Frustrating coolant problem

[AndyMitton]

Hi all,

Having a frustrating coolant problem

Changed my expansion tank about a year ago and refilled coolant. OEM BMW part.

Not so long ago the coolant warning light came on. So topped it up and wanted to see where it was coming from. Really had to screw the cap on to get it to seal; appeared to be the cap.

The light came on again. But it wouldn't always be on. Would usually be under acceleration.

So got worse recently so I bought a new cap. And since then its far worse. It seems to blow a load of water out as soon as it gets warm. The light is still intermittently on. Usually it comes on under acceleration and on the motorway.

The blower temperature is generally cold but gets warm under acceleration and on the motorway is fine. Temperature gauge is always as has been before. Engine has not overheated. Cooling fan comes on when idling for long periods of time and there is no evidence of water and oil mixing.

Its a 3.0 M54 (54 plate).

Cheers

Andy

 

[AlienZed]

Have you bled the sytem to get the air out, on mine theres a bleed screw on the top hose near the rad,changed mine and the rad over xmas took me a while to purge the air out but all fine now,
Moz

 

[hopz121]

Sounds like you have not bled the system properly to me, i would be careful until its fixed as if it overheats you are going to have even bigger problems, The M54 engine doesn't like overheating at all!

 

[AndyMitton]

OK guys cheers

I'll have another go bleeding it. Hopefully its as simple as that

Cheers

Andy

 

[Stratts]

May be a bleeding problem, definitely worth filling properly (it can take upwards of 30 minutes to top up and bleed it properly).

I would also consider maybe a restricted coolant flow. It is not blocked as otherwise that would cause overheating, but a restricted flow will build up pressure causing the cap to blow. Under acceleration the water pump is working harder and maybe this is having a better effect at easing the blockage (hence the warm air).

I have seen old partially blocked radiators have minor impacts on the cooling system, just something to consider...

 

[AndyMitton]

Thanks for that

I vented the system according to the BMW procedure.
It worked OK for a bit but then the coolant light came on. Then the hot and cold air started again.

Opened the bonnet arriving at work; there's coolant trickling down the header tank. I can't tell whether its coming from the top hose or cap.

 

[Stratts]

I would do two things:

Stop driving it any major distance as you are running the risk of overheating it (or at least being stuck while it cools down a bit)
Find the source of the leak with the engine running and warmed up (with someone watching the temp gauge).

Unlikely to be the cap as these have no source of leaks (unless you've broken it). It should be easy to spot, but if it is the cap then again sounds like a pressure problem??

 

[AndyMitton]

Hi thanks,

Just checked and it is leaking from the cap

Opened the bleed valve and there is a lot of steam coming out of here. A lot.

Bought a new cap a couple of weeks ago...was a Meyle one

Cheers

Andy

 

[Stratts]

Have you got the right pressure rating? Should be 2 bar I think.

Some aftermarket caps are 1.2 bar, worth checking. I have read that these caps are still meant to be fine for everyday use, but maybe not in your case??

 

[AndyMitton]

Have you got the right pressure rating? Should be 2 bar I think.

Some aftermarket caps are 1.2 bar, worth checking. I have read that these caps are still meant to be fine for everyday use, but maybe not in your case??

ill check

i think it has '200' written on top which i am assuming is 2 Bar

I will check

Thanks

Andy

 

[AndyMitton]

yea just got 200 on top of it

Cheers

Andy

 

[yg54sg]

sounds like it needs bleeding fully, i had this problem each time I've done a coolant change, happened when i changed the

1. Go get yourself one of these from the supermarket for £3 : it needs to be the 5L bottle with the wider neck/top like in the picture think its about 1.5 inch diameter http://img.21food.com/userimages/elenaven/elenaven$1821180.jpg this fits exactly inside the neck of the expansion tank.

2. Park on a steep incline with nose pointing up.

3. Fill the bottle with tap water & bmw coolant mixture.

4. Start the engine (from cold ideally so no pressure in the system)

5. Quickly tip the bottle upside down and seat it in the neck of the radiator (i prefer to do the tipping with bottle neck towards the front of the car so no spillage hits the belts etc)

6. Have someone rev the engine in short bursts to about 3.5k, you will notice bubbles start coming up to the top of the bottle, after about 30 second to a minute, the water will start emptying into the radiator and the bottle will start compressing in on itself i usually find it eats about 1-2 litres before stopping.

After doing that you will notice you have hot air again on the heater ... system is fully bled. There are some bleed screws too you can undo but to be honest i never noticed the difference after messing with all the bleed screws doing it by the book I always end up with the old bottle on an incline You have created a header tank and applied pressure which gets the air out. Hope this helps!

Def never drive it if its overheating aluminium head!

I also found with the expansion tank crack that because bmws work under pressure the coolant leak may never be actually visible, on a cold night i got a torch out, got the engine to temperature and looked around, saw steam coming from a slight crack in the expansion tank with only small amounts of white residue around it. Had it not been at night and cold would never have found that.

 

[yg54sg]

ps... your neighbours will also think your an eccentric english old boy feeding your car mineral water :rofl:

 

[AndyMitton]

Cheers mate I will give this a go

I've re vented and filled again at work tonight. Ass seemed ok. Opened the bonnet when home and there's steam from the coolant cap

Yea I had a similar thing with the header tank. Pin hole in it. Was so hard to spot but found it and replaced with a new OEM One

Haha yes I'm sure the neighbours will have a laugh

Cheers

Andy

 

[AndyMitton]

Well bled it over and over again. Still leaked

Bled it over and over again and out a new OEM cap on. Problem seems to be sorted.