Yes I love the failed GM Engineering! Add 3 pellets of engine coolant sealer because our engines WILL leak!

Thermo I think you do know that there is a air bleed for the coolant system?



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Good discussion on this thread and the consumer can obviously see lessons learned over the years from manufacturers. In general, don't mix.
Common G05 to OAT or HOAT requires complete flush (sometimes several). I led changeovers for coolant production lines, just don't mix them ever. They are colored for a reason.

 

Hi Mark,

I owned two Jaguar XJ40s, one of them for 16 years, and between the two cars I had to replace the head gaskets three times. On each occasion I found that the aluminum head had eroded between a coolant jacket and combustion chamber. I repaired the erosion with JB Weld metal-filled epoxy and all was well for 90K miles. The part of this story that doesn't support the Dex-Cool aluminum erosion theory is that the Jaguar XJ40 uses conventional green ethylene glycol coolant, which is why I personally believe that many of the complaints about Dex-Cool are either exaggerated or unfounded.

Regarding the pellets or tablets that GM specified must be used, they are not described as an anti-corrosion product but rather as a sealant designed to "seal against minor or microscopic leaks and porosity." As I mentioned earlier, Dex-Cool already contains corrosion inhibitors, so it wouldn't make sense that additional anti-corrosion additives would be required. Here's a link to the product page for the sealing tablets:

ACDelco Cooling System Seal Tabs 3634621

Hi Bri's Jag,

Check that section again. The manual states to add "ethylene glycol (DEX-COOL) and water..." Like conventional green antifreeze, Dex-Cool is predominantly ethylene glycol. It is the corrosion inhibitors and other additives that are different and incompatible between IAT, OAT, HOAT and NOAT coolants.

Cheers,

Don


EDITING

 

You do realize that that isn't what it says, right?

 

That's what I perceived from the way that statement read. Maybe I'm still confused I always thought ethylene glycol was the Green classic like the yellow Prestone jug and the orange was the black/silver jug GM Dexcool... From what I gather "now" ethylen glycol is orange to.. Now I'm even more confused. Fu** it I'm just going to Jag and get their specific gallon orange made for the car for $7 more, tired of dancing around everyone's different opinions as to clogged radiators and engine damage. Some Jag owners even use the green. I know they can't be mixed but damn.....

 

That does make sense, and I'd think would indicate that it could be a matter of the aluminum not agreeing with the maybe aged and acidic coolant. As I understand it, aged coolant gets acidic. Would you say that keeping the coolant fresh would be the best defense in keeping those gaskets healthy?

I'm surprised that the JB Weld would patch that, but it always has been legendary - like duct tape... ubiquitous almost.

But on the other hand, I've had many vehicles, and the only head gasket problem on 4 wheels I've had was the Aurora - neither of my Range Rovers or the XJ... not yet anyway.

How religiously do you change the coolant out? I'm thinking of every 2 or 3 years, not the 150,000 miles or 5 years as GM prescribes for their engines. But then again they are more mass-produced and probably rougher duty.
But I will only use the Pentosin SF or have the JLR dealership flush & fill. It's less than $200 for them to do it, including wash & inspection. I think the XJ and 2012 RR are worth that.

Ahh - yes. Very good points. Thanks for pointing that out.

 

There ya go... I agree. Sometimes the few extra bucks are worth it. And our Jags are nice vehicles. They're worth proper care.

 

Ethylene glycol is the primary ingredient in all of the major types of coolant, including IAT (conventional green), OAT (such as Motorcraft Orange/Dex-Cool) and HOAT (such as Zerex G-05). Some also include smaller amounts of diethylene glycol, and some coolants are based on propylene glycol for lower toxicity. But the major IAT, OAT and HOAT brands are all based on ethylene glycol.

The components that are incompatible between types are the corrosion inhibitors and other additives, such as water pump seal lubricants. Theese additives can interact adversely, causing problems such as gel formation or reduction in corrosion inhibitor life.

I've been using Dex-Cool in Jaguars since the early 2000s with no issues that I could attribute to Dex-Cool.

Cheers,

Don

 

The areas of erosion occur in the flat machined areas between coolant jackets and combustion chambers, and they are very shallow, so it doesn't take much JB Weld to fill the erosion, and the repair is sandwiched between the head and the head gasket, so it doesn't have to endure combustion pressures on its own.

Range Rovers are even more notorious than Jaguars and probably equal to BMWs for cooling system problems, and the heads will warp at the first occurrence of overheating. So if you start getting leaks, it's a good idea to preemptively replace all of the hoses, the thermostat, water pump and radiator. I work on a lot of LRs/RRs and their cooling systems are probably the single most common problem area. I'm currently installing a salvaged engine in a 2011 BMW 328i that overheated, warped the head, burned bottom end bearings, scored the crank and allowed a piston to come into contact with the head.

I definitely don't believe Dex-Cool or any other coolant should be relied upon for 5 years or 150,000 miles any more than I believe any transmission has a "Lifetime Fill" of fluid. I think in terms of replacing Extended Life coolant every three years.

The reality is, with most vehicles that are more than several years old, in any 5 year period it's bound to develop a leak somewhere, whether at the water pump, radiator, reservoir, or some plastic component or hose. So it's not that easy to keep the same coolant for 5 years! :-)

Cheers,

Don

 

There are definitely people on here that know what their talking about but when you mix all that in with people that just want to give "their" opinions and lifes horror stories it's probably not fact. Everyone just go to the damn Jaguar dealership and get a gallon that says Jaguar on it, its orange then everyone can sleep peacefully at night. Spend the $7 more, if your on this site you can afford it. End of story!!

 

Clubairth1, no, i am not aware that there is an air bleed valve. When I did the water pump on my car, I simply let the engine bleed itself. Once you start the engine, you can see the air bubbles getting released from the engine by simply looking into the overflow bottle. You can see the air bubbles come out. Right after changing the coolant, it will still be air saturated. That is why you need to let it cool (this minimizes the amount of air that the coolant can hold), forcing the air out of the coolant and on the next initial start, the final air bubbles get pushed out. This is why you normally end up needing to do the final add after the cool down.

Working at a nuclear power plant, we have to be worried about how much gas is dissolved in water as this can have detrimental effects on the pumps and fuel rods. So, you learn lots of "useless" information about things like how much air can be trapped in water and how it varies based on pressure and temperature.

 

Hi Chris,

My understanding was that a liquid has greater solubility of a gas when it is cold and less when it is warm. That is why carbonated drinks remain fizzy when cold but lose their carbon dioxide as they warm up. Have I gotten that backward?

Isn't the biggest problem in an automotive cooling system pockets of trapped air that have to be worked out rather than air dissolved in the coolant? Any additional information you can provide will be greatly appreciated.

Cheers,

Don

 

Don B, you have it backwards, warmer water can hold more gas. Also, the more pressure that you put on the liquid/gas mix,, the more gas that can go into solution. This is why carbonated drinks are fizzy initially and then over time (kept at a constant temp or changed) will become flat. All chemical processes try and reach an equilibrium. How fast and what that equilibrium is depends on what you are looking at. In the case of a carbonated beverage, the container is pressurized and this is causing air to be push into the liquid and at some point, the amount of air entering the liquid is the same as what is leaving it. When you open the container, you are releasing the pressure (hence the noise you hear initially). This shifts the balance and over time, gases come out of solution to reach the new balance. These are the bubbles that you see. Kinda like if you stir the drink, the bubbles will come out even faster. In short, moving the liquid causes lower pressure points to be created, making for an even bigger shift in the equilibrium, causing the balance to try and shift faster.

You are correct when it comes to the automotive application that the air bubble is essentially "blocking" a coolant channel. This allows no coolant to flow through that channel. I think you can see where that would be bad as the motor has no cooling in that limited area. This is why you normally want to rev the engine some when filling the system as you are changing the flow characteristics, which can dislodge these air bubbles. Keep in mind that the output pressure of the water pump is directly related to how fast it is spinning. The general rules of flow dynamics is that flow rate is directly related to speed, the differential pressure is related to the speed squared, and the power needed by the pump is related to the cube of the speed. In other words, if you double the speed of a pump, it will pump twice as much fluid, its differential pressure will be 4 times as high (ie, 2x2), and the amount of power to move the fluid will require 8 times the power (2x2x2).

So, at idle, the water pump is moving a relatively small amount of coolant. You rev the engine from idle (600 RPM) up to 3000 RPM, the pressure in the system goes up greatly. This not only collapses the air bubble (gases compress when you put more pressure on them, Boyle's Law), but puts more pressure on it, potentially overcoming the grip (friction) it has on the coolant channel. Some may even call this concept "water hammer". You have heard water hammer. If you run your kitchen faucet and then you quickly shut it off, you can heard the pipe bang. That is water hammer. The water was flowing and quickly stopped, creating a pressure point from where the moving water slams into the stopped water. This can be good, it can be bad. I use water hammer to clear a clogged heater core in cars (add a little bit of water to a low point in a rubber hose, quickly apply 100 psi air and let the water slam into the clog, "hammering" it loose). It can be bad in that it can cause pipes to shake violently (hence the noise you hear in your house). These pressure surges are no problem for the internals of your engine block or your rubber hoses.

If you want to learn a little bit about beverage cans, check out this video ( ). I found it interesting. It covers some of what I was mentioning above.

 

Hi Chris,

My prior question did not involve pressure, which is an entirely different variable. When pressure is constant and temperature is the only variable, cold water can dissolve more gas than warm water. I just looked it up to be sure.

Here's a snip from a chemistry website that discusses the effects of temperature on gas solubility;



Here's the link to the web page:

Temperature Effects on the Solubility of Gases - Chemistry LibreTexts

By the way, among the many automotive components my late father designed were water pumps for Ford, GM, Chrysler, Toyota and others, and he wrote some of the first computer programs for automotive water pump design. If I remember correctly, the data and equations available at that time were for much larger pumps, such as those used in power generating plants, which you obviously know something about.

Designing automotive pumps that flowed well at idle and high engine speeds while keeping pressures within a safe range was definitely part of the process, but since the engines in most passenger cars have a similar range of engine speeds, the engineers had plenty of empirical data to get them in the ballpark with any new pump design. One of the innovations Dad was involved in was the move toward electric water pumps driven by PWM signals.

One of the issues he developed methods for dealing with is that despite all of the known equations available in fluid mechanics (from Bernoulli and Euler to Darcy-Weisbach and beyond), none could accurately predict the combined effects of all the losses in real-world systems. I think I recall that some of these losses were due to things like cavitation, turbulence, hysteresis, head losses, friction losses related to the cross-sectional dimensions of passages and the characteristics of features like joints and coolant jackets, heat radiation from components other than the heat exchangers, etc. Since none of the manufacturers were interested in funding research to develop more accurate modeling software and were content to let engineers figure things out by trial and error, Dad developed correction factors that helped more accurately predict system performance and accelerated the prototyping process. I wish he had patented his program, but as far as I know the major automakers may still be using his correction factors.

Cheers,

Don

 

Hi Don, I am also new to owning an XJ6 X351 3ltr diesel and have just discovered that I need to buy some coolant just in case I need to top up.
I can get the genuine Ford stuff from Amazon, but the instructions on the bottle are all foreign, so my question is simple:

Does it need to be diluted?

If so, with what, because I would imagine using tap water is a big, no, no!

Your knowledge on this subject will be greatly appreciated.

Thanks

 

Hi jagtwit,

Welcome to the Jaguar Forums! It's great to have you with us!

Coolant or anti-freeze that is prediluted is usually marked on the label to that effect, often with the ratio "50/50" and "Do Not Dilute" or "Pre-diluted" on the label. If there are no such markings on the label, the coolant should be diluted to the ratio given in your Owner's Manual (usually 50/50 unless you live in a very cold climate). Dilute with distilled water, or at the very least, demineralized water.

As you said, tap water should never be used due to the presence of minerals and electrolytes that can interact adversely with the anti-freeze additives and metals in your cooling system.

Do be certain to identify the correct coolant specified for your vehicle. I don't see the diesels here so I have not researched that for myself. There are many varieties of coolant chemistry in use today, and many of them cannot be intermixed without the risk of potentially serious problems.

Cheers,

Don

 

Well said!! Just got my XJL and all I am doing FIRST is focusing on the fluids, hoses and belts!! What did I see when the sun came up this morning - seriously low coolant in the tank. Who would have thought it!!!

 

Excellent post and advice - thank you, Don.

 

When purchasing a vehicle without reliable service documentation, I find it useful to check the condition of maintenance fluids before indiscriminately replacing all of them inexpensive test strips will tell you definitively whether the brake, p/s or coolant needs to be changed immediately, as well as provide verification of the PO's maintenance habits. Engine oil analysis, particularly on an expensive car such as yours, is also a good idea. You're probably going to do an oil+filter change anyway. Blackstone Labs receives and analyzes oils from vehicles world-wide. They also provide some verbiage along with raw numbers.

FWIW, the shop that services my car uses Pentofrost SF (pink) coolant.

 

Thank you for that information - appreciated.