Any tips on refilling a M20B25 cooling system?

[e30_Turbo]

Hello all,

Been having some troubles with refilling my cooling system, having swapped heads due to a missing exhaust stud.

Over the last few days I have refilled and let her tick over with the heater blower on about 5 times, each time results in boiling water in the expansion tank and the gauge heading for red after 5 mins.

The heater blower is still not putting out hot air, only warm on start up, which I think is just heat soak.

I've removed the expansion tank and positioned it higher than the rad and pipework, jacked the front of the car up and tried to use the small bleed valve as well, but I am now where I was three days ago, a 250bhp super kettle!!

The bottom of the rad seems to stay cold, the top 2 inches seems to be very hot and the bottom rad hose is stone cold too, so any ideas?

I've done a search and tried every method I could find, but no joy, any more??

Your help is much appreciated as I've been car-less for nearly 3 weeks now, everything else is sorted but the last bit is kicking me in the nuts bigtime.

Thanks,

Mark.

[tim_s]

not sure really, but is the thermostat opening ok? no water pumping at bottom rad hose? you could try filling all the hoses and seeing if that helps it along etc - bit of a bodge but might help. you measured how much coolant its taken?

[e30_Turbo]

not sure really, but is the thermostat opening ok? no water pumping at bottom rad hose? you could try filling all the hoses and seeing if that helps it along etc - bit of a bodge but might help. you measured how much coolant its taken?

The more I think about it the more the thermostat seems to be a more likley candidate.

For the last few months the car has not gone much over 1/4 in the gauge in the car, my ECU was telling me it was running about 70-80'c most of the time, so maybe it was jammed open then, maybe it jammd shut one day causing the overheating and now is still shut which is why the rad and bottom hose is staying cold....hmm....I have another one in the shed..hmmm.....not to fussed about going out in the snow again tho.....will try tomorrow night.

I'll update when I've swapped them over, here's to hopeing that is the problem

Thanks, Mark.

[Globulator]

I changed the coolant in my M20 325i and didn't even have to bleed it. If the new thermostat and bleed screw do not solve it then I'd start wondering about the alignment of the head gasket and cooling passages.

Pumping the radiator hoses can sometimes help on tricky ones - while it's switched off and the cap is off.

Spent about 5 hours bleeding a Citreon once tho

[chu346]

I think you should try it without the thermostat. If its that's your problem. If not then I'd draine it and refill pumping all the hoses at the same time as filling and open the bleed screw until it starts spilling out LOADS of water. I take it you know that you should put the heater on whilst doing this but keep the blower off.

[telski789]

when i do mine i take the bleed screw right out,then get someone to hold the expansion tank way higher than the bleed hole and keep filling it until its pouring out of the bleed screw constantly then put the screw right in before lowering the expansion tank. make sure the heater is full on during warm up. if that doesnt sort it then maybe the thermo.

Tel

[e30_Turbo]

Just a quick update......another hour in the snow, one spare thermostat removed from spare housing, removed my old "original" BMW thermostat, swapped them over.......bottom hose warmed up straight away....has held temp between 1/4 and 1/2 for a good 10 mins idle, held same temp after a few miles of driving, well happy

Thanks to all for your help...... kind of answers a few questions too, like why there was no real problems with the head gasket when it was removed, although a bit out of shape on 3, inlet side.

Just need to figure these damn noisey tappets out now.....another job to do in the snow!! Yipee, not

[Mops]

sounds like thermostat to me aswell. I'd remove it and run car without and confirm it's working ok without it (saves you buying it if that's not the cause of the problem).

I see you run MSnS, I'm doing a ms2 install in for now stock e30 325i, I was wondering if I could have a look on your VE/AFR and ignition maps, just to have a look you know

[fixedwheelnut]

A tip for the future I always take one of the temp sensors or blank plugs out to let water/coolant out from there first then let it come out of the bleed screw, never had a problem doing it that way.