bmw 520i engine

[tyler xp]

the engine idles erratically and over heats had the head gasket done and new head.but still got this problem?any help

[Kev_UK]

Idling: timing could be out, fouled spark plugs, air filter clogged.
Overheating: Fan not working, faulty thermostat (try it without the thermostat for a shortsh journey and see if it makes a difference).

[tyler xp]

hi,took the thermostat out no diffrence,new spark plugs new air filter.had timing done.and fan seems fine,could it be air pipes conected wrong.feel like scraping it now.

but i cant its cost loads so far.

[bruce5755]

You've probably got an air-lock in the cooling system.  After doing a head gasket job on a BMW, it's quite common to get an air-lock, it's imperative that the cooling system is bled out to prevent overheating.  Try removing the heater pipes from the heater valve unit while you fill up the radiator, till all the air is out of the system.

[dougielogan]

Put car on a very slight incline facing uphill, make sure the radiator is bled first, it will have a plastic bleed screw (you will need a largish flat screwdriver) don't over-tighten. once the water comes out of that hole peplace the plastic plug. there will be a bleed screw somewhere on the front of the head maybe on the themostat housing which you will need a 8mm sockec or spanner for( be careful they are usually tight and almost rounded ) and continue pouring water in until the water comes out and then tightenn That might do the trick. The most common fault is to forget to bleed the actual radiator.  

[Loosehead]

Have you investigated whether this car is covered by the potential Nikasil bore problem? Try a google on BMW Nikasil

[tyler xp]

hi tried bleeding had her running for over an hour didnt over heat so took her for a little run and she went to red again.bleed her for a couple of hours.cheers tyler xp

[Hippy]

Mine does this. You have to open the heater controls, turn on to very hot inside, then bleed the heater. Take off one of the tubes from the bulkhead to the cylinder head at the bulkhead end with engine running. Keep pouring water into the filler until it pours out of both heater and flexible hose. Put pipe back and tighten. It's a flippin' nuisance. If you try to do this when it is over-hot and you can hear the water boiling then it will never work. Let it cool down and try again.

The ignition or injection timing might be too advanced, that would cause erratic tickover and also spluttering when accelerating. However, retarded ignition means engine is smooth lacks power and overheats.

[tyler xp]

thanks hippy try that in the morning.

let you know if it works hope so.got a crypton tuner up tomorrow to check timing.

thanks again. tyler xp