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Peter Zavarelli
Peter Zavarelli, Auto Mechanic
Category: Car
Satisfied Customers: 36414
Experience:  Technical Consultant at Just Answer
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Just bough a jaguar s type sport 2,5, 2003 model. all seems

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hi, just bough a jaguar s type sport 2,5, 2003 model.
all seems well. however 'coolant low' light came on - went away after a while on its own. checked the coolant level and seemed ok. However, when the car is cold and I try and take the coolant cap off, there is a lot of pressure and the coolant starts to leak out - when cold - which seems a little weird.
Oil colour is clear
coolant colour is fine (red)
any thoughts?

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.
I try to be here most weekdays and some weekends. If you respond and I do not respond back right away I will do so as soon as I can.

Is the upper radiator hose hard when squeezed when the engine is cold ( overnight sit or several hours of sitting ) with the issue of the pressurization of the cooling system?

Have you replaced anything to try and resolve this issue here at all?

Let me know, thanks, Pete.

Customer: replied 10 months ago.
Hi, thanks for getting back - I haven't checked the hose as yet - and wont be able to until i get back from work this evening
I was thinking about releasing the air by opening the cap very very slowly but haven't done that yet.
only got the car yesterday - nothing done to it. drives fine otherwise - the ac and heater are all working normally. the temperature gauge is also staying bang in the middle and there is no overheating sign.
very confusing...

It almost sounds like air is trapped in the cooling system. This will create unwanted pressure which will cause the issue your seeing with the pressure under the cap as well as can force an air bubble around the coolant level sensor intermittently setting off the low coolant warning. This won't cause an overheat as there is enough coolant in it to allow the engine to cool properly.

I would have the system bled of air ( usually the best way is with a coolant vacuum machine by a shop or dealer) and it would also be a good idea to have the thermostat replaced as it can stick in some cases causing pressure issues as well.

But this does sound like air trapped in the system needing purged/bled out.

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. I work on delivering the best answer and help here but in some cases, it can be difficult to do without seeing the vehicle.

Thanks, Pete

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Customer: replied 10 months ago.
Thanks Pete - that makes sense.
will it damage the car if I drive it for the moment without bleeding the air immediately?
and also, can I bleed manually by opening the cap very slowly?
how much does it cost to get this done? (do you provide this service - where are you based?)

You're welcome

As long as it is not overheating at all then it is o.k. to drive it but if it starts to overheat then you want this looked into and repaired.

Usually, I have taken the cap off slowly when cold and ran the engine with it off revving it up and down at a standstill to help purge the air and top off the coolant as needed. It will make a mess but this usually works.

Thanks Pete

Customer: replied 10 months ago.
Many thanks. That answers it perfectly.

Your welcome Andy

Customer: replied 10 months ago.
Actually - one last thing - if done manually, is there a chance that the flowing coolant can damage the metal in the engine bay - or will it be ok?

It will be messy and may get on wiring or hot exhaust so I always recommend a shop to do it with a vacuum fill to prevent this mess.I have done it before carefully and rinsed off any coolant that spills and made sure no wiring connections got any water in them.

Customer: replied 10 months ago.
Great. Thanks again.

Your welcome