[SOLVED] Radiator Level Light and Engine Overheating

[gizmo]

Hoping someone can help.

Car: BMW 330i Sports Automatic. X-reg (year 2000).

The other day, the radiator light came on the dashboard. I opened the cap on the black tank (expansion tank I believe) and noticed low water level, so topped up. As I did so, water came out the bottom but the tray prevented me from seeing where. I attempted to drive it home but it overheated after about 3 miles so I turned it off and got recovery to take care home.

Next day I removed bottom tray and noticed water coming out Return Hose (smaller hose that runs below alternator) where it joins the expansion tank. So I got a new one and fitted it (quite a big job as it turned out).

I bought a 5 litre bottle of coolant and poured in 2,5 litres into the black expansion tank, with the intention of putting 2.5 litres of water in too, but the coolant level was already to the brim. I took it out for a test drive this evening and within 3 miles, it was overheating again. I pulled into a restaurant and got 4 litres of water that I also poured in gradually. The level of water would gradually reduce over the seconds...it just kept going in. Eventually, it settled. I restarted the car and drove home.

I kept expecting the heat reading to get high again but it didn't seem to...stayed at mid point. But all of a sudden, the radiator level light on the dash came on again about a mile from home, but the heat level did not rise. There does not appear to be a leak...I see no water coming out.

So now I am confused. The temperature seems to have settled but the radiator light has come again but it if its not leaking out, it must surely be full? Maybe the engine would get hot again soon after but I didn't want to risk getting stranded so I just parked it back at home on the drive at this point. The fan spins and it has had a new belt fitted the other day...the one that spins the alternator and water pump.

So, my assumption is an air-lock that I caused during filling after the new hose...which has now perhaps got itself free? Or is it more likely to be water pump? I have no experience of modern radiator systems...the last time I had radiator problems was a 1977 Opel Kadett when I was 21 that was easy to work on and fix!

Any advice?

 

Edited June 23, 2016 by gizmo

[Ragamuffin]

I hope you have got away with doing any damage to the top end of your engine with the reaching of boiling point a couple of times. It could possibly be an air lock, as these engines can be tricky to bleed properly. You need to use the bleed valve on the engine, and there is a tip, its getting the car on ramps to make sure the air is forced out.

[R2D2]

This reads like a how(not)-to on diagnosing a coolant leak. As above, hopefully youve got away with it, but you may have warped your rocker cover in the process if the engine has got too hot, in which case you may notice an oil leak in that area in the near future.

The only other reason you will be losing water without it leaking is if your head gasket is gone, however being a 6 pot engine and having an aluminium block i highly doubt thats the case. My money is on either an air lock or a leak that you dont notice as its only happening when the coolant is being pumped round (ie, youre driving at the time).

Please, please take your car off the road and have a proper look at whats going on otherwise youll cause serious damage. If i were in your position i would do the following:

- Properly top up and bleed your coolant levels (its very easy, and if youre stuck theres a how-to in my water pump replacement thread here)

- Turn your engine over and give the cooling system a good looking over, keeping an eye on the temperature at the same time. If it goes past midway point, switch off the engine immediately. The most likely culprits are joints in the pipes, split pipes, radiator leak or expansion tank leak. Any of the above may become obvious with the engine running in idle. Do all of the above with the expansion tank cap ON, otherwise the system wont pressurise and the coolant will boil over quite quickly.

- If youre certain that none of the components are leaking, take your car down to a garage (somehow) and get the cooling system pressure tested. Theyll be able to tell you whether your head gasket is ok.

 

Hope this helps. Keep us informed on any progress. 

[330dsupertourer]

Me personally I'd jack the front NS corner of the car making the header tank the highest point. (Having checked the water level first) start the car up and allow it to reach temp gradually as it warms up I'd crack the bleed nipples one at a time until it's a constant smooth flow of fluid with no air bubbles coming out. Once your happy the air is out, drop it down, turn it off, let it settle for a mo, crack the pressure cap and let the car settle

[gizmo]

Gents

I sorted it in the end, and thanks for the help.

I bled the system using the bleed valve...quite a bit of air come out. Continued until it ran as solid fluid, topped it up some more, and all seems to have been well.

I did notice a bit of smoke a few times if I lifted the bonet coming from the side of the engine (opposite to where the alternator is) and I worried, as you have said, that I might have blown a seal or something. But that seems to have eased off of late so I think (and hope) it was some spilt oil burning off because I changed the oil and filter while it was up on the jacks. I didn't have a funnel and so a few desert spoon sized spills took place. I tried to wipe most of it off but some did trickle down the side.

Since doing the work I've driven it on two 110 mile trips and two 15 mile trips, and so far, the temp has remained at central and the cars been fine. I'll keep an eye on the oil level though just in case.

Thanks again for the advice.

Edited June 23, 2016 by gizmo

[R2D2]

Good work. Keep an eye on that smoke situation though, its exactly what happened to me. The valve cover is very prone to warping if the engine overheats and it causes oil to leak on the back and exhaust side of the engine. The oil then runs onto the heat shielding and burns off.

Good luck