head gasket?any ideas

[dodgydoughnut]

just fitted and got running my m50 325i,had to fit new thermostat housing as was cracked.runs up fine and drives nice.but
cruise along at 30-40 and temp sits at half,give it a boot full and temp slowly goes up to 3/4 or so,and dont like comming down to quick.
so far tried,new water pump,clean coolant system all out,themostat s/h 80(but good)and now themostat with center removed.all does the same.radiator is aircon type large size.
feel abit lost.not using water,smoking or anything,no mixing of fluids.
engine came from unknown doner,but turns out to have thermostat cut apart.

[macas]

Is the system bled properly?
Im not calling you thick my friend but i had the same problem,i thought i had bled mine properly but i hadnt,it took me about 45 mins to bleed mine correctly.

[e30-EVN]

Make sure you've bled the coolant system properly mate!! Sounds like trapped air to me....

Try pressure bleeding the system by blowing hard into the expansion tank with the bleed screw open. It will be obvious if there is any air in there as it will spit! Fill some more and keep blowing until its a pure stream of coolant coming from the opening. When this happens, while blowing close the bleed, job done!

Now regardless what people say of this method I've dropped an m50 in my car and recently m52, the m50 covered over 5000 miles and the m52 is still going great. Temp guage sits halfway consistanly and when in traffic it goes just above half then the fan kicks in and she goes straight back to half

[dodgydoughnut]

ive read about it,its my first m50 so still learning,any way heater blows hot,radiator gets hot all over,filled header tank to top and removed screw,blown (mouth)header tank untill just water comes out bleed and refitted screw quick.run it for about 20miles.gets up to 3/4 and scares me.got a trackday booked for 2 weeks time

[e30-EVN]

Your over filling it for a start mate, about halfway up the bottle is normal. Otherwise there is no room for the water to expand.
If you have bled it thoroughly overfilling will be your issue!

[E30BeemerLad]

Are you using a brown M20 coolant sensor for the gauge?

[dodgydoughnut]

ok.
filled to top,undone bleed screw next to cap,blow down until water halfway down and only water coming out bleed,tighten.then run.
thats what i done tonight after changing water pump (had play)
will check it tomorrow.
dont beleve its head gasket as it runs too well with no symtoms

[dodgydoughnut]

yes brown sensor from my m20 which always read ok

[dodgydoughnut]

tried bleeding again tonight,car lifted as high as i can at the front.blow water out run for about 45min with cap off,pumping hoses etc,heater blows hot,gauge sits at 1/2.took out for drive.give it some beans on my private track,goes up to red quite quick and sits there.dont really come down with fans on and driving at constat 40mph.
got back home.let cool down and done a sniff type head gasket test and came up blank.
so seems like gauge is lieing to me.engine sat on drive in the red and doesnt smell mega hot or blow coolant out or anything out off the norm
any more ideas.going to try an after market gauge tomorrow.

[e30-EVN]

what temp stat are you running mate?

sounds like a standard 90 to me
fyi im running an 80-88 in my m52 and she sits on halfway consistantly, only moves just above half in traffic when the fan cuts in and she goes back down to half

[dodgydoughnut]

i got a 80 form danthe,but gone back to a cut out centre one at the moment,so no stat really

[12345kevin]

I had similar symptoms with mine originally, temp went to about 3/4 when pushing on or on track days. Turned out to be the radiator, got hot all over but was not flowing as well as it should.

Changed to a nice new one and now stays on the 1/2 all the time

[e30-EVN]

that was going to be my next point if im honest mate, either that or a duff water pump not functioning as it should

[dodgydoughnut]

right,looked again tonight,
it has a new water pump (this is the third)so not that
stat has centre cut out.not that
heater blows fine
temp gauge just creeps up the more you drive,so fitted an after market gauge into top hose.run it around a bit and was reading 100 at 3/4 on original gauge.so not gauge
now i snapped the top hose pipe off the frigging rad.

new rad coming tomorrow,the old looks good from the back,but quite furry and corroded from the front
hope and praying its the rad.....

[dodgydoughnut]

just fitted new rad,run it up the road and gauge sits at half,looks like its sorted..............................
just hope running it hot for the last couple of evenings aint done no damage

[e30-EVN]

if it didnt hit red she should be ok mate!

glad to hear you have it sorted