Hey fellow 5'ers, I have a problem that, frankly, I've grown VERY tired of.

I've owned my 545 since '06. It has had its fair share of cooling system problems - water pump replacement, thermostat replacement, cooling hoses, secondary pump, etc. I have DIS/INPA/PROGMAN and an Actron 9150 professional code scanner with PID maps and readiness checks. I have a bit of mechanical experience (took 2 years of formal automotive repair classes, both in high school and college), and have repaired a few things on my car, including replacing my alternator.

Problem: Periodically, the car will throw up yellow/red temperature warnings. When it first started happening I freaked (that was late 2010 - see my original thread HERE)! After a trip and 1 day stay at the local dealer, the dealer verdict was: nothing. "MAYBE it's the hoses - there is some weepage/leaking that could be causing variable pressures" was the official $150 diagnosis. Since this, I've changed upper/lower radiator hoses, aux water pump, various secondary hoses, etc. Yet, the warning still pops up. It will gong, show a warning, then promptly disappear. It may repeat this in rapid succession a few times, then...all is well. The system has been drained, bled, refilled, etc a few times - it's probably one of the cleanest cooling systems based on the relative short time coolant has stayed in over the pass couple of years before I drain and refill. I've monitored the temps when these gongs go off (use the live PID mapping feature of the scanner for this). Temps stay between 205 and 215F. Sometimes the temp gong will go off after the car has sat all night and is WELL below normal operating temps (around 80F a couple of times). In INPA, I've tested the electric fan - it reaches its maximum blow with enough force to make a street ho jealous! It also works as it always had - periodically based on ambiant temps, unless the AC is on, then its much more active.

I've pretty much grown as used to it as I can over the past couple of years, but I'm seriously contemplating unloading the car and would like to have this resolved before I put her up for sale. My final solution attempt may be to buy an OPSS diagnostic head and reflash/code the DME (I won't even attempt this using the INPA K+DCAN cable I use for diagnostics). DIS doesn't show any temperature-related failure points. Has anyone out there encountered this crazy gremlin? I'd LOVE to hear your thoughts!

 

DIS has nothing to do with it. But if you have a untrustworthy cable I wouldn't do anything and leave it at that.

You don't need the OP(P)S head to reflash the DME. You said you have Progman right? Have you updated the DME? If you can't reprogram through Progman then use WINKFP to flash it. Keep in mind you'll have to align DME-> CAS afterwared. DO NOT mess with CAS just align the two back up after a flash or you won't be able to start the car. I've done it several times. I cannot attest to your cable, battery charger, or skill level so if you don't feel comfortable about any of those then don't attempt to do it.

 

how come you haven't tried changing the temperature sensor?

 

Sorry about the delay man. Thanks for the reply. I've been remiss to reflash the DME for a couple of reasons.

The first is a custom tune performed @ EuroRev some years back (back in 08 I think). DME updates predate this install.

The second is my cable. I get a few "Data Transmission Interrupted" messages (I've tried edits to transmission protocols, etc). For coding, persistance generally pays off and after several attempts, the code changes stick. However, I don't want to risk a fault updating the DME.

Power supply is sufficient to supply +14v/55 amps. As for skill level, I'm versed yet continually learning

 

Temp sensors have been changed - both the lower radiator-hose mounted themal switch (which controls the fan), and the temp switch mounted near the water pump. Contemplating yet another thermostat, just to eliminate that from the list. However, with warnings even at start-up from cold soaking, the thermostat wouldn't even be a factor at that point.

 

short in wiring running to sensors? that could be intermittent and wouldn't care if the engine was cold

 

I'm going to resistance-check the wiring from the sensors to the DME. You may be on to something....I'll keep you posted! Thanks for the suggestion.