Coolant mysteriously disapearing - Page 2 - Chevelle Tech
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post #16 of 24 (permalink) Old May 17th, 11, 1:55 PM
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Tom
 
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Re: Coolant mysteriously disapearing

Let me tell you about a personal experience that took several years to locate and fix.
I built the persent SB400 that's in the 70 back in 1998. After 4-5yrs, the coolant level in the radiator went down slightly---------not much. In time, it went down in an increasingly shorter period. I checked EVERYTHING, including replacing hoses and taking the radiator to the shop. NOTHING. Nothing out the tail pipe, nothing on the driveway. ZERO indication anywhere of a leak! No water in the oil, no oil in the coolant. And the engine always ran fine. One day (I do not know why), I decided to pull the plugs. BINGO, a tiny bit of water dribbled out of #2 hole. I pulled the intake and the right head. The chamber and piston were VERY clean------------------as in steam cleaned! I could NOT FIND the source of the leak. FINALLY, I noticed a tiny light colored path in the #2 combustion chamber between the valves. To make a long story short, it was a VERY TINY pin hole (had to use a magnifying glass to see it) which me and my machinist decided was a casting flaw where the metal in the roof of the chamber (on the water jacket side) was EXTREMELY thin and the tiny pin hole had developed. I rounded up a matching head, had it machined to match the other head and put it all back together. This occured about 3yrs ago. Haven't added an ounce of water since.

Tom Parsons
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post #17 of 24 (permalink) Old May 17th, 11, 2:03 PM Thread Starter
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Lou
 
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Re: Coolant mysteriously disappearing

Both tail pipes appear steam cleaned. Could both heads or gaskets be leaking!?
I will see what the leak test shows and try the bottle test.
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post #18 of 24 (permalink) Old May 17th, 11, 2:20 PM Thread Starter
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Re: Coolant mysteriously disapearing

Thanks for the tip. That is quite a story Tom. Especially seeing how long it took to find the problem. In my case, in the absence of an external leak and radiator cap over flow possibility, I am considering pulling both heads. The plugs on the right bank and the rusted tail pipes have me thinking both should be removed and inspected.
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post #19 of 24 (permalink) Old May 17th, 11, 5:03 PM
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Re: Coolant mysteriously disapearing

Hi Lou, you don't mention if the heads had been rebuilt or not, but from your description of the issue it sounds as though you may have some cracked heads where the exhaust guides end! It happens when removing the guides in the "wrong" direction.

It acts exactly as you describe with respect to losing water and not noticing any visual deposits! When these head get cracks like these the water more or less boils away as it leaks. It's also leaks worse during "normal" operating temps!

(Add) I'm not certain this is your issue, but the "signs" are present!

Thanks, Gary in N.Y.

P.S. The exhaust guide in most BB (early) heads MUST be removed from the bottoms up through the tops (they must be knocked out from the chambers), they are "stepped" in size and pass through the cooling system, they are water-cooled! They also go in only in one direction as well, from the tops (valve spring side)!
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post #20 of 24 (permalink) Old May 17th, 11, 6:19 PM Thread Starter
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Re: Coolant mysteriously disapearing

Quote:
Originally Posted by GOSFAST View Post
Hi Lou, you don't mention if the heads had been rebuilt or not, but from your description of the issue it sounds as though you may have some cracked heads where the exhaust guides end! It happens when removing the guides in the "wrong" direction.

It acts exactly as you describe with respect to losing water and not noticing any visual deposits! When these head get cracks like these the water more or less boils away as it leaks. It's also leaks worse during "normal" operating temps!

(Add) I'm not certain this is your issue, but the "signs" are present!

Thanks, Gary in N.Y.

P.S. The exhaust guide in most BB (early) heads MUST be removed from the bottoms up through the tops (they must be knocked out from the chambers), they are "stepped" in size and pass through the cooling system, they are water-cooled! They also go in only in one direction as well, from the tops (valve spring side)!
Thanks Gary. Engine was rebuilt in 1988, 2 or 3 owners ago and the receipt from the builder provides no details on what may have been done to the heads. If they are cracked at the exhaust guides, does it mean they are ruined?
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post #21 of 24 (permalink) Old May 18th, 11, 12:45 AM
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Tom
 
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Re: Coolant mysteriously disapearing

Here's the engine after I pulled the right head. Notice how clean #2 piston is.


Tom Parsons
TC# 474
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Light travels faster than sound. That is why some people appear to be bright until you hear them speak. (unknown)
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post #22 of 24 (permalink) Old May 18th, 11, 1:48 PM
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Re: Coolant mysteriously disapearing

Lou, Did you retorque the intake? Maybe the gasket is seeping.

Jeff
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post #23 of 24 (permalink) Old May 18th, 11, 3:31 PM
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Re: Coolant mysteriously disapearing

That #2 looks just like the plug pulled from the backside of my windstar.
Enought coolant leaked into the cylinder after shutting off---it would not restart within 5 minutes due to hydrolock.

Boy----that head sure was clean for that cylinder
I just needed a head gasket----no an easy job in a minivan

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post #24 of 24 (permalink) Old May 18th, 11, 4:02 PM Thread Starter
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Smile Re: Coolant mysteriously disappearing

Thanks to Mike and Bob for recommending the coolant pressure test. Borrowed a coolant leak tester from Advance Auto and bingo! Discovered leaks at heater core hoses on firewall, top radiator hose also. Explains the coolant loss.
I hope. Going to try leak tester with engine running to eliminate the head gasket or crack possibilities.
I am surprised I could not detect these leaks under normal operating pressure. Of course I was not aware I had a problem until the radiator hose collapsed. I suspect that they were fine enough that traces of the coolant evaporated.
Thanks to all who responded. This proves to me once again the value of this site.
Lou
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