1994 s500 W140 Bubbling Sound in Heat

[sulman2703]

The past week has been pretty hot here in Chicago. My 94 s500 has been keeping me cool, even through Chicago traffic. The engine temperature gauge also indicates the temperature to be at the normal level. A few days ago, I parked the car after a 30 minute car ride, turned it off, and walked out. I could then hear a bubbling/boiling noise coming from the coolant overflow tank.....I think the sound was coming from there. I could also still hear the coolant circulating through the pipes. Is this something to be worried about, it hasnt done it ever since....

[JimF]

Check the radiator cap . . . might be time to replace it???

[sulman2703]

I will take a look at the radiator cap today.....Are you thinking that if it is worn, that the fluids aren't pressurized and the boiling point of the antifreeze is lower? If the car is not heating up, do you think its even a real problem. The level of the antifreeze is normal.

[JimF]

Originally Posted by sulman2703

I will take a look at the radiator cap today.....Are you thinking that if it is worn, that the fluids aren't pressurized and the boiling point of the antifreeze is lower?

. . . precisely.

[sulman2703]

Hey Jim

I checked out the radiator cap, but it looks good. I noticed the antifreeze level was a bit lower, I could not see any markings that would indicate how high the level should be. Should I just fill it to the neck? Also....won't I need to get the specific Mercedes antifreeze from the dealership?

[syljua]

Not to upset you,

but, bubbling in your cooling water could also indicate a connection
with the cylinder and that exhaust is getting inside the water (blown
head gasket). If so, you should be able to smell exhaust from
the cap. Other signs will be white smoke in exhaust.

br,
syljua
W140 S320 1998

[sulman2703]

Hey,

Would there be a change in driving if the head gasket was blown. The boiling sound only occurred once and has not repeated itself. There is no loss of power, no white smoke, the oil level is full and is uncontaminated......The car is running great, and no overheating (it was nearly 100 today in Chicago, drove about 100 miles)...

[JimF]

Originally Posted by sulman2703

Jim
I checked out the radiator cap, but it looks good. I noticed the antifreeze level was a bit lower, I could not see any markings that would indicate how high the level should be. Should I just fill it to the neck? Also....won't I need to get the specific Mercedes antifreeze from the dealership?

It can't be real low so just add distilled water to fill it to the break point just above the 'seam' level.

You can't tell by looking whether a rad cap is good; if there's ridges in the rubber, it probally s/b replaced.