FatCat

Hey guys, I have a question. I have lost some coolant while changing a thermostat and want to refill. Here is the problem! When I take the cap off, it is full so I run a few minutes and and take the cap off and coolant blows out of the radiator cap. The coolant is still cool or Luke warm at most. Shouldn't the coolant level go down when you lose it? Every other vehicle I have does. Hahaha could this be caused by a blown head gasket? The car isn't overheating.

FatCat

Also if I start up with the radiator cap off, coolant trickles out of the top.

oldalaskaman

reading thru your posts, dont you have two cylinders that are low, and are they next to each other?

FatCat

According to the guy I bought it from yes. I have not had a chance to do a comp check to verify which 2 and he did not know either.

Thanks

oldalaskaman

I'd pull plugs and look for either wet ones , or really clean ones, that'll tell you if its a head gasket, among other things, make a note of which cylinders and which side, it may just be burping it self, mine does that , but only a bit from the built up pressure, no reason to worry till you actually know

FatCat

Ok I'll check tha now, what do really clean ones mean?

oldalaskaman

it means you have a small water leak thats turning to steam and cleaning your plugs, still not good. they will look brand new compared to the other ones and just slightly moist

FatCat

Oldalaskaman your help is always timely and good. Thank you from a guy who is learning!

oldalaskaman

tsw71

I'm assuming it was not losing coolant prior to the thermostat swap, right ?You likely just introduced some air into the system while changing the thermostat. Until you burp the air out, it'll keep doing what you are describing. Best way to do this is elevate the front of the car with jacks or ramps and run the engine with the cap off. Once it gets up to running temperture, the thermostat will open and the air buble will be released. You'll see the coolant level drop when this happens. Then just fill it and cap it. Done.

scottyp99

This isn't my thread, but there is something that I don't understand here. I don't get how an "air bubble" can keep coolant from flowing through an engine. The water pump takes coolant from the bottom of the radiator, and pumps it into the engine, right? The coolant doesn't have anywhere else to go but through the thermostat housing and into the radiator, completing the cycle. Why would an air pocket somewhere in the system affect anything? It seems like the air would just get pushed into the radiator. Is this something that is peculiar to Corvettes, maybe because of the position of the radiator, or something?


Keep the shiny side up!
Scott

oldalaskaman

the op's question was , whats causing the pressuring out the radiator cap even when cold...air , the cause of the air has a multitude of reasons, and fixes. not as common with the C3 as the
C4

FatCat

I will try this! Thanks

FatCat

Ok so! I took the cap off and jacked up the front. Started the car let it run and once it got up to running temp it shot coolant all over the place! Does this sound right for an air pocket? Once I shut it off, it will take coolant but maybe because it lost about half a gallon. What say you?

FatCat

BTW oldAlaskaman, the plugs are really wet

FatCat

To give you a reference the car spewed coolant as if it were possessed!!!!! Haha

briankeery

Could you have the thermostat in upside down?

FatCat

I have the spring side in the block. Is that right?

briankeery

Spring down is correct. You said you ran the car to operating temp. Did the thermostat open and coolant level drop before the eruption? The procedure would be to monitor that upper hose and when it goes hot and the coolant drops, top it up and then get that rad cap back on.

You mentioned wet plugs...which ones? Pictures here are VERY helpful in regards to troubleshooting.

FatCat

The coolant level never dropped, I had to shut the car off because all the coolant was shooting out so fast. I only pulled the front 2 plugs on the drivers side and the were both wet. They did not smell and I tasted (I know not a great idea) and there was no taste either.