Hi everyone,
i am relatively new to this forum, but jump on everyday and at least have a look as i'm always learning something new. Everytime iv'e had a problem iv'e only really had to do a search and it's been answered already. I have been working to get my vette going now for almost a year, what was going to be just a complete bushing replacement turned into a "while i'm in there" job and have subsequently done an entire suspension, steering, driveline and brake resto.
But Just when I think i'm all done, I pull into my drive from after getting back from the exhaust shop and a huge plume of steam bellows out from under the bonnet.
It turns out it was puking out from the expansion tank overflow hose all over the headers.
I have replaced the radiator cap and cannot see any bubbles coming up inside the radiator at all, after my suspicsion of a blown head gasket.
The car is a BB with AC and has another hose attached to the back of the expansion chamber which seems to attach to the AC/heater box, I can't get under the car at the moment to confirm this, but there is definantly another hose attached.
When I started the car up with the radiator cap off, coolant puked out of the overflow hose back into the radiator. this would indicate to me that there is pressure getting into the expansion tank from the "other" hose causing it to spill out everywhere.
In everyone's wisdom, and i know there's allot on this forum, what could be the possible cause here.
As I am quite young and poor (vette induced) I have to save up everytime I need to fix another problem, And I'm so close to getting the thing registered and on the road I can taste it, unfortunately I can also still taste coolant in the air too.
I will post some before and after pics when I'm done too, until then any input would be extremely appreciated.

thanks heaps,
Llew

 

Apply the "KISS" principle. Check the t'stat. Make sure all the other hoses are good and not collapsing. Radiator clear? Not plugged with trash. Water pump? Belts? No bubbles in the tank is a good sign. I'm assuming you started the car with the radiator cap off and watched the tank then. How old is the radiator? Maybe needs the old flush & clean.

 

I have no idea how old the rad is, all hoses seem good too. I havn't flushed it yet but I will do this ASAP and see if that helps. will change the t'stat at the same time.
It just struck me as being odd considering all posibilities to be puking so much fluid. cheers for your input.

 

Which tank do you have? Is it the brass or the aluminum?

Where is it located?

Is it original (stock/OEM) ?

 

Have you filled that tank to the top? It should only be filled about 1/2 way.

 

I had a simular problem with my 69bb, which is probably plumbed ( is that a word?) the same as yours. Anyway, I have 3 hoses out of my expansion tank. Small hose, maybe 3/8" to radiator, and 2 3/4" for the heater. Basically, the tank is in the center of a hot water loop from the water pump to the heater control valve, then to the heater core, then to the tank, then back to the intake manafold. Or reverse, but you get the idea. I never quite figured out why the heater water went through the overflow tank. So, if you blew a head gasket and got exhaust pressure into the water jackets it could travel through the heater hoses. Try clamping the heater hoses--vice grips or c clamp-- and see if you get bubbles from the radiatior overflow hose. Does sound like a head gasket to me.

 

It is the brass tank (the long cylindrical one with harrison written on it) and it is in the stock position i believe (tucked under the right hand guard)

And I see what you mean about being plumbed to the heater core, this might explain why it was blowing back through the expansion tank when i had the rad cap off and I couldn't see any bubbles in the rad.... because they were coming through the expansion tank...Bugger!.... I guess it may well be the head gasket, i'll try clamping the heater hoses and see if any bubbles come up through the radiator.
If so i guess i'll have to take it in top get fixed... I'm not quite ready to tackle the engine yet.

Thanks for all your input.... greatly appreciated.