When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Any help much appreciated! My '68 big block drives fine, doesn't "appear" to be overheating according to the gauge, but Im not sure if the gauge is accurate or not...anyway, I drive it around, no problems, no steam, doesn't seem to be overly hot, but when I come home and shut it off, a few minutes go by and it spews coolant out of the overflow. Why is it doing this?? It's a recent purchase so Im not familiar with it, I've never driven it over a couple of miles thus far. The guy I bought it from knew Nothing about it. it's had 200 miles put on it in the last 13 years. It's a 427 car, and has an early non matching 427 or 454....the jury is still out on that one. anyway, seems to run just fine other than that. I installed a new thermostat tonight (because I didn't know what else to do) but havn't had a chance to drive it around yet. Thanks for the help in advance.
Sounds like to much water in the system and it is getting rid of the excess .It will stop once it gets rid of the extra .The radiator level is about 2 inches down from the top to allow for expansion .
Antifreeze/coolant expands and increases in volume as it gets hotter in any car, not just your 427. When you shut the car off after driving it, the water pump stops circulating the coolant through the radiator and the coolant in the engine block and cylinder heads gets REALLY hot and expands, increasing the overall volume in the cooling system. The extra volume has to go somewhere, so it goes out the overflow. Most cars have an overflow reservoir/container to catch the hot overflow and then when the engine cools off and the coolant contracts/loses volume it sucks it back into the engine. Do you have an overflow reservoir on your car? If so, the level in it should always have some space to allow for expansion. There should be a minimum and maximum fill line on the reservoir, measured when the engine is cold.
Antifreeze/coolant expands and increases in volume as it gets hotter in any car, not just your 427. When you shut the car off after driving it, the water pump stops circulating the coolant through the radiator and the coolant in the engine block and cylinder heads gets REALLY hot and expands, increasing the overall volume in the cooling system. The extra volume has to go somewhere, so it goes out the overflow. Most cars have an overflow reservoir/container to catch the hot overflow and then when the engine cools off and the coolant contracts/loses volume it sucks it back into the engine. Do you have an overflow reservoir on your car? If so, the level in it should always have some space to allow for expansion. There should be a minimum and maximum fill line on the reservoir, measured when the engine is cold.
Actually, no, I sure don't. The overflow tube goes straight to the bottom of the car, and thus so does the hot coolant......I'll have to install one. Thank you very much!
No, they left the fluid level where it was after puking out the lil bit of excess. 427 or 454. Pad right in front of right cyl head. Clean it off and get the numbers from it. Also, pull a valve cover and get casting number from a head. We can get an idea what you got...
No, they left the fluid level where it was after puking out the lil bit of excess. 427 or 454. Pad right in front of right cyl head. Clean it off and get the numbers from it. Also, pull a valve cover and get casting number from a head. We can get an idea what you got...
scotish44 - My '68 small block puked out coolant as well because it was overfilled. Once it was filled to the correct level, no more overflowing.There is a "fill to when cold" mark on the expansion tank.
scotish44 - My '68 small block puked out coolant as well because it was overfilled. Once it was filled to the correct level, no more overflowing.There is a "fill to when cold" mark on the expansion tank.
Thanks...no expansion tank, just a hose that goes straight down.
One thing I notice that has not been mentioned is the radiator cap. Make sure it is holding the correct pressure. Not sure on this particular car, but probably 15 lbs or so.
I had an old accord I almost replaced engine cuz of constant coolant loss. Then I looked at the radiator cap! Gasket was gone! And I know better. At least I like to think I do...
I had an old accord I almost replaced engine cuz of constant coolant loss. Then I looked at the radiator cap! Gasket was gone! And I know better. At least I like to think I do...
Thanks...no expansion tank, just a hose that goes straight down.
This is what the 1968 AIM calls the radiator supply tank and a photo of the tank on my 68 convert. I have also seen tanks that are thinner and longer than the mini- beer keg that is on my car. The radiator pressure cap and the overflow tube are on the supply tank. Note that I hav an electric fan and have removed the belt driven fan and fan shroud.
Last edited by ronarndt; 08-11-2018 at 03:28 PM.
Reason: typo
Any help much appreciated! My '68 big block drives fine, doesn't "appear" to be overheating according to the gauge, but Im not sure if the gauge is accurate or not...anyway, I drive it around, no problems, no steam, doesn't seem to be overly hot, but when I come home and shut it off, a few minutes go by and it spews coolant out of the overflow. Why is it doing this?? It's a recent purchase so Im not familiar with it, I've never driven it over a couple of miles thus far. The guy I bought it from knew Nothing about it. it's had 200 miles put on it in the last 13 years. It's a 427 car, and has an early non matching 427 or 454....the jury is still out on that one. anyway, seems to run just fine other than that. I installed a new thermostat tonight (because I didn't know what else to do) but havn't had a chance to drive it around yet. Thanks for the help in advance.
it really doesn't matter what the casting or no's on the pad are as you can make a 454 block into a 427 engine. a 427 is internally balanced and a 454 is externally balanced. the easiest way to tell is just check the balancer,they look different and have different no's.
I had the same issue and it drove me crazy until I realized what was happening. It had been over 40 years since I had driven a car that did not have a reservoir. Set the coolant level about 2 inches below the seat of the filler opening. Make sure you have a good cap, get it tested or buy another one. Go drive, monitor the temp, and see if it pukes when you get back. If it does not puke or dribbles only slightly you are probably close to ok. If there is no problem it may drip for a few drives and then find it's happy spot. If it keeps dripping or if it pukes a bunch let it cool and see where the level is and report back.
This is what the 1968 AIM calls the radiator supply tank and a photo of the tank on my 68 convert. I have also seen tanks that are thinner and longer than the mini- beer keg that is on my car. The radiator pressure cap and the overflow tube are on the supply tank. Note that I hav an electric fan and have removed the belt driven fan and fan shroud.
Ah Ha! Thank you! Makes sense. Now if that thing doesn't cost 500.00 I'll track one down. There is a mounting spot on my fender right where your tank is.
Ah Ha! Thank you! Makes sense. Now if that thing doesn't cost 500.00 I'll track one down. There is a mounting spot on my fender right where your tank is.
The hose from the radiator cap goes into the top of the tank.....where do the other two go? Does one "T" back into the bottom radiator hose? then there's a third
If you have a pressure cap on the radiator, it would not have an expansion tank. As you can see in that photo, there is just a small metal tube coming from the top of the radiator to feed the expansion tank, if that is your system design. Just fill the radiator to the line on the SIDE tank (part of the radiator); if no line, just fill to 2" below the bottom of the radiator cap fitting.
Run it till up to normal temps, shut it down and watch it for 10 minutes to see if any excess is dumped. Wherever it is, just leave the coolant in that state. It is possible that your radiator has a lot of 'lime' build-up in it that reduces the radiator's ability to dump heat. If so, you can get some "radiator CLEANER" (not radiator flush) and go thru the process to get rid of that stuff on the inside of the cooling fins. That will give your cooling system more capacity to dump heat and will allow your engine to run somewhat cooler. {Note: The thermostat does NOT set the engine's operating temps; it only sets the MINIMUM operating temp for an engine. Changing the T-stat to a lower temp unit will not help you unless the cooling system has adequate capacity to reject all that heat.] Your '68 engine came with a 180*F T-stat from the factory.If it has a 195*F stat in it, swapping to a 180* stat MIGHT allow the engine to run somewhat cooler.....but I doubt that will help any.
Ah Ha! Thank you! Makes sense. Now if that thing doesn't cost 500.00 I'll track one down. There is a mounting spot on my fender right where your tank is.
Scotish44
If your 68 427 still has the original configuration copper radiator you don't need an external expansion tank. The expansion tank is built into the radiator. You just don't fill the radiator full. The external expansion tanks were only used on cars with aluminum radiators in 68.
08-10-2018, 09:53 PM
68 big block regurgitates water/antifreeze??
