I have a 93 firebird formula and it has an LT1 engine. However I been having trouble with the cooling system, I have purged the system many times and still it starts to boil over after 30 mins. I just bought a new radiator and water pump and a cooling temp sensor.. The only thing I dont know about the cooling system is if the heater core has anything to do with it. My only concern is if the heater core is clogged, or not allowing the coolent to flow?? (Do you think it would trap an air pocket cuasing it to boil over?) Not allowing to purge the cooling system correctly?? Should I replace every sensor that is involved with the readings of the cooling system? Please help i really need this car running.

Thanks Mike

 

What about the thermostat?

 

What do you mean by "boiling over"? Perhaps loosing coolant out of the overflow tank?

 

do the coolant fans come on?

 

It has to build pressure in the system to function properly. Ckeck the cap and then get a pressure pump and check for pin hole leaks. Then check compression on all of the cylinders.

 

Did you install the radiator? If so, check the small hoses directly below the radiator cap. The top one should go to the overflow tank, and the bottom one should go to the return line. They are the same size and are easy to mix up. If you mix them up, the car will do exactly what you are describing. I did it on mine back when I first got it, and it took me a while to figure out what was wrong with it.

 

If you are talking about it boiling from the overflow tank, then mine did the same thing. I changed the radiator cap and purged the system and havent had a problem since

 

Yes i did replace the radiator cap, and the cooling fans do come on at a certain temp. however, it does have a new thermostat, what do you mean pressure pump and check for pin hole leaks? does the heater core tend to get clogged up and does it have anything to do with the cooling system...........

 

Did you happen to get the right thermostat??????? Sometime auto stores will give you the wrong one... Did it cost around 15~20 dollars????

 

ya thats about how much i paid for a thermostat.. i even test the thermostat in a boil pot of water to see if it opens up... thats doesnt seem to be the problem.. once am done putting all the stuff in then i will try to purge the system once again, i will put a new heater core, water pump, radiator and cooling sensors, upper and lower hose. if that doesnt work then what?

 

What about this. This sounds like your issue.

 

Like I said, check those hoses, and make sure you look at them closely. It took me 2 months to figure this out after I bought many thermostats, radiator caps, antifreeze and etc and wasted a lot of money. Wasting money sucks. You seem to be dead set on your heatercore or buying all those parts so go ahead, but the small easy and free to check things can sometimes save you money...

 

Yeah dude i also think thats your problem. Why don't you save some cash and read 69gto96z's reply.

 

My car has the same problem. I checked this, and the hoses are installed correctly.

The Car runs fine, and cools fine, as long as I'm moving at highway speeds. but any in town driving, and it gets hot very fast, and the fans don't seem able to control it.

Let me ask you guys this. If the car is sitting in my driveway, should I be able to leave the radiator cap off, start the car, and watch the coolant flow through the system??

What happens, is after the thermostat opens, and the coolant starts flowing through the system, it will start violently blow out of the radiator. I've always thought it was trapped air inside the system, coming to the radiator, and finally finding a place to exit the system. But if that were the case, you would expect it to stop, after the system has been fully inventoried with coolant.

Now I never thought about air being trapped in a clogged heater core. And that seems plausible, but my heater works fine.

I don't loose any coolant through leaks, I don't have water in my oil, and I'm not seeing any signs of the engine burning water... I can't imagine an air leak into the system that doesn't show up elsewhere, especially considering the system runs under pressure.

Help.

 

Are you 100% sure your fans are coming on? If it is cooling while your moving, but not while sitting still, that sounds like a fan problem. You can run the car with the cap off, that is how I purge air out of the system in mine to get the big bubble out, then use the bleeder valves to get the rest out of the system. Make sure when you are bleeding the system that you have the heater all the way on. This will allow any air bubbles that could possibly be trapped in the core to come out. Have you recently changed the thermostat? If so are you sure it is the LT1 specific thermo? Most of the people who work at the part's store dont have a clue about LT1's, and will sel you a short, standard SBC thermo.