coolant getting low ! 560

[560er]

Hi all I have 1990 560 euro spec, my problem in short is it loses coolant while running, if in town after around 3 to 5 day's the low coolant light pops up. on high way maybe after 100km (around 60 miles) i've changed the following: 1- resrve tank cap 2- radiotor 3- thermostat 60c (it's hot around here ) 4- water pump aux fan and fan clutch are ok. i've filled the radiotor and left the cap open then ran the car and waited to warm up i've notice that the coolant is going up after some time and kept getting up!! maybe there is a presure biulding up some where ? one mechanic told me that i need to change the head gasket, but there is no white smoke, no water with oil. the coolant is getting out throw the cap because i notice the coolant around that area on firewall. the car is running smothly and accelation is good should I change the head gasket or am I missing something? thanks in advance.

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[DrB300SE]

I'm in the middle of changing out my water pump (89 300SE). I used a bottle of UV Liquid ($6 US at parts store) and a standard black light bulb to locate the leak.
Try it, it's easier than guessing.

[daniel_pvq]

i found the coolant leak on mine (86 560sec euro) in the heater valve solenoid diaphragm. right next to the batery. very easy to take apart and replace that diaphragm.

[Berde]

If the UV light does not show anything, then it could be an internal loss. But, before you replace the head gasket, check the radiator pressure. It should keep around 14 PSI when engine not running. Then, run the engine and if it is well pass that then you have compression from the cylinders getting into the cooling system, which is typical of head problems (gasket damage or cracked head). Not always when an issue with the head arises there is water in your oild or visversa. When the thing escalates to that then usually the car will overheat in a matter of hours and will gulp mounstruos amounts of coolant. Snap-on tools makes a very good Cooling system pressure check with diferent adapters to conform to different size necks openings. Hope is just a heater hose gone bad, which is not serious and an easy fix and that my comments show you some light! G.L. with the fix Bud