For the simple pressure bleed I described below it makes no difference
whether rear is up, nose up, or level. For major filling/bleeding I
prefer nose down but it doesn't make that much difference for me. The
radiator bleed screw is the highest point of the system. Raising the
rear makes it a little less so and lets gravity do more of the bleeding
before you start the engine. This is also the operating principle of the
Libby bong and that works quite well.

Mark

Mike Miller wrote:
> Nose down? I always heard nose up�
>
> Hmm.
>
>
> On Sep 8, 2013, at 2:41 PM, mark drillock wrote:
>
>> To do a simple bleed of the radiator you need to have the rear tank
>> full, cap closed tightly, then start the engine and warm it up. That
>> builds pressure in the system from heat expansion as the coolant warms.
>> The cap has to be closed tight and able to hold pressure. After a while
>> you open the radiator bleed bolt a turn and let the pressure out there.
>> If there is air in the rad it will hiss or bubble out. Once it streams
>> coolant without bubbles it is done. You may need to repeat. If you go
>> for a drive and fully heat the system there should be considerable
>> pressure ready to push air out of the bleed after you loosen it. If your
>> system does not have pressure inside after it warms then you have a
>> problem somewhere. You can still bleed the system but in another way.
>>.................