Coolant disappearing

STAYSLIDEWAYS

MEMBER
2004 HYUNDAI ELANTRA
4 CYL
FWD
AUTOMATIC
170,000 MILES

For the last few months I have had to keep buying coolant to fill my radiator. I cannot find a leak. I have parked it over cardboard overnight and everything to see where it is leaking but there were no marks. I pressure tested the lines and it has a slow leak because there is a tiny hole in one of the lines but not big enough to let any coolant out. I know for a fact the hole is not the problem. When it runs, the pressure is a little higher than recommended. Pressure testing the lines also checks the head gasket I believe and the head gasket is fine. I believe its the thermostat not opening enough but I need some more advice.

2 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

A coolant pressure tester cannot test if you have a head gasket letting coolant into the cylinder to be burned. Also, if exhaust gases are coming into the cooling system can test for that. You need to do a chemical block test. You can rent the tester at auto zone but they make you buy the chemical for the tester. Also when loosing coolant with no visible leaks a lot of people overlook a bad radiator cap not holding the correct pressure and loosing coolant that way.