1984 Volvo 240 gl over heating at idle, I recently got it started changed the oil and coolant, however I don't see the coolant drain plug it's neither at the top or bottom, and when I start it it fills the tank on the side that u pour the coolant into, it idles then after a few seconds it idles a little higher and then starts over heating, I changed the coolant thermostat and the gasket on it seems to be leaking very little coolant is coming out from there, and I hear a sound like something is boiling, and when I start the car the tank fills up and the cap starts leaking out when it gets to filled, it's almost as if the lines are clogged but they aren't and I'm thinking it's the temp sensor but I don't know if anyone can help please thank and you.

 

If you changed the thermostat and bled the system then I would start looking at maybe a bad head gasket. I assume the radiator fan is working and the water pump is good. Are you seeing any white smoke coming out of the exhaust pipe. .

 

how old is the radiator ? after 20 years or so they need replacing.

 

Yes, they get partially clogged and can't dissipate the heat - Worse the hotter it is outside and/or with ac on. The radiator cap needs to hold pressure also - have you tested it?

Does it still overheat if you turn the heater on full hot, with fastest fan speed?

 

is there an oily sheen on the coolant in the overflow tank? and is it bubbling exhaust gasses? those indicate blown head gasket.

 

it wouldn't blow hot air

 

also I forgot to put transmission flkid in, the line had a pin hole so it leaked out

 

please say you did not drive the car without transmission fluid...

the heater will only blow hot air if the engine and its coolant are warmed up. and your water pump is functional.

 

If the heater valve is opening and it's not hot (and the water in the engine is) - that means water is not flowing - combustion gasses from a bad head gasket can disrupt the natural flow of coolant in the engine. Those engines did not have a problems with air pockets, the air always bled out easily so -

I would be checking for head gasket damage by noting extreme/too quick pressure build up in the cooling system (with a radiator pressure tester), coolant leaking into a cylinder with cooling system under pressure with engine off, (you might get a misfire when first started if only a small amount of coolant leaks past the gasket) Sometimes the odor in a coolant bottle tells you the gasket is damaged - Fill it up w water, start the car with the cap off - does the coolant fill up and start overflowing immediately? Or if it's boiling out of the coolant bottle with the cap off after running for only a few minutes - you have a blown head gasket.

For a more exact answer you could check for HC gasses being in the coolant bottle. There's this


and i'm sure there are many other options to find HC in the coolant. .

 

I didn't drive it, and I put fluid in but ofc it has a leak, also I put it in and it moved good, and the heater I ran it for 5 min and it got very hot.

 

so I took the cap off at first it started over heating, for some reason when I turn the car off the tank gets empty, so I put more coolant in and turned the heater on, and the heater got hot, then i also put transmission fluid in to so that combined was good, and so the car didn't over heat but the needle went over half, I don't know if it's suppose to or not but it didn't keep going up, and one thing I noticed is the coolant didn't leak out with the cap off, and it doesn't have a oily film but the oil cap got hot which I think is suppose to happen.

 

water is free, coolant/antifreeze is not, just use water while you are trying to understand you have a blown head gasket! You will need the cash for other things.

 

its OK for the needle to go up a little above the middle, you only need to worry if the needle pegs in the red (OR, incase the gauge is wrong, if the engine sounds/smells like its severely overheating, do NOT drive it like that!!!)

 

ok so I found a hose with alot of holes I plan on changing all the hoses, but Its the inlet hose to the raidotor from the coolant tank, so i changed it and it still heated maybe I need to bleed it, I was rushing so I couldn't bleed it properly.

 

the top main radiator hose that goes from the water pump/thermostat housing to the radiator should get warm. if its staying cold, the thermostat may be stuck closed, preventing water from circulating through the radiator.

 

it gets warm also I've noticed the thing the termostach goes in the gasket leaks, not the termostach gasket but the whole thing it doesn't leak constantly it just sizzles
could that effect anything?

 

any coolant leakage means it is not holding pressure, and if it won't hold pressure, the coolant boils at a lower temperature and then it overheats that much easier.

I would replace all coolant hoses, the thermostat, the thermostat gasket, and inspect the water pump.

 

yes ok so I'll change the hoses and gaskets, I changed the termostach and the water pump is working, but I'll check and replace the stuff.

 

You may have put the thermostat in upside down when you changed it?

 

So it isnt as bad now but basically when i screw the coolant top all the way it over heats but when i un screw and release pressure the temp goes to normally, also