 | Home > Faults & Fixes (L663) > D250 Coolant Leak |
 
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| Tobers Member Since: 01 Oct 2023 Location: Skye Posts: 48  
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After further testing, it doesn’t seem to be leaking from there, and someone else has told me how to remove the clips. They just slide off apparently, and are easily lost into the engine bay!
A few days ago I had a low coolant warning on the dash. The coolant was indeed low (ie not a sensor issue). There is dried coolant spray under the bonnet in this area. I have replaced the radiator cap with a new genuine one, but no difference. As it happens I just went out to test everything and it looks like there is no leak from this specific connection, but I think it is coming out from under the new radiator cap. I did run to get the car up to temp then did a few fast, high revving sprints. I haven’t caught it “in the act” yet, but have seen coolant all over the outside of the tank and dripping down. When cold, the coolant level is below the minimum mark so I don’t think I have overfilled it. Any clues? I’d take it to a dealer if they weren’t 100 miles away and in the throes of chaos after their recent hack. |
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15th Sep 2025 5:01pm |
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| Crazymind Member Since: 11 Jun 2024 Location: Glasgow Posts: 322
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That’s a “Clic-R” style snap clamp. If you haven’t Clic-R pliers (they have jaws shaped to engage the little latch), Place the pliers on the clamp’s latch tab, squeeze, this pops the latch open. At that point The clamp springs loose, and you can slide it back along the hose.you can reuse them as well. Just check they still have tension.
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15th Sep 2025 7:48pm |
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| Tobers Member Since: 01 Oct 2023 Location: Skye Posts: 48
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That's really useful thanks.
I am now suspecting a head gasket issue after further testing. Will see if I can do a combustion gas test tomorrow to see if that is the case. I am seeing bubbles in the coolant flowing into the header tank, like a fizzy drink. LR Assist coming tomorrow. |
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15th Sep 2025 8:26pm |
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| lightning Member Since: 23 Apr 2009 Location: High Peak, Derbyshire Posts: 3480
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That's not good news, please update when LR Assist have been out.
l have not heard of any head gasket issues with the 3.0. How many miles has it done? At least it's under warranty. |
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16th Sep 2025 7:05pm |
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| Tobers Member Since: 01 Oct 2023 Location: Skye Posts: 48
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28k miles and just under 2 years old. D250 HSE.
It has been recovered to my "local" dealer (100 miles away in Inverness) who had a loan RR Velar waiting. Dealer said to expect a wait of "several weeks" due to the warranty system being  . I'm not too bothered as I could do with keeping some miles off my car!
Unfortunately I couldn't get a combustion gas test done prior to the recovery so I am now in the hands of the LR gods. Worst case is head gasket. Best case is another faulty tank cap. Could also be the tank itself. Or something else. But the fact it blows the coolant out when up to temp at high revs indicates a high pressure problem of some sort. Bubbles in the coolant flow to the expansion tank are a worry. I will keep you all informed. |
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16th Sep 2025 7:25pm |
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| ruben Member Since: 04 Feb 2021 Location: ASTURIAS Posts: 380 
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Paradoxes of life... I sold my beloved D3, with me since new in 2006, which was strong as a locomotive and left like that with almost 500,000 km, for exactly the same problem... Nobody ever knew the real problem….that you describe... poured through the expansion vessel under high demand... there was never overheating or power loss, or restricted modes or other alarms... nothin….but Bubbles were seen, and there were no traces of Co in the expansion tank... they always said that these bubbles were normal... and they, dealers, changed the expansion vessel, valve cap, water pump, EGRs... I always thought there was air in the system... I don't know anything about it to this day since I know it's out there... and the paradox is that the need for change brought into my life my current Defender D250 exactly the same as the one you have that problem described..money on the sidelines, I almost went crazy...I hope it doesn't happen again…... Paradoxes of life!! Defender 110 SE I6 D250 23MY
ExDiscovery 3 TDV6 SE |
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16th Sep 2025 10:53pm |
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| Tobers Member Since: 01 Oct 2023 Location: Skye Posts: 48
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Further update on this.
Eventually, the dealer got around to doing a diagnosis and, as I expected, found combustion gases in the coolant. This causes over-pressurisation in the coolant system especially at high revs, and resulting coolant being forced out of the expansion tank cap. I knew all of this from my own investigations. They are now going to strip the head to check what the cause is. The tech expects one or more loose head bolts, saying they have had others with the same. It could also be a failed head gasket or a crack in the head or block. But I think his initial idea is right as I’ve heard of other loose head bolt issues. It sounds to me like some basic manufacturing defect. I’m surprised they haven’t done a recall. I’ll start another thread on this once I have the full diagnosis from the dealer when they have stripped the head down. |
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9th Oct 2025 8:56pm |
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| lightning Member Since: 23 Apr 2009 Location: High Peak, Derbyshire Posts: 3480
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lt's the only such failure l have heard of. So hopefully (despite what the dealer said) yours is an isolated case.
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9th Oct 2025 10:28pm |
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| Crazymind Member Since: 11 Jun 2024 Location: Glasgow Posts: 322
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I think the dealer refers to some early 3.0 Ingenium blocks, coming from the factory with inconsistent thread depth or finish in certain cylinders as especially #5 and #6 near the firewall.
When torqued, those bolts technically met spec, but the clamping load was slightly below ideal. after a many heat cycles, the gasket begins to leak combustion gases into the coolant jacket. JLR quietly tracks these through internal “Quality Incident Reports” (QIRs), not public TSBs — meaning your dealer may fix it under warranty but won’t call it a “known issue.” Very curious to see what is the cause… |
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10th Oct 2025 8:09am |
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| Tobers Member Since: 01 Oct 2023 Location: Skye Posts: 48
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Ah, that’s interesting. It is a late 2023 build, so some time from the early 3.0 6 cylinder engines. Maybe it had been sitting on a shelf for a while. The dealer’s tech was definitely leaning towards the “loose” head bolt situation.
Anyhow, I’ll keep you all posted. |
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10th Oct 2025 2:22pm |
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