Ok my cars cooling system is basically all freakin' new. Brand new radiator, upper and lower hoses, water pump and just put in 195 thermostat hoping it would fix my problem. Also the fan is on all the time and I know it's working. When I drive my temperature is all over the place. goes allllll the way up to the red range.....then back down and a lot of times stays there for the entire ride and as long as the car is warm. If the car gets cold though, it does this again. It's starting to get very bad last time I could see the coolant boiling in the overflow tank! Also, it's not leaking a drop anywhere!! PLEASE what could this be????? There's nothing left......Thank you!

P.S. my car is a 91' 305 TBI RS

 

are you going by the stock gauge or do you have a reliable aftermarket gauge? have you checked for coolant flow and are you sure all air is out of the system?

 

Sounds like you need a new radiator cap, and your system isn't all the way full of water, and you don't have any antifreeze in it.

Get a new cap, fill it all the way, and use about a 70% water / 30% AF mix.

 

Just bought a brand new cap today.....have checked levels constantly throughout the day to make sure Im good and full, seems to be as full as I can get it. Just did a complete drain a few days ago when I redid new water pump, it's mixed about 50/50 water to AF. Also, Im sure it's not the gauge, I could actually see the coolant boiling in the overflow tank earlier. Any more hints please? Really frustrating....

 

try checking your timing.


there is a tech artical on this site on how to do it... be sure to disconnect the connector before you check it.


if your timing slipped, it would cause the car to overheat.

 

Has it bubbled in the tank since you got a new cap?

 

i agree with rb, my beretta did the exact same thing, was a 4 dollar radiator cap

 

Hasn't bubbled in tank again yet...but hasn't had proper chance really. Before my troubles started I used to run at constant 160 and would never ever move from there. Then started when the engine was really cold and I drove it would get realllly hot then cool way back down to 160 and stay there. Then finally since I put the new 195 thermo in, which is same temp I had before, now it actually gets to the overheating point, then drops down after you shut the car off a few mins and restart it. Basically all the troubles center around starting the car and it overheats from being very cold. It is now running hotter than normal for my car though even when not overheating, and this worries me.

Just a lil while ago I turned the car on with radiator cap off. When it got to the temp that the thermo opened, the fluid was going like halfway down, then back up to gushing out the radiator. Then back down then way back up. Kept heater on whole time very hot air. Seems like the fluid is acting strange, maybe not enough/or too much? Mechanic friend of mine said lotta times when the temp goes up and down its not enough fluid in the system.,... This is also really hard to get a grip on because its worst and easiest to tell whats happening when the car has gotten really cold which takes at least three hours.

 

That's what it's supposed to do.

Put the new cap on it, ignore the gauge reading, and see if it stops the boiling.

Pressure in the cooling system raises the boiling point. So does antifreeze. Under 15 psi and with a mix of AF, your water doesn't boil at 212°, it's more like 260°. Take away the pressure, it boils at more like 235°. The factory fan setting doesn't even begine to start cooling until the temp reaches 235°. Therefore, a bad cap will alow the coolant to boil, at a completely normal cooling system operating temp. Boiling by itself does not indicate overheating.

Worse yet, once it forces the fluid out, if it leaks, it can't suck it back in; so the next time you drive the car, it's low on coolant. Vicious cycle.

The cap is a major, important, crucial part of your cooling system. You probably have now fixed it just by replacing the cap.

 

Thanks for all the tips. Gonna let it cool for a few hours then recheck it and drive to work....will see what happens after that and report the results when i get home.

 

Further; check the bottom rad hose. There should be a coil spring wire in it. This prevents the bottom rad hose from being sucked closed and collapsing when things get hot and soft.

The wire coil is in there from the factory but many replacement hoses don't include a new one.

 

Might what to check to make sure the front airdam is still there. I fought with mine for a couple of weeks following an engine replacement before I found that the airdam had been taken off and not put back on.

 

same symptoms my 96 cutlass had..new intake gasket solved it....

 

Updated...ok changed radiator cap...thermo new....topped off coolant had some air in there. Now worse than ever. When I start up, never fail the temp goes crazy. I stop the car on side of road for 1 minute, turn it back on and every time the temperature goes right back down to normal within 30 seconds. Now while driving, every 10 mins or so it goes up to 250 stays there a couple mins, then dips back down to normal temp again. This is VERY confusing. Hope its not an intake gasket how hard is that? I know the lower rad. hose is from napa but it was installed by a GM goodwrench shop...so guessing they must've installed the right one. Also Air dam is there and just perfect. Its not that anyways because it'll do it while just idling also. Im pulling my hair out here! of course this happens before a big road trip Im supposed to leave for on thurs...

 

try taking the thermostat out...let the car run , and see if it still overheats....Ive bought bad thermostats before. Try the simple solutions first.....check around the intake for any leakage.
Dont drive the car until you get this figured out! Heat kills !

 

Are you sure they dident give you a standard rotation water pump instead of the reverse rotation? That would cause it.

 

As for thermostat...Im going to put a different one in today. A mechanic said the one I put it, a Napa superstat, is to thick and he's had bad luck with them. Replacing with a normal thinner 180 degree therm this time. I guess this is what Im leaning towards since the new thermostat actually made it instantly worse than the last one. *I wasn't overheating before just getting very warm then back down* If THAT doesnt work, I'll try running with no stat see what happens. As for water pump I donno I went to the parts store gave him all my info and it fit perfect so...beats me. I can feel it flowing towards the thermo when I hold the top hose and release though, how else would I tell? I was starting to have this problem before my last water pump started leaking also.As for other leaks I can't find a drop anywhere.....will update later on.

 

another update....bought another thermostat, this time from autozone. It peaked at first but stopped and came back down without stopping the car this time! then it stayed at a cool 150 degrees perfectly with no fluctuating, actually a lil lower than it used to be! HOPING this stays, have to wait for it to cool down for a few hours and see if it still peaks at startup..hoping that was just some air in the system from doing the thermostat because I didn't drain just popped stuff off and let a little coolant come out. We shall see! Btw I used a 180 this time with a thinner outside base. Lesson, don't but Napa superstats.

 

Great! I hope the problem is solved for you!