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Ross, Diagnostic and repair technician
Category: Car
Satisfied Customers: 1183
Experience:  Licensed diagnostic and repair technician
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My mini one has had empty header tank and over heated and heating

Customer Question

My mini one has had empty header tank and over heated and heating blowing cold what could be problem
Submitted: 5 years ago.
Category: Car
Expert:  Ross replied 5 years ago.

techmachine :

Hi, welcome to Just answer, my name is Ross, i will help with your question

JACUSTOMER-7cuyicij- : Ok thanks
JACUSTOMER-7cuyicij- : Do you know what problem could be
techmachine :

This may be a silly question, but has there been any obvious signs of leaks?

JACUSTOMER-7cuyicij- : No none
JACUSTOMER-7cuyicij- : That I no of we have had snow today so ground very wet anyway
techmachine :

Ok, the heating will blow cold as soon as the level drops to a certain point, this is because the coolant can no longer be pumped into the heater, this is a normal side effect of low coolant level, for it to have dropped this low, it would have either lost a lot of coolant very quickly or has been gradually loosing it, Although there may not always be obvious leaks, often it can drip when driving when the engine is hot and stop as soon as it cools down, this coolant often evaporates on the hot engine so leaves no signs.

JACUSTOMER-7cuyicij- : I put coolant in tank but drove it again straight away still went to over heat but I stopped straight away my partner who isn't a mechanic says it could be head gasket
techmachine :

It is possible, however because the level was so low simply putting water in there will probably cause air locks, this will cause it to overheat, its vital the air is expelled from the system. If it over heats during this process, we can move on to the next step.

Is there any signs of water in the oil ( white gunk on the filler cap or dip stick) or oil in the water? (oil slick on the surface of the water in the tank)?

JACUSTOMER-7cuyicij- : Not that I no of
JACUSTOMER-7cuyicij- : Is that all u can tell me
techmachine :

Ok, this is a sign of head gasket failure but its not conclusive by any means.

First, ideally you need to examine the underside of the car, starting with the radiator and all of the pipes and connectors to the engine head and block and water pump for any signs of leaks, the system should be pressure tested so if water is escaping from somewhere it will show up. If this does not show any obvious leaks it could be the head gasket, this can be checked using a block or sniff test which tests for signs of emissions in the exhaust, also a compression test may be necessary, this is advised to be done before diagnosing a head gasket due to the cost of the repair.

Common causes of this are leaking radiators or water pumps, if there is nothing obvious it could simply be a faulty radiator cap, these contain a pressure release valve which if becomes faulty will allow steam to gradually escape and the level to drop.

JACUSTOMER-7cuyicij- : Ok so best book it in for garage to have a look at
techmachine :

A garage will have the correct equipment to quickly and positivity identify the problem so is the best way to go.

You can do the basics your self by getting under the car as well as you can with a torch to look for visible leaks.

Check for signs of white gunk on the dip stick or oil filler cap.
Excessive white smoke from the exhaust when the engine is hot

JACUSTOMER-7cuyicij- : Ok thanks
JACUSTOMER-7cuyicij- : Is it safe to drive it home it's about 3 miles away
techmachine :

If its over heating, i wouldn't advise it, the engine will reach damaging temperatures very quickly but the over heating may be due to air in the system so if you can, remove the filler cap, set the cabin heater fan on full and set to HOT, start the engine with the cap off and let it idle, if you can, gently squeeze the radiator pipes, this will help push air out, you will probably notice the level in the tank drop as air bubbles come out, top up as necessary, then replace the cap, its vital you get hot air back, as soon as it starts blowing hot in the car, you can keep this blowing hot, this will keep the engine cool, providing the temp gauge does not rise beyond normal, it will be fine to drive.

Expert:  Ross replied 5 years ago.
Hi Jayne, I hope you have had some luck with your car, If you do need further help with your coolant loss problem please feel free to get back to me.

Otherwise, good luck and remember Im always here if you ever need me, Im eager to help. Regards, Ross.