Bleeding technique - assistance needed

Post by **Simon Jones** » Mon Mar 31, 2008 12:12 am

Further to my recent post about water coming out the expansion tank (http://www.igmaynard.co.uk/bongo/forum/ ... sc&start=0), I've flushed the system out, but I've got a few q's about the bleeding process.

I've decided to use the traditional method as described in the manual & coolant factsheet. So as I understand it, the process with the bleed pipe is:

*Remove bleed plug
*Set bleed pipe at a downward angle
*Fill up coolant to the flange on expansion tank
*Run engine until themostat opens (lower rad pipe warm)
*Refit bleed plug
*Attach filler cap
*Run engine until thermostat opens again
*Repeat cycle 4 or 5 times

The thing I'm uncertain of is exactly what I'm expecting to come out the bleed pipe. At various stages today I had: nothing coming out, plain hot water, frothy hot water & some steam too. I realise that the frothy stuff indicates there is air in the system, but at what point is the bleeding complete: when nothing comes out, or when I get a steady flow?

What seems to be happening is that when it gets up to the point where the thermostat opens, the pressure build up & the level in the expansion tank rises & blows out the top. The pressure seems to be independent of the engine speed. I figure if the head gasket is leaking, then the pressure would build up with the revs & would overflow regardless of whether the thermostat is open or closed.

I'll have another go at bleeding again in the morning, but would appreciate any guidance.

mikeonb4c · Post by **mikeonb4c** » Mon Mar 31, 2008 1:28 pm

Simon. All I can remember (and bear in mind I was working on my own so couldn't watch the bleed pipe all the time) is that I used a lot more coolant mix than was theoretically needed as I wanted to be confident I had a solid (i.e. no air) stream of coolant issuing from the bleed pipe before I plugged it. It was this that cuased so much grief running round to top up the header tank before the level dropped too low and my efforts were undone. But I must have got it right as its run since with no hiccups.

Dont know if this helps....good luck!

Post by **Simon Jones** » Mon Mar 31, 2008 2:25 pm

Thanks for the tip Mike. I've spoke to Haydn & I'm going to give the see-saw method a go. I think the info in the fact sheet is wrong: it says to start with the hose downward, but all this does is drain the coolant out. The manual shows a picture of the pipe raised to steering wheel level. This makes a lot more sense & tallies with the see-saw method.

csermanni · Post by **csermanni** » Mon Mar 31, 2008 7:50 pm

I had to bleed mine using the method in the manual ...
... never did get a solid stream of coolant, just periodic burps of coolant and steam.

Not had a problem since (touch wood ...) ...

However ...

I'm almost frightened to make this suggestion to so many experienced Bongo owners ...,

But ...

Would it not help to create a vacuum on the bleed pipe, in order to draw the air out?

There ..., too late ..., I've done it ...

Crash helmet on ...

lizard · Post by **lizard** » Mon Mar 31, 2008 7:55 pm

csermanni wrote:I had to bleed mine using the method in the manual ...
... never did get a solid stream of coolant, just periodic burps of coolant and steam.

Not had a problem since (touch wood ...) ...

However ...

I'm almost frightened to make this suggestion to so many experienced Bongo owners ...,

But ...

Would it not help to create a vacuum on the bleed pipe, in order to draw the air out?

There ..., too late ..., I've done it ...

Crash helmet on ...

All suggestions are helpful.

Keep suggesting.

Peg leg Pete · Post by **Peg leg Pete** » Mon Mar 31, 2008 9:08 pm

Sounds good to introduce a vacuum

helmet off

Post by **Simon Jones** » Wed Apr 02, 2008 1:09 pm

Tried the see-saw method, but kept the funnel with some liquid in at all times to ensure no air could get sucked back in & also used it to back-fill the system. The same problem occurs: get to normal temp & the air bubbles start to come out the funnel until it eventually turns into full blown kettle-effect with huge bubbles & water gushing out. definitely getting pressure from somewhere.

I've decided to whip the head off this weekend & have a look at whats going on. Will keep you posted. Will also have a look at the turbo as another thread suggests this could be relevant. Although I dont have water getting into the cylinders I am getting pressure at higher revs - is it possible the exhaust gas is getting into coolant via dodgy seal in the cooling scetion of the turbo?

flashgordon69 · Post by **flashgordon69** » Wed Apr 02, 2008 8:55 pm

When you bleed the system you should never let it run long enough to boil the coolant, you shouldnt get clouds of steam and huge eruptions from the bleed pipe

The Great Pretender · Post by **The Great Pretender** » Wed Apr 02, 2008 10:18 pm

csermanni wrote:I had to bleed mine using the method in the manual ...
... never did get a solid stream of coolant, just periodic burps of coolant and steam.

Not had a problem since (touch wood ...) ...

However ...

I'm almost frightened to make this suggestion to so many experienced Bongo owners ...,

But ...

Would it not help to create a vacuum on the bleed pipe, in order to draw the air out?

There ..., too late ..., I've done it ...

Crash helmet on ...

Makes sense, evacuation is used on air con, but remember if you could remove all the air from the system when the coolant is heated it gives off gas bubbles.

maxheadroom · Post by **maxheadroom** » Thu Apr 03, 2008 6:41 am

Just to say when I have refilled coolant on my own, I have actually filled some water into the bleed pipe from a hosepipe. This did seem to help push air out of the expansion tank.

Bleeding technique - assistance needed

Bleeding technique - assistance needed

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Re: Bleeding technique - assistance needed