1971 chevy c10 custom I6 overflows coolant after each trip

[trevarthan]

Carburated I6 250. Every time I come back from a trip the radiator overflows coolant from the overflow tube near the radiator cap. I replaced the radiator cap immediately when I noticed this happening. Still happens with the new cap. Doesn't seem to be overheating yet. Still has a quart of coolant in the fill bottle in the engine compartment.

Is this a head gasket, or something else? I blew a head gasket once on a 4 cylinder truck, years ago. It did the same thing, but it often burned white smoke too. I suppose it just depends on where the gasket blows.

I just bought the truck a month ago, so I don't know the history. Thanks!

['68OrangeSunshine]

What temp is your thermostat? [195F* is stock]
What is your coolant mixture ratio? [50:50 is nominal]
How may tiers in your radiator? Is it the L6 radiator? V8 radiators are wider. [Two-tiers thick might be standard for a small L6 in temperate climate, but not enough in a tropical climate.]

[Classic Heartbeat]

Stop refilling the radiator and it will stop leaking the fluid. When the radiator is filled with cold fluid then you start your truck up to warm it up the coolant expands because it is hot. There isn't any place for it to go so it goes out the overflow tube. If you hook up an overflow bottle, once the radiator cools back down it will draw the overflow back into the radiator. We have the collant recovery systems for $59.95 WES

[In The Ten Ring]

Wes is a great guy to deal with.

My truck will do this once I get it running again....I don't have an overflow tank either.

[trevarthan]

I haven't been filling the radiator. The coolant bottle on the side of the engine compartment has been slowly depleting. I think it had 3 quarts in it when I bought it and it's down to 1 quart now.

I don't know if the radiator is stock, but I'm guessing it is. The engine has 94k miles on the od. So stock I6 radiator.

I'm in Tennessee. Not tropical. Hell, not even warm yet. It's been a strangely long cold winter.

[trevarthan]

Pints, not quarts. Sorry. I just checked the label. Photos incoming.

[trevarthan]

Photos attached. I have no idea how much of that is stock.

[Greasey Harley]

Head gasket? I'd run a leak-down test.

[Lattimer]

You realize the bottle you took a photo of is the windshield washer fluid, right?

Stock, these trucks do not have a coolant recovery bottle. The overflow just goes to the ground.

[SS Tim]

That is the washer fluid bottle.
The radiator is an overflow design.
This means during normal heating and cooling it stays contained in the design air pocket by short filling the radiator. Any excess is drained as in the case of an overfill or overheat.
The design cold fill level is about 3" below the filler neck (see picture).

I'd strongly suggest you buy a owners handbook (owner's manual) and download or buy a service manual.
http://67-72chevytrucks.com/vboard/s...d.php?t=558016

[trevarthan]

I feel slightly stupid, but that's fine. I learned something. So, it's not normal for it to continue draining like this when I'm not filling it.

Is there anything that could be causing this besides a head gasket leak?

[SS Tim]

First thing to do is correct the level and just drive the truck. It should loose very little coolant over time (weeks/months) and it should not overflow.

You probably don't have a problem and the books should get you up to speed on a lot of the normal maintance needs your truck has.

However if you think you have a cooling problem a visual check of the coolant while running for bubbles is a start. Talk to your local shop and see if they can run a block check for you (special tool). Basically it tests for combustion gases in the cooling system while running.

[litew8]

If you feel the running temp is beginning to climb and the radiator is puking coolant, I'd replace the radiator and see if the problem goes away. Radiators go bad too. idk if they can test them, but probably can.

[jabborabbo]

SS Tim knows his stuff. I'll add that when I bought my '67 GMC from the original owner, he had a 9 pound pressure cap on the radiator - it would puke coolant on the ground out of the vent hose until the level was maybe 6 or 7 inches below the filler cap - it's supposed to be 3 inches as SS Tim said. I replaced the cap with a proper 13 pound pressure cap...then it started oozing coolant from pinholes on one side of the tank (details of my trials and tribulations and happy ending can be found here).

Good luck!