Planning coolant change.

[elbee]

Coolant change is due shortly and I've obviously been revisiting the Haydn videos etc regards bleeding see saw method etc etc .

My question is what's the best method to drain the old coolant?

[Northern Bongolow]

i usually start by opening/removing the expansion tank cap when cold then undo the twist bolt drain at the driverside end of the front radiator, you need about a ten ltr container, turn it anticlockwise to open with a pair of grips, once the bulk has come out you then have choices depending on your confidence and ability.

you could just stick a running hosepipe into the expansion tank top until everything runs out of the rad bottom clear but this doesnt clear the bottom of the engine out, or you could start to remove more pipes, from there i move onto the rear heater pipes and remove those, watch the rear heater plastic connections they are plastic and brittle, then remove the rad hose from under the passy side front where it joins to the radiator, one of the lowest points, then you could remove the top hose under the driverseat to flush out the engine itself.

[mikeonb4c]

Personally, when i've done it i've kept it simple and hopefully reduced risk of difficult air bubbles by only draining from the radiator and not opening the rear heater draincock. I toik the view that on my Bongo the old coolant was crystal clear and there was no rust staining on the header tank, so although some old coolant might be left in the system it would be diluted to the point of insignificance by the new coolant.

[cmm303]

Northern B's advice about removing hoses AND flushing through them is the only way to flush out the old coolant really thoroughly. I'm sure it is quickest as well. Northern B knows!

My view is from somebody a lot less experienced and confident. Old hoses that haven't been moved for a while can need a bit of rough persuasion and there are those possibly fragile plastic spigots he mentions. On the up, hoses come off the plastic spigots (radiator hoses and heater matrix) cleanly whereas I found metal spigots were messy with corrosion and I felt the need to clean them up before putting hoses back on.

I didn't want to push my luck with hose connections so opted to flush my system without removing hoses using the "Cain Alternative" as per fact sheet which involves flushing with the hot water whilst the engine is running. I think theoretically it should avoid bleeding but lots of air seemed to be introduced with the water so it needed see-sawing as well. Flushing was fine for replacing with the same type of coolant but I could not guarantee it was good enough for swapping to/from OAT. Took 3+ hours. Steps are in this link: http://www.igmaynard.co.uk/bongo/forum/ ... 15#p674256

Yesterday I replaced the coolant in a mate's van at his place on the way back from camping. Had none of my tools etc etc. He lives out in a rural village and his van is his only means of transport. Failure was not an option! So I wasn't touching any hoses. He has posh taps so could not rig a hot water hose up. I took a simple approach.

1. Drain and flush from radiator as described by Northern B.
2. Shut off radiator drain, fill and replace radiator cap. Flush through from expansion tank to bleed pipe until only a tint left. Takes an age!
3. Bleed from scratch using water (radiator, expansion tank, see-saw no engine, see-saw with engine, see-saw with hot engine and thermostat open). Takes up to an hour.
4. Engine off, cool a bit, drain radiator and leave - NO REFILLING
5. Slap up lunch, a beer and a laugh 1-2 hours!
6. Flush through radiator and bleed pipe as per steps 1 and 2 above with water.
7. Drain radiator.
8. Fill and bleed using antifreeze. Up to an hour.

Total time from finding the bonnet catch, finding screwdrivers, failing with posh hot taps, to everything tidied up was 6 hours. Actual work time was 4+ hours including removing the split charge relay with a foot long screw driver that had been screwed into and across the join of the fresh air intake before the LB was in place, grrr.

How thorough is it? When you drain the system from the radiator, I reckon there are a couple of litres of coolant left behind, say 15%. When I've drained a second time after mixing it all up that drops to 7%. Then with the flushing through the bleed pipe and final drain before installing antifreeze I would have thought it will be well below 5% old. How's my maths?

Lesson? Both the timid hands-clean dont-touch-a-hose methods take a while! Neither give a 101% clean flush.

[Northern Bongolow]

i think that just about sums it up chris, spend a bit of time, there are no short cuts, do as much or little as you feel is right or you are able to get the result. .

[elbee]

Sorry for delayed response, been away, thanks to all for above advise

[wonkanoby]

i would back flush the heater matrix as well