Andrewsvette

Hey guys!
This is my first vette and love it 1994 LT1 auto, muffler deletes.
However yesterday driving home from Dallas it was 105* out and I look down and the analog temp is at about 260* and the digital is about the same and the oil temp was getting warm too so I pulled over and had a wrecker get it home, this morning I started work on it, I suspected thermostat because it was loosing coolant out of the overflow tank, and no external leaks. I replaced the thermostat and noticed the radiator was filthy so I pulled the radiator and flushed it as well as the block but did not pull knock sensors, I even blew out the AC coils. Drained and cleaned the overflow tank, pressure cap looks good and made sure the water pump was working. I buttoned everything back up and added coolant and burped the system as best as I could. My pops and I let it idle in the driveway for about 25 minutes and everything was normal while we checked for any leaks or overflow which was good it would get to 190 then cool back down to 184ish so I thought it was good and went for a test drive took it slow for five minutes or so and it was fine I punched it to 70mph and it acted normal I slowed back down and sat at a red light for a minute but shortly after taking off it started getting hot and quick so I eased home and shut her down... The car has 118k miles and with an iron block and aluminum heads I wouldn't be surprised if it is a head gasket however I have no water in the oil everything looks good from the oil filler cap and no steam in the exhaust. Is there anything I overlooked any help is appreciated thanks guys!
Andrew

johnnyjaws

might of still had air in the system

Andrewsvette

Once I got it home I tried burping again, what is the best way to be sure I got all the air out?

desertmike1

It will bleed it-self, keep the recovery tank above the cold line when the engine has cooled down. It take several Cold/Hot cycles, but it will burp air just fine, providing there aren't any leaks. Could you hear the Fans running when it was running hot? A leaking head gasket is allways a possability, especially if the engine has been run hot too many times.

Andrewsvette

I knew I forgot to mention something, yes both fans are working correctly too

hemivett

I have flush kits ($3 at local parts house) on both my heater hoses right before they go into the heater core. This is good for back flushing the heater core, and the top one is great for burping, as it is one of the highest points of the system.

I have to say, those heads dont like getting that hot, and you probably blew one, or both, and warped the heads. (Especially stock gaskets that are 25yrs old) I think my first move would be to do a compression test. Is there any bubbles in your radiator? What color is your oil? h

Andrewsvette

I changed the oil about three days before it happened so it still looks new with no water in the oil

STL94LT1

Doesn't sound like a blown head gasket to me.

Andrewsvette

I'll have to compression test it if I get a chance today, I don't know what else to suspect since I've pretty much verified everything in the cooling system is working or new

Kmcoldcars

To get the block cleaned out well you should pull the knock sensors. When you do a lot of water and rusty junk will probably come out.

Andrewsvette

I might try that later, the block seemed to be flowing good when I was flushing it. By the way how easy is it to warp these heads, I caught it somewhat early the first time and was extremely careful on my test drive yesterday and I really don't want to spend the money to replace the heads but if I do does anyone have any experience with the lingenfelter lt1 heads?

don hall

A head gasket breach would lead to one condition, or all:
coolant (steam) out the exhaust, water in the oil, or coolant pushed into the overflow bottle, and no return siphon.

Your post suggests that you are losing coolant out of the overflow tank.

If exhaust gases were entering the coolant system through a ruptured head gasket, you would see a rapid rise in temp, and coolant would be forced out of the system (block) into the tank.

If the overflow bottle is overflowing, and the surge tank is low on coolant after cool-down, that could be caused by a ruptured head gasket, or a faulty tstat. The LT1 requires a specific tstat.... you knew that, but check.

The key condition is an overflowing tank, and no return siphon during cool-down........ a blown head gasket can be confirmed by pressurizing the block.

Even a damaged rad cap gasket can cause air to enter the system, and prevent a return siphon.

Andrewsvette

I did go back with the correct thermostat, I did use a new radiator cap 15lbs. You are correct it is losing coolant out of the overflow, the overflow cap gasket was junk so I replaced it too. I'm thinking head gasket because with the rad cap off once it gets warm it is constantly bubbling and when I give it gas it gets worse like exhaust is entering the system, eventually it will get too hot and steam the system

don hall

Sure signs of a ruptured head gasket allowing exhaust gases to enter the cooling system. Wish I could provide a simple solution, but a costly repair may be in order.

Good luck!

Andrewsvette

I'll do it myself I've got plenty of engine building experience from my '71 chevelle's 350 to my dads '71 challenger 383 and 440 engines lol just a little labor intensive is all. I might try and take pics of everything for anybody else needed future reference

don hall

Photos may be a big help to other forum members........ thank you.

Andrewsvette

10-4 unfortunately I might not get to it until next week I work oil field and I'm gone a week at a pop

don hall

Oil in Texas.......?

Looking forward to your "on the road again" post.

Andrewsvette

Will do!