Coolant system just won't bleed!!

[walnuttreeart]

Hi, we've been at it 3 days on and off now, trying to bleed the coolant after changing out the pipes (one split under the passenger seat so we had to be towed home - thought it best to replace the lot while we're there, given that I seem to have managed to avoid blowing the head gasket !).

We followed the factory instructions in the manual, no joy.

Today we diligently watched the 3-part video series and followed that procedure - seemed to have got all the bubbles on the cold engine part by seesawing. Got her warmed up and now we're just getting big globbets of air puffling out the funnel fitted to the bleed hose under the passenger seat.

We can't seem to get it hot enough for the thermostat to open as air just keeps pouring out. The fan came on just now but thermostat was.still closed.

Please - any ideas what we're doing wrong or if there's another problem we've missed that's preventing it from working?

Thank you

[g8dhe]

Presumably a diesel ? Did it get very hot ? Head gaskets don't normally fail but cracked heads is a common result.

[walnuttreeart]

Thanks for the reply Geoff. Yes it's a diesel. It got very hot when it failed, but I think I was able to pull over soon enough that it wasn't running overheated for very long after the coolant all dropped out.

There's no smoke blowing out the back and the oil looks clean - are there other signs I can look out for that would tell me the head was cracked?

We think if we could just get the thermostat to open it might work, but the bottom pipes are remaining stubbornly cold.

Wish I knew more about it all - the manual and YouTube guide are brilliant, and we've got an ex-Royal Engineer helping, but we're stumped!

[g8dhe]

There is a lot of discussion on this matter! These links are to Steve Widdowson's work on the diesel engine and its problems;
Basic fan operation www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=48872

Cooling system diagram www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=35902

coolant flow - (follow up to cooling diagram) www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=36433

Pipe - expansion tank to heater circuit return www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=49505

Mazda thermostat - A few observations www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=39193

Water pump - opinions please www.igmaynard.co.uk/bongo/forum/viewtop ... =3&t=47381

A cracked head is typical of the problem you describe provided it has been fully bled as the crack opens up when hot and squirts gases into the coolant system.

[walnuttreeart]

I'm going to book it into my local garage to pressure test the cylinder head and see if that's what's causing the problem.

That's for your advice and links. I'm working my way through those, although a lot of the info is stretching my ability the understand!

[Bob]

It will be good if you can get it to a Bongo Friendly garage, they understand the cooling system quirks.

Let’s hope you get sorted.