BMW E39 528I 1997 overheating issue - United Bimmer Community

**eddieq** · 09-14-2012, 08:50 AM

Hi guys,

60k miles
car is in mint cond, everything works

Hope you are able to help me here, don't know if this is an air lock.

Here is my problem, my car overheated, I took the car to the bmw garage where they replaced:

The thermostat and thermostat housing
Waterpump

Few weeks later car over heated again, this time same garage done the following:

Pressure tested the cooling system, car passed this twice
They also done a block test which the car passed

They bled the cooling system and all was ok again for a few weeks.

Now the car has overheated again and I can't seem to find out what is going on.
I just seem to have loads of air in the system, has anyone else had this issue?

**kung Fu Master** · 09-14-2012, 10:55 AM

might be your viscous fan.

DEATH2000 · 09-15-2012, 01:05 AM

How do you know you have "loads of air in the system"?

Check your fan clutch. Roll up a small newspaper and with the car running slowly insert it into the fan blades. If the newspaper stops the fan, then your fan clutch is gone. The fan will spin freely with the engine running giving the appearance its working, but wont provide any cooling power to the engine.

**eddieq** · 09-15-2012, 02:42 AM

Thanks for your messages..
When I try to bleed the air out of the system, there are loads of bubbles coming out of the beeld screws ;-(, the stream of bubbles never seems to end.

I just did the test which you suggested and my fan stopped right away. Looks like I will need a replacement, thanks ;-)

DEATH2000 · 09-15-2012, 07:03 AM

For bleeding, try elevating the car. Air rises, so your more likely to get more air out of the system with the engine elevated a few inches.

To bleed the system run the car for several minutes until the temp is within normal range. Then turn the heater on MAX. This will cause the thermostat to open circulating more coolant through the system. Then you can open the bleed screw.

My fan clutch has failed too and my car was the same way. It started overheating until i got onto the highway or drove pretty past. In normal traffic it would overheat pretty quick. Its good to catch early because in some cases it can cause the fan to disentegrate causing massive damage and ripping through hoses. Hit up www.bimmerspecialist.com for a replacement. I find their prices to be quite competitive. I use them for all of my OEM parts.

**eddieq** · 10-22-2012, 08:23 AM

Hi, I'm really in need of some help here ;-(

My BMW E39 1997 523I Saloon has an overheating issue which has become a bit of a puzzle.

Ok, so things which have been changed.

thermostat housing, thermostat (thermostat has been changed twice now)
waterpump.
viscous fan
expansion tank and cap

Tests performed and past: pressure test / combustion test / leak down test / sniff test all have been past with no problems.

The only thing which hasn’t been replaced is the radiator and some hoses.

I have checked the radiator myself, when the car overheated the top radiator hose was really hot however, the radiator seems to have cold spots on it, and the bottom hose is stone cold, the coolant is not circulating therefore im thinking the radiator is blocked? I don’t know what else to do.

Do you have any clue as to what could be my problem? I don’t want to spend much more cash on this ;-(

DEATH2000 · 10-23-2012, 12:33 AM

You have replaced everything that would normally cause an overheating issue. The coolant entering the radiator should be hot, and the coolant leaving should be cold, to cool the engine. When you feel and squeze the hoses you should be able to feel the coolant in the hose, and with the cap off you will notice a slight rise in fluid level. Should you just feel air, then their is an issue.

**eddieq** · 10-23-2012, 02:25 AM

Thanks for your reply..I had the system pressure bled where a pressure tester was put onto the expansion tank, I was with the mechanic when this was done, all the air was bled from the system, only had coolant coming from the bleed screws.

When the car overheats I’m getting steam from the bleed screws, the top hose is roasting where I can’t touch it, only a few patches of the radiator are hot the rest is stone cold, the bottom hose has no heat in it at all.

Only thing I can think of is a blocked radiator, I removed the bleed screw at the bottom of the radiator and white gunk came out then coolant started to flow. the radiator is only 3 years old ;-(.

I don’t want to go back to the garage as I’m being charged a fortune every time I’m there and it seems they are just guessing.