hi there - i'm hoping to get some help with an overheating issue (i've read lots of posts but not sure if any match my issue...). i'm driving a 1993 w124 (300ce).

i replaced the thermostat about 2 months ago to fix a previous cooling issue and it worked like a charm..

now it seems like the issue is back again, so yesterday i popped the hood open and noticed that the pipe that goes from the radiator to the thermostat (circle in pic) was pinched shut, obviously from some kind of vacuum created internally!!!

after about 30 mins the vacuum went away but i also turn the car on (not the engine just to the first key stop).

appreciate to hear your ideas on what this could be!

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i'm wondering if the vacuum is being caused by a blockage somewhere in the rad?? if the thermostat opens when the engine is hot and is trying to suck in coolant but is not able to?

any easy way to check this theory?? any ideas are appreciated!!

Try a new radiator cap!.
I had the same thing happen to my 560SEC and an Indy MB mechanic happened to witness it and told me to check my radiator cap. I replaced the cap and it has never happened again.

__________________
1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.

If this happens to the top hose it is normally the radiator cap.

If this happens to the bottom hose the radiator needs to be cleaned out.

Pooka

Look at this link:

http://mgaguru.com/mgtech/cooling/cool_204.htm

Ignore the article, just look at the second photo down, where he is pulling open the little valve. This is what allows the coolant back in the radiator when the engine cools. If it gets gunk on it then it gets stuck shut. You can clean it if you want. Or you can just buy a new cap as was mentioned.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Thanks guys, it probably is the radiator cap simple things first! I will check tomorrow first thing in the AM.. after reading the article tho that wouldn't seem to explain the heating issue?

when i'm driving on freer roads (ie. not stop / go traffic) the temp is OK but in stop and go or when idling the temp will rise to around 100... rad cap probably needs cleaning / changing but won't fix overheating??

Sorry, your post seemed mainly about the pinched hose. No it won't help overheating. I do't have that car, but there should be either an electric fan or a thermostatic fan clutch. Either way the fan kicks in when the temp gets up around 100 or so. However I am not sure that 100 C is considered "bad'. There have been lots of post on normal operating temp. You might try searching on that.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

ya i've seen members reporting temps in the 90 - 100 range but makes me worried to see it jump from 85 to 100 or in some cases 105 / 110! i'm thinking the temp should stay more consistent at least

Check your Aux fan(s) to see if it engages(105C I believe), and your Viscous drive main fan, it may be bad.

__________________
1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.

yep aux fans do kick in right around 105C!! unfortunately, only 1 comes on (driver's side) and the pass side will come on if I hit it a bit... rusted motor on the inside or something? Is it possible to wd40 it or something?