Dear Forum,

Have a 91 300E 4MATIC. The outside temp. right now is around 5 degree's C. Car is running at 120 degree's C with a short 5 minute run around the neighbourhood. The fans on both sides of the radiator (fore and aft) are working. When i turn the car off i can hear fluid noise from the radiator, does that mean the fluid is still circulating. In an ideal environment where the radiator is full of coolant isn't it impossible to hear the fluid circulate in there because it should technically be full of fluid?

Since the fluid is still running i dont think it's my water pump, i dont see steam so i dont think it's a leak in the hose.

What the Hell can it be?
(I will check the oil when the car cools down)


Jman

I'm not a tech, but here is what I would look at if it were happening to me.

1. Flush coolant and replace with original mb coolant at the correct water to coolant ratio.

2. Check thermostat for proper operation.

3. check for bad hoses.

4. check radiator water filler cap and replace if necessary.

5. check for proper operation of the water pump

6. check that fan and fan clutch are operatng properly.

7. check for worn or slipping belt.

I wouldn't do it necessarily in the order I listed.

I would start with checking everything, then flushing, then checking more mechanical items like cap, thermostat, pump, etc.

Alon

Have you checked your coolant level? If the level is low, what you are hearing could be what coolant you have left boiling. Has your heater been working properly the past week or so? If coolant is low, the heater may not work properly. If the level is low, then you have to find out why, leaks, boiling off, never checked???

Replace the thremostat. The noises you hear is the coolant boiling inside the cooling system.

Thanks guys,

I checked an hour later and discovered that the coolant was half-way below the indicator level ! I will go to the dealer tomorrow to get more coolant, but what was there so little fluid left? Boiling off, what would cause this?

Thanks for the recommendations

Jman

Say hey, it's probably the thermostat. If tha't not it then it's the radiator core plugged up or the water pump (doubtful). I'm betting on the t-stat. If it doesn't open, the coolant in the block just percolates away. Be careful with the MK103, hi heat is flirting with a blown head gasket..