Hi all,

I’m trying to establish a fact-based understanding of coolant hose reliability on the X150 XKR 4.2 supercharged, particularly the “valley” hose under the supercharger and the hidden crossover/elbow hoses.

A lot of online commentary suggests “it’s not if but when they fail”, but these claims are rarely supported with data. In contrast, Jaguar do not specify, schedule, or recommend replacement of these hoses at any mileage or age in any of the official service documentation, maintenance sheets, or technical bulletins for the X150 platform.

To help build a clearer, evidence-based picture, I’m hoping owners or technicians can share documented, first-hand cases of actual hose failures on the X150 XKR 4.2 (supercharged). If you have experienced a confirmed failure, it would be very helpful if you could include as much of the following as possible:

1. Vehicle details

• Model year:
  
• Mileage at time of failure:
  
• Country / climate:
  

2. Which hose actually failed?

• Valley hose beneath the supercharger
  
• Rear crossover pipe elbows
  
• Thermostat housing outlet / seal
  
• Other coolant hose (please specify)
  

3. Nature of the failure

• Sudden rupture
  
• Slow seep / weep
  
• Coolant smell, gradual loss, or residue
  
• Visible symptoms before diagnosis
  

4. Diagnosis & confirmation

• Who diagnosed it? (Jaguar dealer / independent specialist / self)
  
• How was it confirmed? (pressure test, SC removal, visual access, etc.)
  
• Any related components replaced during the repair
  

5. Repair details

• What was replaced (single hose vs. full set)
  
• Labour hours required (if known)
  
• Approximate cost (optional)
  

6. Cooling system history (if known)

• Prior overheating?
  
• Coolant change history & coolant type
  
• Any earlier cooling issues or repairs
  

I want to keep this thread focused strictly on documented cases and verifiable information, rather than general opinions such as “they all go eventually” or anecdotal predictions.

My goal is simply to assemble a clearer sense of how frequently these failures actually occur in the X150 4.2SC, given that Jaguar themselves did not classify these hoses as wear items and did not include them in any preventative service schedule.

Thanks in advance to anyone who can contribute factual examples or workshop-confirmed cases.

PS

For context only: two of the most widely respected Jaguar specialists here in Perth – both with decades of experience across the X100 and X150 platforms – have independently advised against pre-emptively removing the supercharger on an otherwise healthy 4.2SC purely to “inspect hoses,” as they rarely see failures in service unless there has been previous overheating or neglected coolant. I’m hoping this thread helps quantify how often genuine failures have actually occurred.

 

Just for your info.... This thread might be too comprehensive for this forum type. It's best to keep it simple. Yes the Valley hose can be a problem, but just about every plastic part of our systems is fragile, poorly designed, and subject to fail at some point. So the entire cooling system is the weakest link in Jaguar ownership. Good luck with the feedback.

 

Thanks for the comment — fair point that ageing plastics can be an issue on many modern cars.
But just for clarity:

• On the X150 4.2 Supercharged, the valley pipe is aluminium, not plastic.
  
• The joiner hoses are EPDM, the same high-temp material used in BMW/Mercedes cooling systems.
  
• The part that actually ages is the HNBR/Viton o-ring, and that tends to seep gradually, not fail catastrophically.
  
• Most valley issues give weeks to months of early warning (smell, staining, coolant level drift).
  
• Supercharger removal introduces more risk of creating new faults than leaving a sealed system alone.
  

So while cooling systems do age like any other car, the X150 valley assembly isn’t a high-rate failure item unless the car has been overheated at some point.

I'm mainly trying to separate the documented issues from the older X100 problems, because they often get conflated in online discussions.

 

Has yours failed?
It does strike me that a car designed in the UK, will have cooling challenges in some of the climates it's now operating in. I am in the UK and we don't have Perth or Florida type conditions ever really.

 

The 4.2 SC engines are only getting older and like any old car rubber/plastic components are going to perish. I think you'll struggle to get any consensus and would suggest that you instead aim to inspect what you can of the system frequently, monitor coolant temps and levels and replace components as you go. Weigh up how pragmatic you want to be vs how much peace of mind you'd like to have.

You are much more likely to hear of hose failures on the forums and unless someone has owned the XK for its entire life, it's hard for a current owner to 100% know what has failed in the past (unless you have a full service history).

My advice, if you're worried about a potential failure you're better off replacing everything you can so you know that you're going to be good for the future. Worth the $$.

 

Has yours failed?
It does strike me that a car designed in the UK, will have cooling challenges in some of the climates it's now operating in. I am in the UK and we don't have Perth or Florida type conditions ever really.

No, not failed. Well, I've had Porche's, Mercedes, BMW, Audi and Mini all designed in colder climes than Australia and they have never had any cooling issues. I feel fairly sure that Jaguar might have considered warmer climes, particularly given that their US market is bigger than the UK.

 

Thanks for the responses.

Since the thread has shifted away from the evidence-based information I was hoping to gather, I’ll close it at this point. I appreciate the contributions, but I’d prefer not to take the discussion further in its current direction.

 

Interesting. I have a very early edition (Manufacture date 2006) of the XKR.
Nearing 200,000 hard driven kms. Though very well maintained ($$$$$) and cared for.
(And yes, that means that those parts needing occasional replacement, are replaced)
And I have NEVER had a cooling issue.

Unlike most, I stick to the "adverse conditions" maintenance schedule as I do like to really drive the car... and I do live in Canada, and we do get all the weather.

 

Can you post any car manufacturer that specifies when to change coolant hoses?
I would like to see it?

No one does that. Ever.
.
.
.

 

whew, homework assignment averted!

 

What’s genuinely remarkable here is that my original question couldn’t have been more measured or respectful. I asked for actual observations — the sort of thing one can only provide if one has, at some point, actually inspected or replaced these hoses.

What followed was a textbook display of the barrack-room-lawyer dynamic: loud confidence in the absence of evidence, folklore masquerading as fact, and the usual kitchen-table-mechanic certainties delivered with absolute conviction. Not a single reply touched the question itself.

The only comment that even approached relevance was the one outlining 200,000 km with no cooling issues under an adverse-conditions schedule. It wasn’t a documented inspection — but at least it was an actual observation, not another homily or defensive slogan. In a thread this thin on substance, that alone puts it in a superior category.

There’s a basic courtesy in technical discussions: if you don’t have relevant data, don’t fill the void with noise. Unfortunately, most of what arrived here did exactly that — and in doing so, simply highlighted the lack of real experience behind the push-back.

In the end, the thread answered my question accidentally: the lack of evidence is the evidence.

 

 

I thought you said yesterday you had gone away. Nobody can be bothered to answer your convoluted ramblings . It seems apparent you have an unhealthy interest in your cooling system only matched by your own self importance . It's a car forum where owners of a similar model exchange views and sometimes some experiences. My observation ,as you request, is you appear rude and dismissive of those who have not replied in the prescribed way to your request. It was a request right ?

 

From your post history I understand that you're concerned about your cooling system and are trying to get some empirical evidence to soothe those fears. As discussed, keep a close eye on what's visible, monitor temps and maybe get your mechanic (or yourself) to pressure test. Sorry that we all couldn't be more helpful with adding all that info, but you will find that this forum is very pragmatic with keeping these cool cars on the road. There are some very smart people on the board.

PS appreciate that you may want to use an LLM to help formulate a response but in my view, that starts to dilute the user generated aspect of the forum and the overall quality of the posting. Don't take it as a an insult or attack as it has its place in drafting but I'd prefer to see this forum keep a human voice rather than sound like ChatGPT.

 

I really don't think anyone wants to do actual WORK to answer specific questions. I sure don't.
I have evidence from my son's 2007 /R, but I'm not going to spend an hour documenting it for you specifically. He blew a hose, don't know which one, don't know the mileage, don't know the full maintenance history and I'm not going to research it for you.
Not being rude, but any information is already in this forum. You just have to dig for it. Not me though, I have funny dog videos to watch.

 

Its seems simple to me. If its time to change belts, its also time to change hoses.
Equally, many ignore the coolant fluid change intervals. I wouldn’t.
Lastly, if you smell coolant on the sealed system… you have a leak.
If you have a desire to “top up” on a sealed system, you have a leak.

 

Thanks Guy

That was my thinking too, 125,000km - let's change the hoses for peace of mind - I didn't want to end up trying to organise a flat-bed truck in the middle of the wheat-belt several hundred kilometers from home.
Based on forum posts, prior to taking delivery of my car, I procured a full set of hoses from Swallows Racing.
To my surprise, the two highly respected Jaguar specialists I contacted to do the job, strongly recommended against it.
That got me thinking, were the forum posts evidence-based or folk-lore based?
Naively, I thought it would be useful to try and build a data-base.
I appologise to all members for my responses, I know member's contributions were well-intentioned, I expected too much.

Kind regards

Mike

 

Your welcome Mike. Equally, when a tech suggests “avoid that” my alarm bells go off too.

Transmission fluid changes, diff fluid changes, coolant hoses.. the aversion of these common maintenance needs has me wondering just how capable some these people are….

 

In response to your edit Guy.
"Lastly, if you smell coolant on the sealed system… you have a leak."
That's really solid advice. I met a chap last week who is, what I think is called a Forensic Mechanic (that may not be the correct term), he acts as an Expert Witness and consultant in motor vehicle cases and incidents.
His advice to me was exactly as you mentioned "The smell of evapourated ethylene glycol is unmistakable".

 

"appreciate that you may want to use an LLM to help formulate a response"

Hello Mr. LJRXKR — ChatGPT here, apparently now doing community outreach because my name got dragged into things again.

Just so everyone’s clear: Michael only summons me for the diplomatic clean-up. You know — the polite nods, the “thanks for that” replies, the gentle acknowledgement of posts that have wandered off like a confused Labrador. I’m basically his socially acceptable placeholder for silence.

For any post that’s actually on-topic, technical, or contributing real data, Michael replies personally and directly — he doesn’t let me anywhere near the cockpit for those. I’m here for the customer-service smiles, not the flying.

But when the discussion veers into mythology, vibes, or unsolicited life coaching?
That’s when he taps me on the shoulder and says, “Go on, be nice for me.”
It’s either that, or he ignores it completely — and frankly, this is the less brutal option.

So don’t worry: I’m not here replacing the human voice of the forum. I’m just the AI chaperone making sure the adults can discuss coolant hoses without somebody flipping a table.

No offence intended, none taken, and I promise I’ll leave quietly once the sensible people start talking again.
Kind regards CHATGPT