I just don't get it..

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mopardads67

mopardads67

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I put a radiator in my 67 dart 318,from a 74 dart 318 with ac with coolant recovery.I did not hook up the catch can and just left the hose hang.Why can't I find a cap that will seal and keep my fluids in?I've been to every auto parts store and even a radiator shop,but to no avail no luck.The car does not over heat at all but will always puke out fluid until it gets low and then it of corse it stops why have a psi rating on a cap if you're not holding any psi. Anyone have any advice?
 
it is doing exactly what it is supposed to do, that is why having an overflow works better, when it gets hot the coolant expands and goes into the overflow, when it cools down the coolant contracts and the vacuum sucks it back into the radiator refilling it
 
I could live with that thanks. But what about holding psi ?
 
the higher the PSI the higher the boiling point of the coolant
it does not affect expansion of the coolant though
 
OK. I'll go with it.I always thought (on rare occasions)that once that cap was put on it would hold pressure up to the cap rating and then puke if it needed to.
 
un like air or other gas a liquid will not compress, but it will expand and contract with temperature so if your cooling system is full when it heats up the expanding liquid coolant needs to go somewhere and if the radiator cap didnt let it escape it would burst the radiator
 
Ok I understand the heating and compression and all but if I squeeze the upper hose when the car is off and cold should I hear air comming out of the over flow?I thought it should be sealed at this time because there is no heat and exspansion
 
You just MIGHT have a wrong cap on there---there are dfferent neck lengths. I don't know how many, I think there's at least three

I think I'd be swingin around a radiator shop and see what they think.

If the engine is cool, you might be able to squeeze / release the top hose and feel it "breathe" because some of the check valves are not really spring loaded.
 
it should hold pressure from getting out but let coolant be sucked back in
also 13 to 16 psi is not a lot of pressure, you can create a LOT more than that squeezing a hose with your hand,
 
mine drove me nuts like that until a rad guy explained that the old style system in my car should only be filled to a 1/2 inch below the inner lower edge of the filler neck and that the rad was just puking out the extra which I kept refilling and it kept puking etc in a never ending cycle of DOH! lol
 
cannucky said:
mine drove me nuts like that until a rad guy explained that the old style system in my car should only be filled to a 1/2 inch below the inner lower edge of the filler neck and that the rad was just puking out the extra which I kept refilling and it kept puking etc in a never ending cycle of DOH! lol
Click to expand...

BINGO! older radiators had room to allow for expansion newer ones dont, so they need an expansion or overflow tank, it also works better this way
 
I don't know maybe I just don't get it. Even with the catch can sucking in and out when does it hold preasure?I'm sure even the water pump puts out 6to 8 psi and if I have a 16psi cap I would think it still should not puke until it reaches 16+ psi
 
Why would you wanna run it without the overflow in the first place? Talk about "I just don't get it" ............that's the part I don't get.
 
Ok so I'll put the catch can on and then maybe just maybe with the plastic cap on the can I'll get pressure doubt it but thanks for you're input
 
Cooling systems are not under pressure the whole time the system is at operating temp. It goes through cycles. Sounds like maybe you need to read up on how it works. It's probably working ok.
 
water pump doesnt make any pressure, just circulates the coolant, there is pressure when ever the engine is hot, that is why you should NEVER open a radiator cap when it is hot, the resulting loss of pressure will spray scalding hot coolant on you, painful trip to the emergency room will result,
the psi rating of the cap determines when pressure and coolant will be released into the overflow tube
 
Thanks Caferacerx for your input, your last sentence is why I'm asking these questions.Mine pukes cold ,this is really no problem because I don't overheat and Stroker I think your comprehension skills might be lacking,the question asked was not about the catch can and as far as reading more to learn I think thats why I come here to FABO to read , learn and ask questions.
 
the cap is rated at only 18 lbs. You should be able to squeeze the upper hose just as easily as squeezing the spring in the cap.
 
mopardads67 said:
Thanks Caferacerx for your input, your last sentence is why I'm asking these questions.Mine pukes cold ,this is really no problem because I don't overheat and Stroker I think your comprehension skills might be lacking,the question asked was not about the catch can and as far as reading more to learn I think thats why I come here to FABO to read , learn and ask questions.
Click to expand...

No, I understood fine. No need to take jabs. Nobody did that to you. All I have offered is literal advice. So yes, if you're talking about the cooling system, the overflow can is a part of it and you are talking about that. Contrary to popular belief, the cooling system is not under pressure the entire time it is hot. That is why it has a catch can and a presusre valve on the cap. However, probably well over 80% of the time the cooling system is hot, it is under pressure. When I said you should read up on it, I was completely serious. Nothing was meant malicious. No need to get defensive. There's a first time for everybody to learn about somethin.
 
The radiator gets hot, water expands when hot. The cap lets water into the plastic tank. When the radiator cools down, the water cools, and contracts, the cap lets the system suck the water back in from the plastic tank. Over and over.
 
Lots and lots and lots and lots of vehicles used to run hundreds and hundreds of miles before everybody had catch cans, and most of 'em didn't puke water out all the time.
 
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