spdrcr29

Hey Guys. I've got a weird one here I can't figure out. Just recently purchased a 71 Convertible w/ LT-1 motor, no a/c, 4spd, w/ 4:11 gears. My problem is that quite regularly the radiator will puke out quite a bit of coolant out of the overflow drain hose. It does not have the overflow tank, just a rubber hose attached at the radiator cap. While driving, idling, etc., it runs at a constant 195 degrees or so +/- some, with absolutely no overheating problems. However, when I come to a stop or shut the car off when stopping for gas or whatever, I notice a huge puddle of coolant that has drained out from the drain hose. After getting back home and the car has cooled off, I usually have to add back a gallon or more of coolant.

I am at a loss as to what is going on. Do any of you have any ideas?

Thanks so much and looking forward to some feedback!!

Kevins77

Its normal. You need a reservoir for that tube to go into. When a radiator gets hot, the fluid expands, and it will spit it out. Thats the normal function of all radiators. This is also why you are adding fluid even when it doesn't spit any out, as you normally fill the reservoir to the fill line for the fluid to be sucked back in when the car cools off.

spdrcr29

Hey thanks for the info. Just seems really strange to be draining out so much at once. Does not appear that the car ever came with the overflow tank from day 1. I see the dimples in the pass side fender where the tank should mount, but they have never been drilled out. Definately considering adding one... Thanks for your feedback!

RunningMan373

A gallon is not normal. Sounds like your radiator cap is weak, as the system pressurizes, if the cap is weak, it will push an excessive amount of coolant out, replace it. 16 or 18lb cap. some spill is normal, but not that much. 2nd, add a coolant overflow bottle, so the overflow can be captured and sucked back in on cool down, Also look around the cap seal area on the rad for distortions and dents, straighten any you find, the cap needs a good seat. C.

wytevette

I have had two vehicles do what you are describing to me, and both of them had to have a new head gasket installed. The head gasket was leaking cylinder pressure into the coolant system and over pressurizing it.

Hopefully that is not your problem, and a new radiator cap will solve it for you.

CheezMoe

Stuck thermostat will cause this too. combination of stuck stat and weak cap will do it for sure!

Gordonm

The LT1s did not have over flow or expansion tanks. The expansion was done in the radiator. You can never fill it up to the top and expect it to stay there. It will find its own level. Mine will usually stay about 3 inches or so below the cap and maintain that. This is normal.

A gallon of fluid does seem like a lot. Let it cool down and see how low it goes. If it is a few inches you are good and this allows for expansion. To low and you may have other issues.

Mike Ward

correct in every detail!

spdrcr29

Thanks so much for your feedback and everyone elses!! I will check some things over this weekend and let you all know what I find.

Ward72

There is a mark on the side outside of the radiator indicating the fill level..my 72 has it; don't fill above this. Also, ensure the sealing surface (where the cap seats) on the radiator is clean and no gouges and that the rubber ring on the cap is clean and not cut. if these are not clean and in good shape, the radiator will push water pass this point. If both are ok, I agree with above, change the cap.

Surfer69

Mine does exactly the same thing, always has. New caps, new engines still the same. Just means you're filling too much. Do what Gordo mentions and you'll be fine. I fill about 1 inch above bottom entry hole. It is what it is.

Jim_Harrison

I had the same problem, head gasket leak.

Q's 68

Same thing on my 68 SB. Once I stopped continuing to try to refill the resivoir everytime, it stopped puking and seemed to have found a comfortable level. Runs at about 180 steady with a new t-stat installed last year.

71406

Same problem on my 71. Installed new cap, kept cold level to the line on the radiator but it still happened. Installed a new DeWitt radiator and the problem went away. Cannot explain why...maybe my old radiator wasn't cooling properly...but I didn't care cause it stopped puking green.

PRNDL

sounds like everyone has you covered already. New owners often overfill the radiator.
Let me quote from the 1968 Corvette Owners Manual. I am guessing 71 is similar, but check your owner's manual.

That's THREE INCHES !! Now I invite you to stick a ruler in your radiator and see how far 3" is. (It's a long way down) Most new owners will fill well above that level. I was doing it for a while and had lots of coolant on my driveway to show for it!

And it's a good idea to add a non-stock incorrect plastic overflow tank to give you a little peace of mind, avoid embarassing situations (Hey! your car is peeing all over my driveway!!) and keep your pets safe.

spdrcr29

Hey guys, thanks for all of your feedback. As I am a new (old) corvette owner, I am also new to this forum. I appreciate everyone's suggestions and ideas!! I did a little snooping around tonight...like a couple of you had mentioned, I did in fact find the words "Full Cold" with an arrow pointing upwards on the side of the radiator where the drain hose hangs down. I was quite suprised to see how low this mark/line was. I haven't measured exactly how far, but appears to be at least 2-3 inches from the top. I must say that I currently have the tank filled higher than that right now. Oops....My fault!

Paying attention to the radiator cap, I found that what is on there is a Stant "Vent-A-Lever" Cap with a 7lb rating. I am certain this is not factory. RunningMan373 suggested replacing the cap with a 16-18lb cap. Not that i'm doubting him, but is this what most of you use? If 16-18 is correct, than whats on my vette now could quite possibly be my problem (other than me overfilling the radiator). Either way, I will most likely replace the cap. I have no clue how old the one on there is. I'll wait to purchase it however until I hear what you all have to say and suggest to buy. Thanks again guys!

Jim_Harrison

Just looked, I have a 13 lb on my radiator and a 16 lb on my overflow tank. Think I'm the wrong guy to ask.

xCCTer

And (I believe) '71 a/c cars don't have the overflow/expansion tank either. Mine likes to stay about 2 inches from the top. Anything above that ends up on the ground. Try a new cap and don't refill it to the top.

spdrcr29

UPDATE: Well guys. I finally replaced the radiator cap with a 15lb rating cap. As I mentioned before, the car had a 7lb cap...one of those Stant Vent-A-Lever styles. I had all kind of problems with it puking significant amounts of coolant out of the drain hose after driving and then stopping for gas, food, etc. Since replacing the cap, I have driven the vette about 100 miles. To my suprise, NO MORE GREEN PUKE!! Hopefully I didn't just jinx myself, but so far so good!! Thanks for everyone's guidance and suggestions!!

Consider this Case Closed!!!