318 Water Pump Bolt That "Always Wants to Leak" Story
I know this is a mysterious but common problem and wanted to document my personal experience (for all posterity) with the bolt that serves to hold the bracket to adjust the alternator on one end and also serves to secure the water pump.
The subject powerplant is a circa 1980 318 block that was rebuilt professionally about 10 years ago using a cast iron 273 water pump (vehicle is '65 Formula S). The last three years the vehicle was being restored, so the engine has not run during that time. I had removed the water pump, cleaned and painted it, and reinstalled it with new gasket, of course.
When I first tried to re-fill the coolant for the first start after restoration, the bolt in question began to leak as soon as I began to fill the system with the second gallon of coolant. I remembered having put a good quantity of brown, sticky Permatex on the bolt threads (including the other 3 bolts that pass into the water jacket) so I was surprised to find a drip. The bolt was already good and tight, but I tightened it further still. No change, still dripped.
OK, I removed the bolt which measured a hair more than four inches. I purchased a new, longer bolt at 4 1/2 inches and coated the threads heavily with the Permatex (which I have been using since the 1970's by the way). Now with even more thread contact and fresh sealant I was sure it was good to go. I even waited a day or two for the sealant to set-up a little more. Same story, as the second gallon of coolant was added, the drip ... drip returned. The more coolant I added, the more it dripped.
I had anticipated a repeat problem like this and had therefore purchased a little tube of aluminized powder sold to stop radiator leaks (this tube had a yellow label with the "Gunk" name). I had used a similar product called "Alumaseal" years ago and had success with it. I started the engine and let it idle while I topped off the coolant level and poured in the aluminum powder concoction. By now the bolt in question was not dripping, it was pouring out in a little steady stream. I could hardly believe how much coolant was passing by and around that bolt! And even worse, I could not and cannot envision how the coolant finds its way out so easily.
I ran the engine for about ten minutes and the stream seemed to have diminished to a drip again. I ran the engine even longer and even the drips seemed to stop (got it to about 190-200 degrees on the aftermarket mechanical temperature gauge). Now, I don't particularly like to "repair" leaks of any kind in such a fashion, but I was in no mood to dis-assemble the front half of the engine today. What was I going to find if I had done so? Well, if and when the leak returns I won't have any choice and I will take it apart and investigate. For now, it's fingers crossed.
And I forgot to mention: I found a tiny puddle of coolant about the size of a nickel on the intake manifold directly under the thermostat housing (so what else is new?) I had taken great pains to clean those surfaces, use a gasket with a very minimum coat of sealer (The Right Stuff), and made sure to torque the two fasteners equally over several stages of back and forth. I dried that area with a rag about three times as it kept coming back. Much later, after I had evidently stopped the bolt leak, I checked again and the puddle was "gone". Did it stop leaking on its own, with the help of the stop leak powder, or did the tiny bit of coolant just evaporate as the intake manifold became hotter and hotter? I can't say. I was not going to tighten the bolts any more until I found how it was going to proceed. Sometimes those little seeps do plug themselves up after a short time.
The amount of coolant loss was maybe a quart or more (see photo).
I know this is a mysterious but common problem and wanted to document my personal experience (for all posterity) with the bolt that serves to hold the bracket to adjust the alternator on one end and also serves to secure the water pump.
The subject powerplant is a circa 1980 318 block that was rebuilt professionally about 10 years ago using a cast iron 273 water pump (vehicle is '65 Formula S). The last three years the vehicle was being restored, so the engine has not run during that time. I had removed the water pump, cleaned and painted it, and reinstalled it with new gasket, of course.
When I first tried to re-fill the coolant for the first start after restoration, the bolt in question began to leak as soon as I began to fill the system with the second gallon of coolant. I remembered having put a good quantity of brown, sticky Permatex on the bolt threads (including the other 3 bolts that pass into the water jacket) so I was surprised to find a drip. The bolt was already good and tight, but I tightened it further still. No change, still dripped.
OK, I removed the bolt which measured a hair more than four inches. I purchased a new, longer bolt at 4 1/2 inches and coated the threads heavily with the Permatex (which I have been using since the 1970's by the way). Now with even more thread contact and fresh sealant I was sure it was good to go. I even waited a day or two for the sealant to set-up a little more. Same story, as the second gallon of coolant was added, the drip ... drip returned. The more coolant I added, the more it dripped.
I had anticipated a repeat problem like this and had therefore purchased a little tube of aluminized powder sold to stop radiator leaks (this tube had a yellow label with the "Gunk" name). I had used a similar product called "Alumaseal" years ago and had success with it. I started the engine and let it idle while I topped off the coolant level and poured in the aluminum powder concoction. By now the bolt in question was not dripping, it was pouring out in a little steady stream. I could hardly believe how much coolant was passing by and around that bolt! And even worse, I could not and cannot envision how the coolant finds its way out so easily.
I ran the engine for about ten minutes and the stream seemed to have diminished to a drip again. I ran the engine even longer and even the drips seemed to stop (got it to about 190-200 degrees on the aftermarket mechanical temperature gauge). Now, I don't particularly like to "repair" leaks of any kind in such a fashion, but I was in no mood to dis-assemble the front half of the engine today. What was I going to find if I had done so? Well, if and when the leak returns I won't have any choice and I will take it apart and investigate. For now, it's fingers crossed.
And I forgot to mention: I found a tiny puddle of coolant about the size of a nickel on the intake manifold directly under the thermostat housing (so what else is new?) I had taken great pains to clean those surfaces, use a gasket with a very minimum coat of sealer (The Right Stuff), and made sure to torque the two fasteners equally over several stages of back and forth. I dried that area with a rag about three times as it kept coming back. Much later, after I had evidently stopped the bolt leak, I checked again and the puddle was "gone". Did it stop leaking on its own, with the help of the stop leak powder, or did the tiny bit of coolant just evaporate as the intake manifold became hotter and hotter? I can't say. I was not going to tighten the bolts any more until I found how it was going to proceed. Sometimes those little seeps do plug themselves up after a short time.
The amount of coolant loss was maybe a quart or more (see photo).
