86 325es running hot

[marc's325ic]

After about 15-20 min of in town driving my car is running hot. i think there is a blockage in the cooling system somewhere. the hose that runs into and the one that runs out of the heater core dont get hot. the main radiator hoses do get hot and are tight. would this be a bad thermostat or a blocked line somewhere? if there is a blockage. would radiator flush from the parts store help free it up? thanks in advance.

[StereoInstaller1]

I had similar issues with my car a couple of years back. There is an electric valve (ball valve style) on the hot side of the heater core. Mine was stuck shut. Being a broke cheapass, I took it apart and drilled a hole in that bitch.

Worked fine for a year or three, until the heater core blew.

HTH,
Luke

[jlevie]

That set of symptoms could be an indication of air in the cooling system. A proper bleed of the cooling system may fix it.

[StereoInstaller1]

That set of symptoms could be an indication of air in the cooling system. A proper bleed of the cooling system may fix it.

And a whole hell of a lot easier than pulling that damn valve!

[marc's325ic]

I open the bleeder valve after the car got hot and nothing but coolent came from it. no air at all. i was thinking it might have been air blocking it. is there any other way besides the bleeder to let air out?

[lordofthewaters]

I make sure the front of the car is higher, then open the bleeder and squeeze the hoses multiple times while bleeding to force air bubbles to move about. All of this of course is done while the car is up to temp with the heater and blower on maximum.

[StereoInstaller1]

marc, I am thinking you have a stuck valve. I sure hope not, but if you do, be prepared for a major pain in the butt.

[marc's325ic]

is that valve located under the dash board where the hoses come into the heater core? would a faulty valve cause problems even when not using heat? if that is the valve, it is a bitch to get out. i removed a heater core before and almost commited suicide it was so bad.

[jlevie]

A bad heater control valve would result in no cabin heat and the hoses would likely stay cold 9no fluid circulation), but it would not cause the car to overheat. But, air in the system can collect in the heater core resulting in no heat and if enough air is present it can cause overheating. The procedure I use to bleed the system is:

1) Using ramps or a jack get the front of the car 1' or more higher than
the rear. That will make the radiator and bleed screw the highest point
on the engine and facilitate removal of air.

2) With the bleed screw open, add coolant until no more air comes out of
the bleed.

3) Leave the filler cap off, or at least loose, and set the heat for max
temp and fan speed. Leaving the cap loose will prevent air that's still
in the system from causing a "coolant fountain" once the engine heats
up. Start the engine and allow it to warm up to operating temp. As it
warms up occasionally crack the bleed screw to release any air and top
up the coolant as necessary.

4) Once the engine is at temp bring it up to 2000-2500 for a few seconds
several times. Then crack the bleed until no more air is released. At
this point the heater should be throwing lots of hot air, which
indicates that the heater core is filled with coolant. You may have to
repeat this a few times to get all the air out.

5) Drive the car a bit, allow it to cool back down, and recheck the
bleed for air. Over the next few days you may get very small amounts (a
few bubbles) of air out of the bleed screw.

[StereoInstaller1]

^X2. No matter how stuck that valve gets, there is a bypass allowing coolant to flow through the motor.