/water.

6.If equipped with a non-pressurized coolant reservoir, rinse, drain, and refill with a 50-70% solution of the coolant and water.

Super Radiator Flush maximizes cooling system efficiency by helping to flush out harmful rust deposits, grease, and oily residue. It uses a strong chelating compound to bind rust and other corrosion deposits to help flush them out of the system prior to installing new antifreeze. Detergents emulsify oily residues. Super Radiator Flush is intended for cars with heavier build ups of rust and radiator and heater core deposits.

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