Author Topic: Overheating--rad hose temp question (Read 2990 times)

colin86325 · « **on:** May 13, 2012, 07:04:50 PM »

Mu car has been running hot recently, creeping past the 3/4 mark. The rad hose on the driver's side is very hot, but the lower hose on the passenger side is not much more than warm to the touch. The radiator itself is about a year old.

I'm guessing that the thermostat is stuck closed.
Is the cool passenger side hose a definite sign of this?

Thanks,
Colin

bmwman91 · « **Reply #1 on:** May 13, 2012, 07:29:15 PM »

The passenger side hose is the cold hose (the coolant that passed through the radiator goes through it). It should remain cool/luke-warm to the touch when the car is warmed up. The top hose shoudl get hot, like you mentioned.

Typically, the thermostats fail in an open position & run the motor too cold (a fail-safe built into their design). It COULD somehow be stuck closed. Before doing much else though, try bleeding the coolant system. Get the car fully warmed up and then park it on level ground. Keep it idling, and have some pre-mixed coolant & water handy for topping-off the reservoir. Take the cap off and open the bleed screw ~2 turns. Rev the motor to 2500RPM. If there is air in the system, it should sputter out of the bleed screw. Once the coolant comes out mostly uninterrupted, you are done & close the bleed screw & tank.

If that doesn't help, then maybe the thermostat is plugged. You'll need a new thermostat (88C one) & a thermostat housing gasket. Make sure that the little bypass groove in the housing is clear before reassembly. Fill the system as high as it will go until the level stops dropping in the tank. Open the bleed screw and rev it to 2500RPM. That should push out almost all of the air all at once. Then close the screw, let it warm up and then open the screw to get the last few bubbles out while revving it.

DesktopDave · « **Reply #2 on:** May 13, 2012, 08:58:55 PM »

Bleeding is a good idea, just be careful not to over tighten that bleed screw and only use a large flat-blade screwdriver.

How old is the engine fan clutch? Is the aux fan kicking on at all?

colin86325 · « **Reply #3 on:** May 13, 2012, 10:04:10 PM »

Thanks guys. Actually my radiator tank is filled a bit over what it should be. I will drain it back to its suggested levels and report back.

I haven't had the system open [messing with hoses] in many months. I know it's a ritual to bleed the system. But I thought I had a handle on it.

I think I overfilled the tank.

I will report back.

DesktopDave · « **Reply #4 on:** May 14, 2012, 07:08:52 AM »

I'd just suck a little out of the reservoir instead of draining it. I'm more suspicious of that hydraulic clutch on the engine fan...does the car overheat when it's idling or when it's running? Or both?

juliea · « **Reply #5 on:** January 19, 2013, 03:24:40 PM »

I'm curious @Desktop Dave - when is the aux fan supposed to kick in? And the aux is the fan in front of the radiator, not the one between the radiator & hte block, right?