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Stumped

OSDart

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First, a little background. I've been mechanic/building for 50+ years and never run across this. New 470 bbm. New Be Cool radiator, New 13psi cap, Be Cool overflow. New 180° t-stat, all new hoses.
Compression test good. Leak-down test good. Checked for combustion fumes in radiator. None. All cylinders free of moisture. No water in oil.
Engine was run on test stand. Several times. No issues.
Now to the problem.
I drove the car two weeks ago to a car show. Ran great without any issues. Two days later I was doing a once-over and there was still pressure on the cooling system. Hoses were still hard. I eased the cap off and checked water level. Was fine.
Saturday I moved it outta the shop, left it ideling, while I moved a few things around. I checked it last night and there was still pressure on the cooling system.
Never run across a cooling system holding pressure for days. Usually the pressure drops when temperature drops.
Any ideas?
 
First, a little background. I've been mechanic/building for 50+ years and never run across this. New 470 bbm. New Be Cool radiator, New 13psi cap, Be Cool overflow. New 180° t-stat, all new hoses.
Compression test good. Leak-down test good. Checked for combustion fumes in radiator. None. All cylinders free of moisture. No water in oil.
Engine was run on test stand. Several times. No issues.
Now to the problem.
I drove the car two weeks ago to a car show. Ran great without any issues. Two days later I was doing a once-over and there was still pressure on the cooling system. Hoses were still hard. I eased the cap off and checked water level. Was fine.
Saturday I moved it outta the shop, left it ideling, while I moved a few things around. I checked it last night and there was still pressure on the cooling system.
Never run across a cooling system holding pressure for days. Usually the pressure drops when temperature drops.
Any ideas?
That is a strange one there. Usually system pressure drops with temp.
 
dont know if this helps. the fleet i have is f--d even after a week i have seen pressure in a lot to all . the rad cap will vent out at its set p.s.i but the seal wont allow it to seep pressure out over time . the maker of that rad is good and the cap seals better than any old system.
 
I've tried three different caps. A 13psi a 14psi and a 16psi. No change. No water in the recovery tank.
 
I've tried three different caps. A 13psi a 14psi and a 16psi. No change. No water in the recovery tank.
not all systems will purge to the overflow tank. most new cars and trucks use a surge tank with out an over flow.
 
Up date!
As I stated, I removed the radiator cap last night and it still had pressure on the system. I checked the water level and replaced the cap. I noticed a small amount of seepage around the t-stat housing so today I thought I'd change the gasket. When I removed the cap there was a good amount of pressure on the system again! Mind you, the car hasn't been started since Saturday and the radiator cap was removed last night.
Now my question. Has anyone heard of a chemical reaction with G05 (Zerex) and distilled water?
Everything is new. Engine, radiator, hoses, water pump, pump housing, G05 antifreeze and distilled water. Only thing different from engine running on test stand and in the car is the addition of the G05 antifreeze and New Be Cool radiator. Sooooooo
 
Last edited:
I run G05 Zerex and Distilled Water in my 71 Bee for two summers now - Around 60/40 mixture good for -30 F

383/432 Stroker With A 22" Wizard Aluminum Radiator - 180 stat - 180 degrees dead nuts all summer long

As temps drop I lose pressure - Coolant mixture still looks brand new after six months of winter storage when I checked this spring
 
Just a thought ,have you contacted Be Cool and asked if they require a specific type of radiator cap? perhaps something they sell for their product?
 
I've had several Be Cool radiators over the years. Never any issues with caps. However, it's worth a call. Hard to understand how a cooling system can build pressure when not in use, unless it's a chemical reaction. I've been running GO5 in my other big block mopar for a couple years without issues. Maybe Be Cool changed their material or coatings? IDK
 
In this case the "chemical reaction" would create a gas to allow pressure to build up.
You could fill up the radiator to nearly full, leave the rad cap off and check after 12-24 hours.
If it filled up the filler neck and overflowed it means something is creating something in the engine.
Could be worth changing coolant to some good quality pre-mixed stuff and see if that solves the issue.
 
New 13psi cap
Just tossing ideas.
What brand of cap? And, have you pressure checked the cap itself?

I've tried three different caps. A 13psi a 14psi and a 16psi. No change.
More head scratching to do. Sounds more like caps are holding more pressure, than their rated for.

System is holding pressure. You'd think if some kind of chemical reaction was going on, it would 'build' pressure. Then it should get enough pressure to over-ride the cap limit, releasing pressure/fluid into the recovery tank.
 
Up date!
As I stated, I removed the radiator cap last night and it still had pressure on the system. I checked the water level and replaced the cap. I noticed a small amount of seepage around the t-stat housing so today I thought I'd change the gasket. When I removed the cap there was a good amount of pressure on the system again! Mind you, the car hasn't been started since Saturday and the radiator cap was removed last night.
Now my question. Has anyone heard of a chemical reaction with G05 (Zerex) and distilled water?
Everything is new. Engine, radiator, hoses, water pump, pump housing, G05 antifreeze and distilled water. Only thing different from engine running on test stand and in the car is the addition of the G05 antifreeze and New Be Cool radiator. Sooooooo
i have never heard of that you might be on to something. builds pressure after you remove the cap all p.s.i gone did not run the engine and the next day you have pressure ? what if that distilled water has lets say rock salt where i work the 5 gallon water bottles from nestle pure life have rock salt in there treatment of the water. why dont you take old milk jugs fill with water let then sit for 5 to 7 days to make your on distilled water . this is a tough one. if you could get a refactor witch is a tool to see what level p.h. the coolant is a good repair shop would have one or a safety clean truck use them to tell if the coolant is tainted / hot. you could take a sample and send it to black stone for a brake down of the chemical compounds.
 
What's the composition of the frost plugs?
Brass freeze plugs. Block was vatted before machine work. I cleaned it with soap and water (twice) before I started assembly.
 
Have you considered electrolysis?
I'll check the coolant today. With battery disconnected. If it's over .300 millivolts I'll flush the system and change antifreeze and add a good corrosion inhibitor. Then re-check.
 
Check coolant voltage. Can't remember the critical value off the top of my head. Radiator to yoke ground is important. Electrolysis is usually a reaction between dissimilar metals but can have other causes. My car ate up 2 aluminum radiators before I chased down the cause. There's a lot on the various forums about this problem.
 
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