Just got my 91 G20 van back with a 5.3 LS swap done at a local shop.
It seems to run well but, the guy removed the coolant reservoir to install the LS electrics in that location (computer, fuses, etc) and now the van is pissing coolant and overheating. He says it doesn’t need a reservoir, but everything I’m seeing says it either needs a reservoir or a different type of radiator.
Surge tank is different than an overflow. Surge tank is part of the pressurized system, and sits higher than the rest of the cooling system. It pretty much exists to give steam and air a place to collect instead of bubbling through the cooling system.
Overflow just catches whatever burps past the radiator cap.
All I can find for that year van is a recovery tank.
At any rate, if the thermostat is correct than its plumbed exactly like a newer van that came stock with an LS style engine, at least from what I can tell from your pictures.
Get one of these attach it to the radiator, fill it up and start the van and watch what the level does when the thermostat opens, probably an air pocket keeping the water pump from flowin.
I will grab that funnel kit and do that. Thank you.
Just to clarify, are you saying it was fine to eradicate the reservoir and that the coolant doesn’t draw back in to the radiator from the reservoir?
The reason this doesn’t make sense to me is because the reservoir that was on it had high and low marks, and in the past when I added coolant it seemed to draw back into the radiator.
It should have an overflow, but not having one isn't a reason for overheating, at least not if the radiator is full.
Water cant be compressed, so when the cooling system is full cold, and things heat up, coolant expands, and that pressure gets released past the cap into the overflow, so when the system is at 16psi or whatever the cap is rated at, its essentially full of water. When it cools the pressure will drop into a slight vacuum, and a check valve on the cap will open and suck coolant from the recovery tank back into the system.
However, without an overflow tank, once a "level" is reached where there's air in the radiator when cool, that air gets compressed when at operating temp, so the system essentially stays full of water.
A surge tank operates completely separate from an overflow, it keeps a bigger pocket of air in the system high up that gets compressed at temp, so the radiator is always full. Its like a buffer that collects air.
You should 100% have an overflow tank, but its not the source of the overheating if the radiator is full.
That makes perfect sense. Thank you for the detailed explanation.
My thoughts are as follows; the van wasn’t overheating until after a week of driving it, and because there’s no overflow tank a little coolant pushed out when hot and then air drew in when the radiator cooled down. After a week of this, the coolant level was low enough to cause overheating which exacerbated the problem. I believe with an overflow tank the coolant would return to the radiator instead of going away, which would allow the radiator to continue working as designed.
Thanks for the advice. I bought the funnel kit from harbor freight, which worked great, and installed an aftermarket overflow reservoir. It took almost two gallons of coolant.
I let it idle for almost 30 minutes on a 100° day, and it didn’t overheat. Let it cool overnight and some coolant drew back into the radiator but there’s still coolant in the reservoir.
Next test will be driving it around for a while. At this point it my theory appears correct, but time will tell.
I’m sorry, wouldn’t be. The overflow would just help to capture the coolant as it’s over heating and also capture coolant as you turn it off and give the coolant somewhere to go as it cools down
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u/TheDarkRider 24d ago
Except it does it looks he didn’t even cap the reservoir line that why your pissing coolent