Coolant Leak / Expansion Tank

[LithiumCobalt]

Mark, sounds like the main culprit is up top somewhere if the valley pan is wet. I’d commence with addressing the expansion tank and dry everything out and then see if that cures the leakage. Hopefully not a freeze plug as those would be a PITA to fix.

[Lee]

Mark, I hate to say it, but I'm leaning toward one of the three freeze plugs in the bottom of the intake manifold leaking. I've had the thermostat housing leak, but it ran down the front of the motor as I recall. I'd get a flashlight and maybe an inspection mirror, and see if you can get a view of the valley pan, and maybe where it's leaking from.

If not that, there are coolant passages at all 4 corners of the heads that could also be at fault.

[mge825y]

Lee & Nick - All good points to ponder. I'm going to need to take a closer look at these to see if I can determine where the source of the leak is.

The head scratcher in all this is the car has been sitting and hasn't been run. The only variable that has changed is the cold weather temperatures in the garage. Maybe if a plug on the bottom of the intake manifold was "iffy" before, maybe the cold weather made it worse?

[Lee]

Mark, this is an excellent excuse to buy a new tool. About 10 years ago, the Model A swallowed a throttle plate screw, and I bought an endoscope/bore scope that worked with my phone to survey the damage. Back then I paid a little over a hundred dollars and thought I was getting a great deal. Today they are ridiculously cheap. It’s an easy way to visualize the valley pan area.

[papawayne]

Mark: It probably hasn't been as cold in Charlotte as it has been here in St. George. However, the best way to replace those leaky caps/plugs is to remove the engine if you've got the time, inclination and place. That way you can visually inspect each one for viability. There's probably some other things you can do for the car while the engine is out too. As previously mentioned, this is a job you only want to do once. With new caps/plugs you can let someone else worry about it. Wayne

[mge825y]

Mark, this is an excellent excuse to buy a new tool. About 10 years ago, the Model A swallowed a throttle plate screw, and I bought an endoscope/bore scope that worked with my phone to survey the damage. Back then I paid a little over a hundred dollars and thought I was getting a great deal. Today they are ridiculously cheap. It’s an easy way to visualize the valley pan area.

Lee - That's a great idea. Just ordered one that will arrive later today. Everybody loves new tools!

[frasern]

When they rebuilt the engine, the block plugs should have been done, but it is easy to miss the ones on the intake manifold, so hopefully Lee is right. Another thing to try is a cooling system pressure tester (I know most people don't have one). The borescope is a great tool, you will be surprised how much it helps, you can also peek inside the bell housing without all that pesky engine R&R.
If you were running 50/50, the cold should have had no effect, probably just coincidence, but it could be the frost plugs that were seeping all along, and the thermostat is fine.

[mge825y]

Mark: It probably hasn't been as cold in Charlotte as it has been here in St. George. However, the best way to replace those leaky caps/plugs is to remove the engine if you've got the time, inclination and place. That way you can visually inspect each one for viability. There's probably some other things you can do for the car while the engine is out too. As previously mentioned, this is a job you only want to do once. With new caps/plugs you can let someone else worry about it. Wayne

Wayne - The endoscope/bore scope that Lee recommended should tell me if it's a intake valve freeze plug. I'm kind of hoping that's all there is - especially since the engine was rebuilt in 2020 and I would have thought those freeze plugs would have been replaced. But, I can always use the scope to look around to block plugs that to check their condition.

The good news is that a while back, I reserved an appointment to have the car trailered to the shop so that they could work on a laundry list of things for me. If all goes according to plan, they will be picking it up in 10-days. The perfect scenario would be for me to determine now what is causing the issue so that I can have them take care of this while they have it.

[papawayne]

Makes sense to me...Wayne

[TonyC]

Having had that issue myself, I would suggest to be prepared for the worst. The common coolant leaks like expansion tank or thermostat mounting would be easy to spot. If you see a coolant leak up top but cannot find its source, I've learned that to be a sign of a leaky freeze plug. Of course, that will mean removing the intake to fix. I did that with my intake two years ago in the late stages of the rebuild; unfortunately, I suspect I may have done something wrong, because it's leaking again (though, admittedly, not quite so often as it was before the plug replacements). Luckily I did buy too many plugs of different sizes for the rebuild, just in case I'd need them in the future...but since the move, I will have to sort through all the boxes to find them.

I did make a note of the size of plugs used in the intake, along with notes of all the plug sizes the engine uses; but they're in the manual, which is in the car. I'll have to open it up to find the size needed, but I can provide that info.

---Tony

[mge825y]

Well, the endoscope/bore scope arrived and I made two attempts yesterday to scope the drain / freeze plugs on the underside of the intake manifold. The 90 degree mirror attachment works great. I can easily see the drain / freeze plug at the rear. But the space between the valley pan and intake manifold is tight and was unable to position the scope to see the one in the middle or in the front.

What I did notice is that there is more coolant in the valley pan as I got closer to middle and up to the front.

The amount of coolant that was on my garage floor was equal to the amount in the fill tank / reservoir. No more has leaked onto the garage floor and The fill tank / reservoir is empty. What I may do is position the scope back under the intake manifold and fill the reservoir and try and see where it's leaking from.

More to come......

[frasern]

Just a thought, before re-filling the tank, dry everything as much as you can, then try to get some brown wrapping paper under there, the location of the leak may be easier to pinpoint.

[TonyC]

That is good advice. I second that. However, if my guess is right based on my own experience, there could be some coolant gelled up under the intake. I know that sounds nuts, but I've seen it; it does happen. You may want to get a few cans of brake-clean spray at Wal-Mart and hit the underside area as thoroughly as you can. Then dry it out and slide the paper in.

I went through both my shop manuals, and I cannot find the size for the intake's freeze plugs. I thought I made a note of the size of those, but it looks like I didn't. Sorry.

---Tony

[mge825y]

Just a thought, before re-filling the tank, dry everything as much as you can, then try to get some brown wrapping paper under there, the location of the leak may be easier to pinpoint.

Fraser - I followed your advice. Instead of paper, I used a manila file folder that I cut to fit and pushed it up in the space between the intake manifold on top and the valley pan. It's kinda tight under there and the file folder was rigid enough to allow pushing it through while also flexing / bending to get into the opening at the rear. I then filled the fill tank with fresh coolant and was able to see the coolant pooling at the rear of the valley pan really fast.

I pulled the file folder out and could definitely tell that the source of coolant is the front center and right corner of the engine.

I ran my fingers under the seal where the fill-tank bolts to the intake manifold and didn't come back with any coolant. There's a hose just below it that runs from the intake manifold to the water pump. That hose is showing signs of dry rot / fatigue and I found some coolant on the under side of the hose where it is clamped to the nipple to the intake manifold.

I'm only guessing, but I could have a freeze plug failure in that freeze plug up front. I could have a bad hose there that runs to the water pump. I could have a bad, cracked or loose nipple fitting for that hose that runs into the intake manifold.

I think I need to have the shop pull the fill-tank and that hose off. While that's off the car, scope under the intake manifold from that end to see if there's a freeze plug issue. Check that hose nipple. Replace the hose with a new one. And remount the fill-tank with a new gasket and
RTV black on both sides.

[Emas9420]

When i was reinstalling my reservoir, I sprung a leak that ran down the valley that then ran down the tranny to the floor. It was almost impossible to see because the way it was leaking only barely coated the edge of the thermo housing but sure enough it was there. I knew immediately it was the reservoir because even though i could not see the leak, it was the only thing that could have affected it.

In your case, I am not sure if it would be the hose because if that is happening with the car off, then i don't see a reason why coolant would be running through there.. at least, i can't imagine the cold temp would change anything with the house, but it could with the metal on the reservoir.
How bad is it leaking when running? specially when up to temp?
Is it possible it's coming from any of the heater hoses running under there? If i were you, I'd pull the reservoir, change out the little hose (i've heard they tend to leak) and rtv the shit out of the reservoir and thermostat housing. I had to rtv it for it to finally seal.