355 Engine Runs Hotter After Coolant Flush and New Radiator

It's fairly normal for the temperature to raise quite a bit before the fans kick-in. The temperature should drop down with the fans on, or as soon as you start moving and air goes through the radiators.

If you still have elevated temps when driving in cool air, or with the fans then here are a few ideas:
- air in the system (did you turn on the cabin heater on while bleeding?)
- not enough coolant (did you top-up coolant when it cooled down?)
- Is the thermostat working correctly?
- Blockage (is the cooling system uniformly hot all over, any "cold" spots?)
- Does the new radiator have enough surface area compared to the original one?

I know these are basics, I'm not trying to offend...

By the way, there is a school of thought on here that the F355 runs too cool with the standard thermostat

There are *many* threads on F355 temps on here...

 

First get an OBD2 reader that can display the coolant temp to verify the gauge is accurate.

I had a problem with an erroneous coolant temp sender once.

Second, (and I don’t think this is the cause of the higher temps, but) you should choose coolant based on the coolant mfg’s recommendation for the vehicle.

IIRC Zerex G-05 is the correct coolant

Also, did you verify whether it’s premix or concentrate and dilute accordingly?

If the car is in fact running hot as corroborated by the engine ecu, the first thing to check is correct fan operation on both sides.


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Make sure both fans are working. They should both kick on around 190 degrees or so. If only one is coming on ......that would possibly explain it. Perhaps something is up with the wiring connector near the radiator you replaced.

 

I raise the rear of the car to force bubbles up, some peoples driveways and garages are not level and run the heater. The after every drive for a few drives I bleed the system with the bleed valves on the hard lines. Its a 348 but I suspect the 355 is the same?

 

The coolant runs though the heater and turning it on turns on the heater pump in the front boot and will flush the bubbles through that certainly exist in those lines.

 

The 355 is self bleeding, but you need to leave the cap off the expansion tank with the engine idling until 1. The thermostat is fully open & 2. It’s finished burping all the air out. As you read above, turn the cabin heater to full heat, fan position 1 and a/c off.

Don’t let the expansion tank run dry. It is ok to trickle distilled water/coolant into the expansion tank while the engine is running. A trickle, so as not to thermal shock anything. When it’s finished burping up all the air, top it off (5cm below the top of the tank) with a trickle of coolant. The top of the coolant should look like you’re lightly simmering a broth. That’s when the thermostat is open and everything is circulating. Then put the cap on the expansion tank and let it run a little longer to build up pressure and check for leaks.

For cold spots, I check all parts of the radiators and hoses for even temperatures all-over. There will be a few degree difference top to bottom of the radiators, but nothing drastic. I use a laser thermometer, or sometimes just my hand for accessible/safe places.

I’ve always bled my 355 with it horizontal, not jacked up front or rear.

HTH.

 

Interesting. BTW, what OBD2 system are you using? That's a nice readout.

 

I am sure you know this but that is oil temperature and not water temp, right?

 

Haha…too funny! Sounds like something I’d do.

 

You are certainly not an idiot! I've done worse and I am sure we all have. I am just glad it was an easy fix and not something that cost thousands of dollars.

 

Hey I'm a pollack. Trust me I get it LOL

 

Dont bother, it's more fun this way