Bleeding problem - what am I doing wrong?

[davejevons]

Having replaced a split hose on our Freda, I've followed the instructions for bleeding, it works fine for the first cycle of 2,500rpm for 3 mins then 1 min idle but on the second the water in the funnel attached to the bleed point seems to boil.

The process I followed was:
fill rad, replace cap
fill expansion tank
loosen rad cap till overflowing and re-tighten
fill expansion tank
connect funnel to bleed valve and fill with water
1min idle
3min @2,500rpm
repeat idle cycle.

Any idea what I'm missing? Two things strike me as possible:
1. Not enough coolant - we only had 1 or 2 litres left and put in a lot of water. But would this make it overheat so quickly?
2. The head gasket has gone?

Any ideas very welcome.

[westonwarrior]

thje process of revving idling can take 45 min to get the temp up, the stat open and all the air out

[Northern Bongolow]

couple of things really.
fill the rad then the expansion tank with the funnel already attatched. ie the bleed pipe open and raised to the same height as the exp tank, this helps bleed the air out as the coolant enters, so makes for less bleeding later.best to get someone to raise and lower the funnel as coolant is going in then a lot of the air doesnt even get trapped it escapes.

then when you think the system if near full repeat the funnel up/down a few times BEFORE the engine is started, then top up as ness.

then start the engine and let it tick over gently for a while (do not rev) then repeat funnel up/down, the waterpump then trys to purge the system gently, and before any heat builds up in the engine/head.

check level again. then set the funnel at the same height as the exp tank with plenty of coolant in each, rev the engine and watch the funnel nearly empty, lift off gas peddle then let the funnel fill, dip funnel if ness to speed it up and purge air, when it is near full rev the engine again until funnel nearly empty, then off gas. repeat this lots of times until the bottom hose is very hot (stat open) and the system will be purged, AT NO TIME LET THE FUNNEL OR THE EXP TANK GO DRY, and please remember that as air is removed it will need to be replaced with coolant. and beaware the coolant is very hot towards the end of the process and can cause terrible burns.
when you are satisfied the system is bled and the bottom hose is too hot to hold cap the bleed pipe off (TAKE CARE) then adjust the level in the exp tank to the correct level, remember to account for the coolant cooling down, this will measure slightly less when cold, so set the levle 10-20 mm high to compensate for when it cools.


hope that helps.