ok my 87 FC N/A will not suck the overflow coolant back into the radiator. why would it do that? i replaced the thermo, heater hoses upper and lower hoses both radiator caps. did a full flush and it gets to 3/4 on the gauge then goes down to half. then the next time i start it up it has the annoying buzzer and idiot light. any suggestions?

 

Sounds like a small leak somewhere. Time to pressure check the system

 

Replace the small diameter hose that connects the radiator to the overflow bottle and clamp it at both ends. A tiny "air" leak in that hose can cause such a problem. May not exhibit any coolant leakage since this hose is not pressurized. If it is a small leak it would only affect the functioning of the system when the system cools and tries to suck the coolant out of the bottle back into the rad.

Could also be another cause, but this is an easy, inexpensive "fix" that will at a least eliminate this as the cause of the problem.

 

I need to follow this thread. My 90' just started the same thing. Each day I look and the overflow bottle increases from the day before. I replaced the radiator cap thinking the seal may be weak, but it made no difference.

 

Go48 hot the nail on the head. You ever tried drinking through a straw with a crack in it? Same thing happens here.

 

was not hose all though i replaced it. i found a Small Crack in the top tank in the Radiator where the hose line comes out. getting the Radiator redone for 75 bucks. Is the Coolant lvl sensor what it comes out of? Cause theres a wire connected to it

 

I found a crack too in the lower radiator.

 

if anyone tells you that you can rebuild a Plastic tank Radiator they are full of ****! Just Fyi. i go to Mike dana radiator on Country club dr in mesa to get it done