[MtManVt]

Hello;

My '68 Mustang 289 seems to be running a little hot. My gauge shows 3/4 hot on hot days in traffic. I can't check the temperature because when I remove the radiator cap lots of coolant comes bubbling out. Much more coolant overflows than other cars I'm familiar with. After 20 minutes or so the temp shows around 190 degrees. Coolant has been flushed and thermostat and hoses are 4 years old.

Does large volumes of coolant bubbling out of a hot raidator sound like I'm over heating ?

Thanks
John Morris
Washington, Vt

[74stang2togo]

are you trying to use the factory gauge or an aftermarket gauge to determine temperature?

The factory gauges aren't terribly accurate, but temps in the 200-210 range wouldn't be out of the ordinary with a 190* thermostat. Getting an aftermarket gauge from Sunpro or Autometer would give you a much more accurate idea of just how well your cooling system is actually working.

Also, most thermostats are only warranted for 1 year because they're a wear part, I usually replace mine every time I flush the system (yearly), especially when they're less than $5 and the gasket is all of $0.98. It's cheap insurance.

Coolant will bubble out of the radiator when opened "hot" at temps as low as 140* (sometimes less, depending on altitude) it's the expansion of the coolant from the heat that causes this builup of pressure, when you open the cap, the pressure has a way out. If you read the cap on the radiator, most (aftermarket anyway) caps have the pressure rating stamped on them. 14-16psi is common, (roughly 2 atmospheres) so that's a good bit of pressure that's wanting releif when the coolant is hot.

[MtManVt]

Thanks for the feedback. I think I'll get a new thermostat. I also read elsewhere in this forum that a tuneup won't hurt. I have a sneaky suspicion that I'm gonna need a new radiator eventually. This one was full of brown water when I bought it.