Bad Thermostat?

[challengermaniac]

Hey guys,

I took my 340 out for a short drive today as in a quick on and back off the freeway(only had the car for over a week) and noticed that the radiator & cap were not very hot (only warm to the touch) upon returning home and once cooled off, I could see I had lost a fair amount of coolant.  I'm thinking this is a bad thermostat (or worst, coolant leaking into the motor).  Does that sound right to you guys?   

[mojavered]

With the temps being cooler this time of the year, might be hard to tell.  Did it have time to warm up?  Thermo gun might tell you a little more.  What temp thermostat is in there right now?  Could coolant level have been low before the cruise?  If you only had the car for a week, have you changed the oil yet?  Might be a good idea anyway and you will be able to see if you have water in the oil.

[72cudamaan]

Heck, there might not even be a stat in it!

[Chryco Psycho]

the system may be just doing their job keeping things cool , the coolant loss could judt be a bad cap

[Cooter]

If the car doesn't have a "Puke tank" then that radiator cap will spit it out on the ground like all these cars did back before recovery systems....Yes, you will periodically loose coolant..This what kept service stations in business and cooling systems clean back in the day..They were CONSTANTLY adding coolant...

[challengermaniac]

Ok, my test plan is to attach a temporary overflow catch to see if the coolant is running out there (I kinda doubt it).  Another possibility would be the cap itself as it looks original and the gasket may be bad, but initionally I didn't see any fluid near it.  Another possibility is either a head gasket leak or cooling jacket leak.  To test for the possibility of a head gasket leak, I understand you would simply fill the radiator full, turn on the motor and let it heat up and watch for air bubbles.  If bubbles appear at the top, it's a head gasket leak.  I can't remember how to check for a water jacket leak, other than to remove bolts that run through the jacket (water pump, and ?) and put new sealant on before tightening them back up.  Any other thoughts?     

[Cooter]

NO, bubbles in the radiator may, or may NOT mean head gasket...This is an old wifes tail...Sure, there will be bubbles, but what it the cooling system has an air pocket? I've seen the cooling system "Burp" air and bubbles come to the highest point, the raditaor...I wouldn't be so quick to go for the head gasket unless you did a BLOCK TEST where the chemical measured the amount of Co2 in the cooling system...This is the only SURE FIRE way to tell a head gasket....

[72cudamaan]

I respectfully disagree with your statement Cooter.  If the head gasket is blown, then you will quite often see large amounts of combustion bubbles force themselves out of the radiator immediately on start up.  But yes, the best and most accurate test is with the co meter.

[Roppa440]

Another source of bubbles on the coolant is simple a leak from something like the header bolts where they enter the water jacket or (as in my case) a cracked head leaking water externally.

[72rtchallenger]

the system may be just doing their job keeping things cool , the coolant loss could judt be a bad cap

  doesnt have to show a leak at the cap to be bad,,and change the thermostat is easy enough and drive it again and see what happens,,may just be going out the over flow hose on the radiator,,and my personal opinion is if it is the head gasket you usually get anti freeze   in the oil,,say 8 out of 10 times but always a possibly that it wont show up