93 300E W124 Overheating

[biking4jesus]

New here so bear with me if i don't know much about these MB's


Back in July, the car blew it's original radiator. Top plastic hose neck cracked about a block from home and we limped the car back. Took it to our specialized MB shop who had serviced this car for us over the last 5+ years. They replaced the following w/ MB parts-
- thermostat
- water pump
- hoses
- radiator (behr) aluminum
- timing belt (tensioners etc)
- new coolant

There was no mention made at the time if the head was damaged and the car showed no signs of that being an issue then.

The car was driven daily in Southern California for a month in 90-100 deg weather and temps ran normal (in the middle). We never saw the temp gauge creep up. We towed the car w/ a uHaul truck to the Bay Area in August for a post-wedding move.

Car has been fine here in the Bay Area, overall cool temps in the 50s-60s and gets us around town, errands as needed. About 2 weeks ago it was rather warm outside (90s) and the car got hot and the needle crept close to the 120 mark but never went all the way to the top. since, the outside weathers temps have been around 70 degrees and the car shouldnt be overheating.



-electric fans are working normally (i can hear/see them turning on and off)
-not leaking coolant or boiling over
-coolant level appears normal while car is off and during operation
-overheating occurs at all speeds but does not increase w/ more speed
-radiator cap appears to be in good shape
-engine fan is hard to spin when engine is hot (meaning clutch is still good?)
-turning on the heater full blast will drop the temp 1/4 down the gauge
-top radiator hose to tstat gets hot (coolant is flowing)
-no loss of power or other performance issues

car has around 250k miles.

thoughts or ideas?

[Wodnek]

My money is on your fan clutch. These are very finicky, even if they don't appear to be bad, they can cause your temps to run hotter.

[Ferdman]

FYI ... Your engine has a timing chain which is on the front of the engine and is covered. Apparently in July the shop replaced the accessory belt tensioner.

I suspect the thermostat is malfunctioning.

[ps2cho]

I think your coolant level is low. Remove the cap completely and pour in MORE coolant. Do not just use visual. If it overflows then just remove some and you are now sure it is full. The shop could have forgot to run the car long enough after the top up. Silly mistakes sometimes happen. Only now on hotter days are you seeing the capacity show its issue.

With all the replacements, it doesn't make sense. Only other item would be pressure loss via the cap so check that it is holding pressure over night. It should hiss in the AM after driving the day before. That or a faulty tstat.

Fan clutch is tested when stone cold. If it spins more than 1/3 of a turn then it is toast.

[biking4jesus]

coolant level is full, im fairly sure of it. ive squeeze the hoses and burped out any air and added a few more ounces of distilled water to the reservoir tank. i'd think that we would have ran into issues w/ coolant level back in July when we were driving in when it was hotter outside.

i'll take a look at the fan clutch and try spinning it again when the car is cold.

if the thermostat was bad, wouldnt the hoses remain cool and not get hot from coolant passing through them?

ordering a new cap is like $5-6 so that is something i'll do

[lee polowczuk]

fan clutch, thermostat,and cap in that order.

fan clutch is easy to eliminate. the others cost next to nothing