Coolant tank keeps puking coolant

[79dentside]

Hey guys, I’m baffled. Last 5 times or so that I’ve used my truck, it pukes coolant out of the resivoir. It isn’t running hot, the son of a gun barely gets to 150 degrees. It doesn’t boil, it just expands and spills out onto the ground. I have lost probably half a gallon of coolant total, but the resivoir still reads the same when the motor is cold. Any ideas?

I put an aftermarket radiator cap on a few months ago or so because it was leaking. I also put a 160 degree thermostat in about the same time. Those were both my initial thoughts, but both are new, just wanted to include that. Any ideas?

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[Ricko1966]

It sounds like you've got a head gasket or a cracked head just starting to leak combustion pressure into cooling system. Tape a plastic bag around the filler neck with no cap on.Start the truck. Does the bag blow up?

 

[Itali83]

Same, I just had the same thing happen to my 87 Jimmy. Never ran hot but would pressurize the overflow tank. Cracked head in my case. There’s really no way to build pressure in the cooling system other than that. Sorry dude.
Ben

 

[79dentside]

Oh nice... well I appreciate the honesty. This is a crate 350 with 24,000 miles, what is the likelihood of a cracked head?

Looks like the time might have come to put the cam in if I have it apart ....

 

[79dentside]

Just to throw some more details out, I went down to look at the truck to see what I could tell with out any tools. I’ve been moving and the tools are still in the last garage.

My overflow jug after loosing about a gallon of coolant in the ground in the last weeks, it is still “FULL” when cold.

Radiator is also almost still full, no oil in the rad, and the cap is the correct PSI.

Inside the head looks good, no coolant. Oil level is also spot on, nothing crazy.

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I understand things are not looking grand for me right now, but you guys still thinking a head gasket? Should I try a new thermostat just for kicks and giggles?

 

[77 K20]

Could try these:

https://www.napaonline.com/en/p/BK_7001006

https://www.amazon.com/Lisle-75500-Combustion-Leak-Detector/dp/B0007ZDRUI

 

[Frankenchevy]

Maybe the spring in the radiator cap is bad or the wrong pressure. It could be bypassing coolant into the puke tank too easily.

 

[79dentside]

Both good ideas. A test kit is good to have, I need to buy one.

As far as the radiator cap, I think it was like 3 or 4ish dollars. Can’t remember, but it was very cheap. It probably isn’t the best quality, but I’m not sure.

 

[77 K20]

Maybe the spring in the radiator cap is bad or the wrong pressure. It could be bypassing coolant into the puke tank too easily.

Due to a porous casting on my Edelbrock intake manifold (I even bought a second one, same issue). I dropped from a 16 lb radiator cap to something like a 8 lb? 9 lb? and do not have problems with coolant dumping into my expansion tank. It operates the same, just at a lower pressure and my boiling point is now a bit lower.

It could be the cap is just bad though...

 

[79dentside]

Due to a porous casting on my Edelbrock intake manifold (I even bought a second one, same issue). I dropped from a 16 lb radiator cap to something like a 8 lb? 9 lb? and do not have problems with coolant dumping into my expansion tank. It operates the same, just at a lower pressure and my boiling point is now a bit lower.

It could be the cap is just bad though...

I have an Edelbrock Intake as well, never considered that. Let me try a new cap first. Thanks all

 

[77 K20]

I have an Edelbrock Intake as well, never considered that. Let me try a new cap first. Thanks all

I have a weird intake manifold for my vortec heads (P/N 7116). It has a special passageway under the carb/TBI to help warm the manifold for cold weather. I'd get a small puddle for coolant inside my manifold after the truck sat overnight. It would then burn off when the truck was started. According to Edelbrock I'm the only person in the whole world that ever experienced this. Twice.

I'd say your manifold is fine and you have some other issue going on.

I was just saying a lower pressure radiator cap doesn't dump a lot of coolant out-


The other thing I did when I lost my head gasket was I siphoned off a bit of coolant out of the radiator so it was an inch or two down from the cap. I started the truck and used a flashlight and watched the coolant circulate. In not much time I could see that there were a lot of very small bubbles in the coolant. The coolant level then started to rise up- as it was starting to look "foamy". After I shut it off it was still there for a bit- then it looked "normal" again fairly quickly.

 

[Blackbeard44]

when you fill the radiator, are you also filling up the puke tank as well??

when motor is cold and cap is on radiator start it up and squeeze the radiator hose, does it instantly become solid-hard to squeeze?

smell the raditor cap does it smell like exhaust?

 

[Rusty Nail]

When you puke into the overflow, does the radiator empty accordingly? ... Are you overfilling the cooling system - the overflow will ensure the correct amount of coolant - umm..160° isn't hot enough imo.. Umm I run them STANT LEV-R-VENT caps...I too think the radiator cap spring could be suspect...they cost double what yours did. A $4 rad cap?

Come on man!

Why the hell would I take a test?

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[79dentside]

Initially I did overfill my overflow tank about month or 2 ago. I filled it to the “FULL” line while cold (which is wrong, I know), I kept loosing coolant and I was trying to be proactive on my levels haha. Turns out it was a split in my radiator cap seal that was leaking. But since then I gave lost at least a gallon and it is still at “full”...

 

[Rusty Nail]

Okay but what's in the radiator? Is it a gallon low?