My 440 GT boils after I switch the engine off

[Wollfen]

So I am still having hot issues with my GT and the new engine. If you all followed my rebuild thread you would know I rebuilt the engine throughout and also replaced all accessories with new parts. I decided to take the car for a drive to check it out after finding an exhaust bolt was leaking coolant. Got that fixed but the coolant still boils and comes out the overflow hose after i turn the engine off. When I use the thermo gun on the radiator while it is running it runs about 194 degrees. Stop the engine and the temp shoots up with coolant ending up on the ground. So, what should I be looking for? And no its not the thermostat, I have sat that in hot water and it opens fine. Plus I left it out too to see if anything changed, it didn't.

 

[The Captain]

On a car without a recovery system the coolant level in the radiator should be kept lower so that does not happen. Try that and see what happens.

 

[cantflip]

Gary, if she is running good without overheating... I would use a pressure tester and check the cap to make sure it matches and holds required pressure. There are those who prefer to put a lower rated cap on the system to reduce pressure and potentially save parts (like radiators) from leaking. 50/50 mix has a higher boiling point, but being in your area, you may have opted for 60% water to improve cooling... lowering the boiling point as well.

I figured you are under control with everything else... a man of your skills and all... but how many liquid cooled aircraft could you have worked on?

Temperatures always will climb once you switch off... the cooling system stops working. If you are curious, you might try a couple zip ties and an old water jug as an over flow bottle... just to see if you'd be happier installing a real bottle. I personally like overflows, they appeal to my lazy side, they are a nice environmental upgrade as well.

 

[polara71]

Gary, if she is running good without overheating... I would use a pressure tester and check the cap to make sure it matches and holds required pressure. There are those who prefer to put a lower rated cap on the system to reduce pressure and potentially save parts (like radiators) from leaking. 50/50 mix has a higher boiling point, but being in your area, you may have opted for 60% water to improve cooling... lowering the boiling point as well.

I figured you are under control with everything else... a man of your skills and all... but how many liquid cooled aircraft could you have worked on?

Temperatures always will climb once you switch off... the cooling system stops working. If you are curious, you might try a couple zip ties and an old water jug as an over flow bottle... just to see if you'd be happier installing a real bottle. I personally like overflows, they appeal to my lazy side, they are a nice environmental upgrade as well.

Well put!

 

[1978 NYB]

x2 Jeff

 

[1978 NYB]

Does this car have a fan clutch?

I had my Challenger do the same thing in Wisconsin 40 years ago during the winter (-15 F degrees). Engine was boiling over. It was the fan clutch.

 

[polara71]

If it didn't start with one it shouldn't need one.

 

[rags]

over heats and boils over with no thermostat?

 

[cantflip]

If it didn't start with one it shouldn't need one.

I will agree with an exception. If a car without A/C gets too far into the southern climates they do tend to run hotter at highway speeds because a fixed fan can't overrun when the air speed exceeds the fan speed. Figured that one out while I was still young enough to drive FL in old stuff that came W/O A/C.

No matter, none of that matches the symptoms Wollfen is having anyhow.

 

[70bigblockdodge]

194° is not hot when running, temp will go up after shut down. Leave it alone and it will settle out and find it's own level may take a 1/2 dozen cycles with a good working system

 

[Wollfen]

I've been thinking about putting in an overflow bottle as it didn't originally have one. But here's the thing, since everything is built to factory specs and all parts are new, I would think the car should run like it did back in the day. I also make sure I only use the most expensive premium gas in the car too. The car was built for unleaded, nothing about it has been changed from original spec. The only thing I can think of is, maybe the water pump has the wrong number of vanes? Finding an AC specific water pump is damned hard nowadays and I don't remember what I put in.

 

[Yatzee]

So I am still having hot issues with my GT and the new engine. If you all followed my rebuild thread you would know I rebuilt the engine throughout and also replaced all accessories with new parts. I decided to take the car for a drive to check it out after finding an exhaust bolt was leaking coolant. Got that fixed but the coolant still boils and comes out the overflow hose after i turn the engine off. When I use the thermo gun on the radiator while it is running it runs about 194 degrees. Stop the engine and the temp shoots up with coolant ending up on the ground. So, what should I be looking for? And no its not the thermostat, I have sat that in hot water and it opens fine. Plus I left it out too to see if anything changed, it didn't.

I custom made a coolant recovery tank from 3" ABS plumbing parts and built it to handle almost two liters of fluid. The inlet from the rad was plumbed to the bottom and a drain was put on the bottom as well. The tank has a side poly tube to indicate the fluid level. I was totally surprised how much expansion of the fluid occurs between hot and cold. Using a 13 lb cap it was about 1/2 a liter but having a dual operating rad cap the fluid was sucked back into the system when the engine cooled down. I upped the cap pressure to 15 lbs and surprisingly the engine temperature dropped slightly, and with an 80%/20% water/glycol mix it dropped even more. The car never sees freezing conditions. I think the rad cap is one of the most overlooked components of the cooling system and it pays to find out what the original value was because down through the years owners do some pretty funky things when it comes to the proper value of the cap. For the first time ever, I tried one of the Gates heat-shrink rad hose bands in place of a gear clamp and they not only look great they work great as well. To remove the hose you merely cut the band with an Exacto knife.

 

[Wollfen]

Hmmm 80/20 mix huh? That would certainly have significant cooling affect at that ratio, makes me wonder what the cars ran back in 1971? That's something I hadn't thought of too. The radiator cap is a 16lb unit too, even though I haven't got a pressure tester, it seems to have the right amount of tension on the spring giving it the "squeeze test" compared to other caps I have around here.

 

[300rag]

I know it may be a stupid question, but when you fill it up do you leave the level about 1" below the filler neck to allow for expansion?

 

[Wollfen]

I know it may be a stupid question, but when you fill it up do you leave the level about 1" below the filler neck to allow for expansion?

Around 3/4's, I'm going to check where the coolant level is today now that it dumped a whole lot on the garage floor and report back.

 

[Ross Wooldridge]

Yup - this is normal for all cars. Overflow/recovery bottle or let it burp out until it doesn't do it anymore. I know - makes a mess of the floor, and also a trail of dried coolant under the car too...

 

[cantflip]

Hmmm 80/20 mix huh? That would certainly have significant cooling affect at that ratio, makes me wonder what the cars ran back in 1971? That's something I hadn't thought of too. The radiator cap is a 16lb unit too, even though I haven't got a pressure tester, it seems to have the right amount of tension on the spring giving it the "squeeze test" compared to other caps I have around here.

If it bothers you, the parts store loaner tools usually include one. Test it at the counter and you're done.

 

[Wollfen]

I checked the coolant level and the top tank showed none, then I squeezed the top radiator hose, it is empty too. It definitely is having issues, so my next plan is to be methodical about this, I am going to take the radiator out and have it hot tanked, then rodded to clean out any possible obstructions. If they report back it is clean, then I will move onto the next thing being the water pump. After that, if that checks out I will take the car to a radiator shop and they can hot flush the entire system. Hopefully I will have the issue fixed by then.

 

[LocuMob]

If you are curious, you might try a couple zip ties and an old water jug as an over flow bottle...

I use a Mountain Dew bottle as an overflow, if it passed tech at the track (not my car) it's good enough for me. I agree with the lower lever in the radiator also. I would fill mine all the way, take a drive and it would boil over every time. I make sure I can see the antifreeze when I open the cap, but I don't find it all the way to the top anymore.

 

[LocuMob]

194° is not hot when running, temp will go up after shut down. Leave it alone and it will settle out and find it's own level may take a 1/2 dozen cycles with a good working system

This also. It took me about a week or so to get it at the right level. My car didn't run hot, just puked out coolant when I shut it off. I'd try that before taking everything apart. I hate doing that once it's all together.