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Upper radiator hose sucks in under heavy load

R

regal

New member
this is a big problem as it is constricting coolant flow from the upper radiator to the thermostat housing . My question is what could be causing this? surely someone here has had this issue. thank you for any input . my car is a 97 regal GS
 


Your thermostat is stuck closed.

Coolant flow is from the lower radiator hose to the water pump through the engine, out the thermostat and upper radiator hose to the radiator to be cooled and recirculated. The lower hose usually is reinforced so that it doesn't get sucked close under high demand and the restriction of the radiator. The upper on the other hand is not since it will always be under higher pressure. Because the thermostat is stuck shut, or is not opening properly, your pump is pulling all it can and it's flowing through the engine and the highest restriction and therefore low pressure area now becomes the outlet of the thermostat. And that is why it gets sucked closed.

Jeff
 
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Ok l I had ordered a new one anyways. ill install it and report back thank you for a quick and direct response .
 
Ok the thermostat fixed the issue. I found another source of a potential issue. The PO had installed one of those stupid vent radiator caps. The cap was preventing the cooling system form building pressure . This is likely what caused the old thermostat to age prematurely. Luckily I caught it before any real damage was done .
 
the caps let coolant out after 16 psi, then suck the coolant back in as the car cools. so its kinda normal if thats what you mean by vented.

its why you have a over flow tank.
 
the old radiator cap was defective. the cap was preventing the system from building any pressure at all
 


then the over flow tank would have been over flowing.

caps do wear out, the spring goes bad, or the rubber seal fails.
 
it wasn't overflowing at all which is strange . All I know is it seems to be much happier now and staying between 180 and 190
 
I've never had a rad cap that was weak not cause an overflow, especially since I live in southeast Texas where the temps get into the high 90's at night.

Make me sure you get the thing bled out properly, take it for a spirited drive around the block with a couple of full throttle romps through 2nd at least then park it and allow it to cool overnight then top off the overflow. Check it for the next few days. There are bleeder screws as well but I'm sure you already did that.

Jeff
 
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