Has anybody had a water temperature reading that is too low by 30 degrees? On the big summer drive this weekend I was crusing at high speed in 102 degree temperature on 600 mile 3 day drive. My water temperature reading was at the solid line between the 120 and 190 call outs. I presume this is about 150 degrees. The oil temperature was rock solid at 210 varying only slightly dropping below 210 at high speed and low RPM. Oil pressure correlated perfectly with RPM and oil temperature. The engine seemed to running perfectly as per normal. A/C was on and working perfectly - fans were on. The temperatue modulated with driving conditions between 140 at high speed down hill and 170 stuck in trafffic. It sounds to me like a stuck open thermostat. I checked water level in reservoir and it was down slightly but not empty. The fact that the signal to the gauge was modulating with driving condition makes me think the guage temp readings were accurate and reading a low water temperature. Has anybody had this problem with F355? Thanks
Your car is 8 years old - T-stats don't last for ever in any car (I've done a couple in two VAG cars in the last year at 6 & 7 years old). Same symptons you describe. WHat happens is the spring that closes the Stat gets old & lazy & so the thing is not so much stuck open but more that it just isn't closing properly. If you can sit in traffic & then as you pull away the temperature drops quite quickly then odds are you have a lazy Stat. Good idea to get it fixed - quite a number of engine managment systems trigger mixture settings etc off engine temperature to some degree AFAIK - I'd assume the 355 is new enough to have that happen rgds I.
I just boiled the original stat that came out of the car and sitting it was at 34 mm in boiling water it was 42mm slightly shy of 44 spec. I'm tempted to put the original back in. Any thoughts?
Dave, I would be more inclined that the temp sensor for the gauge is bad...they can and do go bad. I had skyrocketing oil temps on a 78 308GTS once, a new sensor fixed it. I just don't see how the water temps could ever be that cold in those ambiant temps. I'm out here in Eastern WA today (Tri-Cities)....must be 107 degrees or so...AFRICA HOT! I'm in Yakima tonight, heading to Goldendale, then to the gorge, and west to Portland.... Dave
That's fine but the problem looks more like its then not closing up quickly enough. The only way to be sure would be to put a brand new stat in & boil them together. What you will most likely see is that your existing stat will open sooner and more gradually. The new stat will open later and faster. Then when you take them out the water the old stat will take longer to close - i.e. the spring is old & weak. It might be a sensor but then you'd probably see much more erratic behaviour on the gauge. As you surmised in your first post the gage seems to be behaing fairly consistently. Running generally too cool is a classic symptom of an old T'stat with a weak spring. rgds Iain
Iain, are you sure with a 39 degree Celsius outside air temp? Dave, were the fans cycling? If they were, then that might confirm my suspicion the gauge is at fault. If they were not, then I would say Iain is correct. When the oil temp sensor failed on the Veglia gauge on my 308, it was not at all erratic, it worked normally, and consistently, it just read about 50 degrees F higher than normal.
Pretty much, as far as I know the outside air temp doesn't make a huge difference. The ability of air at 20 deg c to absorb heat from the radiator isn't really any different to that of air at 39 deg c. A high reading on a guage might well indicate a bad sender as a product of too much voltage (because at the end of the day these gauges are basically just voltmeters with different scales marked on them!). A Low reading and especially doing what the OP has described is a classic symptom of an old/weary T'stat. Boiling an old stat on its own won't tell you much unless it sticks shut (in which case the car would be overheating anyway). As I said, you need to compare them. Obviously Ferrari Stats ain't cheap so my suggestion would be to go and buy any old T-STat from the local Autofactor that's rated to the same temperature and compare with that. I'm almost certain he'll find what I described - i.e. the new stat will open later but faster and it will close much faster as it cools. I.
After a couple of hours I removed the T-stat from the front of the motor - if anybody wants to know the trick - PM me. I boiled the original T-stat which I had saved from the 30K with the suspected failed one (16 months old) which I removed from the car. Both T-stats opened virtually at the same rate. If anything the newer one seemed to have a slightly bigger throw about 0.5mm but other than that there was no difference that would explain the 30 degree anomaly in the temperature guage. On advice of the local dealer, I re-installed the newer one, and will be taking it to them Friday. they'll get to it the following Tuesday.
My low temp problem was solved by the local dealer - My guage was reading low - but it was a compound failure involving the sending unit as well. Replaced both and works fine.
