V6 - Angry funnel eruptions whilst bleeding after reaching normal temp

[bourne2bongo]

Just replaced several of the coolant pipes on the V6, after finding dripping from junction of top rubber hose to driver's side metal pipe. She has smelled 'hot' after a few 30+ minute runs recently (maybe the leaking coolant evaporating?), and metal pipe end looked quite rusty.

To bleed, we're following the see-saw method (with a jug), as per factsheet and youtube videos (watched several times). I've also read loads of posts on the forum about how to do this - I'm guessing lots of new Bongo owners do this too!

So, being careful not to let air in at either end, the coolant reached normal running temp (11 o'clock on the dial), and front and rear heaters we're blowing nice and hot, and got turned off. A few small bubbles, and satisfying larger burbles and gulps seen in the jug over this time, just as in the videos. Coolant is steaming hot and the top of radiator is nice and hot.

Then about 12 - 15 minutes in to the process (3 mins at 2,500 revs, 1 min at idle, see-sawing all the time), coolant EXPLODES out of the jug. It's a violent and continuous eruption - really dangerous as it's shooting out - and nothing at all like the videos.

We turned off the engine (previously idling). and coolant erupted even more violently from jug, so restarted engine again (now erupting as before). During this time, small amount of coolant burped out of the expansion tank, but majority shooting out of the bleed pipe/jug.

After 60 finger-burning seconds, the eruptions stopped completely, presumably as the system cooled (engine still idling). Then it started for a few seconds - violent eruptions again - and stopped again just as suddenly. Switched the heaters back on, and it stopped again for longer. Stopped engine, replaced air bleed pipe bung and put hands in ice water!

I've scoured the forum for similar stories, and closest I can find is for a diesel (not a V6 petrol like ours) and that has similar symptoms, but from cold. Our only goes 'volcanic' when getting towards hot, well after dash shows normal running temp / top pipes feel hot.

Bottom hose felt cold throughout.

Is this something to do with thermostat either partially or fully opening, and/or a blockage in the system? Should we fit a new stat and radiator?

[teenmal]

It would be worthwhile checking/replacing the thermostat .

This jug /funnel/sea saw method of bleeding these vehicle IS Very Dangerous.

[bourne2bongo]

Thanks for the reply teenmal

Think I'll order a replacement thermostat and radiator- can't find a receipt in the history for a replacement for either - and there was some sludge in the old coolant so may be blocked.

So is it usual to see a continuous, uninterrupted 60 second eruption (coolant shooting a foot or two out of the 2ltr jug) in the V6s around the point that the thermostat ought to be opening? I'm just a bit surprised not to have come across more mentions of it here or on YouTube, etc.

Thanks again for your help

[Northern Bongolow]

the bleed process you describe sounds nothing like the videos ive seen. (we made em). the bleed process in the vids is a far more gentle affair, it sounds from your description like you are pushing it too fast, you do a non running bleed, then a ticking over bleed, then a gentle rev bleed then bring up the revs.
if you get things too hot too quick the likely hood is you will be heating air not coolant causing the volcano effect you are seeing. air/liquid when reaching steam point expands massively.

https://www.google.co.uk/search?q=liqui ... e&ie=UTF-8

pm me your number if you wish, and we can have a chat about it.

[bourne2bongo]

I'm pretty sure we're following the process as you described ... cold see-saw, then tick-over see-saw, then 2.5k revs for 3 mins, and 1 min idle

Really kind of you to offer help - THANK YOU - will PM you now

[bourne2bongo]

After a late night call from Northern Bongolow, and a patient couple of hours this evening, i'm happy to report Dobby's coolant now seems completely air-free, with no damage seemingly done.

During this third attempt at a bleed, almost all the air was removed before the engine was even turned over. Lot's of massaging of pipes, listening carefully for gurgles (there were plenty to start with), allowing air to escape by loosening clips, wiggling pipe ends, priming the other side of the stat with gentle pipe squeezes, and thinking it all through before even the cold see sawing started, seemed to make a huge difference.

After idling for a good while (front and back heaters getting good and hot) we heated the engine slowly, mostly between 1200 and 1500 rpm for 30(ish) seconds at a time then back to idle. Throughout the bleed I checked pipes, listened for gurgles, felt for temp changes and cold spots, etc. No sudden changes noticed. No dramatic eruptions this time. Hardly any bubbles at all in fact, whereas the first couple of attempts had resulted in burps much like in the YouTube vids.

After a while, the thermostat opened and the bottom pipe started to heat. Another minute of two and I could only hold the bottom pipe in my hand for 2-3 seconds before it was too hot, both at the stat and radiator ends.

A stress free process - two person job - and no burns!

As was patiently explained to me, the violent eruption of coolant was caused by an airlock. This super-heated steam was then allowed to escape harmlessly (if a little dramatically) through the air bleed hose and expansion tank, rather than forcing the cylinder head(s) of the V6 to burst/crack.

I think I followed the factsheets and videos pretty carefully the first two times but was probably on the road to some expensive repairs. I only got my head around this vital Bongo maintenance procedure properly (and hopefully didn't goose the heads!), with the aide of an amazing member of Bongo Fury, who took the time to help me understand what was really going on. I was then able to solve my own problems, with a few top tips thrown in.

It was this kind passing on of knowledge that got me and Dobby through the gate. Massive thanks to Northern Bongolow for going well above and beyond . And I hope I can pass the same knowledge on to others one day.

[Bob]

Well done to all.

[Northern Bongolow]

glad it worked out good, and please pass your knowledge on.

[Glenda]

Great work. Well done NB!

[ade33]

I've rarely been a member of such a helpful forum.

That sounds pretty scarey - I'm glad our V6 didn't do that mid-bleed. I'd have been tempted to take a tree-branch to it, in a John Cleese stylee.

Though I did spend forever on the cold see-saw process, to the point where not that much air came out during the engine runs.

Did you get properly burnt? Hope you're ok bud.

[haydn callow]

In the start to this topic it was said. "" when we reached normal temp on the gauge". If my memory serves me, the gauge reaches 'normal' when the coolant temp reaches about 30c.....it will then stay at 'normal' until the coolant temp reaches about 110c....
( normal relates to 11,0 clock on the gauge) once the gauge moves up from 'normal' you are overheating fast.
The critical point when bleeding is when the bottom hose goes hot (stat has just opened) , unless the gauge has been modified it is pretty useless for reading temp......this is why many peeps fit a after market temp gauge.