Technical Flathead Cooling System Advice Please and Thank You (PS, Not an Overheating Issue)

Hi all again, OK, as mentioned in my other post, I had hotrod reliability issues this past weekend that included losing about a gallon of coolant over about 100 mile distance from the coolant recovery tank overflow. The engine has always run cool at 170-180 degrees, including while it was spitting out coolant (165 thermostats if I recall correctly...but that was a few year back since I put them in) and seemed to purrrr along at 60 mph highway speed like a champion! Other than showering those following me with coolant (and the issue with the condenser failing yet again...but that is not what this thread is about).

When we got to our destiny, I checked the coolant level and had to add a gallon of water and observed what I thought was an abundance of foam in the water/antifreeze mix when I re-started it. So, not wanting to hurt the motor, I shut it down fearing a head gasket failure.

I'm home now and the diagnostics begin:

• compression check 160 in number 2, 165 in number 6, and 170 for all others
• pressurized the cooling system, held 5 1/2 lbs for 15 minutes
• ran the test for CO in the coolant, none
• re-torqued cylinder head bolts, no movement on any of them
• no coolant in oil, no oil in coolant
• I still need to check the functionality of the pressurized rad cap.

So it would seem all is good with the head gaskets/block...I'm now guessing that the foam in the coolant was probably an excess of air from the pumps cavitating while operating with a gallon less coolant. Again, I'm thinking good news.

So do I assume that the coolant loss was a result of the pumps flowing more coolant than the rad could flow, then overpowering the 7 lb cap and then filling the recovery tank until it overflowed (the bottom of the overflow hose is where the coolant was coming from)? If so, any suggestions what to do about it?

My flatty has 2 new waterpumps (Speedway Motors when installed about 500 miles ago), a custom radiator shop built brass rad (I need to check how many cores), a 7 lb rad cap and a homemade coolant recovery tank. At 60mph, with my 29" tires, 3.78 rear gears and 1:1 3rd gear will be turning around 2600-2650 rpm (the motor seemed happy there and pulled down some pretty good fuel economy).

Any thoughts or help out there? And the following is to show my coolant recovery tank, location, etc. The rad cap was off when the photo was taken.

 

Hate to say it, but I think you’ve got a head gasket on the way out. Might be leaking just enough to evaporate the coolant at running temp. Just went through this with mine last year. I would always lose a little coolant but it never seemed to smoke out the tail, leak, etc. then one day it let go. Copper gaskets split between the copper sheet and the fibrous center. I replaced them with composite gaskets and haven’t lost a drop in 6 months

 

I'm afraid of that...I too have the copper gaskets and was thinking if replacement is required, studs (replacing the grade 8 bolts and washers), and Felpro composite gaskets are my next plan. When I pulled the plugs, all 8 show exactly the same color, no sign of one or more cylinders ingesting coolant.

And the leak was definately coming from the bottom of the coolant recovery overflow hose (which may have been pressurized by cylinder pressure from head gasket... though I haven't been able to duplicate the issue or see any telltale in the shop diagnosis even running the engine at 2500-2700 rpm while at operating temps..

 

Do you have aluminum heads? I couldn’t tell from the photo. If you’ve got stock heads I’d stick to bolts. I had studs with aluminum heads. Pulled them all, cleaned them and resealed with permatex #2. I did the Speedway method of torquing (right to left-left to right up and down). Hopefully you don’t have to go through all this. Maybe go to a shop that can run dye in the coolant and check it with a black light?

 

I have the UV dye for the coolant...but didn't need it to see that the coolant came out the overflow tube. LOL. The little green spots on the black frame below it were clearly evident. Yes, I have a set of original Eddie Meyer aluminum heads (this is the engine in my avatar), torqued using the original sequence to 45lbs.

 

@anothercarguy I like the coolant recovery tank. Clever idea. I'm joining the head gasket jury. Lucky to get it while the car is at home and before it gets real messy.