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I invent stupid usernames
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Discussion Starter #1
Curious if the following are symptoms of a bad head gasket, couldn't find anything that's an exact match so I figured I'd ask here.

Small block 350 in a 78 C15 pickup is losing some coolant, albeit slowly, and I know where a lot, if not all of it is going. When I turn the heater on I smell antifreeze so I know my heater core is leaking, but what bothers me is that when I first built the motor it would get up to 220 degrees before the 195 degree thermostat would open, then it would go back down to around 200 and stay there unless it was really hot out. after I drilled a tiny hole in the thermostat it hasn't got above 210 even at highway speed. Normally I wouldn't be worried about this but I saw in another thread that having to drill a hole in the thermostat to get it to open is just a crutch for bigger issues such as air in the cooling system caused by a bad head gasket. This coupled with the fact that before I pulled my intake, my number 5 spark plug looked cleaner than the rest, although after putting the intake back on with new gaskets, it seems to look more like the rest of them, so I'm thinking that was because of a vacuum leak. Any thoughts on this issue, or lack thereof? There is no white smoke from the tailpipes and as far as I know I can't see any bubbling in the radiator when I have the cap off. I have a valve that I can block coolant from the heater core if that would be something to try. Just want to get it figured out soon because I need to take it on a 300+ mile round trip in a couple weeks.
 

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Fix the heater core, pull the plugs...coolant leaking into the chamber will show.
 
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You've already described what the plug(s) will look like if you have coolant getting in a cylinder. Fix the obvious leak (heater core) and monitor consumption. You're original cooling system description and thermostat issue aren't big ones. Coolant temps at 220 are nothing to worry about. 235-240 is where crap starts happening.

Run it. If there is an issue, then it will show up soon enough.
 

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I invent stupid usernames
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Discussion Starter #5
You've already described what the plug(s) will look like if you have coolant getting in a cylinder. Fix the obvious leak (heater core) and monitor consumption. You're original cooling system description and thermostat issue aren't big ones. Coolant temps at 220 are nothing to worry about. 235-240 is where crap starts happening.

Run it. If there is an issue, then it will show up soon enough.
What you're saying is I really have nothing to worry about? I have just under 3000 miles on this motor if that makes any difference. When you say I already described what the plugs will look like, do you mean when I said that one was cleaner?

Sent from my VS996 using Tapatalk
 

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I invent stupid usernames
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360 Posts
Discussion Starter #7
When you have a coolant leak into a cylinder, the spark plug will not just be a little cleaner than the others....it will be spotless, steam cleaned, and look like it nearly just came out of the box.
Thank you, I will pull the plugs again and make sure.

Sent from my VS996 using Tapatalk
 
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