MazdaspeedDX

i was coming home on the interstate tonite, doin about 75 at 3300 rpms, and i look down and the temp gauge is on the H!

so i let off to about 50 at 2500 rpms and crank on the heat (im in VT and its about 40 degrees F out but i wasnt running it cause my alternator is Ify)

the engine wasnt coming down much, but it did a little and the heat that was blowing wasnt heat, it was very cold, i could see my breath in the car.

so i pulled into a rest stop, and popped the hood, it all look ok, it wasnt smoking or anyhting, so i went and sat in it, and the gauge was coming down.

so i took off, keeping it at 55-60 and the gauge went right back up! grrrr!

i made it home.....but what gives?!



thanks

MazdaspeedDX

i checked it out, and the belt wasnt put on the waterpump when the alternator was installed....could that have been what made it overheat? i checked the fluid, and it was fine.

Davard

Having lost that belt more than once, yes, that will cause the engine to overheat. It would also keep hot water from reaching the heater core. Make sure that when you put everything back together that the fan still comes on when it gets hot, as the fan thermoswitch tends to fail if it gets too hot (like when the water level gets too low).

Edit: the belt may have been installed, but cheap belts will climb out of the groove at high rpm. Any belt that is ribbed on either side (inside or outside) will be prone to this. Seen it happen many times. (Autozone belts are famous for this).

bougha

Do you have too much pressure in the coolant system, are there bubbles / oil? Is the oil gray (then there's water in the oil) In the worst case you might have broken cylinder head gasget / cylinder head.

Davard

There are several different temp sensors. There's one that tells the fan to turn on, one that tells the computer that the engine is up to temp, and then one that tells the temp gauge what to read. The fan thermoswitch is on the thermostat housing, and tends to fail when it gets too hot.

Then there is the thermostat. It actually has too openings in it. One large and one small. They usually fail in the open position, but they can fail closed too. When you change hoses, you should always change the thermostat.

Davard

Jesse justs loves it when I use the wrong form of a word. I wonder what was on my mind at that time?

The fan on all the time sounds like either a bad relay (although, most relays fail open), or a jury-rig (right, Jesse?) to work-around a dead thermoswitch.