Why does my car over heat at idle???

Question

I noticed about a week ago that my car (1988 BMW 735i) overheats at an idle, but cools very quickly when I hit the accelorator pedal. I dont have to be moving, but when I use the gas pedal it cools within about 10 seconds. I opened the hood, and noticed that the a/c condensor froze up and that belt was not spinning. Thinking that this was my problem, and that it was just slowing the fan, I cut the belt to the a/c condensor. This did not help. Car still overheats at and idle. Today I went to work, and when I got to the parkinglot my car spewed all the coolant, and my windows fogged up. I am thinking that it is the heater core, but was wondering if I was right for one, but also if the two problems were related, and how to fix the first problem. I do not know why the car over heats, but the fan still spins at idle I have checked this. Thank you for any answers or help with my problem.

Answer 1

You have a leaking heater core. This is why your windows fog up. Check the floor pan on the passenger side, and it will be wet with coolant. It is overheating because it gets low on coolant, and spews the rest out. The engine heats up more as soon as you turn the engine off, and it will spew the rest of the coolant out when it does. When you hit the accelerator it moves what little coolant that is in the engine fast enough to cool down. The belt doesn't spin the AC clutch all the time, only when it needs to kick in to cool the system more. Your AC may not even have anything wrong with it, if it worked OK, and cooled the car off inside. Sometimes they will make ice on them, but if its not cooling the car inside, then you need it serviced, and maybe the expansion valve or filter replaced. Hope this helps you and you can use my advise. Good Luck!!!

Answer 2

well i see several problems here. the a/c condenser is a radiator looking thing usually in front of the radiator. what you probably meant was the a/c compressor. what worries me is that by cutting that belt, you might have also disabled the water pump. look at the huge pulley on the bottom of the engine, and then look for the pulley right above it, if it has no belt you disabled the water pump. if you got to work and the coolant puked out, you probably got it so hot that it basically boiled and blew the cap. the heater core would not have anything to do with the car overheating, unless one of the hoses are leaking. Now what I think is that you were just simply low on collant. I redid the engine in my Kia, and much to my dismay, i didn't remove and replace the freeze plugs, so now they leak coolant, so i eventually end up with really low collant, which causes my engine to overheat, putting it in nuetral and revving to 1500-2000 rpm, it goes back normal. as your car does. so, the two concerns are that 1) you have a collant leak, so your running out of fluid and 2) the beltching of the collant, makes me think you severly overheated the car, which may have caused you to blow a head gasket, warp a head, crack a piston or some other issue that will cause you extensive repair costs. don't drive the car, fill the coolant, full, and the overflo tank. then start the car and see if you can see a leak, check under the car, both radiator hoses and the heater hoses, and any other hose that comes from the radiator or engine that has coolant flo. if you see no leaks, get some dark food coloring, perferably about 10 ounces, dump it in the radiator, replace the cap, run the engine at 2000 RPM for about 2 minutes, or untill the fan comes on, if electric, then idle the car, get a heay rag and slowly and carefully remove the cap, take it to the first detent and let the pressure blow off, then remove it, remember the coolant can be as hot as 230 degrees, so it will burn the living **** out of you, check the coolant and see if any dye is in there, or if it is diluted pretty good, if so this lets you know the water pump/thermostat is working, but your not done, find the upper hose that goes to the engine, this is where the thermostat is, you want to remove it when the car is cool. there should be 2 bolts, remove them, and the thermostat should be in the housing, you will want a replacement gasket before trying this. put the thermostat in the freezer for 10 minutes, this will ensure it is closed, then boil up some water, and throw it in, if it works it will pop open fully, if it works then both the water pump and thermo is good. next step is removing the radiator and having it flushed, if it still over heats. after all that you should have found the issue, as the only parts are the radiator, the hoses, the thermostat, the water pump.

Answer 3

My guess is that you have a restriction. Either the restriction is in the heater core, or the thermostat is sticking. I'm guessing the heater core. The restriction was keeping enough coolant from reaching the engine. When you hit the accelerator you forced enough fluid by the restriction to provide enough coolant to cool the engine down some. I would absolutely get the heater core replaced! Get the thermostat replaced also while your at it. It's the cheaper of the 2 fixes. And then get a good flush. Your problem should go away with these 2 procedures. If not you have a fan that's not working properly. Or you have a collapsed hose.

Answer 4

Has to be one of two things.....Either your coolant level is low, and at idle, the water pump would not circulate a large enough volume to the rad, to cool the engine. Second possibility is that the fan belt is loose and the fan is not turning fast enough to draw enough air through the rad to cool it. With both these scenarios, if you rev the engine, the water pump will immediately circulate the coolant faster, and the fan will draw a higher volume of air through the rad.....both resulting in cooling the engine.

Answer 5

Check you Cooling fan clutch it sounds like it is not pulling air across the radiator when you are idling.the fan can spin but not be pulling enough air. you also might consider placing a pusher fan in front of the ac condensor and radiator to help push air thru

Answer 6

Electric fan or mechanical fan? If you thought the a/c unit had something to do with it, I'm guessing mechanical fan. If so, Could be bad fan clutch. Doesn't spin the fan fast enough at idle.

Answer 7

The problems are very important that I recommend searching for an independent BMW-exp shop.! Expert repair is needed to prevent "Serious-damage" to all affected systems. Ask/Seek/and You shall find help. Good luck!

Answer 8

i'd check your fan at idle.
if your car is hot, and it's not spinning... it's just going to keep getting hotter.

when you start moving you will move air across the rad and cool down the engine. sounds like thermostat and pump are find to me.

Answer 9

have the coolant system flushed and see what happens your car should have the electric cooling fan ... um i think it is just your coolant is failing.

Answer 10

you need to replace your thermostat and flush your radiator also pressure test your radiator cap. as far as your ac-coils frezzing up your compressor is not workiong properly,or you are low on freon.