E39 528 overheating

[okgo]

Hi guys,

A little help if possible.

I was driving my 99 528 yesterday (it has 120k) and all of a sudden the temp gauge, that previously never moved from centre went into the red, so I instantly moved over and stopped popped the hood to have a look, there was no fluid in the bottle, so I slowly released the cap and all the fluid rushed back into the bottle from the radiator (not sure if this was the wrong thing to do) I then set off again and its back to the middle and looking ok..Now bearing in mind it previously never moved, on my 30 mile jaunt up the A3 it did saunter about going up to edge of red then dipping back down..

Now from what I can tell the rad has no leaks, and the fan works, why is it doing this, I have ruined a car in the past by letting it overheat and warping the head, I don’t want to do it again, but would like an indication of what is wrong..

Thanks for any help.

[sparks_E39]

Get it looked at, try and avoid driving it. It's about the right time for the cooling system to fail, mine did at 120k although I caught it before it overheated, about £350 for a new cooling system.

[okgo]

You think?

It doesn't seem logical to me though, water cannot heat up and cool down as quick as the needle suggest..

[sparks_E39]

Could be a faulty thermostat or sensor, to be on the safe side I would go and get it checked out for peace of mind.

[john_p]

Air bubbles in the cooling system maybe? The coolant temp sensor relies on a heated coil which is cooled by the passing water - so if an air bubble goes past the sensor it registers as an overheat. Perhaps this happened in your case?

[okgo]

Went back to it when cold, and realised the exapand bottle was almost empty So filled her back up and it seems fine. I am stupid

[sparks_E39]

okgo said:

Went back to it when cold, and realised the exapand bottle was almost empty So filled her back up and it seems fine. I am stupid

If its empty when cold it has a leak I suspect, its meant to be full and the indicator to be level with the top of the filler... the only way it wouldn't be full when cold is if the car is leaking, I would get it looked at mate to get some peace of mind. A coolant leak might not be obvious at first, it is not uncommon in these cars but at around £350 for a permanent fix its worth doing, if you cook the engine you would be looking at £1000 minimum for a decent replacement excluding fitting. Has the "check coolant level" message appeared? Thats how I stumbled upon my problem, same engine as you, same mileage.

Edited by sparks_E39 on Tuesday 20th October 18:53

[okgo]

Nope. no message.

I will wait a few days and see what the level is. Is radweld not going to work then?

[sparks_E39]

okgo said:

Nope. no message.

I will wait a few days and see what the level is. Is radweld not going to work then?

I've heard it can but I wouldn't trust it on a permanant basis. If you drive it keep some water with you, I tend to in any car I have owned. I strongly suspect that you have a leak though mate and I certainly would if I were in your position be getting it to a garage and trying to avoid driving it in the meantime. Mine was very slow, in 120 miles it didn't move at all, then it went down a bit more. Turned out to be the radiator after we put pink antifreeze in it, the whole left hand side of it was covered. When the car is warm get under the bonnet and see if you can spot anything around the hoses, don't open the filler cap if the engine is hot.

[Victor101]

A 1999 528i with be a TU twin vanos engine with the electronic thermostat and this may well be the issue. At this age and mileage it really is ready for a new radiator and water pump - do these and the 'stat plus a coolant change and she should be okay. After 10 years BMW rads are normally shagged, partially blocked with silt, bowing out at the bottom and encrusted with flies and road crap.

[okgo]

So is it fair to say that £350 will cover it?

With the car costing well under £2k, and me using it so infrequently I am inclinved to go for the cheapest fix out there...

[Victor101]

£350 should cover it, or parts at least. A rad will be around £150 from a factors or Euro Car Parts but be sure it's the right one that clears the air con pipes. An electronic stat will be around £40-50 (more from BMW) and a water pump around £30. It's not too bad a job for DIY, but refilling the cooling system is tricky - basically you remove the bleed screw from the rad and refill very slowly (a litre at a time) through the top hose with the ignition on and heater set to hot. When the coolant starts to dribble from the radiator top outlet, the rad and the engine are full so refit the hose and run the car up and down the road until the heater starts to blow warm air. Do a final top up and slacken the bleed screw until it just dribbles coolant and it's all done.
Be aware that the M52 engine is one that really should not be overheated. If the head gasket goes, that's the end of the engine.

[okgo]

My A/C doesn't work, could it be linked?

[Victor101]

No. That'll just be a buggered condenser or a porous pipe. However, a non working AC fan won't help.

[okgo]

Right so used radweld, and all seemed to be fine no leaking etc.

Went to drive it down the A3 for about 30 miles today, it overheated, I pulled over..

There was no heat going to the matrix so no cabin heat, and the coolant was cold. So I got the AA out, he reckons its the pump, so its one to a mechanic to be looked at.