Why is my Jaguar XK losing coolant?

Short answer: On the X150 XK and XKR, slow coolant loss is often a cracked plastic coolant pipe. The common ones are the outlet crossover pipe and the heater inlet and outlet pipes in the engine valley, plus the thermostat housing. These plastic parts get brittle with heat and age. Owners who replaced one often replaced all the plastic pipes while they were in there. A pressure test finds the leak. Don't keep topping up and driving, because overheating can ruin the V8.

Symptom: The coolant level drops slowly, a sweet smell after driving, a low coolant warning, dried coolant crust around the top or back of the engine, or a temperature gauge that creeps up.

What to check first

1. Have the cooling system pressure-tested to find the leak.
2. Look around the thermostat housing and the top and back of the engine for crust or wet spots.
3. Ask the shop to check the plastic crossover and heater pipes in the engine valley.
4. Watch the temperature gauge and stop driving if it climbs.
5. If one plastic pipe has cracked, ask about replacing the others at the same time.

Likely causes

1. Cracked plastic coolant crossover pipe. Sits under the intake in the valley.
2. Leaking heater inlet or outlet pipe. None
3. Leaking thermostat housing. One owner replaced theirs at home.
4. Loose clamp, hose or radiator. None

What it usually costs

One 2013 XKR owner on Jaguar Forums replaced the thermostat housing themselves for about $120. Owners didn't post shop prices for the crossover pipes. That job means removing parts of the intake, so get a written quote.

Is it safe to keep driving?

Not for long. Owners warned that any coolant loss on these V8s is a serious risk, because overheating can damage the engine. If the gauge rises or the warning comes on, stop and let it cool. Verify with a mechanic.

DIY or shop?

Shop for the valley pipes unless you're experienced. The thermostat housing and hoses are a reasonable DIY.

Recalls, bulletins and complaints in plain words

• No coolant pipe recall: NHTSA lists XK recalls for these years, such as 10V332 (in-tank fuel pump on 2010–2011 XK) and 15V038 (exterior lighting), but none for coolant pipes. If your car is part of a recall, the dealer fixes it for free.
• NHTSA complaints: 6 keyword-matched complaints for Jaguar XK 2007–2015 (of 52 unique complaints queried, NHTSA complaints API by model year, queried 2026-10-21; keywords: coolant, antifreeze, overheat, water pump, thermostat, leak) (NHTSA returned no complaint data for 18 model-year queries). This counts complaints that mention these words. It is not a defect finding.

What owners report

• In Outlet Crossover Pipe & Heater Inlet/Outlet Pipe Replacement on Jaguar Forums, X150 owners walked through replacing the plastic outlet crossover pipe and the heater pipes, with part numbers for the front and rear pipes. The advice was to replace all the plastic coolant pipes at once rather than one at a time.
• In Slow coolant leak on Jaguar Forums, owners chasing slow coolant loss recommended a pressure test to find it. A 2013 XKR owner said they replaced the thermostat housing themselves for about $120. Members warned that any coolant loss on the V8 is high risk and shouldn't be ignored.

Quick tip

On these Jaguars, ask for receipts for the plastic coolant pipes. If they're original, budget for them.

Vehicle focus: 2007–2015 Jaguar XK and XKR (X150), mainly the V8.

Safety / mechanic note

Low coolant can overheat and ruin the engine. Verify with a mechanic.