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Anthony, ASE Certified Technician
Category: Toyota
Satisfied Customers: 11750
Experience:  ASE Master Automobile Technician with over 20 years exp. in this field.
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Scion xb: 06 scion xb 250k miles, coolant feeding out of radiator

Customer Question

06 scion xb 250k miles, coolant feeding out of radiator and overfilling overflow tank, causing vehicle to overheat once coolant reaches low level in radiator. coolant filler neck appears to have hairline crack, could this cause radiator cap to not seal and give me the peramiters that im having? any ideas? thanks!
Submitted: 1 year ago.
Category: Toyota
Expert:  Anthony replied 1 year ago.
Hello!If you remove the cap when cold and the radiator full then start the engine does coolant start to overflow very quickly?
Customer: replied 1 year ago.
Not quickly, real slow. When warm, thermo open, radiator cap on, I disconnect over flow tube at filler neck and coolant consistently flows. I'd say at the pace of a cup an hour
Expert:  Anthony replied 1 year ago.
Does the water stop overflowing with the cap off and the engine running?
Expert:  Anthony replied 1 year ago.
And it not overheat?
Customer: replied 1 year ago.
Only comes out overflow tube when running. drove almost 100 miles today with no issues, only overheated at the tail end of drive
Expert:  Anthony replied 1 year ago.
Ok, if you remove the cap and let it warm up then raise the rpms to about 2000 and let it run that way does coolant come out of the radiator?
Customer: replied 1 year ago.
I see it circulating in the filler neck but does not come out
Expert:  Anthony replied 1 year ago.
Ok, i see. What you are seeing is a small leak in the head gasket thats starting to push water out of the radiator. This first shows up slowly and only when the engine is under a load. Eventually it will show up at idle and you will see it come out of the radiator cap. The parts stores sell chemicals that you can put in the cooling system that will seal a small leak like you have and they work well in that instance. The best brand i used is called Blue Devil and heres a picture of the product:

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