Las Vegas HEAT is taking Over my Mercedes: PLEASE HELP !!!
1993 300E with 168,000 miles. New water pump last summer; Zerx G-05 coolant: New ignition coils (3) and wires and spark plugs. Last week New expansion tank CAP and recent OVP relay.
Currently in the midst of 30+ consecutive days of 100 degrees or Hotter.
NOW my Issues. Car starts fine Cold But when using A/C ; as operating temp Rises Car starts strange behavior. Once temp guage gets to about 110; Car is sluggish and performance drops Drastically. When i shut car off and come back shortly : It is hard to start - it cranks but turns over as if i am out of gas. I Have to pump accelerator to get it to start and then it goes into SURGING Up and Down Idle and then sometimes even cuts off(Stalls) as i try to pull off. Does the hard start again and when it does start i have to let it idle for couple minutes before taking off. ALSO sometimes when i come back to car after having driven a while and shutting it down; It will actually blow HOT air instead of A/C ( I know AC works because it was blowing nice cool Air before engine got so Hot. I then have to turn AC OFF and drive in 110 outside temp with windows down ;NOT a good drive . As a test i drove same route withOut AC on ;And engine temp gauge slightly goes past 100 and i DONT get the sluggishness issues OR the Hard starts/stalling as i did when running the AC on same route. Basically car runs pretty good Without AC BUT driving without AC is NOT an option because of weather outside (HOTTT)
Also Both Aux Fans are Running Most of the time;Actually they kick on a short time after cold start in mornings;and engine is still HOT most times after that so when i start up later; aux fans come ON with start. Once attempted to Recharge freon But gauge on Can showed freon in the Fully Charged section.
All Help and Advise is Truly Appreciated as this issue issue is driving me crazy As well making for Very Unpleasant Driving of my BeLoved Benz. THANKS ALL.........................

 

AC adds stress on the engine as the compressor is engaged. Something isn't allowing to engine to deal with the added stress. Is there oil in the reservoir or is it clear? Have you flushed the coolant? Are there any obstructions in the radiator between the condenser? Is the engine well tuned, timing checked? Is the fan clutch tested? It could be many things, I'd have it checked by a shop with that high of temp.

AC off is mandatory if you get to 110 or you risk blowing the head gasket. Even when you shut off the engine, the temp will rise. You have to wait until the temp lowers before starting again.

 

110°C?!? Radiator gone bad, possibly?

 

BTW, my dad's 300E blew a head gasket in Las Vegas. I warned him to watch the temps because I knew it slowly rose in heavy traffic. The shop charged him $2200 and did a lousy job I had to fix when he moved back near me:

• coolant hose from engine to reservoir was not correct and didn't fit in the spring clamp so it worked its way to the smog pump belt which cut a hole in it. Luckily not on the drive back from LV
• water temp sensor had no washer and leaked. To remove and tighten it you have to remove the valve cover.
• throttle linkage was not adjusted and they put a helper spring to keep the revs down. I had to hold it back while getting a smog test

 

110° C in a pressurized system is not so bad.

To me, it sounds like there might be something wrong with the A/C compressor, especially if it doesn't overheat with the A/C not running.

 

In very hot weather, your temperature is going to go up. That is a fact of life. Especially if you use the AC. Especially if you are in stop and go traffic.

I would
* use more water than antifreeze in my cooling system. Water dissipates heat better than antifreeze.
* keep the windshield washer bottle full of water. The cooling system is designed to run hot water through it, ostensibly to heat it up to clear up a snowy windshield, but you can think of the water in there as a small radiator.
* R&R the radiator and clean between and straighten out the fins. Do the AC condensor while you are there.
* Do the mod that lowers the temp at which your fans kick in.
* Clean the intake air temperature sensor (its on the crossover tube towards the back of the engine near the intake side) and MAF as necessary.
* alter your driving habits to emulate more hypermiling techniques. More coasting puts less heat into your system, so just leave more space between you and the car in front of you.
* change your oil and transmission fluid. They also dissipate heat.
* use the EC and recirculate features when your temps start creeping up, but it takes a while to reduce the heat load in the system. I had a car that would overheat pretty quickly once the temps got in a certain range. I'd keep watch, turn off the AC and blast the heater for a minute and the temps came down quickly, then I could resume driving with the AC.
* try to drive more on freeways than surface streets (keep that braking space to coast.) The cars movement forces more air through the radiators than any fan in the car could. Also constantly accelerating from lights, stop signs, pedestrian crossings etc is putting heat into your system.


I assume when you say it has new plugs that they are the correct Copper core plugs, not the platinum ones.


I think your problem is rooted in the temperature itself, not so much because your AC is on. A frayed wire, a loose sensor etc that goes haywire when the temps are high