Engine rebuilt but bubbles in header tank.

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Ciaoflyer
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Engine rebuilt but bubbles in header tank.

Post by Ciaoflyer »

Ok, rebuilt DJ 2.1 injection engine and it has now done 500 miles so ready for oil change. However, I am getting bubbles in the header tank causing a gap of about 2cm from top of tank, just above the rubber pipe that comes out of the right hand side. Now, I am assuming it is not the head gaskets as I replaced both of these with sealant on both sides. Can a leak in the system cause these bubbles? The tank behind the flap sometimes goes up and down. Your advice will be appreciated.
1988 Autohomes Karisma DJ 2.1 Auto

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Mocki
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Re: Engine rebuilt but bubbles in header tank.

Post by Mocki »

Any pipe junction can cause air to be sucked in as the engine cools if it’s not air tight , although it may not be apparently leaking coolant ( could be leaking coolant but at such a low volume it evaporates immediately and so is invisible)
A hairline crack or pin hole in the head may also cause the same , but normally this will cause much over pressure of the cooling system .

Of course it may just be you need to bleed the system again, it’s almost impossible to completely eradicate all the air as some gets trapped in the heater rad(s) and taps .

It could also be the pipe tween the header tank and the top up tank leaking and sucking air in or the pressure cap not pulling the coolant back as the engine cools , leaving a gap at the top of the bottle as the coolant contracts .
Try another bleed and keep your eye on it would be my first move .
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Ciaoflyer
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Re: Engine rebuilt but bubbles in header tank.

Post by Ciaoflyer »

Thanks for this! I just had a thought, the level in the header tank always sits just above the pipe on the right which goes to bleed rail, could it be that there is simply not enough coolant in the header tank?

If I remove header tank cap the level rises to the top, then tighten cap and Rev engine bubbles appear, level drops then bubbles disappear. Are those bubbles from opening the dalek cap?
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Aidan
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Re: Engine rebuilt but bubbles in header tank.

Post by Aidan »

if you remove the cap when the system is pressurised then the boiling temperature of the coolant goes down so it boils and then when it re-pressurises after the cap is on it stops boiling
if the level is constant with a small air pocket in the header tank and not pushing much coolant out of the tank into the top up tank, and always drawing it back when cold then it sounds like it's okay

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Mocki
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Re: Engine rebuilt but bubbles in header tank.

Post by Mocki »

The headertank should be full to the brim when cold and the same when it has cooled back down to cold

If you open the header tank cap when the engine is cold but running and Rev the engine the level will drop , as you reduce the revs the level will rise as the waterpump slows down .

I always Rev the engine and fill that extra up to the brim and put the lid back on before reducing the revs down so no air is kept in the headertank from the get go

If you think the bleed rail maybe a factor, check it isn’t blocked , it’s common for the bleed rail pipe to get blocked in under maintained systems
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Re: Engine rebuilt but bubbles in header tank.

Post by Ciaoflyer »

Thanks guys for this, very interesting! I have opened the cap while it is cold and now topped to the brim! Will keep an eye on it and top up as required.
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Re: Engine rebuilt but bubbles in header tank.

Post by Ciaoflyer »

Mocki wrote: 23 Nov 2020, 19:40
If you think the bleed rail maybe a factor, check it isn’t blocked , it’s common for the bleed rail pipe to get blocked in under maintained systems

Thanks, when I put engine back together the bleed rail was blocked and I cleaned it all out, some prune had put in radweld to cure previous leaks.
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Re: Engine rebuilt but bubbles in header tank.

Post by Mocki »

Maybe worth checking it again then, that stuff is a Bugger to get rid of , it hides in the radiator ( and the heater rad ) and escapes again
Steve
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Re: Engine rebuilt but bubbles in header tank.

Post by Ciaoflyer »

Mocki wrote: 24 Nov 2020, 17:44 Maybe worth checking it again then, that stuff is a Bugger to get rid of , it hides in the radiator ( and the heater rad ) and escapes again

Yes I think it is air, ran it today and level in header has dropped to top of pipe again, will add more coolant in the morning when cold.

This is the first time I have ever bled a vehicle so a learning curve!
1988 Autohomes Karisma DJ 2.1 Auto

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