1969 C10 8/350 coolant usage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Sven · 08-08-2011, 12:49 PM

One question I have regarding coolant use. I fill her up, doesn't seem to leak at all, the exhaust isn't an unusual color and there's no coolant in the oil but the coolant level drops during use. I've replaced the hoses, rad cap and thermostat and she runs pretty cool. Well, unless I let her run out of coolant.

What do you think? Anything I should be looking at? I know she's an old lady and deserves to be a little demanding at times, but I don't want her to hurt herself.

-Steve

Lee H · 08-08-2011, 12:57 PM

How much are you replacing and how often? To what level in radiator are you filling it to? These older system find a level about 3 inches below the neck, filling above this just goes out the overflow hose while your driving.
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Sven · 08-08-2011, 01:06 PM

I usually fill to the bottom of the neck, anytime I look and see it low. 3" below would sound about the level it's finding, because when I fill the rad it'll take about half a gallon to fill it completely.

Maybe I'm overfilling? I'll pay specific attention to the level next time and if it's 3" I won't worry about it. Thanks for the info ...

-Steve

fastwillie 696969 · 08-08-2011, 01:09 PM

most likey a pinhole in the radiator ,get a pressure tester and see if you can find the pinhole or crack tank or seam .

Sven · 08-08-2011, 01:27 PM

OK, thanks. I have some surgery planned on the truck so a little downtime required. I'll pull the radiator and take it to the shop to be checked/tested/repaired.

-Steve

'72customdeluxe · 08-08-2011, 01:57 PM

My original motor was that way, no external leak and no water in the oil. Replaced the intake gaskets which helped. Head gasket went shortly after. I would do both
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cdowns · 08-08-2011, 06:51 PM

people waste alot of coolant by filling when the engine is not up to temp and filling to the bottom of the neck

MagmaJct · 08-08-2011, 09:14 PM

I remember reading somewhere, (the source escapes me at the moment), that the level should be about 4" from the filler. However, if you are losing coolant, it's possible you're losing it as steam. When the surrounding air is hot enough, steam is quite dry so you may see no evidence of it.

Performing, or having a pressure test performed would be a wise decision.

MARKDTN · 08-09-2011, 07:57 AM

Do you have an overflow bottle? There may be a leak in the hose going to it. As said, a pressure test would be a good tool to help diagnose.

**D.PASSMORE** · 08-09-2011, 09:09 AM

Its common for the coolant to stay about 3" below filler when cold. Driving my 5th, 67-72 model, 25 years and alot of miles - its always the same.

08-08-2011, 12:49 PM	#1
Sven Registered User Join Date: Dec 2009 Location: Laveen, AZ Posts: 69	1969 C10 8/350 coolant usage One question I have regarding coolant use. I fill her up, doesn't seem to leak at all, the exhaust isn't an unusual color and there's no coolant in the oil but the coolant level drops during use. I've replaced the hoses, rad cap and thermostat and she runs pretty cool. Well, unless I let her run out of coolant. What do you think? Anything I should be looking at? I know she's an old lady and deserves to be a little demanding at times, but I don't want her to hurt herself. -Steve __________________ 1969 Chevrolet 4x4 C10 Pickup

08-08-2011, 12:57 PM	#2
Lee H Registered User Join Date: Jun 2010 Location: Upland Ca Posts: 4,147	Re: 1969 C10 8/350 coolant usage How much are you replacing and how often? To what level in radiator are you filling it to? These older system find a level about 3 inches below the neck, filling above this just goes out the overflow hose while your driving. Posted via Mobile Device __________________ 1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703

08-08-2011, 01:06 PM	#3
Sven Registered User Join Date: Dec 2009 Location: Laveen, AZ Posts: 69	Re: 1969 C10 8/350 coolant usage I usually fill to the bottom of the neck, anytime I look and see it low. 3" below would sound about the level it's finding, because when I fill the rad it'll take about half a gallon to fill it completely. Maybe I'm overfilling? I'll pay specific attention to the level next time and if it's 3" I won't worry about it. Thanks for the info ... -Steve __________________ 1969 Chevrolet 4x4 C10 Pickup

08-08-2011, 01:09 PM	#4
fastwillie 696969 ~Rest In Peace~ Join Date: May 2005 Location: CALIFORNIA NOR CAL Posts: 9,707	Re: 1969 C10 8/350 coolant usage most likey a pinhole in the radiator ,get a pressure tester and see if you can find the pinhole or crack tank or seam . __________________ is it fast ? it has a lighting bolt donut? B___H please, I can remove 90% of your so called "beauty" with a kleenex

08-08-2011, 01:27 PM	#5
Sven Registered User Join Date: Dec 2009 Location: Laveen, AZ Posts: 69	Re: 1969 C10 8/350 coolant usage OK, thanks. I have some surgery planned on the truck so a little downtime required. I'll pull the radiator and take it to the shop to be checked/tested/repaired. -Steve __________________ 1969 Chevrolet 4x4 C10 Pickup

08-08-2011, 01:57 PM	#6
'72customdeluxe Registered User Join Date: Jan 2008 Location: Tejas Posts: 691	Re: 1969 C10 8/350 coolant usage My original motor was that way, no external leak and no water in the oil. Replaced the intake gaskets which helped. Head gasket went shortly after. I would do both Posted via Mobile Device __________________ '72 cheyenne super step, '05 long bed gmc

08-08-2011, 06:51 PM	#7
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: 1969 C10 8/350 coolant usage people waste alot of coolant by filling when the engine is not up to temp and filling to the bottom of the neck __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

08-08-2011, 09:14 PM	#8
MagmaJct Registered User Join Date: May 2008 Location: Mesa, AZ Posts: 281	Re: 1969 C10 8/350 coolant usage I remember reading somewhere, (the source escapes me at the moment), that the level should be about 4" from the filler. However, if you are losing coolant, it's possible you're losing it as steam. When the surrounding air is hot enough, steam is quite dry so you may see no evidence of it. Performing, or having a pressure test performed would be a wise decision.

08-09-2011, 07:57 AM	#9
MARKDTN Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 2,165	Re: 1969 C10 8/350 coolant usage Do you have an overflow bottle? There may be a leak in the hose going to it. As said, a pressure test would be a good tool to help diagnose. __________________ '83 K20-TPI '73 C10 '79 C10-ex-diesel(SOLD) '07 Tahoe(Son driving) '14 Suburban-DD '71 C10-current project

08-09-2011, 09:09 AM	#10
D.PASSMORE One of the First Join Date: Jan 2000 Location: St. Augustine,FL. Posts: 4,059	Re: 1969 C10 8/350 coolant usage Its common for the coolant to stay about 3" below filler when cold. Driving my 5th, 67-72 model, 25 years and alot of miles - its always the same. __________________ DAVID PASSMORE ST AUGUSTINE ,FL ZIP 32084 '71 SWB K/10 CUSTOM DELUXE (Chili) '72 BLAZER K/5 Muscle Truck (Mule) '72 LWB K/20 CHEYENNE (Blackie)

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