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peterpete190
peterpete190, Auto Technician
Category: Jaguar
Satisfied Customers: 29118
Experience:  Auto repair Technician with 17 years experience.Past ASE and other certifications.
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S Type low coolant level. Stopped & level about 1/3 down

Customer Question

S Type low coolant level. Stopped & level about 1/3 down expansion tank. Removed cap, and level went to over-full. Checked next day, when cooled, and had lost around 1/2 litre of coolant.
JA: How many miles on the car? How has your mileage been lately?
Customer: Around 120k miles. Do quite a lot of long runs - at least once a week.
JA: What is the model/year of your Jaguar?
Customer: 2004 S-Type 2.5 petrol.
JA: Are you fixing your S-Type yourself? What have you tried so far?
Customer: Haven't tried anything, yet. Not all that mechanically monded! Just thought I'd check whether any obvious likely problems before taking to garageeeeeeeeeeeeee.
JA: Anything else you want the mechanic to know before I connect you?
Customer: Explansion tank was replaced about 2 years ago; otherwise, no.
Submitted: 2 months ago.
Category: Jaguar
Expert:  peterpete190 replied 2 months ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

When the engine is hot or coolant is under pressure after driving the level can drop some in the reservoir then rise once the cap is removed and is normal to a point.When cold it will sit at the correct level and if it was low then this indicates a coolant leak.

What has to be done from here is to have the coolant pressure tested with an engine coolant pressure tester.Once this is done any leaks found will need repaired to resolve this fault.You can get any shop/garage to pressure test the cooling system to locate the leak.In some cases when no leaks show up when tested coolant dye has to be added to the system to then use a dye tracer light to locate the leak needing repaired from there.I have seen leaking hoses and radiator as well as a leaking water pump as the most common causes.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated ( should be a link to click on here or above).You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

Customer: replied 2 months ago.
It was the low coolant level alarm that caused me to stop and check the level. This hasn't happened before in 6 years of ownership. Is the problem necessarily a leak, or could it be an air-lock, sensor, or thermostat problem?
Expert:  peterpete190 replied 2 months ago.

If the level is below the minimum in the coolant reservoir then there is a leak that needs located and repaired.You would need to have the coolant system pressure tested to locate the leak.

If the fluid level when cold is at the proper level then there is no leak and the fault is the coolant level sensor in the reservoir at fault needing replaced.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete

Customer: replied 2 months ago.
The coolant sensor must be working, as the level was low in the reservoir when I stopped as a result of the alarm. However, when I checked the level the next day, when cold, it had not fallen by anything like the amount it seemed top have when the alarm occurred. I therefore thought there must be an explanation other than leak or reservoir sensor.
Expert:  peterpete190 replied 2 months ago.

If the reservoir is not venting as it should due to a faulty cap this can cause a vacuum in the reservoir pulling down the fluid level.I have seen this occur and is the easiest and fastest repair to replace the cap.This is common.I would try this.I dont see this as a leak or thermostat issue and if the warning came and went then the sensor is working and I would lean more on the cap as the cause.

Let me know if you need anything else and feel free to rate my help here or above ( should be a link to click on ) as this is how I receive credit for my time.Your 5 star rating is appreciated

Thanks Pete