I drive a 97 firebird formula, and after a race i pulled over and heard a hiss. I opened the hood and it was steaming from behind the engine. And a steady coolant drip comng off the torque converter. So after about 15 minutes i drove it a couple blocks. No leak no hiss.continued driving and checking for about an hour. No temp spikes. Heater blows hot air. No continued leak.any ideas of what it could be? Or if i should still worry?

 

I'm not super familiar with the LT1 engine but, about the only things I can think of that would leak by the back of the engine would have to be a head gasket, assuming no cracks.

 

There's a steam pipe/crossover tube on the rear of the cylinder heads.

The only other thing back there that could leak coolant would be the intake...well that or a HG

 

Not on a LT1

 

Not on the LT1. No coolant through the intake.

Yes on an LT1. The LT1 does have the steam pipe coming off the back of the heads.


OP, hows the coolant level? Just because it's not hitting the ground or steaming doesn't mean it's not leaking. These engines are reverse cooled and when they get low on coolant, they allow air pockets, which makes more air pockets from steam in the heads, which pushes coolant out, which allows more air pockets. It's a run away effect.

The steam pipe on the back of the heads are banjo bolted on (like the brake lines), those seals do fail when trying to hold coolant and water in for almost 20 years. Easy to check, reach back there and see if there's any signs of coolant leaking.

 

Yes on a LT1

 

When I bought my SS, the steam pipe bolt seals appeared to be leaking. I removed the banjo bolts and the seals were so deteriorated that it was no surprise there was a leak. Definitely check those.

 

The thing that sucks is once those bolts have been in there for a while it's almost impossible to get them out without rounding the bango bolts off or breaking them.

 

Agreed. Those are NPT fittings, so they are tapered threads. They tend to bite hard. When I did my rebuild, I got some 1/4-NPT to AN-6 adapters and went AN-6 all they way after that. Much easier to work on, looks better too.

 

Careful, its NOT a taper thread, running a NPT fitting in will work but you will run the risk of cracking aluminum head if you use to much force.

 

You can get a coolant pressure tester from any auto store and put 18psi while the engine is cold and see if you can spot where the leak is coming from.


As stated, no coolant is plumbed through the intake.

 

No? Huh. Well the 1/4 npt fit nicely, I figured since the npt is tapered it'll stick out a bit, it's not leaking. Just don't over torque it like you said.

 

Same here, NPT fittings work fine, but, its def a straight female thread. Same as 60e cooler line fittings in case.

GM loves their washer seals and O rings.

 

Far better than the paper gasket bullshit of old(er).