My new XK8 came with green antifreeze and as I could not get any assurance of a flush I did just that in a move back to Dex-Cool orange.
While waiting for my cat to cool between radiator flushes I mixed (in a test tube, not in the car) traditional green antifreeze and orange Dex-Cool. I could not get a reaction but I did notice they did not mix well with the green tending to rise, i.e. is lighter.

So I wondered are the horror stories of jelling and system blockage based on any documented facts?

 

When I Mitivac'd out about 2 quarts when I repaired the "low coolant level" float in the top tank, I noticed my coolant was Orange with a green tint. but I saw no signs of gelling.

 

Did you add heat?

 

They do gel, heat and time required. And it makes for quite a mess to clean out. Customer's cars, not mine. Not certain how long it takes to become a mess but do know the longer it's in the worse it gets.

 

i must admit I put the mixture in microwave then got distracted so I really should have done that before I posted.

 

This is an excerpt from an 'autoblog.com' article about Orange and Green Coolant:

Q: Can I mix green coolant with orange coolant?

This is one of those questions that is usually asked after the fact, and usually engine damage has already occurred. The green and orange coolants do not mix. When mixed together they form a gel-like substance that stops coolant flow and consequently the engine overheats.

There are some coolants that claim compatibility with Dexcool, but I would rather err conservatively and add what the system is supposed to take rather than take the gamble. To guard against major engine failure, read on.

What exactly happens when these coolants are mixed?

The coolants chemically react and form a gel rather than a liquid. The coolant stops flowing through the system, clogs up coolant passageways and water jackets, radiators, and heater cores. The water pump overheats and fails due to a lack of lubricant in the coolant. Head gaskets blow, heads warp, and the engine suffers major damage.

So what are the guidelines on maintaining engine coolant?

Here's the bottom line when it comes to cooling system maintenance. Whether you are running Dexcool (the orange stuff) or ethylene glycol (the green stuff), inspect the coolant level and the condition/protection of the coolant at every oil change. In addition, completely flush and refill the system every 2 years or 25,000 miles whichever comes first. These actions will avert the problems associated with Dexcool or any other coolant product.

Watch for signs of oil or rust.

The color of healthy engine coolant is green (for ethylene glycol) or orange (for Dexcool). A rusty color indicates that the rust inhibitor in the coolant has broken down and it can no longer control rust and scale buildup. The system must be cleaned/flushed and a fresh 50/50 mix of coolant installed to restore integrity. A milky color indicates the presence of oil in the system. This is not good; it usually means that a head gasket, intake manifold, or transmission oil cooler is leaking oil or transmission fluid into the engine coolant. This is a deadly mix that will kill an engine or transmission in short order. Address the problem immediately!

Slippery coolant is a sign of good coolant.

The engine coolant should feel slippery to the touch and smooth (like the engine oil). If it feels gritty, the coolant is dirty and should be flushed and replaced with a fresh 50/50 mix. If the coolant does not feel slippery then it has lost its lubricity (the lubricating and rust inhibiting agents have deteriorated) and the system is at risk for rust and scale buildup, as well as water pump wear.

Use your nose.

Change the coolant if it smells burned. Also change the thermostat; it's probably gone bad because it was exposed to overheating (or it caused the overheating). Overheating damages the bi-metallic spring that opens and closes the thermostat valve. Most importantly, find out what caused the system to overheat and repair it, or face major engine damage.

 

Gelling is indeed real. Search Google images using "automotive coolant gelling" as your search phrase and see what turns up. Some of this stuff looks so bad you could grab a butter knife and spread it on your morning toast if you chose to do so. I wouldn't go as far as eating that toast, however....

 

I changed the coolant on my 04 XXKR @14K miles last season. The OEM Jag Orange coolant will gel on it's own. The Gel mess seems to work it's way to the highest point in the cooling system. When I pulled the top pug on the intercooler I found it to be packed with gelled coolant, dito the intercooler radiator. Ater sucking the Gel that I could reach out with a fluid pump and then flushing the entire system, all was well. Be sure to mix the new coolant with distilled water.

 

Great discussion makes me, and probably others, think "what if someone added a bit of the wrong coolant over the last x# of years ? "

Obviously the solution is to flush the coolant for new. I have a copy of the detailed instructions about this topic and plan to follow them.

I think this has been asked before but I can't remember if it's ever been answered: When we follow the instructions does it leave any "old" coolant, however diluted, in the system ?

If it does, are there any steps to clear that out ?

Thanks guys,
John

 

I'm looking for those instructions. Can you link or post?

 

The Jaguar procedure in JTIS only covers draining the radiator. Here's the 2001MY instructions:

XK8 -Cooling System Drain & Refill - NA.pdf

And for Supercharged:

XK8 -Cooling System Drain & Refill - SC Engine.pdf

This leaves the old coolant in the Heater, the Atmospheric Recovery Bottle, some in Expansion Tank and hoses.

Adequate but if you want to be thorough then 'backflushing' is more effective in removing residual coolant.

My preference is to do two intermediate fills with plain water, running up to temperature and allowing to cool between each before finally filling with 50% coolant/50% distilled water mixture.

Graham

 

After two such cycles over time, I can still clearly see a pinkish cast in
my coolant which is Zerex G-05.

BTW, when flushing with plain water it is best to add a measured
amount of undiluted coolant according to the calculated requirement
against system volume, then top off with water as required.

The reason for this is that adding 50/50 to an unknown amount of
residual plain water will not yield a final 50/50 ratio.

In fact, with the amount of residual water present, it will be almost
impossible to achieve 50/50 even by adding full strength coolant.

Achieving 60/40 requires introducing more full strength coolant
after dumping a significant amount of the mix resulting from
adding full strength to residual water. Such a waste.