Well... yes, and no. The KPa scale is absolute. Zero KPa is a perfect vacuum, and 100 KPa is sea level air pressure. So, a true 100 KPa cooling system pressure would have no cap at all. I suspect some manufacturers mess up how KPa is used, and are selling caps marked as "100 KPa" that are in fact 200 KPa: 100KPa is sea level pressure, and another 100KPa above that, for a total of 14.7psi above ambient sea level pressure. I suspect a cap labeled 100KPa or 200KPa is "probably" the same pressure, 14.7psi above ambient, a very common pressure for coolant systems. Now as for what a "140KPa" cap is, who knows.

 

Let me preface my remarks by stating that I am no coolant expert. I find it interesting that Jaguar specifically recommends a 200kPa cap for the Jaguar F-Type while the 140 kPa cap seems to be recommended for the S-Type, Super V8, Vanden Plas, XF, XFR, XFR-S.

I have been unable to understand why one would want to monkey with what is recommended . Here I copy an explanation from a reputable radiator authority. " Pressurizing the system raises the boiling point of coolant, so in extreme conditions, this creates a buffer by allowing it to run at higher temperatures.Doing this prevents damage to the car, engine overheating and helps keep the system running smoothly. It also means that manufacturers can build engines with higher operating temperatures, which is especially common in performance vehicles. The radiator cap is a vital part of this process.

When choosing a radiator cap, it’s important you stick with the specified pressure for your system, as each additional pound above this increases the boiling point by 1.4°C..

So, can someone explain the benefits of using a 140 kPa cap so just in case my engine goes south when it comes to a warranty question I can look intelligent and tell Jaguar your cars should have 140 kPa and not 200 kPa.

 

In the context of this thread, the reason is to lower stress on weak cooling system components. Whether that's good for the engine is a separate issue - in this context.

 

Yes, my point, and the point that Jaguar might be making, is that a lower than 200 kPa rated cap will produce less, quite a bit less strain on the cooling system components, and the point of the discussion about the plastic components concerns the inability of the first versions to cope with the high pressures.

In terms of longevity of the plastic components (especially those that have seams) lower pressures are better.

With regard to any variation in marking standards, we are (at least I am) talking about OEM caps on Jaguars, not after-market caps…OEM caps, and I have referenced the caps on my X-Type at 100 kPa and the Jaguar-supplied cap now on my F-Type (140 kPa) to replace the original cap (200 kPa). These will all be using the same measuring system.
With regard to the point that some of the sources for the 140 cap do not mention the F-Type….well, the engines they DO mention are the same engines used in the F-Type.

And, to repeat, I did not ask for a lower pressure cap. Jaguar supplied the lower pressure cap with the “version two” pipes and hoses that I ordered. This was not an arbitrary decision on my part.

My 2 year experience with the lower pressure cap (140) in place of the 200 kPa cap on my F-Type V6S shows me that the engine operates as it always has, no difference of any kind, regardless of ambient temperature, or driving conditions. Therefore, I must ask in what way a higher pressure cap would affect the engine in a positive way? Yes, the boiling point of the coolant rises with a rise in pressure. But I have no need to subject the first generation pipes on my car to higher than necessary pressure….THAT might indeed affect the engine!

 

Sorry if I am still confused.

So, are you saying that in choosing a radiator cap one should disregard the specific specified pressure of the system for your automobile and go with a lower pressure?

I have a hard time digesting this.

 

Now I also understand the reason why in Germany there are almost no failures of these cooling pipes it, we drive here mostly below 30 C and the water comes rather not to boil. Thus also no large pressure up to 2 bar. The question is whether I can save the new lid with 1.4 bar?
Andi

 

Quick question:

Is the coolant/flanged pipe issue related only to the 6 & 8 cylinder models, or does it also apply to the 4 pot turbo?

BEST !

RWS

 

Fully respect the idea and ordered one of these caps from FCP-EURO for 2.99 plus 5.99 shipping...usd.

But, respectfully, what comes on a 2022 or 2023 F type today? It is possibly your dealer gave you the wrong part too.

Great idea/hypothesis - am just trying to get more data. Agree, xfr's get used hard and if they come with the 140 it is just odd to have 200 on the F-type. Like I said, I bought a 140 cap...

 

YES. Since your car and definitely since mine was built, specifications for many elements have been changed. A simple example: the oil originally specified for these engine was 5w20. It is now 0w20. Which are you using? Many of the unseen and seen parts of the F-Type (and every other JLR car) have been changed - often subtly, and the part numbers are changed with those alterations.

Flanged pipes have been failing. A probable contributing factor is the high pressure in the cooling systems (200 kPa cap). Two ways of dealing with this: redesign the pipes so that there are no seams, and for existing flanged pipe systems, change to a lower-pressure cap. Best solution: aluminum pipes; the redesigned no-seam plastic pipes are far more robust than the original flanged pipes, but in general terms the lower the pressure in the system - while still providing a more than adequate coolant boiling point - the better. The 200 kPa pressure caps are likely only necessary in the most extreme service. Lower pressure = less strain on flanged (or any) parts.

To repeat, my F-Type is fitted with the 140 kPa cap and has been for two years. The cap was provided to me by my excellent dealer as part of the complete cooling system upgrade pack. Of this pack of pipes and hoses etc, including the 140 cap, I have so far fitted only the cap, so the car still has its original flanged pipes in place. The car has been used in very high ambient temperatures in both highway and city traffic. Zero issues with the 140 cap and so far no issues with the early flanged pipes. Why would I want to subject the pipes to higher pressure than necessary?

 

Back to the OP question... I haven't heard of any failures of the new pipe design and it seems as though the original flange weak point has been eliminated. But, I recognize there really isn't a lot of history. I, personally, would probably leave the new/redesigned version alone, but I wouldn't argue against going to the aluminum while you're in there. The parts cost is minimal and you're already dealing with most of the labor.

One thing I WOULD recommend (while you're in there) is to preemptively replace the water pump. You have enough time/mileage that it's more likely to be the next point of failure, and it involves the same access labor.

Meanwhile, I'm riding with one of each.

 

I live in AZ and I switched to a 140 cap the moment I saw the 200 fitted! I have had no issues at all and just completed a 2k mile road trip to TX and back. A properly operating cooling system should never near 29 psi, or even 15 for that matter. If the radiator, cooling fan pack, water pump, and thermostat are functioning properly a typical cooling system only sees 6 to 8 psi, even in extreme conditions. My logic for why I lowered the cap release pressure is to save the engine (head gaskets in particular) in the event of a system critical failure. I would rather see coolant and steam blowing out of the cap release than warping the cylinder heads or engine block.

Regarding the aluminum pipe retro fit, I have done it on my car and had no issues, something Jaguar should have done from the start imho. You should be aware that split plastic-welded seam is not the only failure point for the early pipes. They can also break where the two pipes fit down into the engine block. That's how they failed on my wife's 5.0l Range Rover! Unfortunately, no one yet is producing aftermarket aluminum pipes for the NA engines ;-(

 

Ok, I have resolved the radiator cap issue.....

 

No pressure release. That will do it.

 

 

As the cap is unmarked, at what pressure is it rated?

 

Ah,,,,,,,that is the point of the cap...besides, of course, the fact that it hides the ugly yellow sticker......

 

So following this thread particulary concerning the 140kpa VS the 200 kpa cap. My question is: does this apply to V-8 engines as well? I noticed that everyone discussing this is running the V-6.

 

So I took a look at my car and have the new metal units.

No signs of ever a leak (had the plastic original things on before)....solid attachments all around.

I bought the 140 cap. But I actually think I'm better protected leaving the 200 cap on the car as it can take hotter fluid. No, will I ever see it, probably not, but the person running 140 says he's been fine too so in theory it should not get to 140 even.....but if I ever had a very hot engine, I want to keep it cooled for as long as possible. The extra block protection of holding on at 190 versus blowing off at 140 is worth it to me...so I am leaving on the 200 cap because I think it is safer for the engine. And that is my vote.

Dumbing down the system is not wise and in my prior car days, we would increase the radiator cap pressure to protect our engines. So, my car is staying at 200. An overheated engine is expensive...

 

The engine bay is the one thing we could have used more E-type influence....it is ugly. Your cut cover and red and this are nicely done!

 

I very much agree with you and will not tinker with my 200 cap. That is why I went with the aluminum pipes don't you know....

Like yourself, I do feel better protected with a higher temperature rated cap. As I understand this a higher pressure cap helps to boost the boiling point and better protects the system from boiling over.

We do get many days here of over 100 degree temperatures and after all these years I have been fortunate and have never had an issue with cooling.