Kris CLK55

Hello all

So I have a '01 CLK55 AMG and since few months I have a strange overheating issue. I bought the car second hand with 74k (Kilomiters) mileage. Drove it for a year with no issues with no overheating. The car started overheating with A/C on only and when kept for 20 min on idle or if I'm stuck in traffic for 15 min or so. When i turn the A/C off, the temps drop to its usual 90*C 92*C and stays there even if I'm still stuck in traffic. I live in Dubai where summer is 50*C to 55*C day time so I know its rather hot but the first summer I drove the car I had no such issues and I'm very heavy footed lol

Now when that happened I replaced following parts;

Radiator
Engine fan with fan clutch
Fan shroud
Coolant flush and new coolant in (Coolant was clean)
Had the coolant cap checked and its fine
Had the car diagnosed at Brabus with no faults regarding cooling system (Only O2 sensor on bank 2 showed fault)

All fans are working fine (Both A/C fans and engine fan)

I did diagnostics using my A/C panel and it showed one fault (Secondary coolant recirculating pump). Had it checked and its working plus I guess its for heating system only right?

Another thing is when the temp needle starts going up or down (Above normal temp 90ish*C it fluctuates. Doesn't just climb up smoothly but rather jumps up and down for a while and then goes up (Same happens when i turn the A/C off. Takes about 1 minute to fluctuate its way down to normal temp and stays there).

I'm running out of options here so any help is highly welcome.

Thank you

blackopal

Sorry to ask the obvious but did you change the thermostat as well? I'm guessing you might have given the other work you have done.


There are some earlier threads on overheating that it might be worth reading through as well

Kris CLK55

Thermostat has not been changed but I assume thermostat would cause overhear regardless A/C on or off and switching off AC would not result in almost instant temp drop to optimal.

And yes I went through all the overheating posts but none had the same symptoms as mine and no conclusive cause was pointed out.

I'm just tired of spending money on "possible" causes and I'm really looking for definitive solution at this point.

Just to mention, the fan clutch is aftermarket (Fibi brand)

Kris CLK55

Just had a look at the car again and I noticed something, as soon as I start the engine and turn the AC on bot AUX fans go full speed and stay full speed all the time. Never switch off or slow down... I found it strange but then I thought it actually cools the system more then running on stage 1.