Too cold!? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

Martin · 02-06-2002, 05:58

On the weekend I put in a new water pump, 77degree thermostat, completely removed the radiator and cleaned it internally and externally.

After filling it with coolant I started her up and let it idle to bleed the system. 20mins had passed and the guage only got as far as sitting inbetween the blue mark and the first line. Gave it a few revs, guage still wasnt moving over that line, so I let it idle for another 15mins just incase there was anymore air to bleed.
So went for a quick drive and it only ever moved around inbetween the blue mark and line. Even redlining a few times it still wasnt getting any hotter.
Previous to doing this it would sit around where the 'N' and 'O' is on the guage.

Thinking that if its running too cold then fuel consumption would be greatly increased?? Well after filling up today, the fuel economy was the same as the previous tank, thats even with it idling an extra 35min. It had a full tank in it when I changed the coolant.
Also it seems that oil pressure has increased, it sits about half a bar higher at idle, slightly higher at cruising and a full bar higher at high rpms.

So im wondering, even though the economy is about the same, should I be worried about it running so cool? Should I put the standard 92degree thermostat back in?

Aussiblue · 02-06-2002, 06:12

I would put the original spec t-stat back. The extra fuel might not stand out in total consumption but it will accelerate engine wear. If overheating is a problem add a thermo fan that it switched via a relay to the air cond compressor clutch wire (ie when you the extra load of driving the compressor while sitting at the lights you'll get extra air to the radiator). The original thermo will work and keep that engine at the right temp.

Aussiblue · 02-06-2002, 06:57

Also note engine coolant temp is used by the ECU to change air fuel mix, spark timing, idle rpm and emission controls. You won't get optimal performance running cold. Some so called performance T -stat that make the engine run cold have reportabley a) forced the ECU into limp home mode and b) enriched the mix to the point the catalytic converter has caught fire.

Aussiblue · 02-07-2002, 05:42

If you do want to fool the ECU into thinking the engine is not yet hot so you get a little more advance the way to do it is to have a dash mounted switch that swiches out the coolant sensor and switches in a resistor of a 5.500 ohm or similar. Not good for the engine or trans in prolonged use but for the traffic light grand prix. Could also try a pot/variable resistor as well as the switch and dial in the fake temp you want.

Martin · 02-08-2002, 07:32

Thanks Aussie, you certainly know your stuff.

Overheating wasnt a problem but im kinda paranoid about it blowing the headgasket. The water pump gasket was slightly leaking, when I pulled off the pump, and spinning it by hand, it sounded and felt kind of 'rough'. Decided to replace it while I was there because as you probably know, its not exactly a fun job and I didnt particulary want to do it again the near future.

Same went for the radiator, may as well give a thorough clean when I had the chance.

Went to my local Ford dealer and they dont even stock the Dual Acting Thermostats. :oo1: :oo1: Do you have an idea on what aftermarket brand is the best?

Aussiblue · 02-08-2002, 07:39

The one Repco sell; Trident I think, is OK. Try to get one with a jiggle pin rather than the tiny semicircular hole.