70 Lt-1 Radiator -What were they thinking?

[mcsrnka]

Exactly how is the radiator for the 1970 Lt-1 supposed to work long term without an expansion tank? I've had two near boil overs in the last two years. Anyone have any recommendations as to how often to check the level?
I'm thinking my jack compartment will become a coolant carrier compartment as insurance ;-)

 

[Vettehead Mikey]

I'm sure your car actually has an expansion tank, some are built into the rad, others are external.

Do you have a brass or aluminum rad?

 

[vette-dude]

You can buy an inexpensive aftermarket expansion tank kit at most local parts houses. You have to have one to run at a Drag Strips or possibly other type racing and it is a good way to check your coolant level without steam cleaning your eyebrows. The kits are usaully less than $10.


Randy

 

[Ripp 73]

Greetings

Hello Mcsrnka

Just wanted to say Greetigs and Welcome to the . Lots of great information around here. Enjoy yourself.

~Ripp

 

[rainman]

I've never had a problem with the stock radiator in either of the LT-1s I've owned. This includes a 6 hour trip in 90 degree heat where the car was never turned off. Check the level of the coolant. It should not be filled to the top. There is a line on the passenger side that shows how high the level should be. I would suggest not getting an expansion tank. If you continue to have boil overs the problem is probably something other the the lack of an expansion tank.

 

[mcsrnka]

Thanks

Thanks for all the info. I have a feeling that the radiator was replaced at some time with a non lt-1 radiator. Since it's not leaking I'll look into a cheapo expansion tank and search out a reproduction lt-1 radiator.

 

[Bullshark]

Rainman is correct!!! 70 L-T1's did not have an expansion tank


Bullshark

 

[Vettehead Mikey]

Rainman is correct!!! 70 L-T1's did not have an expansion tank


Bullshark

All systems without an overflow/recovery tank (like '73 and up) have an expansion tank. In the case of the LT-1s, it's internal to the radiator.

99% of the complaints of boil over are due to over filling.

 

[mcsrnka]

In looking inside it I think I have the right one. It appears to be brass, 4 row core, and there looks like there is an internal tank on the side that faces the engine. I've got the mark on the side that says where to fill it cold. It seems the problem of overheating only happens after it has spent some time in the shop. When I check the radiator after the overheat I'm about a gallon low.

 

[stingray70]

Time to check everything over ?

Exactly how is the radiator for the 1970 Lt-1 supposed to work long term without an expansion tank? I've had two near boil overs in the last two years. Anyone have any recommendations as to how often to check the level?
I'm thinking my jack compartment will become a coolant carrier compartment as insurance ;-)[/QUOTE] You modify anything ? I'm total stock and owned over 20 years and car runs at 170 degrees ! Your radiator, pump etc. in good shape ? I hear 'water wetter' works well in big blocks. Something sounds wrong as I'm the envy of my car club as the car runs so cool - only thing different I have is run 20/50 Castrol oil. good luck

 

[mcsrnka]

Real cool also

Normally, it runs very cool also. It almost worries me how cool it runs. It's like every once in a while, something stops working, dumps a whole bunch of coolant and then I get the overheat. Fill it back up and it's good for a while.

 

[stingray70]

something odd like a sticking thermostat or faulty water pump ? I'd consider a radiator flush to start with. is the radiator original ?

 

[Vettehead Mikey]

Normally, it runs very cool also. It almost worries me how cool it runs. It's like every once in a while, something stops working, dumps a whole bunch of coolant and then I get the overheat. Fill it back up and it's good for a while.

How do you know for sure that it's overheating? Puking fluid is not necessarily a sign of overheating.

 

[Hib Halverson]

It true that 70s have no high-fill or expansion tank, but that's irrlevant to an overheating or "near-boil-over" problem.

I'd check the level of coolant in the radiator each time you go to run the car but do it before you start.

If you're experiencing overheating in an engineering sense, ie: the pressure cap releases and you boil over, then you need to diagnose why the car is overheating and repair that.

When you cay "near boil over" can you describe the symptoms a little better?

What's the coolant temp when this happens?
Does coolant or steam come out the overflow hose?
Is the stock air dam in place?
Is cooling system components in good condition?

 

[mcsrnka]

A little clarification

Let me explain the situation a little better. The car normally runs very cool, sub 170 degrees. Everyonce in a while, I'll be driving it and the temp gage will sky rocket up to the red. I say every once in a while but it's probably every 100-200 miles. When I pull over, let it cool down and check the coolant level I'm a gallon short of the "fill to this line" on the side of the radiator. I've started checking the level before I go out each time and I'm seeing the level drop slightly after I've put about 50 miles on it. I don't see any leaks, but I did redirect the overflow tube to shoot out by the windshield washer tank. Before when it was straight down, it would spray on my headers and make a lovely smoke signal while driving. My guess is that it's either squirting it out the overflow tube as I drive or I'm burning it.

 

[Vettehead Mikey]

That's a very different story!

If you've got no signs of an external leak, then it must be disappearing internally. Have you checked your oil for a 'milky' presence? You might want to also run the engine with the cap off and watch for bubbles inside the expansion tank.

 

[mcsrnka]

The oil looks great and it doesn't burn any. The engine was fully rebuilt about 800 miles ago by a local speed shop. What would the bubbles indicate?

 

[Vettehead Mikey]

The bubbles would indicate a leak between the combustion chamber and the coolant passages. Possibly a blown head gaket.

 

[mcsrnka]

Excellent! Now I'll have an answer when my wife asks why I'm just standing there staring at my vette!

 

[mcsrnka]

Problem Solved

After careful consideration of how much money I might have to spend to fix the disappearing coolant problem, I opted for the cheapest first. A new Radiator Cap, this solved the problem.