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About a month ago my coolant reservoir kept getting low, then gradually had to start buying bottles and filling it up every few days, it’s not the head gasket, there no milky sludge in oil, heat works, no white smoke none of that, today I let it run and looked like it was coming out of this hose pictured but was only dripping and wouldn’t cause flood it made, anyone know different locations to look because I can’t find it Hose below the serpentine belt is the one I seen dripping and there a hole from the plastic right below that is where it’s dripping from
If at front of engine M276 3.5NA , these are the coolant possible leak points :
01. Water pump leaking, it has a weep hole for when it leak
02. Plastic fitting for input of coolant from radiator ( cooled ), big hose. This marry to the water pump. Has rectangular seal.
03. Thermostat housing. This is coolant (hot) output to radiator. It uses seal too.
04. The small parallel pipe at front end of cylinder head which parallel both cylinder head coolant out, before it enters thermostat housing.
This one the leak will also enter the V bank. This is a Bi-tch to replace.
Coolant under extreme pressure seeks relief... I suggest you buy a tank cap plus the part where coolant is leaking. Radiator crimps all around both L+R sides and the plastic elbow pipe/O-Ring at fireall when engine has shaken enough on its old mounts.
What causes some of the heat damages you are facing is extended oil change schedule meaning poor lubrication.
Its best to dump oil at 5k Mi despite MB saying "once a year". You can but it's not your best interest.
Get a cooling system pressure tester. Apply some pressure to the reservoir. Get out a flashlight and look for where the coolant is pouring out. Remove the belly pans and get underneath if necessary...
I bought my car in they replacing the radiator and a hose was loose they said, but they finding oil in the reservoir….. is this a separate issue or leaking radiator and hose cause oil in reservoir? If not what would cause the oil in reservoir??
I bought my car in they replacing the radiator and a hose was loose they said, but they finding oil in the reservoir….. is this a separate issue or leaking radiator and hose cause oil in reservoir? If not what would cause the oil in reservoir??
Question is what oil? Choices are:
-1- engine oil from coolant exchanger
-2- tranny oil from radiator exchanger
Hopefully it's No1.
BTW... you likely have extreme heatsoak causing this. So look up CPS leaking oil into engine harness...
Last edited by CaliBenzDriver; Apr 1, 2025 at 05:38 PM.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
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