E39 Overheating - United Bimmer Community

**jay** · 01-15-2008, 07:15 AM

Hi All
Firstly isn't great that you can ask a question about your car before you have to get your chequebook out.

So to my problem:
I have a 1996 E39 (520iSE Auto)
Yesterday it started overheating and temp gauge goes into RED.
There is no heat in the passenger cabin
From reading posts in this forum I have changed the
- Thermostat
- Waterpump
- and both belts.

The tortion cooling fan was replaced approx. 3 months ago. So I am expecting this to be OK.

The coolant was refilled as recommended in this forum and I do not see any air coming out of the bleed screws on both the Radiator and Thermostat housing.

However, when the coolant starts to heat up, I get a very steady trickle of water seeping out from under the coolant filler cap. This in turn goes in the cavity section of the radiator and leaking coolant can be seen coming out just above the lower hose, on the same side as the filler cap.

The exhaust is clear and there is no water residue inside the oil filler cap and oil dipstick.

I have to constantly fill up the coolant, as for yesterday, I managed a 2 min journey in 2 hrs, because of the overheating.

I would greatly appreciate any assistance or recommendations you could make.

Thanks to all in advance.

Jay

**dinan540** · 01-18-2008, 02:31 PM

E39 have crap for radiators. I would suggest looking at the radiator more closely. If you are not careful about overheating, you will blow you head gasket. I would also replace the cap. The radiators leak at the plastic tanks or the plastic neck where the radiator hoses attach to the radiator.

**Dan** · 01-20-2008, 11:57 AM

you've got air in the system; tall tell sign is hot gauge but cold air. strange how e39's are self bleeding systems so i wonder why water is pissing out of the expansion tank.... hum...

when was the last time you serviced the cooling system?

**jay** · 01-28-2008, 05:15 PM

Thanks for your comments.

A quick update...
I have now replaced the radiator and what I find is that after filling the coolant as directed, when the car is cold, making sure that all air has been removed from cooling system.
I usually drop my kids to school in the morning and the car starts to get warm, at the same time the cabin heating gets warm too.
I then drive to work, which is approximately 13 miles. I park up, usually in a residential area near work at just before 9am.
When I return to my car at about 6pm, I find a big pool of water under the car and I have to refill the coolant.

It definitely is an air lock as the pressure is building up, therefore causing the coolant to leak out from under the filler cap. But I cannot figure out what is causing this airlock.

There is a housing into which 4 of the hoses connect to, it is located near the throttle linkage, could this be my problem area, or even the heaters in the car ??

Thanks in advance.

Jay

**Dan** · 01-29-2008, 11:40 AM

where you find white powdery residue is where you find your leak.

**jay** · 01-30-2008, 03:53 PM

Hi Dan

No powdery residue as the water always leaks out from the filler cap, as a result of increased pressure in the cooling system.

At the time when the system is virtually empty and no water in the bottom hose.

Thanks

Jay

**Numark318i** · 01-30-2008, 05:29 PM

hmm.

does the car make a slight whining noise. or any sign of the water pump going out again?
are you sure you sealed teh water pump correctly?(the gasket?)

have you tried to change the cap? when you filled the system after replacing the radiator did you run teh car and put let the fluid be pulled in?

**jay** · 01-31-2008, 01:16 PM

Hi Numark,
Thanks for your reply.
I do not get any whining noise, and the Water Pump is new with new seals.
Same for the Thermostat, I replaced the seals.
I haven't yet replaced the Filler cap, but this only seems to leak when pressure has built up in the cooling system.
When I fill the coolant I fill it to as far as it will go with both bleed screws open, the one on Thermostat housing and the other next the coolant filler cap on radiator.
I set the car Heater to max heat, start the car. With assistance to keep revs at 1,500 rpm, I see the water pulled into the engine and I keep topping up until no air comes out of the bleed screws.
I then close the filler cap and both bleed screws.
I then leave the car running until heat comes out of the heaters in the car and the temp guage shows normal running temp.
At this time I open the bleed screws one at a time and let any further air out, then close them.

Am I doing this wrong ?

Could any part of the cooling system get blocked in any way, I ask because when the pressure has built up, it feels like the bottom hose of the radiator is empty.

I am lost and don't know what else to try.

Thanks

Jay

**Numark318i** · 01-31-2008, 03:45 PM

hmm.

well check the bottom hose. Disconect it and see if there is water pumping out? Maybe try to spray hose water in one end and see if it comes out smoothly on the other end? before doing this make sure its ok. I figure it would be, seeing how only water and coolant runs through there.

**dinan540** · 01-31-2008, 06:30 PM

Jay,

Sorry to hear about your cooling problems. I had an issue with my cooling system for a year. I replaced everything and it would still leak coolant after it built up pressure. I never found out the source of the issue, but I did discover that my radiator prematurely failed 3 times. I have since replaced it with a zionsville superduty cooling kit (aluminum radiator, resorvoir and electric fan). I did that last February and I haven't had a cooling issue since. I have no idea why my cooling system was overpressurizing, but it was. I even had an indy shop do a compression check on the engine, pressure test the cooling system, analyze my coolant and oil. Everything was fine.

Hope this helps.

Paul

**jay** · 03-04-2008, 08:08 AM

Hey All

Thanks for all your help, looks like I finally found what the problem was...

And you will NEVER in a million years think is was this....

The seal on the radiator drain plug needed replacing, all for the cost of £2.78 GBP for a new drain plug as BMW don't sell the seals separately.

Found this problem after I went to a BMW garage and they performed a Pressure Test on the cooling system.

The funny thing was that the new radiator I had purchased, only had 1 of the 2 seals on the drain plug that it came with. So it had the same fault.

Hope this helps anyone who may have a similar problem.

All the best, Jay